WO2022226292A1

WO2022226292A1 - Laser-based gasification of carbonaceous materials, and related systems and methods

Info

Publication number: WO2022226292A1
Application number: PCT/US2022/025921
Authority: WO
Inventors: Charles J. BROWN; Morgan S. HELLER
Original assignee: Brown Charles J
Priority date: 2021-04-22
Filing date: 2022-04-22
Publication date: 2022-10-27

Abstract

Gasification of carbonaceous materials using laser energy to controllably heat the carbonaceous materials so as to control pyrolysis and the resulting product gases. In some embodiments, measurements of one or more conditions relating to the pyrolysis are made, and the measurements are used as feedback for controlling the heating. In some embodiments, one or more laser heads having multiple laser-beam outputs are used to perform the heating. In some embodiments, pyrolysis is assisted by providing one or more oxidants and/or implementing one or more supplemental heat sources. Other embodiments are also disclosed.

Description

LASER-BASED GASIFICATION OF CARBONACEOUS MATERIALS, AND RELATED

SYSTEMS AND METHODS

RELATED APPLICATION DATA

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application Serial No. 63/178,156, filed April 22, 2021, and titled “LASER-BASED GASIFICATION OF CARBONACEOUS MATERIALS”, which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

[0002] The present invention generally relates to the field of gasification of carbonaceous materials. In particular, the present invention is directed to laser-based gasification of carbonaceous materials, and related systems and methods.

BACKGROUND

[0003] Fossil fuels can provide an answer to the growing energy demand of developed and developing countries. The greater availability and lower cost of coal relative to other fossil fuels make it a leading energy resource for electricity generation across the world. On the other hand, coal is a source of environmental concern, not only for its greenhouse impact in terms to carbon dioxide, but also for the health and safety impact of conventional coal extraction methods on workers and local environments.

[0004] Coal devolatilization is a process in which coal is transformed at elevated temperatures to produce gases, tar, and char. Functional groups of the original coal are mainly released as gases and can be reasonably predicted by first-order reaction models. Tar, defined as condensable species formed during coal devolatilization, is a major volatile product, composing up to 50% of coal weight for bituminous coals.

[0005] Coal, like all other sources of energy, has a number of environmental impacts, from both its mining and its use. Coal mining raises a number of environmental challenges, including soil erosion, dust, noise, and water pollution, and impacts upon local biodiversity. Steps are taken in modem coal mining operations to minimize these impacts, although they are still of considerable concern, and environmental reparations are costly. Continuous improvements in technology have dramatically reduced many of the environmental impacts traditionally associated with the use of coal in the vital electricity generation and steelmaking industries. Viable, highly effective technologies have been developed to tackle the release of pollutants, such as oxides of sulfur (SO_x) and nitrogen (NO_c), particulates, and trace elements, such as mercury. However, more recently, greenhouse gas emissions, including carbon dioxide (CO₂) and methane (CH₄), have become a concern because of their link to climate change.

SUMMARY OF THE DISCLOSURE

[0006] In one implementation, the present disclosure is directed to a method of producing a product gas from a mass of carbonaceous material, wherein the carbonaceous material includes a pyrolysis chamber within the mass and defined by surrounding portions of the carbonaceous material. The method includes inserting a laser head into the pyrolysis chamber, wherein the laser head is configured to output and direct laser energy to a target portion of the surrounding portions of the carbonaceous material; while the laser head is present within the pyrolysis chamber: heating the target portion of the carbonaceous material with the laser energy emitted from the laser head so as to sustain a desired pyrolysis state that produces the product gas from the carbonaceous material; concurrently with heating the target portion, obtaining measurements of at least one condition of the target portion having a known correlation with the desired pyrolysis state; and controlling the heating of the target portion as a function of the measurements of the at least one condition of the target portion; and extracting the product gas from the mass of carbonaceous material.

[0007] In another implementation, the present disclosure is directed to a method of producing a product gas from a mass of carbonaceous material, wherein the carbonaceous material includes a pyrolysis chamber within the mass and defined by surrounding portions of the carbonaceous material. The method includes inserting a laser head into the pyrolysis chamber, wherein the laser head is configured to output and direct laser energy to the surrounding portions of the carbonaceous material; while the laser head is present within the pyrolysis chamber, irradiating multiple regions of the carbonaceous material with multiple laser beams emitted from the laser head so as to sustain, at the multiple regions, a desired pyrolysis state that produces the product gas from the carbonaceous material; and extracting the product gas from the mass of carbonaceous material.

[0008] In yet another implementation, the present disclosure is directed to a laser-head assembly for gasifying a carbonaceous material that defines a pyrolysis chamber formed therein when the laser head is located in the pyrolysis chamber, the pyrolysis chamber having a first longitudinal axis. The laser-head assembly includes a laser head having a length and a second longitudinal axis along the length that is designed to be substantially parallel to the first longitudinal axis of the pyrolysis chamber when the laser-head assembly is present in the pyrolysis chamber, the laser head including: a plurality of laser outputs distributed in a circumferential direction at least partway around the laser head for delivering laser energy to portions of the carbonaceous material.

[0009] In still another implementation, the present disclosure is directed to a laser-based gasification system tuned and configured for producing a product gas from a mass of carbonaceous material via a pyrolysis chamber within the mass and having walls defined by surrounding portions of the carbonaceous materials. The laser-based gasification system includes a laser head having a plurality of laser outputs; one or more lasers for providing the laser energy to the laser outputs of the laser head; and a control system configured to control the laser energy output by the laser outputs so as to pyrolyze the carbonaceous material consistently throughout the pyrolysis chamber so as to produce a desired product gas.

[0010] In a further implementation, the present disclosure is directed to a product gas composition produced by a process including inserting a laser head into pyrolysis chamber formed in a mass of carbonaceous material, wherein the pyrolysis chamber is defined by surrounding portions of the carbonaceous material; and when the laser head is located in the pyrolysis chamber, heating the surrounding portions of the carbonaceous material with energy emitted from the laser head so as to produce the product gas composition from the carbonaceous material; wherein the product gas composition so produced comprises from about 1% to about 10% by mole carbon dioxide, from about 1% to about 10% by mole carbon monoxide, from about 20% to about 30% by mole methane, and from about 40% to about 50% by mole hydrogen.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For the purpose of illustrating the invention, the drawings show aspects of one or more embodiments of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:

[0012] FIG. 1 is an isometric diagram illustrating a conventional underground coal gasification (UCG) system and process for producing a product gas from a coal seam;

[0013] FIG. 2 is a elevational view of a section of a coal seam illustrating physical aspects that occur within the coal seam during UCG;

[0014] FIG. 3 is a flow diagram illustrating an example product-gas-production method of the present disclosure, wherein laser-energy is used to heat a carbonaceous material so as to cause the carbonaceous material to pyrolyze and form a product gas; [0015] FIG. 4 is a high-level block diagram illustrating an example laser-based gasification system that can be used to perform a product-gas-production method of the present disclosure, such as the example product-gas-production method of FIG. 3;

[0016] FIG. 5A is a flattened view of a portion of the inner wall of a pyrolysis chamber in a carbonaceous material, illustrating an example pattern for heating the inner wall so as to cause the carbonaceous material to pyrolyze, wherein the irradiation regions abut one another;

[0017] FIG. 5B is a flattened view of a portion of the inner wall of a pyrolysis chamber in a carbonaceous material, illustrating an example pattern for heating the inner wall so as to cause the carbonaceous material to pyrolyze, wherein the irradiation regions overlap one another;

[0018] FIG. 5C is a flattened view of a portion of the inner wall of a pyrolysis chamber in a carbonaceous material, illustrating an example pattern for heating the inner wall so as to cause the carbonaceous material to pyrolyze, wherein the irradiation regions are spaced from one another;

[0019] FIG. 6A is a transverse cross-sectional view of a pyrolysis chamber and surrounding portions of a carbonaceous material, illustrating the formation of a generally circular pyrolysis chamber as pyrolysis is performed on the carbonaceous material, wherein the laser head remains at the bottom (relative to FIG. 6 A) of the pyrolysis chamber;

[0020] FIG. 6B is a transverse cross-sectional view of a pyrolysis chamber and surrounding portions of a carbonaceous material, illustrating the formation of a generally rectangular pyrolysis chamber as pyrolysis is performed on the carbonaceous material, wherein the laser head remains at the bottom (relative to FIG. 6B) of the pyrolysis chamber;

[0021] FIG. 6C is a transverse cross-sectional view of a pyrolysis chamber and surrounding portions of a carbonaceous material, illustrating the formation of a generally circular pyrolysis chamber as pyrolysis is performed on the carbonaceous material, wherein the laser head remains at the geometric center of the transverse cross-sectional area of the pyrolysis chamber;

[0022] FIG. 6D is a transverse cross-sectional view of a pyrolysis chamber and surrounding portions of a carbonaceous material, illustrating the formation of a generally rectangular pyrolysis chamber as pyrolysis is performed on the carbonaceous material, wherein the laser head remains at the geometric center of the transverse cross-sectional area of the pyrolysis chamber;

[0023] FIG. 7A is cross-sectional view of a portion of a deposit of carbonaceous material containing an access well and a lateral pyrolysis chamber joined to the access well, showing a flexible laser-head assembly being inserted into the lateral pyrolysis chamber via the access well; [0024] FIG. 7B is a cross-sectional view similar to the cross-sectional view of FIG. 7A, but with the laser-head assembly located in a first gasification location and pyrolysis having been fully performed at this location;

[0025] FIG. 7C is a cross-sectional view similar to the cross-sectional view of FIG. 7B but with the laser-head assembly located in a second gasification location and pyrolysis having been partially performed at this location;

[0026] FIGS. 8A to 8C are cross-sectional views along the longitudinal axis of a portion of a bore-type pyrolysis chamber, showing a timelapse progression of pyrolysis within the pyrolysis chamber and three snapshots in time;

[0027] FIG. 9 is a cross-sectional view along the longitudinal axis of a portion of a bore-type pyrolysis chamber, illustrating progression of pyrolysis within the pyrolysis chamber as a laser head is moved along the pyrolysis chamber;

[0028] FIG. 10A is a side view of an example laser head having gas-delivery outlets and gas- collection inlets located on opposite ends of the laser head for, respectively, delivering one or more gases (e.g., oxidant(s), heating gas(es), etc.) to a pyrolysis chamber and removing one or more gases (e.g., product gas) from the pyrolysis chamber;

[0029] FIG. 10B is an enlarged cross-sectional view of the tether attached to the laser head of FIG. 10 A, showing internal components of the tether;

[0030] FIG. 11 A is an isometric diagram illustrating an example UCG system and arrangement of the present disclosure, showing the initial arrangement of a first access well, a second access well, and a pyrolysis chamber extending between the first access well and the second access well;

[0031] FIG. 1 IB is an isometric diagram corresponding to the example UCG system and arrangement of FIG. 11 A, illustrating the pyrolysis chamber at the beginning of heating the carbonaceous material with laser head; and

[0032] FIG. 11C is an isometric diagram corresponding to the example UCG system and arrangement of FIGS. 11 A and 1 IB, illustrating the injection of an oxidant flow and the pyrolysis chamber after pyrolysis has continued for a period of time. DETAILED DESCRIPTION [0033] INTRODUCTION

[0034] In some aspects, the present disclosure is directed to methods of producing a product gas from one or more carbonaceous materials, including, but not limited to, any of a variety of ranks of coals and any of a variety of oil shales, among other, by heating the carbonaceous material using laser energy in a controlled manner so as to produce the product gas in a desired composition. In some embodiments, the laser-based heating is accompanied by heating via an additional heat source, such as one or more heated gases, such as steam.

[0035] As will become apparent from reading and understanding this entire disclosure, a feature of this disclosure is the use of laser energy to heat the carbonaceous material in a highly controlled manner so as to control the state of pyrolysis in order to produce a product gas having a desired composition. Methodologies disclosed herein leverages the property of laser heating that heating occurs only when the target material, here, carbonaceous material, is being irradiated with laser energy. Generally, solid carbonaceous materials, such as coal and oil shale, have relatively low thermal conductivities that result in heating be contained to or within each laser spot on the carbonaceous material being irradiated. Consequently, when the target material is not being irradiated, heating does not occur. This binary and instantaneous application of heat or no heat allows for relatively precise control of the heating of the target material and, consequently, relatively precise control of the product gas. As described below in detail, this unique way of controllably heating carbonaceous material can be enhanced by implementing a feedback mechanism that constantly or continually monitors the heating and/or other condition(s) of the state of pyrolysis so as to provide even more accuracy and precision to the heating / pyrolysis.

[0036] As those skilled in the art will readily appreciate, a product gas produced by pyrolyzing a carbonaceous material contains one or more calorific gases, such as methane and hydrogen, and one or more other gases, such as carbon monoxide and carbon dioxide, among others. The composition of product gas in terms of its constituent gas species varies as a function of, for example, the temperature and other conditions (e.g., presence of an oxidant, presence of contaminants, etc.) at which the carbonaceous material is devolatilized. To produce a product gas of a desired composition, the conditions of devolatilization need to be controlled to the conditions required for the desired composition. As discussed below in detail, laser-based gasification methods of the present disclosure provide the necessary level of control. [0037] Typically, the carbonaceous material will be present in a mass of material, such as in a natural underground deposit, either undisturbed or disturbed by prior extraction operations. However, in some cases, the carbonaceous material may be present in another form, such as in a surface mass, such as a pile, formed from already extracted carbonaceous material. Fundamentally, there is no limitation on the form of the mass of the carbonaceous material, although underground deposits are particularly suited to many of the methodologies disclosed herein.

[0038] In embodiments involving natural underground deposits, gasification methods of the present disclosure can be more cost efficient, more environmentally sound, and more effective at producing high-quality product gas than conventional gasification methods. Other aspects of the present disclosure are directed to laser-based pyrolysis systems for enabling gasification of carbonaceous materials to produce product gas of a desired composition. In some embodiments, a laser-based heating system of the present disclosure is particularly configured for gasifying portions of natural underground deposits of carbonaceous materials using one or more pyrolysis bores within the carbonaceous materials.

[0039] In further aspects, the present disclosure is directed to laser-based gasification systems for performing any one or more of the laser-based gasification methods disclosed herein, or portion(s) thereof. In additional aspects, the present disclosure is directed to laser heads specially configured to effect gasification methodologies of the present disclosure in pyrolysis chambers within a carbonaceous material, such as may be formed or otherwise present in natural underground deposits of the carbonaceous materials. In yet further aspects, the present disclosure is directed to product gas compositions that can result from the proper tuning of a laser-based gasification process of the present disclosure. These and other aspects are described in detail below. However, prior to describing the various aspects in detail, general information that may assist the reader in understanding and appreciating some example applications of the inventions disclosed herein is presented first.

[0040] It is noted that throughout the present disclosure and the appended claims, the term “about” when used with a corresponding numeric value refers to ±20% of the numeric value, typically ±10% of the numeric value, often ±5% of the numeric value, and most often ±2% of the numeric value. In some embodiments, the term “about” can mean the numeric value itself. [0041] GENERAL

[0042] The economics of adding new coal power capacity in the United States using existing technologies and mining practices has become increasingly difficult to justify, given rising prices, greater scrutiny of the health, climate, and other environmental hazards associated with coal power and the emergence of a collection of alternatives, mainly wind, solar, with the baseload provision being provided by newly available natural gas and nuclear power plants. Direct replacement of old, dirty coal plants with cleaner, cheaper, less risky alternatives would be a far better solution. Clean coal could indeed be part of the energy mix and could offer this potential.

[0043] Underground Coal Gasification

[0044] Underground coal gasification (UCG) is a technique for realizing benefits of cleaner and environmentally friendlier energy production. UCG is a technique for acquiring the energy from unworked coal, i.e., coal still in the ground, by converting it into a calorific gas that can be used, for example, for industrial heating, power generation, and manufacturing hydrogen, synthetic natural gas, or diesel fuel. UCG technology allows countries that are endowed with coal to fully utilize their resource from otherwise unrecoverable coal deposits in an economically viable and environmentally safe way. In UCG, the gasification reactor is a cavity within the coal deposit itself so that the gasification takes place underground instead of at the surface.

[0045] FIG. 1 illustrates a basic UCG process 100 that involves drilling three wells into a coal seam 104, a first well 108(1) for injection of a feed gas (oxidants) flow 104 (water/air or water/oxygen mixtures), a second well 108(2) some distance away to bring the product gas 116 to the surface 120, and a third well 108(3) at an end of the coal seam that acts as an ignition well, through which an ignition source 124 is provided. The coal at the base of the first well 108(1) is then heated to temperatures that would normally cause the coal to burn. However, through careful regulation of the flow of the oxidants 112, the coal does not burn but rather separates into a product gas 116.

[0046] Various chemical reactions, temperatures, pressures, and gas compositions exist at different locations within a UCG gasifier 128 that is forced to form within the seam 112 under proper conditions. The gasification channel within a UCG gasifier, such as UCG gasifier 128 of FIG. 1, is normally divided into three zones: an oxidization zone, a reduction zone, and a dry distillation and pyrolysis zone. In the oxidization zone, multiphase chemical reactions occur involving the oxygen in the gasification agents and the carbon in the coal. The highest temperatures in the gasifier occur in the oxidation zone due to the large release of energy during the initial reactions. The following reactions occur in the oxidation zone:

[0047]

393 .8 Kj

[0048]

231 .4 kJ

[0049] 2CO + 0₂ - 2C0₂ + 571 .2 kj

[0050] In the reduction zone, the main reactions involve the reduction of H₂0(g) and C0₂ into H₂ and CO at high temperatures within the oxidation zone. The following endothermic reactions occur in the reduction zone:

[0051] C + C0₂ -> 2CO - 162.4 kj

[0052] C + H₂0(g) - CO+H_{2 —} 131.5 kJ

[0053] Under the catalytic action of coal ash and metallic oxides, the following methanation reaction occurs:

[0054] C + 2H₂ -> CH₄ +74.9 kj

[0055] Following ignition and the delivery of the feed gas (air or oxygen) and steam via the feed gas flow 112 injected into the first well 108(1), product gas 116 is then drawn out of the second well 108(2).

[0056] In one method of UCG, vertical wells are combined with methods for opening a pathway between the wells. In another method of UCG, inseam boreholes use technology adapted from oil and product gas that can move the injection point during the process. Generally, the main criteria used for identifying the resource areas with potential for UCG can be summarized as seams of 5m thickness or greater, seams at depths between 200m and 600m from the surface, greater than 100m vertical separation from major aquifers, greater than 100m vertical separation from major overlying unconformities, and less than 60% ash content. Other factors that generally need to be considered include impermeable layers of strata surrounding the target coal seam, absence of any major faults in the area, low values for sulfur content and ash content, environmental and hydro geological conditions, and license conditions that might be imposed by regulatory and planning authorities.

[0057] For example, another UCG process 200 performed within a coal seam 204 is depicted in FIG. 2. In this example, an injection well 208(1) provides a feed gas flow 212, and a combustion front 216 within the coal seam 204 is initially ignited at the root 208(1)A of the injection well. Combustion then occurs along the coal seam 204 until it reaches one or more production wells 208(2), thereby forming a cavity 220. The rate of propagation of the combustion front 216 is determined by many factors, such as gas flow kinetics, and variations in temperature, spoliation levels, etc. The cavity 220 formed during gasification is generally tear-drop shaped, and the passage(s) 224 to the production well(s) 208(2) is/are narrowed and can be obstructed, thereby yielding low combustion levels and restricted outflow and yield of combustible products 228, for example, calorific gas such as syngas.

[0058] There are a number of risks associated with UCG practices, including, but not limited to: heavy faulting; overburden composition; potential leakage of produced gases/byproducts into aquifers; maintenance of the ignition reaction (e.g., ground water or flow instabilities quenching the reaction); subsidence due to cavity collapse; seam thickness variability; coal conditions inductive to lateral combustion and uncontrolled growth; emissions or migration of potentially harmful combustion products; and potential for contamination.

[0059] Coal Pyrolysis and Devolatilization

[0060] Coal pyrolysis and gasification are complex processes that involve many interactions of chemical and physical phenomena. In coal conversion processes, such as combustion or high temperature gasification, the extent of pyrolysis is an important parameter. Increasing amounts of coal converted directly to gaseous species would reduce the remaining material, i.e., char, that can be converted by relatively slow char-gas reactions. Coal pyrolysis and devolatilization is always the first step and plays a fundamental role. Coal rank and properties significantly influence heat and mass transfer, as do reaction rates. Therefore, conversion times, yields, and gaseous emissions depend on the original source material. However, there are general findings that can be considered. A key to understanding the phenomena occurring thus lies first in the characterization of the initial coal and then in describing the primacy devolatilization phase and the released products. Thermochemical conversion of coal in practical systems results from a strong interaction between chemical and physical processes at the micro level and also at the reactor level, i.e., the level of the surrounding environment, such as within an in-situ natural carbonaceous material deposit.

[0061] It is well known that coal devolatilization is a process in which coal is transformed at elevated temperatures to produce gases, tar, and char. Functional groups of the original coal are mainly released as gases and can be reasonably predicted by first-order reaction models. Tar, defined as condensable species formed during coal devolatilization, is a major volatile product, composing up to 50% of coal weight for bituminous coals. [0062] At low temperatures (or low heating rates), coals initially form char and volatile species (tar and gas) that are still in the condensed phase. The tar in the condensed phase can be released with a proper kinetic rate and can interact with char in cross-linking reactions to increase the residual char and produce further gas. At high temperatures (or high heating rates), coals directly decompose to gas and tar and form more aromatic char structures. Lignitic coals first move through an activated state in the condensed phase and then undergo a real decomposition reaction. The transition temperature, where gradually high temperature decomposition prevails, is between 800K for 1200K depending on the aromatic structure of the coal.

[0063] For ease of describing main characteristics, the description of gas species is simplified herein. However, those skilled in the art will readily understand the additional complexities in real- world applications and instantiations. Light gases typically produced are ¾, C¾, and a mixture of C2-C5 hydrocarbons. The main oxygenated products are typically CO, CO2, and H2O. Other oxygenated species are typically present at lower concentrations. As an example, formaldehyde, methanol, ketene, and acetic acid can form from primary pyrolysis.

[0064] Upon heating, bituminous coals undergo molting and pyrolytic decomposition, with a significant part forming an unstable liquid that can escape from the coal by evaporation. The transient liquid within the pyrolyzing coal causes softening or plastic behavior that can influence the chemistry and physics of the process. The extent of pyrolysis is known to be influenced, directly or indirectly, by temperature, heating rate, and exposure time. In standard methods, the amount of coal converted to volatile matter is determined at low temperatures, slow heating rates, and long exposure times. As a result, relatively low volatile yields are obtained, and also the resulting char is much less reactive. These effects have been recognized, and some studies have been reported on this aspect. The extent of pyrolysis increases significantly with temperature, with an apparent plateau or a peak in the weight loss curve at 900°C - 1100°C. Effective pyrolysis therefore occurs in the region of 500°C - 800°C, with greater yield at higher temperatures.

[0065] EXAMPLE EMBODIMENTS

[0066] Before presenting example embodiments, it is noted that the example embodiments are primarily directed to UCG. However, UCG is not the only application of the disclosed technology. Consequently, the term “carbonaceous material” as used herein and in the appended claims, refers to any solid, liquid, or gaseous carbon-containing material suitable for use as a fuel, i.e., a material that can be consumed to produce energy. Included within the scope of this term are fossil fuels, including coal, oil, natural gas, and oil shale, biomass (e.g., plant materials and animal wastes used as fuel), coke, char, tars, wood waste, methanol, ethanol, propanol, propane, butane, ethane, etc. Those skilled in the art will readily understand how to adapt the overall methodologies of the present disclosure to the carbonaceous material at issue.

[0067] As noted above, aspects of the present disclosure utilize laser energy to heat a carbonaceous material in a controlled manner, sometimes in the presence of a non-laser heat source, so as to produce a product gas of a desired composition. Such laser energy may be generated by any suitable laser and does not necessarily require any particular wavelength or spectral band to be effective. Therefore, the term “laser” as used herein has a broad meaning and refers generally to a category of optical devices that emit a spatially and temporally coherent beam of light otherwise known as a “laser beam”. In some embodiments, the term “laser” refers to “conventional” lasers (such as CO2 lasers, YAG lasers, and fiber lasers, among others), as well as solid-state lasers (such as double heterostructure laser diodes, quantum well laser diodes, quantum cascade laser diodes, etc.). Fundamentally, there is no limitation on the type(s) of laser(s) that can be used in a method, system, or apparatus of the present disclosure as long as it can effect the desired heating.

[0068] Example Laser-Based Gasification Method

[0069] Referring to FIG. 3, an embodiment of the present disclosure is directed to a method 300 of producing a product gas from a mass of carbonaceous material having a pyrolysis chamber defined by surrounding portions of the carbonaceous material. While the carbonaceous material and the mass of such material may be any that are suitable for producing a product gas, a common example combination is coal as the carbonaceous material and a natural underground coal deposit, or coal seam, as the corresponding mass of the carbonaceous material. The pyrolysis chamber may be any suitable passageway within the mass of carbonaceous material that is sized and shaped to allow product gas production according to the method 300. In some instantiations, the pyrolysis chamber may be formed using a boring process, such as a lateral boring process. In some instantiations, the pyrolysis chamber may be formed for the specific purpose of performing the method 300, while in some instantiations the pyrolysis chamber may be an artifact of prior boring for another purpose, such as during past extraction operations for extracting one or more portions of the mass of carbonaceous material or exploration, among others. In some instantiations, the pyrolysis chamber may be a fissure or other natural void within the mass, among others. Fundamentally, there is no limitation on the nature of the pyrolysis chamber as long as it can be used to perform the method 300. It is also noted that while the method 300 is described relative to a single pyrolysis chamber, it may involve two or more pyrolysis chambers, each of which may be utilized according to the method. Further, and as noted above, the mass of the carbonaceous material is not constrained to an underground deposit. Rather, the mass can be located aboveground, such as in a freestanding pile or other form of previously extracted carbonaceous material.

[0070] In some embodiments, the pyrolysis chamber may be connected to a surface above and/or adjacent to the mass of carbonaceous material, depending on the location of the mass, via a first access well. The first access well may be a preexisting well, for example, from a prior extraction process, or a new access well specifically sunk for performing gasification to produce a desired product gas according to the method 300. In either case, if the pyrolysis chamber is not already present, the first access well may be used in forming the pyrolysis chamber, for example, using lateral boring techniques, such as known lateral boring techniques. In some embodiments, the first access well itself may be used as the pyrolysis chamber.

[0071] In some embodiments, the first access well may function as an injection well for providing a heating flow (e.g., of steam) to the pyrolysis chamber to assist laser-based heating, for providing an oxidant flow to the pyrolysis chamber for participating in pyrolysis, and/or for providing an extraction flow for causing any produced product gas to flow out of the pyrolysis chamber, for example, to a product-gas-collection system. In some embodiments, the first access well may also or alternatively provide a pathway for inserting a laser head into the pyrolysis chamber (see, e.g., block 305, described below). In some embodiments, the first access well may provide production functionality, in addition to heating flow, oxidant flow, extraction flow, and/or laser-head insertion functionality, to carry the product gas produced by the method 300 to the surface. To provide multiple functionalities, the first access well may include two or more separate passageways for providing the differing functions. Such passageways may or may not be concentrically located relative to one another and/or may have differing lengths depending on the functions involved and the configuration of the pyrolysis chamber. Alternatively, such passageways may be containing in a tether that connects to a laser head (see, e.g., FIGS. 10A and 10B).

[0072] In some embodiments, a second access well may optionally be used to connect the pyrolysis chamber to equipment, such as a product-gas collection system, located on the surface. As with the first access well, the second access well may be a preexisting well or a new well sunk to perform the method 300. The second access well, when provided, will typically be spaced, for example, horizontally, from the first access well. In some embodiments, the first and second access wells may be spaced from one another on opposite ends of the pyrolysis chamber. In some embodiments wherein a second access well is present, the second access well may function as a production well for removing the product gas produced by the method 300 and/or may function to provide a passageway for engaging the laser head with the pyrolysis chamber, among others. Additional access wells beyond the first and second access wells can be provided as needed to suit any particular need for a desired application.

[0073] At block 305, a laser head is inserted into the pyrolysis chamber in any suitable manner, such as via either the first or second access well, if present, as mentioned above. The laser head may have any suitable structure and configuration for effecting the heating of a target portion of carbonaceous material surrounding the pyrolysis chamber so as to perform the method and commensurate with the type(s) of laser(s) used to effect the heating. In some embodiments, one or more lasers may be integrated into the laser head, with the laser head further including a lens system for appropriately configuring and directing, for example, by scanning, one or more laser beams generated by the integrated laser(s). Each integrated laser may be of any suitable type, such as a solid-state type or a non-solid-state type. In some embodiments, laser energy may be provided to the laser head from one or more lasers located remotely from the laser head, such as on the surface of a geological formation in an underground gasification embodiment. In such embodiments, the laser energy may be provided to the laser head via one or more fiber optic cables, such as may be provided in a tether that tethers the laser head to a surface-based laser system.

[0074] The laser head may be tethered, wirelessly and/or wiredly, to one or more systems that may be present on the surface. Examples of systems to which the laser head can be tethered include, but are not limited to, a laser system, a laser-head movement system, a laser-beam control system, a pyrolysis-state-detection system, and a product-gas collection system, among others. In some embodiments, when any of these systems is present, each may be under the control of a human operator and/or a master controller. The master controller, if present, may be operated under human and/or automated control. A detailed example of a laser-based gasification system 400 having at least one laser head and various types of systems for operating each laser head and the gasification system generally is described below in connection with FIG. 4.

[0075] As alluded to above, in some embodiments it is important to precisely control the extent of pyrolysis that the laser energy causes to occur in the adjacent carbonaceous material so as to produce a product gas having a desired composition. In such embodiments, it can be desirable to control the extent of pyrolysis by controlling the amount of heating that the laser energy causes at multiple irradiated regions of the carbonaceous material exposed within the pyrolysis chamber. In some examples, the laser beams that the laser head outputs are scanned over these irradiated regions in a highly controlled manner, such as by controlling one or more of the irradiation residency time that each laser beam remains at any given irradiation site with each irradiated region, the frequency that each irradiation site is irradiated, the power density of each laser beam, and the duty cycle of each laser beam, or any combination thereof. In some examples, the irradiated regions are configured to be as continuous with one another as possible and/or to minimize gaps and/or overlaps between the irradiated regions. Some example configurations of irradiated regions are presented in FIGS. 5A to 5C and discussed below.

[0076] Referring to FIG. 5A, this figure illustrates an example heating pattern 500 for heating the carbonaceous material with a plurality of laser-beams (not shown) emanating from a laser head (not shown) made in accordance with the present disclosure. In some embodiments, laser beams can be scanned to create the pattern 500. In some embodiments, the pattern 500 can be created using fixed outputs, such as by using beam expanders and/or other optics known in the art. In this example there are 20 irradiated regions 504(1) to 504(20) that are each irradiated by one or more laser beams. It is noted that FIG. 5A illustrates a flattened view of the illustrated region of a cylindrical-bore-type pyrolysis chamber having a curved irradiated wall 508, which has been flattened for illustrative purposes. As seen in FIG. 5A, the 20 irradiated regions 504(1) to 504(20) are generally rectangular regions that abut one another so as to completely cover the entirety of the illustrated portion of the irradiated wall 508. When the irradiation is performed uniformly across all of the irradiated regions 504(1) to 504(20), the induced pyrolysis will likewise be uniform, assuming uniformity of the carbonaceous material forming the irradiated wall 508.

[0077] FIG. 5B illustrates another example heating pattern 520, showing 10 irradiated regions 524(1) to 524(10) that may be similar to the irradiation regions 504(1) to 504(20) shown in FIG. 5A. As seen in FIG. 5B, however, each irradiation region 524(1) to 524(10) is oval in shape and overlaps with other ones of the irradiated regions. In this case, the overlap regions may experience higher temperature increases than non-overlap regions when the scanning is uniform. However, if the sizes of the overlap regions are minimized, then the impact on the heating and resulting product gas will be negligible. [0078] It is noted that while FIG. 5A illustrates abutting irradiated regions 504(1) to 504(20) and FIG. 5B illustrates overlapping irradiated regions 524(1) to 524(10), in other embodiments the irradiation regions may be spaced from one another such that gaps are present between adjacent ones of the irradiated regions. For example, the carbonaceous material being heated by the irradiation is thermally conductive to one extent or another, such that the portions of the carbonaceous material in the gaps will be heated by conduction from the irradiated regions, and this conductive heating may be sufficient to achieve the desired pyrolysis.

[0079] FIG. 5C illustrates an example heating pattern 540 that may be suited for embodiments in which heating is accomplished while moving the corresponding laser head (not shown, but see FIG. 9 and its accompanying description below). In this example, there are 15 irradiated regions 544(1) to 544(15) arranged into three groups 548(1) to 548(3), each having a corresponding width Wl, W2, W3, with adjacent ones of the groups spaced apart at corresponding spacings SI and S2 that define corresponding non-irradiated regions 552(1) and 552(2). As with the irradiation regions 504(1) to 504(20) of FIG. 5A and the irradiation regions 524(1) to 524(10) of FIG. 5B, each of the irradiation regions 544(1) to 544(15) of FIG. 5C may be irradiated by one or more laser beams (not shown), such as by scanning or fixed output as mentioned above. When the laser head (not shown) is moved along the pyrolysis chamber, the grouped irradiation regions 544(1) to 544(15) will typically move in unison with the laser head. Thus, FIG. 5C may be considered to illustrate a snapshot in time. Consequently and assuming the movement of the laser head and grouped irradiated regions 544(1) to 544(15) is toward the left relative to FIG. 5C, at a later instant in time, all or a portion of non-irradiated region 552(1) will be irradiated by the group 548(2) and all or a portion of the non-irradiated region 552(2) will be irradiated by the group 548(3). Those skilled in the art will readily appreciated that the size of each width Wl through W3 and the size of each spacing SI and S2 can be determined as a function of variables, such as the speed at which the laser head is moved, the residence time for the laser beams utilized, and the progress of the pyrolysis induced by the heating, among others. Those skilled in the art will readily appreciate that only three groups 548(1) to 548(3) are shown for convenience and that more or fewer groups can be used.

Also, as with other examples, the number and shape(s) of the irradiated regions 544(1) to 544(15) can be any suitable number and shape(s) desired to suit a particular application. In addition, the areas of the irradiated regions can vary depending on variables such as laser power, number of laser outputs, the type of the carbonaceous material, etc. Fundamentally and generally, the only limits on the areas of the irradiated regions are imposed by physical limitations of the components of the laser system.

[0080] To effect irradiation and heating of the irradiated regions of the surrounding carbonaceous material, the laser head may include a beam-scanning system that scans the laser beams in a suitable manner for ensuring coverage of the corresponding one(s) of the irradiated regions. In some embodiments, the beam-scanning system may include any sort of scanning mechanism for each laser beam or group of laser beams, as a particular design warrants. Examples of scanning mechanisms or components thereof include, but are not limited to, moveable reflective and/or refractive elements (similar to, e.g., a digital light processor (DLP)), controllably moveable gimballed lensing system, controllably moveable gimballed laser-diode support, and/or a rotatable lensing system that rotates around a longitudinal central axis of the laser head, among others, or any combination thereof. In addition, differing laser beams can be directed with differing angular coverages, for example, as measured relative to a longitudinal central axis of the laser head. Fundamentally, there is no limitation on the beam-scanning system and arrangement of laser-beam outputs that can be provided to a laser head of the present disclosure. It is noted that in other embodiments the laser outputs may be fixed. The laser power provided for irradiation may be continuous or intermittent as needed to suit the particular application at issue.

[0081] In some embodiments, the laser-beam outputs may be partitioned into sets so that differing sets emit their laser beams at differing times, such as in a predetermined sequence. The partitions may be made longitudinally along the length of the laser head and/or circumferentially around the circumference, or portion thereof, of the laser head. Such partitioning may be particularly useful when available laser energy is limited and it is desired to gasify the longest length of a pyrolysis chamber as possible while the laser head remains stationary. As a simple example, say that the laser head includes 30 sets of laser-beam outputs spaced from one another along the length of the laser head, with each set including 8 laser-beam outputs distributed 360° around the laser-head’s circumference and with a single laser providing the laser energy for the entire heating process. The eight laser-beam outputs in each set are scanning-type outputs that provide full 360° heating coverage, and the laser-beam outputs in adjacent ones of the sets provide contiguous heating regions. Assuming that heating parameters allow for both scan-style heating in combination with a duty cycle that allows the laser energy from the single laser to be continually sequenced among the 30 sets, the full laser power from the single laser can be provided to each of the 30 sets to effect heating. Such sequencing can be effected in any suitable manner, such as providing a rotating optic (lens(es) and/or mirror(s)), DLP (or the like), or other optical switch. The sequencing can be any suitable sequencing among the sets. As noted above, the partitioning of the laser-beam outputs may additionally or alternatively be in the circumferential direction of the laser head. It is noted that the example with 30 sets is merely exemplary and that more or fewer sets may be used. In addition, more than one laser can be provided. Those skilled in the art will readily understand how to devise and implement a laser-energy-sequenced configuration by working out a suitable irradiation plan using this disclosure as an enabling guide and knowledge in the art.

[0082] In some embodiments, the laser head may be configured to direct laser energy 360° radially about the longitudinal axis of the pyrolysis chamber, either continuously or intermittently. This may be accomplished in any one or more of a variety of ways, including having multiple fixed or rotating (e.g., about a longitudinal central axis of the laser head) laser-beam outputs distributed circumferentially around an exterior of the laser head or one or more movable laser beam outputs that rotate about the longitudinal axis of the pyrolysis chamber, and any combination thereof. In some embodiments, the laser head may be configured to direct one or more laser beam at an angle less than 360° radially about the longitudinal axis of the pyrolysis chamber, such as 270° 180°, 120°, 90°, among others, either continuously or intermittently, and in any one or more directions, such as upward, downward, laterally, etc. Fundamentally, the laser head can be configured relative to the manner in which the laser beam(s) is/are emitted in any way suitable for the application at issue.

[0083] Due to the use of laser energy for causing and driving the pyrolysis, either alone or in combination with a non-laser heat source, the shape of the pyrolysis chamber can be highly controlled by suitably controlling heating parameters, such as beam power density, beam residence time, beam cycle duty, and scanning pattern, among others. FIGS. 6A through 6D illustrate some example pyrolysis chamber transverse cross-sectional shapes that are possible using suitably controlled heating and pyrolysis. FIG. 6A illustrates a generally circular pyrolysis chamber 600 that is formed after some amount of pyrolysis has been achieved in a carbonaceous material 604 using a laser head 608. In this example, the original pyrolysis chamber is a cylindrical-bore-type pyrolysis chamber 600', with the laser head 608 being located at the bottom (relative to FIG. 6 A) of both the original pyrolysis chamber 600' and the larger pyrolysis chamber 600 formed after pyrolysis of the carbonaceous material 604. In this example, the heating and pyrolysis is performed via five scanning zones 612(1) to 612(5) scanned by one or more laser beams (not shown) emanating from the laser head 608. In this connection, it is noted that the number of laser heads used to scan each scanning zone 612(1) to 612(5) may increase as the pyrolysis chamber 600', 600 becomes larger and larger as pyrolysis progresses. For example, the area that each laser-beam can scan may be a fixed size such that, as the pyrolysis chamber 600', 600 gets larger and the area of the carbonaceous material that must be scanned in each scanning zone 612(1) to 612(5) increases, that area becomes larger than an individual laser beam can scan such that another laser beam needs to be activated to cover the larger area.

[0084] FIG. 6B illustrates a generally rectangular pyrolysis chamber 620 formed in a carbonaceous material 624 using six scanning zones 628(1) to 628(6), with a laser head 632 present in the original cylindrical -bore-type pyrolysis chamber 620' and still present at the bottom (relative to FIG. 6B) of the pyrolysis chamber 620. As noted above, the rectangular shape can be easily formed by suitably controlling the heating and corresponding pyrolysis precisely with the corresponding laser beams (not shown) in scanning zones 628(1) to 628(6). Aspects of the scanning zones 628(1) to 628(6) not specifically described can be the same as or similar to the scanning zones 612(1) to 612(5) described above relative to FIG. 6A. An advantage of a rectangular or other shape (e.g., polygonal) is that it is more efficient in the usage of as much of the carbonaceous material as possible for gasification.

[0085] Each of FIGS. 6C and 6D illustrate, respectively, a circular pyrolysis cavity 640 and a rectangular pyrolysis cavity 660 similar, respectively, to pyrolysis chambers 600 and 620 of FIGS. 6A and 6B. However, in the examples of FIGS. 6C and 6D, the corresponding laser heads 644 and 664 are located at the geometric center 640A, 660A of the respective pyrolysis chamber 640 and 660, with each of the laser head being initially located within a corresponding original cylindrical -bore-type pyrolysis chamber 640', 660'. FIGS. 7 A to 7C illustrate a laser-head assembly 700 that could be used to create each of the pyrolysis cavities 640 and 660 of FIGS. 6C and 6D.

[0086] In FIG. 6C, the circular shape of the pyrolysis chamber 640 is formed using 8 scanning zones 648(1) to 648(8) that each scan a 45° arc so as to provide 360° continuous circumferential coverage of the entire wall 652A of the carbonaceous material 652. In FIG. 6D, the circular shape of the pyrolysis chamber is formed using 8 scanning zones 668(1) to 668(8) that each scan a 45° arc so as to provide 360° continuous circumferential coverage of the entire wall 672 A of the carbonaceous material 672. Those skilled in the art will readily understand that the number of scanning zones, the configurations of the scanning zone, and the shape of the pyrolysis chambers of the examples in FIGS. 6 A to 6D are merely examples and that each may be different as needed to suit a particular design and application. Those skilled in the art will also readily understand that the scanning zones in FIGS. 6 A to 6D are illustrated in two dimensions and that the actual scanning zones will typically be three-dimensional, extending into and/or out of the plane of the page containing each of FIGS. 6A to 6D.

[0087] Because the laser energy from the laser head can be precisely controlled in a heating - no heating binary manner at any location within the pyrolysis chamber, the gasification system can be designed to detect non-carbonaceous material, such as bedrock, that abuts or is present in an underground deposit of the carbonaceous material, and, upon detection, stop irradiating. In this manner, laser energy is not wasted and any negative consequences of heating non-carbonaceous material, such as inducing cracking within a barrier layer abutting a natural deposit of the carbonaceous material, can be avoided. In addition, gasification of as much of the carbonaceous material as possible can be performed without being concerned with encountering non-carbonaceous material. Detection of non-carbonaceous material can be performed by measuring one or more conditions of the pyrolysis (see block 315 of FIG. 3 and corresponding description below) and determining whether or not the measured condition(s) is/are anomalous and/or meet one or more conditions expected of another material, among other determinations that can be made to detect the encountering of a non-carbonaceous material.

[0088] In some embodiments, the laser head may include a positioning structure for properly positioning the laser head within the transverse cross-sectional shape of the pyrolysis chamber. For example, the pyrolysis chamber may have a circular transverse cross-sectional shape and the laser head may be designed to be centered within the circular transverse cross-sectional shape. In this example, the positioning structure may include one or more sets of arms (e.g., three or more arms per set) that engage the walls of the pyrolysis chamber and maintain the laser head centrally within the transverse cross-sectional shape of the pyrolysis chamber. Such arms may be spring-loaded and/or controlled using one or more actuators, among other things.

[0089] In some embodiments, the laser head may be rigid in a direction along its length so as to be supported in a cantilevered manner from a laser-head support that holds the rigid laser head in a desired position within the pyrolysis chamber. When the pyrolysis chamber is of the linear-bore type that extends to a surface of a geological formation containing the carbonaceous material, the laser head can be rigid even when present on the surface (i.e., be permanently rigid), since a laser head need only be inserted into a linear bore that opens to the surface. However, when the pyrolysis chamber is not immediately accessed from the surface, such as in a lateral-bore-type pyrolysis chamber formed down an access well, an entire long laser head cannot be permanently rigid, as it would not be possible to insert it into the lateral-bore-type pyrolysis chamber. To accommodate such a situation, the laser head may be provided, for example, with pivoting joints that can pivot about one or more axes to allow the laser head to snake through non-linear passageways and/or non linear transitions between passageways. The pivoting joints may be located between rigid links that each contain one or more laser outputs. The laser head would include one or more locking mechanisms that releasably lock the pivoting joint to make the entire laser head rigid. The locking mechanism(s) can be any suitable mechanism(s) that provide the locking feature. For example, adjacent links may become electromagnetically attracted to one another via electromagnetic mechanisms or one or more tensioning cables can be used to firmly draw the rigid links into locking engagement with one another, among many other locking mechanisms.

[0090] The laser-head support may be suitably sized to substantially fill the transverse cross- sectional area of the pyrolysis chamber and provide adequate support for the cantilevered rigid laser head. If needed, the laser-head support may be similarly segmented with pivotable joints and include one or more locking mechanisms for locking the segments together once the laser-head support is in the pyrolysis chamber. The laser-head support may further include stabilizing features for fixedly stabilizing the laser-head support and corresponding cantilevered laser head within the pyrolysis chamber. The laser-support head may further include a traction system for moving the laser-head support and laser head along the pyrolysis chamber, and the stabilizing features can be integrated with the traction system, as needed. FIGS. 7A to 7C illustrate an example laser-head assembly 700 comprising flexible-rigid laser head 700A and flexible-rigid laser-head support 700B.

[0091] FIG. 7A illustrates the laser-head assembly 700 partially inserted into a lateral-bore-type pyrolysis chamber 704 from an access well 708. The pyrolysis chamber 704 is where the laser head 700A will be deployed for use to create a product gas 712 (FIG. 7C). As can be seen in FIG. 7A, the flexible laser head 700A is shown snaking around the transition from the access well 708 into the pyrolysis chamber 704. Once the laser-head assembly 700 is in proper position, the locking mechanisms of each of the laser head 700A and the laser-head support 700B are activated so as to make both of these components rigid. The result of making the laser head 700A and the laser-head support 700B rigid is shown in FIG. 7B. As also seen in FIG. 7B, this embodiment of the laser-head support 700B also includes a traction system 712 that both effects movement of the laser-head assembly 700 along the pyrolysis chamber 704 and centers the laser- head assembly within the transverse cross-section of the pyrolysis chamber. Further, FIG. 7B shows the state of the pyrolysis chamber 704 after the laser head 700A has fully pyrolyzed the carbonaceous material 716 that was originally surrounding pyrolysis chamber 704 and just before the laser-head assembly 700 is advanced to its next location for a next round of pyrolysis as shown in FIG. 7C. As can be seen in FIG. 7B, the laser-head support 700B maintains the laser head 700A in a fixed position as heating and pyrolysis is performed 360° around the circumference of the laser head. FIG. 7C shows the laser-head assembly 700 after being moved from its initial position (FIG. 7B) and after the laser head 700A has been operated to pyrolyze a portion of the carbonaceous material 716 desired to by pyrolyzed at this new position. Not shown are the laser-beam outputs, sensing elements, and other features of a laser head as described above.

[0092] Referring again to FIG. 3, at block 310, when the laser head is engaged with the pyrolysis chamber, the target portion of the carbonaceous material defining the pyrolysis chamber is heated with energy from the laser head so as to sustain a desired pyrolysis state that produced the product gas from the carbonaceous material. Generally, the product gas is produced from pyrolysis and other thermally initiated reactions induced in the carbonaceous material by the heating that the laser head causes. In some embodiments, the surrounding portions of the carbonaceous materials are irradiated with one or more laser beams output by the laser head in a continuous or intermitted pattern to any desired extent circumstantially around a longitudinal axis of the pyrolysis chamber, such as 360°, 270°, 180°, 120°, 90°, among others, and in any desired direction(s), e.g., upward, downward, laterally, etc. The laser head may be controlled to heat the surrounding carbonaceous material defining the pyrolysis chamber while the laser head is moving, is stationary, or is intermittently moving and stationary, as desired for a particular application.

[0093] As discussed above, a benefit of heating the surrounding portions of the carbonaceous material using laser energy is that heating temperature(s), and therefore the state of pyrolysis, can be highly controlled by controlling one or more heating parameters, such as laser-beam power density, laser-beam duty cycle, and irradiation residency time, and irradiation site frequency, among others. Providing such high levels of control allows the gasification reactions to proceed in highly predictable manners such that the composition of the generated product gas can be tuned to a desired compositional makeup of differing gases in desired mole ratios.

[0094] For example, laser-based gasification and pyrolysis described herein may produce variable heating rates, e.g., from 25°C/s (slow pyrolysis) to 10,000°C/s (flash pyrolysis) simply by adjusting the relevant heating parameter(s). In contrast with conventional heating mechanisms and without limiting to any one particular theory, advantages achieved by laser-based pyrolysis of the present disclosure, such as the product gas production method 300 of FIG. 3, include, but are not limited to, greater levels of pyrolysis, greater control of pyrolysis, greater pyrolysis rates, higher efficiencies, tunability of the composition of the product gas, and less waste, among others.

[0095] In some embodiments, pyrolysis is aided by supplying one or more oxidants (e.g., air or oxygen) and/or non-laser-based heat (e.g., via a heating gas, such as steam) to the pyrolysis chamber. In some embodiments, the oxidant(s) and/or heating gas (or other heat source) may be provided via the first access well. The flow of the oxidant(s) can be carefully controlled as a function of the extent and advancement of the pyrolysis to keep the pyrolysis conditions (e.g., temperature and rate) within design parameters so as to control the advancement of the pyrolysis and resulting composition of the product gas that the pyrolysis produces.

[0096] The heating at block 310 is performed so as to sustain the desired pyrolysis state. However, those skilled in the art will readily understand that, in practice, this mean that the heating is performed to achieve as close to a desired pyrolysis state as practicable. This is so because skilled artisans will appreciate that the conditions of pyrolysis, especially in natural underground deposits, are subject to sometimes not insignificant variations caused by varying conditions that can occur. Such varying conditions can include, but are not limited to, variations in the composition of the carbonaceous material, variations in presence of voids, variations in moisture content, and variations in delivery of oxidant flow (e.g., due to encountering an unknown fissure), among others. Consequently, those skilled in the art will readily understand that in practice, it may be the case that the desired pyrolysis state is neither always precise from one location to another within the pyrolysis chamber nor is its maintenance always possible to maintain. Thus, those skilled in the art will understand that “to sustain the desired pyrolysis state” is to be understood to account for any unavoidable variabilities while at the same time requiring a sense of intent of the implementer of method 300 to control the heating in a manner that sustains, within limits of practicalities, the state of pyrolysis linked to a desired product gas composition.

[0097] In some embodiments, the heating of the target region of the carbonaceous material surrounding the laser head may be performed while the laser head is stationary within the pyrolysis chamber. For example, the laser head can continue to scan each laser beam with the same directionality so as to continually and incrementally cause the carbonaceous material at that location to continually pyrolyze and produce the desired product gas. An example time-sequenced view of one location within the carbonaceous material is shown in FIGS. 8A to 8C, which are in scale relative to one another, showing the progressive pyrolysis at three snapshots in time within a bore- type pyrolysis chamber 800. In this example, the laser head 804 remains stationary while a set of laser beams 808 (only some labeled for convenience) are scanned over the same target region 812A of the carbonaceous material 812 to cause pyrolysis to continue at increasing depths into the carbonaceous material. As time progresses from FIG. 8 A through to FIG. 8C, the effective diameter DE of the pyrolysis chamber 800 increases as pyrolysis continues.

[0098] In some embodiments, the heating of the target region of the carbonaceous material surrounding the laser head may be performed while the laser head is moved within the pyrolysis chamber. For example, the laser head may be provided with multiple laser-beam outputs along its length, with the leading (in the direction of laser head movement) laser beams from those laser-beam outputs causing the initial pyrolysis of the carbonaceous material, with one or more successive sets laser beams continuing pyrolysis at increasing depths into the carbonaceous material. In some embodiments, the laser head may be moved in a continuous manner or an intermittent manner, or a combination of the two. An example of pyrolysis created while a laser head 900 is being moved within a pyrolysis chamber 904 is illustrated in FIG. 9.

[0099] As seen in FIG. 9, the laser head 900, which provides four laser-beam-output zones 908(1) to 908(4) along its length, is moved from right to left (as indicated by arrow 912) during the pyrolysis of a moving target region 916A of a carbonaceous material 916 surrounding the pyrolysis chamber 904. In this example, for each of the laser-beam-output zones 908(1) to 908(4) the laser head 900 outputs a corresponding plurality of laser beams 900(1) to 900(4). The laser- beam-output zone 908(1) is the leading laser-beam output relative to the direction of movement 912 of the laser head 900, and the laser-beam-output zone 908(4) is the trailing output relative to the direction of movement of the laser head. At the instant in time shown in FIG. 9, the effects of the corresponding laser beams 900(1) to 900(4) output by the laser head 900 on the carbonaceous material 916 are shown at the four corresponding respective laser-beam-output zones 908(1) to 908(4). Here, the regions of the carbonaceous material 916 in the laser-beam-output zone 908(1) is being pyrolyzed by the laser beams 900(1), the regions of the carbonaceous material in laser-beam- output zone 908(2) is being pyrolyzed by the laser beams 900(2) and has been pyrolyzed by the laser beams 900(1), the regions of the carbonaceous material in the laser-beam-output zone 908(3) is being pyrolyzed by the laser beams 900(3) and has been pyrolyzed by the laser beams 900(1) and 900(2), and the regions of the carbonaceous material in the laser-beam-output zone 908(4) is being pyrolyzed by the laser beams 900(4) and has been pyrolyzed by the laser beams 900(1) to 900(3), with the effective diameter of the pyrolysis chamber 904 increasing as the laser head 900 is moved 912 and as additional ones of the laser beams heat and pyrolyze the regions. Those skilled in the art will readily appreciate that the four laser-beam-output zones 908(1) to 908(4) are used in the example for convenience and that the number of laser beams along length of the laser head 900 can range from two to tens or hundreds, among others.

[0100] Referring back to FIG. 3, at block 315 measurements of at least one condition of the target portion being heated that has a known correlation to the desired pyrolysis state are obtained. Generally, the measurements at block 315 are obtained concurrently with the heating of the target region. The measurements do not necessarily need to be obtained simultaneously with the heating, for example, if simultaneous heating would interfere with the accuracy of the measurements. Examples of conditions that may be suitably correlated to the state of pyrolysis include, but are not limited to temperature of the surface of the target portion of the carbonaceous material, the physical composition of the target portion, and the composition of one or more products of the target portion already pyrolyzed, such as the product gas, tar, char, etc., among others. In this connection, the laser head may be outfitted with one or more suitable sensing element types that participate in obtaining measurements. For example, for temperature measurements, the laser head may include sensing elements for infrared-based thermal sensing. As another example, for physical composition of the target portion, the laser head may include sensing elements based on laser technology, such as disclosed in U S. Patent No. 10,928,317, titled “FIBER-OPTIC BASED THERMAL REFLECTANCE MATERIAL PROPERTY MEASUREMENT SYSTEM AND RELATED METHODS”, and issued on February 23, 2021, to Foley et ak, which is incorporated herein by reference for its teachings on relevant techniques.

[0101] As a further example, for pyrolysis product detection, the laser head may include “electronic nose” sensing elements for sensing presence and/or relevant amounts of individual components of the product gas. These are simply a few examples of sensing elements, and those skilled in the art will readily appreciate that other sensing elements can be used depending on the condition(s) being measured. It is noted that in some cases, a single sensing element may be used for the target region, while in some cases multiple sensing elements may be used for differing regions with the target region. It is further noted that some types of sensing elements, such as infrared and laser-based sensing elements can be moveable, for example scannable to take measurements at differing locations. Each type of sensing element may be part of an overall pyrolysis monitoring system that can be continuously or continually used to determine the state of pyrolysis for comparing to the desired pyrolysis state to effect heating control.

[0102] At block 320, the heating of the target portion of the carbonaceous material is controlled as a function of the measurements of the at least one condition of target portion at block 315. For example, the pyrolysis monitoring system, and/or other part(s) of an overall laser-based gasification system, may use suitable algorithms for comparing condition measurements to corresponding parameters of the desired pyrolysis state and, based on the comparisons, for determining one or more control signals for controlling the heating of the target region in a manner that maintains or attempts to maintain, as much as practicable, the pyrolysis occurring at the target zone as close as possible to the desired pyrolysis state. In some embodiments, the parameters of the desired pyrolysis state may be determined based on a-priori testing of the carbonaceous material that is the subject of gasification. Such testing may be performed either in-situ or ex-situ , or both, depending on the testing methodologies performed.

[0103] If in-situ testing is performed, then the laser-based gasification system may be deployed for a testing phase, wherein the laser head is placed, sequentially, in one or more pyrolysis chambers, with the laser-based gasification system being operated so as to create a range of differing pyrolysis states, with the resulting product gas for each pyrolysis state being assayed to determine its composition. Once all of the testing data have been reviewed and a desired product-gas composition has been selected, operating parameters for the desired pyrolysis state can be determined. Then, the laser-based gasification system can be deployed for product-gas production using the operating parameters corresponding to the desired pyrolysis state. In some embodiments, in-situ testing may be performed at multiple differing locations as needed depending on the composition of the natural carbonaceous deposit at issue. In some examples, all multi -location testing may be performed prior to stating any product-gas production, while in some embodiments, multi -location testing may be performed intermittently with product-gas production. For example, testing may be performed in any one pyrolysis chamber or related set of pyrolysis chambers prior to initiating product gas production.

[0104] If ex-situ testing is performed to determine parameters of the pyrolysis state and the corresponding operating parameters for the laser-based gasification system, then one or more samples may be taken from one or more locations within the mass of material targeted for gasification and tested in a suitable testing laboratory. Once the parameters of the desired pyrolysis state is determined, the operating parameters for the laser-based gasification system that will cause the desired pyrolysis state in situ may be determined for the product-gas production phase.

[0105] At block 325, the product gas resulting from the pyrolysis caused by heating using the laser head is extracted from the mass of carbonaceous material. The extraction of the product gas can proceed in any suitable way, such as using conventional product gas extraction equipment or any other suitable extraction technique. For example, extracting the product gas resulting from the pyrolysis may include providing an extraction flow from the pyrolysis chamber to cause the product gas to flow to a suitable collection system, which may include one or more storage tanks (e.g., surface-mounted tanks) and/or processing equipment to process the product gas in one or more of a variety of ways. The extraction flow may be a positive-pressure flow induced by flowing an extraction gas into the pyrolysis chamber. The extraction gas may be separate from or combined with any oxidant flow provided for pyrolysis, as mentioned above. The extraction flow may be a negative-pressure flow induced, for example, by a vacuum system. For example, the vacuum system may include one or more fans that draw the product gas from the pyrolysis chamber. In some embodiments, a positive-pressure flow on an inlet end of the pyrolysis chamber may be used in combination with a negative-pressure flow on an outlet end of the pyrolysis chamber. If provided, product-gas processing equipment may include, but not be limited to, constituent gas separation equipment, pressurizing equipment, liquification equipment, and flow-gas removal equipment,, among others, singly or in any suitable combination. Fundamentally, there are no limitations on the type(s) of processing equipment that can be used.

[0106] In some embodiments, some or all of the activities of the foregoing blocks 305 through 325 may be repeated at differing locations within one or more pyrolysis chambers. For example, a first pass through method 300 may proceed with the laser head stationary at a first location within a pyrolysis chamber, such as at a first position along the length of a bore-type pyrolysis chamber. Then, the laser head may be moved to a second position within the bore-type pyrolysis chamber along the length of the pyrolysis chamber and the activities at block 310 through block 325 repeated at the second position. This type of repetition may continue until a desired amount of the carbonaceous material along a desired length of the bore-type pyrolysis chamber is pyrolyzed. As another example, once the method 300 has been performed in a first pyrolysis chamber, the laser head may be moved to a second pyrolysis chamber, wherein activities at blocks 305 through 325 may be repeated. Similar to the same-chamber example, the repeating of moving the laser head from one pyrolysis chamber to another may be repeated until a desired pyrolysis has been performed in a desired number of pyrolysis chambers. Those skilled in the art will readily appreciate the variety of ways in which various activities in blocks 305 through 325 can be executed and repeated as desired.

[0107] Example Laser-Based Gasification System

[0108] FIG. 4 illustrates an example laser-based gasification system 400 (“gasification system”, for short) that is configured to perform a gasification method of the present disclosure, including the method 300 of FIG. 3 and any method derivable from the above-detailed description of the method 300. In the example shown, the gasification system 400 includes one or more laser heads 404 (collectively shown as a single laser head), each of which is deployed to a corresponding pyrolysis chamber (not shown) during use. At a high level, each laser head 404 includes a plurality of laser-beam outputs 404A (only a few labeled to avoid clutter) that outputs a corresponding laser beam (not illustrated) to irradiate the carbonaceous material (not show) with energy sufficient to heat the carbonaceous material to a desired temperature to cause the carbonaceous material to pyrolyze and produce a product gas. The laser-beam outputs 404A output laser beams generated by a laser system 408, which can take any one or more of a variety of forms.

[0109] For example, in some embodiments each laser-beam output 404A may include a scanning means, such as scanning optics, gimballed mount, etc. In some embodiments, each laser- beam output 404A may be a fixed output. Examples of fixed outputs include suitable optics, such as beam-expanding optics, fiber bundles, etc. In some embodiments implementing fixed outputs, the fixed outputs may be configured and/or utilized to increase the size of the irradiated regions as the pyrolysis chamber grows in size due to continuing pyrolysis. For example, a beam expander may be a variable beam expander. In some embodiments, each laser-beam output 404A may include both scanning features and beam expanding features, among other variations.

[0110] For example, the laser system 408 may include one or more lasers 408 A (collectively shown as a single laser) that provide laser energy to the laser-beam outputs 404A via optic fibers (e.g., in one or more optic-fiber cables), collectively shown as optic-fiber cable 408B. At a high level, multiple laser heads are provided so as to be able to heat relatively large areas of the carbonaceous material exposed to the laser head 404 within a pyrolysis chamber. In this connection, it is desired to cause relatively large areas of the exposed carbonaceous material to pyrolyze at any given time so as to produce relatively large volumes of product gas in an effective and efficient manner. As those skilled in the art will readily appreciate, the number of laser-beam outputs 404A and the number of lasers 408 A providing laser energy to those laser-beam outputs will depend on, for example, physical limitations of the relevant current laser technology (e.g., output power, efficiency, optic-fiber-cable capacity, etc.) and associated monetary costs. While it is desirable to make the laser head 404 as long as possible (e.g., tens of feet or hundreds of feet or more in length) and provide as many laser-beam outputs 404A as needed to suit such long lengths, it is recognized that for practical applications that tradeoffs in laser-head length and number of laser-beam output may need to be made in order to deploy a gasification system of the present disclosure, such as the gasification system 400, in an economically and commercially successful manner.

[0111] Each laser may be based on any suitable technology, such as CO2 lasing technology, YAG lasing technology, optic-fiber lasing technology, solid-state lasing technology, etc. In some embodiments, the output wavelength(s) of the lasers need not necessarily be selected and/or tuned to specific absorption spectra of the target carbonaceous material, although in some cases the lasers can be so selected or tuned. In some embodiments, each laser 408A may be located remotely from the laser head 404, while in some embodiments, each laser may be located onboard the laser head, depending on the technology at issue. In some embodiments, one or more lasers 408A may be located remotely from laser head 404 and one or more lasers 408A may be located onboard the laser head.

[0112] Each laser head 404 may further include a plurality of condition-sensing elements 404B (only a few labeled to avoid clutter) that are used to sense one or more conditions within a pyrolysis chamber (not shown) in which the laser head is deployed. Examples of conditions that can be sensed, as desired, include, but are not limited to, distances (e.g., to measure pyrolysis-chamber size / extend of pyrolysis) and conditions of pyrolysis as may be discernable in any of a variety of ways, such as temperature, material composition of irradiated face, and makeup of product gas, among others. Depending on the configuration and needs, the condition-sensing elements 404B may be of the same type or differing types, with the type of each condition-sensing element 404B corresponding to the condition it is deployed to measure. Depending on its type, each condition sensing element 404B may be or comprise, for example, lensing for light-based sensing (including infrared), ultrasound transducer(s) for ultrasound-based sensing, or radar component(s) for radar- based sensing, among others. Depending on various factors, such as the type of each condition sensing element 404B, the directionality of each condition-sensing element, and the coverage area for each sensing element, one, some, or all of the condition-sensing elements may be pivotable so as to allow the sensing element to be directed to the desired region(s) of interested. In some examples, one, some, or all of the condition-sensing elements may be of the scanning type so as to be able to conduct areal scans, such as in a manner discussed above relative to scanning the laser beams to effect areal heating. Fundamentally, there are no limitations on the nature or type(s) of condition sensing elements 404B.

[0113] Depending on the configuration of the gasification system 400, the laser head 404 may include either one or more gas-delivery ports 404C or one or more gas-collection ports 404D, or both. The gas-delivery port(s) 404C, if provided, may deliver one, some or all of an oxidant flow, a heating flow, and a extraction flow for, respectively, assisting the pyrolysis, heating the pyrolysis zone, and assisting with removing the product gas. The gas-collection port(s) 404D, if provided, may collect the product gas and any remnants of the oxidant flow that may be present and any extraction flow that may be present. Providing the laser head 404 with both gas-delivery and gas- collection ports 404C and 404D allows many aspects of the laser-based gasification process to be performed locally within the pyrolysis chamber. If one or both types of gas-delivery and gas collection ports 404C and 404D is/are not provided, then other type(s) of execution methods may be provided, such as conventional surface-based methods of delivering one or more gases downhole and conventional surface-based method of collecting one or more gases from underground, among others. FIG. 10A illustrates an example laser head 1000 that includes both gas-delivery ports 1004 and gas-collection ports 1008.

[0114] Referring to FIG. 10A, which illustrates the laser head 1000 deployed in a pyrolysis chamber 1012 located within a carbonaceous material, in this example, the laser head 1000 is tethered to surface equipment (not shown) such as a laser system, an oxidant-flow system, a heating flow system, and a gas-collection system via a tether 1016. The laser head 1000 has a length, L, with the gas-delivery ports 1004 being present at one end of the length L and the gas-collection ports 1008 being present at the opposite end of length L. This arrangement allows for creating a generally uniform and laminar flow of gases in the space surrounding the laser head 1000, as illustrated by arrows 1020. Not shown to avoid clutter are other components of the laser head 1000, such as laser-beam outputs and any condition-sensing elements that may be present. It is noted that the locations of the gas-delivery ports 1004 and the gas-collection ports 1008 can be reversed. In other embodiments, the gas-delivery ports 1004 and the gas-collection ports 1008 can be located elsewhere, such as at locations distributed along the length L of the laser head. Those skilled in the art will readily appreciate how to organize any gas-delivery ports and gas-collection ports for any particular design and application of a laser head.

[0115] FIG. 10B shows an example configuration of the tether 1016. In this example, the tether includes an outer sheath 1016A that contains 1) an optic-fiber cable 1016B that delivers laser energy to the laser outputs (not shown) from one or more lasers (not shown) and, optionally carries optical signals to and/or from any condition-sensing element that may be aboard the laser head 1000 (FIG. 10 A), 2) a gas-delivery conduit 1016C for delivering one or more gases to the gas-delivery ports 1004, 3) a gas-collection conduit 1016D for collecting gas via the gas-collection ports 1008, and 4) electrical cabling 1016E needed for operating and/or controlling any electronic equipment (not shown) that may be aboard the laser head and/or laser-head support and/or to carry any electrical signals that may be generated onboard the laser head, among others. Examples of electronic equipment include, but are not limited to, a traction system, scanning motors, digital-light- processors, and onboard sensors, among others. Examples of electrical signals generated onboard the laser head 1000 include, but are not limited to, signals from onboard pyrolysis-chamber sensors and signals from other onboard electronics and/or onboard equipment. Those skilled in the art will readily understand the wide variety of electronic equipment that can be placed aboard a laser head and/or laser-head support of the present disclosure.

[0116] Referring back to FIG. 4, the example gasification system 400 may also include, among other systems, 1) a measurement system 412 that includes all of the physical equipment, physical components, and/or software needed for sensing and measuring conditions within a pyrolysis chamber, including the condition-sensing elements 404B aboard the laser head(s) 404, 2) a laser- head-movement system 416 that includes all of the physical equipment, physical components, and/or software needed for moving the laser head, including for deployment and/or for moving one or more laser heads between discrete pyrolysis sessions and/or during one or more continuous pyrolysis session(s), 3) a gas-delivery system 420 that includes all of the physical equipment, physical components, and/or software needed for storing, supplying, and delivering one or more gases, such as one or more oxidants, one or more heating gases, and/or one or more extraction gases, to one or more pyrolysis chambers, including storage vessel(s) and delivery system(s), and 4) a gas-collection system 424 that includes all of the physical equipment, physical components and/or software needed for collecting, processing, and/or storing one or more gases, such product gas, excess oxidant(s), and/or extraction gas(es), from one or more pyrolysis chambers, among others. Each of these systems may be composed of conventional elements to the extent that any specialized element(s) are not needed to practice a gasification system of the present disclosure, such as the gasification system 400 of FIG. 4. Those skilled in the art will readily appreciate the many ways that each of the systems 412, 416, 420, and 424 can be embodied, including the wide variety of equipment, components, and software configurations for executing these systems and that skilled artisans will be able to make and use these ways for the relevant gasification-system designs using only knowledge in the art and this disclosure as a guide.

[0117] In some embodiments, non-laser heating of the carbonaceous material in the pyrolysis chamber may be provided by a heating source other than one or more heating gases. For example, each laser head 404 may include an onboard heat source 404E or a component of an offboard heat source (not shown). Examples of such other heat sources can be found, for example, in U.S. Patent No. 7,225,866, titled “IN SITU THERMAL PROCESSING OF AN OIL SHALE FORMATION USING A PATTERN OF HEAT SOURCES” and issued on June 5, 2007, to Berchenko et ah, which is incorporated herein by reference for its teachings of heat sources.

[0118] In this example, the gasification system 400 includes a control system 428 that controls all operations of the gasification system either automatically or manually, or a combination of automatically and manually. As those skilled in the art will readily appreciate, while the control system 428 is illustrated as a single block in FIG. 4, all of the control functions that the control system performs need not be centralized. Rather, embodiments of the gasification system 400 may have any one or more control subsystems, such as one or more laser-control subsystems 428A, one or more measurement control subsystems 428B, one or more laser-head-movement control subsystems 428C, one or more laser-head stabilization control subsystems 428D, one or more gas- delivery control subsystems 428E, and one or more gas-collection subsystems 428F, among others.

In some examples one or more of the control subsystems can be a standalone control subsystem and/or one or more of the control subsystems may be networked with one another and/or to a master controller 428G, among other architectures. Those skilled in the art will readily appreciate the many ways that the control system 428 can be embodied, including the wide variety of hardware and software configurations for implementing the control system and that skilled artisans will be able to make and use these ways for the relevant gasification-system designs using only knowledge in the art and this disclosure as a guide.

[0119] As those skilled in the art will readily appreciate, the control system 428 can include many algorithms for performing a wide variety of tasks that the gasification system 400 must perform during deployment for gasifying a mass of carbonaceous material. Some of these algorithms include pyrolysis-control algorithms 432 that control the pyrolysis that occurs in any one or more pyrolysis chambers in which one or more laser heads 404 are deployed. Depending on the configuration of the gasification system 400 and the manner(s) in which pyrolysis can be controlled and the state(s) of the pyrolysis can be determined, the functionalities that the pyrolysis-control algorithms 432 need to perform can vary. Examples of functionalities that the pyrolysis-control algorithms 432 can provide include, but are not limited to:

• controlling laser-power density provided to the carbonaceous material, in some embodiments as a function of measurements of the state of pyrolysis and/or the size and/or shape of the region(s) of the carbonaceous material being pyrolyzed and/or movement of the laser head(s) 404;

• controlling laser-beam scanning of the carbonaceous material, for example via the laser-beam outlets 404B of the laser head(s), in some embodiments as a function of measurements of the state of pyrolysis and/or the size and/or shape of the region(s) of the carbonaceous material being pyrolyzed and/or movement of the laser head(s);

• controlling the movement of the laser head(s), in some embodiments as a function of measurements of the state of pyrolysis and/or the size and/or shape of the region(s) of the carbonaceous material being pyrolyzed;

• controlling sequencing of providing laser energy to various ones of the laser-beam outputs, in some embodiments as a function of measurements of the state of pyrolysis and/or the size and/or shape of the region(s) of the carbonaceous material being pyrolyzed and/or movement of the laser head(s);

• controlling the amount of oxidant gas(es) provided to the pyrolysis chamber;

• controlling the amount of non-laser heating, in some embodiments including controlling the flow of one or more heating gases (e.g., steam) to the pyrolysis chamber;

• controlling the sensing of one or more conditions within each active pyrolysis chamber;

• controlling collection of sensor data;

• comparing condition measurements to one or more predetermined parameters for a desired pyrolysis state that produced a desired product gas; and

• conducting in-situ pyrolysis testing to determine one or more parameters of a desired pyrolysis state, in some embodiments as a function of the constituency of the product gas, and any combination thereof, among others. [0120] Those skilled in the art will readily understand that the pyrolysis-control algorithms 432 and the associated computing hardware 436 that executes the machine-executable instruction 440 that embody the pyrolysis-control algorithms 432 will be in operative communication with the necessary systems, such as, for example, the laser system 408, the measurement system 412, the laser-head-movement system 416, the gas-delivery system 420, and/or the gas-collection system 424, among others, as needed to receive the necessary data (e.g., condition measurements, location information, component statuses, etc.) from these systems and to provide the necessary information, such as control signals, status information, operating parameters, etc.) to these systems. The computing hardware 436 includes memory 436A, which can be any type of physical storage memory, including, but not limited to non-volatile memory (e.g., solid-state, optical, magnetic, etc. hard-drive memory, and/or other type of long-term storage memory) and volatile memory (e.g., RAM and/or cache memory, among other types). Fundamentally, there is no limitation on the type(s) of the memory 436 A, the number of memory devices that compose the memory 436 A, and the physical location(s) of the memory device(s) that compose the memory 436 A, other than that the memory is not in the form of any transitory signal. Many types of computing systems, computing architectures, and programming styles are ubiquitous and well-known in the art and are usable to implement the pyrolysis-control algorithms 432, such that it is not necessary to describe these in detail for those skilled in the art to implement them for any application and design that may be devised using the present disclosure as a guide.

[0121] EXAMPLE INSTANTIATIONS - Laser-based UCG

[0122] FIGS. 11 A through 11C illustrate an example instantiation of a laser-based UCG system 1100 (hereinafter, “UCG system” for short) as deployed in accordance with aspects of the present disclosure. Referring first to FIG. 11 A, in this example, the UCG system 1100 is deployed to perform gasification on a portion of a natural underground coal seam 1104 that lies beneath the earth’s surface 1108, an aquifer 1112, and overburden 1116 that includes a sedimentary rock layer 1116A that seals the coal seam from the aquifer. In this example, the UCG system 1100 includes a first access well 1120 and associated surface equipment 1120A (e.g., a laser system, an oxidant-supply system, etc.; see, e.g., FIG. 4), a second access well 1124 and associated surface equipment 1124A (e.g., a gas-collection system, etc.; see, e.g., FIG. 4), and a pyrolysis chamber 1128 that extends from the first access well to the second access well and contains a laser head 1132 located within the pyrolysis chamber 1128 for delivering laser energy to the coal seam in which the pyrolysis chamber is formed. Depending on the particular history of the portion of the coal seam 1104 selected for UCG, one, the other, or each of the first access well 1120 and the second access well 1124 may be a preexisting well or one, the other, or each of the first and second access wells may be a new well sunk for the specific purpose of performing the UCG. Correspondingly, the pyrolysis chamber 1128 may be a preexisting bore or other void or may be a newly formed bore or other void formed specifically for performing the UCG. In some embodiments well-known boring techniques can be used for forming the first and second access wells 1120 and 1124 and the pyrolysis chamber 1128 as needed.

[0123] As illustrated in FIG. 1 IB, laser energy from the laser head 1132 is then used to raise the temperature of the coal walls of the pyrolysis chamber 1128 to a pyrolysis temperature along the entire length, Lc, of the pyrolysis chamber. Depending on the length Lc of the pyrolysis chamber 1128 and the length, LH, of the laser head 1132, the laser head may need to be moved to perform pyrolysis along the entire length Lc of the pyrolysis chamber 1128. The surface equipment 1120A of the first access well 1120 is used to feed one or more gases, for example, oxidant gas(es), into the pyrolysis chamber 1128 to support the pyrolysis reaction within the pyrolysis chamber. In this example, the coal surrounding and defining the pyrolysis chamber 1128 is heated to 360° around the circumference of the pyrolysis chamber, and the resulting pyrolysis reaction proceeds in the coal seam 1104 radially outwardly from the initial bore of the pyrolysis chamber until an optimum pyrolysis radius, Rp, is reached, as illustrated in FIG. 11C. In some embodiments, the optimum pyrolysis radius Rp can depend on any of a number of factors, such as the thickness, Tcs, of the coal seam 1104, the stability of the coal seam, and any limitations of the laser head 1132 (FIGS. 11 A and 1 IB) in delivering the laser energy to create the necessary heating, among others. In this connection it is noted that while the pyrolysis chamber 1128 is shown as being horizontal, for example, to conform to the stratification geometry of the coal seam 1104 and other geological layers, such as the sedimentary rock layer 1116A (FIG. 11 A), the pyrolysis chamber, or any other pyrolysis chamber disclosed herein, does not need to be horizontal. For example, the angle of the pyrolysis chamber 1128 or other pyrolysis chamber may form any suitable non-zero angle relative to geological horizontal. Furthermore, any pyrolysis chamber of the present disclosure may alternatively not be straight. For example, a pyrolysis chamber of this disclosure, such as pyrolysis chamber 1128 may be curved. It is noted that while FIGS. 11 A to 11C illustrate pyrolyzation of the coal seam 1104 in a single pyrolysis chamber 1128, any number of additional pyrolysis chambers (not shown) can be created and utilized to gasify a larger extent of the coal seam. [0124] While not limited to one particular theory, the laser-based-heating approach to gasification of the present disclosure can achieve any one or more of a number of advantages over conventional gasification techniques. These advantages include, but are not limited to: 1) direct delivery of optical power through long fiber-optic cables made possible, for example, through the provision of high transmission communication S1O2 fibers; 2) the ability to condition specific high- energy intensities required for heating coal and/or other carbonaceous material to a desired pyrolysis state; 3) the ability to heat an entire length of a pyrolysis chamber, thereby creating greater area for pyrolysis; 4) the ability to provide direct primary heating of secondary heat sources, such as steam injection; 5) the ability to precisely control the constituency of the product gas from the pyrolysis; and 6) high levels of reliability (e.g., approaching 1,000,000 hours or more) necessary for long service life and performing multiple ignition programs with the same equipment, among others.

[0125] In some embodiments, implementing systems and methods of the present disclosure result in significant energy gains compared to conventional methods. For example, FIG. 11C depicts a scenario in which a volume of coal having a diameter, D (generally 2 x Rp), and the length Lc is heated using via laser to produce a product gas. The following Table I describes physical properties of an example illustrative, but not limiting, underground coal deposit:

Table

Physical Property

Value

Specific Heat Capacity (J/kg K)¹ 1.38

Density (kg/m³)¹ 1.35 x 10³

Calorific Value of Volatiles (kJ/m³)² 9 x 10³

Pyrolysis Temperature (K)³ 1100

Length (m) 600

Diameter (m) 20

¹ Typical for bituminous coals

² Known values for conventional UCG (9 kJ/m³ to 11 kJ/m³)

³ Optimum temperature for pyrolysis

[0126] The total energy, Q, required to raise a body of mass, m, from a starting temperature, Ti, to a final temperature, T2, is given by:

Q=mCp(T_{2 -} Ti) wherein Cp is the specific heat capacity of coal. Results of this calculation for a range of operating volumes are given in the following Table II: TABLE Energy Value

Required to raise volume to ignition 3xl0⁸ J (D = 0.3m; L = 600m)

Yield from combustion of seam 2xl0¹³ J

(D = 20m; L = 600m)

Gain 7xl0⁴ J

[0127] Without being bound to one particular theory, the energy gain according to some embodiments can result, for example, in some 70,000 times the energy used to heat the seam to ignition. Additionally, 3xl0⁸ Joules of energy are required to raise 180 m³ of coal to the ignition temperature of 800°C. In some embodiments, usable lasers include, but are not limited to, lasers capable of delivering continuous power outputs 1 lpW to lOOkW, which can provide the total required energy in a matter of minutes.

[0128] In some embodiments, systems and methods disclosed herein include providing one or more gases, e.g., oxidant gas(es), heating gas(es), extraction gas(es), etc., into the linkage bore from an injection well in a controlled manner. Without being bound to one particular theory, the one or more gases facilitate the production of a product gas. The composition and rate of the one or more gases introduced into the linkage bore can vary depending on the size of pyrolysis chamber, amount of carbonaceous material surrounding the pyrolysis chamber, the temperature required to produce the product gas and other variables. In some embodiments, these systems and methods can include controlling the one or more gases provided to the linkage bore to increase the product gas- producing conditions.

[0129] In some embodiments, these systems and methods produce a product gas comprising from 1 percent to 10 percent, by mole, carbon dioxide, from 1 percent to 10 percent, by mole, carbon monoxide, from 20 percent to 30 percent, by mole, methane, and from 40 percent to 50 percent, by mole, hydrogen. The methods of producing a product gas described herein offer several advantages to conventional methods including a high ratio of hydrogen gas to carbon monoxide due to the highly controlled pyrolysis that can be performed. For example, in some embodiments, the mole ratio of hydrogen gas to carbon monoxide of the product gas produced is from 4: 1 to 50: 1. In some embodiments, the mole ratio of hydrogen gas to carbon monoxide of the product gas is from 10: 1 to 20:1. In some embodiments, the mole ratio of hydrogen gas to carbon monoxide of the product gas produced is about 15:1. In some applications, producing significant amount of hydrogen is highly desirable. For example, as a carbon-free fuel it can be combusted as a fuel gas in combined-cycle gas turbines (CCTGs) without CO2 emissions. Going forward, it is also a fuel of choice for fuel cells, both for stationary power generation and electric vehicles. In addition, hydrogen is a valuable chemical feedstock used, for example, in hydrocrackers in the refining sector.

[0130] In some embodiments, a ruggedized fiber laser beam delivery system is used within any of the above-described methods. In some embodiments, the laser beam delivery system includes laser injection head technology or optical assemblies capable of achieving desired pyrolysis parameters in an underground setting.

[0131] In some embodiments, these methods include further processing or refining the product gas. Refining techniques include removal of impurities, carbon capture and other gas processing steps. In some embodiments, the product gas is further refined to produce a clean product gas. The clean product gas can be used, for example, to generate power, provide feedstocks for chemical products, provide feedstocks for fuel products, and other similar uses.

[0132] Without being bound to one particular theory, these systems and methods can achieve significant cost efficiencies over conventional coal energy extraction technology. For example, some embodiments can significantly reduce the number of personnel required to operate the production operation, thereby reducing the resources and human capital needed to produce the product gas.

[0133] In some embodiments, a method of laser-assisted drilling of wells or bores in underground carbonaceous materials, such as oil shale, includes using a laser that emits at wavelength and illumination conditions to meet the absorption bands of water present in the carbonaceous material. For example, granite and shale deposits contain about 5 wt.% water to 7 wt.% water, which allows for laser-scabbing techniques that rely on the explosive response of the superheated water in the body of the shale or rock, to effect large scale tracking effects and/or removal of material and production of hydrocarbons. In some embodiments, methods of extracting hydrocarbons from shale oil include deploying an ultraviolet laser down a bore hole, wherein the ultraviolet laser volatilizes hydrocarbons present in shale oil, the volatilized compounds are then collected, refined and used to create energy, chemical feedstocks, or fuel feedstocks according to methods known to those of skill in the art. [0134] EXPERIMENTAL EXAMPLE

[0135] A system used to perform experiments included a steel containment vessel containing a block of dry bituminous coal of unknown origin, predrilled with a 6mm bore throughout its length.

A high power CO2 laser was focused into the bore with a ZnSe lens of focal length 100mm, and air assist was blown coaxially through a flat-tipped Cu nozzle at a flow rate of 2 l/min. A continuous- wave CO2 laser (Rofin Sinar DCOIO) gave an energy output of around 40 W/cm² at a wavelength of 10.6 pm. The general procedure was to seal the coal sample chamber into which the laser beam was fired. Gas flowed through the borehole, and then progressed through to a Dreschel bottle filled with 60mm of water. Gas exiting the Dreschel bottle was fed to a nozzle. Gas samples for various exposure conditions as shown in Table III below were extracted for subsequent analysis by mass spectrometry. The gas exit temperature was measured with a K-type thermocouple.

[0136] Pyrolysis was conducted at various incident laser power levels. All laser powers generated a pyrolytic reaction that occurred rapidly on laser exposure. Both gaseous products and some particulates escaped from the reaction vessel, and the particulates were caught in the liquid volume of the Dreschel bottle. Pyrolysis of the samples was a continuous process that could be observed for as long as the air and laser energy was allowed to flow through the system. High levels of ignitable gas were observed for power levels above 150W, as shown in Table III. On termination of the laser beam above the ignition threshold of 100W, the gas mixture composition changed such that it could no longer maintain ignition of the burn-off flame.

Table III

Power (W) Air flow rate (1/min) Note 50 2 No gas 50 6 No gas 50 8 No gas 50 10 No gas 50 12 No gas 100 2 Gas / no ignition 100 6 Gas / no ignition 100 8 Gas / no ignition 100 10 Gas / no ignition 100 12 Gas / no ignition 100 2 Gas / no ignition 150 2 Gas / ignition 150 6 Gas / ignition 150 8 Gas / ignition 150 10 Gas / ignition 150 12 Gas / ignition 200 2 Gas / ignition 200 6 Gas / ignition 200 8 Gas / ignition 200 10 Gas / ignition 200 12 Gas / ignition

[0137] Gaseous products produced above the ignition level of 150W are summarized in the following Table IV:

Table IV

Product/Temp Laser-ignited UCG Conventional UCG Estimated Temp. 900°C 1600°C H2 45 54 CH4 22 10 C02 3 14 CO 7 16 S <1 <1

Other hydrocarbons 12 6

[0138] Table IV illustrates the average gas composition of laser-ignited UCG (LUCG) pyrolysis, in mole %, at 150W power level compared to conventional UCG processes, such as those described at the Central Mining Institute, Katowice, Poland, Reported May 2015, UK Energy symposium, Kegworth, UK, which is incorporated by reference herein. [0139] These gases represent a typical hydrocarbon product mix from low temperature coal carbonization process. Refinement of these products in subsequent catalytic steps, such as hydrogenation, could significantly increase their calorific value.

[0140] The above results demonstrate the feasibility of delivering an LUCG process for the production of product gas from coal beds. Results have shown that low levels of laser irradiation in a narrow bore bitumen coal deposit of < 150W/cm², whilst capable of generating a product gas, appears to be insufficient to convert sufficient levels of hydrocarbons for ignition at standard temperature and pressure (STP). Higher levels of laser illumination at > 150W/cm² appear to be required for the generation of ignitable product gas which contain product gas similar to those found in low temperature carbonization processes. At this power density, removal of the laser illumination reduced the product gas composition such that a sustainable combustion process was terminated. It is worth noting that the power levels used in these experiments are similar to those found in domestic lighting systems. As such, the process offers the opportunity to use industrial scale laser energy to control product gas production levels and the possibility to control product yield, since the product gas composition is heavily dependent on reaction temperature. Moreover, the use of methanation reactions such as catalysts of steam, could significantly enhance the calorific value of the product gas, converting the hydrogen component into greater levels of C¾, C₂H₅, and other alkanes and higher molecular weight hydrocarbons.

[0141] The accompanying figures contain illustrations allowing for an explanation of aspects of the present invention. Notably, the figures and examples above are not meant to limit the scope of the present disclosure to a single embodiment, as other embodiments are possible by way of interchanging some or all of the described and/or illustrated elements. Moreover, where certain elements of any example or illustration can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present disclosure are described, and detailed descriptions of other portions of such known components are omitted so as not to obscure any inventive aspect. In the present specification, an embodiment showing a singular component should not necessarily be limited to other embodiments including a plurality of the same component, and vice-versa, unless explicitly stated otherwise herein. Moreover, the present disclosure encompasses present and future known equivalents to the known components referred to herein by way of illustration. [0142] The foregoing description of the specific embodiments so fully reveals the general nature of the invention that others can, by applying knowledge within the skill of the relevant art(s) (including the contents of the documents cited and incorporated by reference herein), readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Such adaptations and modifications are therefore intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0143] Various modifications and additions can be made without departing from the spirit and scope of this invention. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments, what has been described herein is merely illustrative of the application of the principles of the present invention. Additionally, although particular methods herein may be illustrated and/or described as being performed in a specific order, the ordering is highly variable within ordinary skill to achieve aspects of the present disclosure. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.

[0144] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.

Claims

What is claimed is:

1. A method of producing a product gas from a mass of carbonaceous material, wherein the carbonaceous material includes a pyrolysis chamber within the mass and defined by surrounding portions of the carbonaceous material, the method comprising: inserting a laser head into the pyrolysis chamber, wherein the laser head is configured to output and direct laser energy to a target portion of the surrounding portions of the carbonaceous material; while the laser head is present within the pyrolysis chamber: heating the target portion of the carbonaceous material with the laser energy emitted from the laser head so as to sustain a desired pyrolysis state that produces the product gas from the carbonaceous material; concurrently with heating the target portion, obtaining measurements of at least one condition of the target portion having a known correlation with the desired pyrolysis state; and controlling the heating of the target portion as a function of the measurements of the at least one condition of the target portion; and extracting the product gas from the mass of carbonaceous material.

2. The method of claim 1, wherein the carbonaceous material is in situ within a geological formation, and the pyrolysis chamber is manmade chamber within the geological formation.

3. The method of claim 2, wherein the pyrolysis chamber comprises an induced fissure within the geological formation.

4. The method of claim 2, wherein the pyrolysis chamber comprises an elongate bore formed within the geological formation.

5. The method of claim 4, wherein the elongate bore is a lateral bore extending from a primary bore.

6. The method of claim 1, wherein the laser energy is provided via one or more laser beams, and heating the target portion includes scanning the one or more laser beams on the target portion of the carbonaceous material.

7. The method of claim 6, further including scanning the one or more laser beams is controlled as a function of the measurements.

8. The method of claim 7, wherein the measurements are measurements corresponding to temperature of the target portion.

9. The method of claim 1, wherein the laser head has a length and a plurality of laser-beam outputs spaced from one another along the length of the laser head, and each laser-beam output is configured to output a corresponding laser beam for providing a portion of the laser energy to the target portion of the carbonaceous material.

10. The method of claim 9, wherein each laser-beam output is a scanning-type output.

11. The method of claim 10, wherein each laser-beam output includes one or more movable reflective and/or refractive elements.

12. The method of claim 11, wherein the target portion of the carbonaceous material extends in a direction parallel to the length of the laser head, and the method further comprises controlling the scanning-type outputs so as to provide a laser-power density that is substantially uniform across the target portion along the length of the laser head.

13. The method of claim 1, further comprising establishing a pyrolysis zone within the carbonaceous material surrounding the pyrolysis chamber, and continuing to heat the target portion until all of the carbonaceous material within the pyrolysis zone has been pyrolyzed.

14. The method of claim 1, wherein the carbonaceous material comprises oil shale.

15. The method of claim 1, wherein the carbonaceous material comprises coal.

16. The method of claim 1, wherein the laser head is present at a first end of an optic-fiber cable, and the method includes using multiple laser-beam generators to input laser energy into the optic- fiber cable at a second end opposite the first end.

17. The method of claim 16, wherein the optic-fiber cable contains multiple fiber bundles, and each of the multiple fiber bundles receives laser energy from a corresponding one of the multiple laser-beam generators.

18. The method of claim 17, wherein the laser head is partitioned into multiple laser-emitting sections, each of the multiple laser-emitting sections receiving laser energy from a corresponding one of the multiple laser bundles.

19. The method of claim 1, wherein obtaining measurements of at least one condition of the target portion includes receiving electromagnetic energy from the target portion.

20. The method of claim 19, wherein receiving electromagnetic energy from the target portion includes receiving the electromagnetic energy via optic fibers used to deliver the laser energy to heat the target portion of the carbonaceous material.

21. The method of claim 1, wherein the laser head is connected to a tether, and extracting the product gas includes extracting the product gas via a passageway of the tether.

22. The method of claim 1, further comprising providing an oxidant to the pyrolysis chamber.

23. The method of claim 22, wherein the laser head is connected to a tether, and providing an oxidant includes providing the oxidant via a passageway of the tether.

24. The method of claim 1, further comprising heating the target portion with a non-laser heat source.

25. The method of claim 24, wherein heating the target portion includes heating the target portion with steam.

26. The method of claim 25, wherein the laser head is connected to a tether, and heating the target portion with steam includes providing the steam via a passageway in the tether.

27. The method of claim 24, wherein the non-laser heat source includes a heating element integrated with the laser head.

28. The method of claim 1, wherein the pyrolysis chamber has a length, and heating the surrounding portions of the carbonaceous material is performed while moving the laser head along the length of the pyrolysis chamber.

29. The method of claim 1, wherein inserting the laser head into the pyrolysis chamber includes inserting the laser head via a first access well.

30. The method of claim 29, further comprising forming the pyrolysis chamber from the first access well.

31. The method of claim 29, wherein the first access well contains an insertion passageway for inserting the laser head into the ignition bore, and an extraction passageway for extracting the product gas.

32. The method of claim 29, wherein extracting the product gas is performed via a second access well.

33. The method of claim 32, wherein the first and second access wells are spaced from one another, and the pyrolysis chamber extends from the first access well to the second access well.

34. The method of claim 29, further comprising forming the first access well.

35. The method of claim 34, further comprising forming the second access well.

36. The method of claim 35, further comprising forming the pyrolysis chamber to connect the first access well with the second access well.

37. The method of claim 1, wherein the desired pyrolysis state occurs when the target zone has a reaction temperature in a range of about 600°C to about 1200°C.

38. The method of claim 1, wherein the desired pyrolysis state occurs when the target zone has a reaction temperature in a range of about 600°C to about 800°C.

39. The method of claim 1, wherein the product gas comprises from about 1% to about 10% by mole carbon dioxide.

40. The method of claim 1, wherein the product gas comprises from about 1% to about 10% by mole carbon monoxide.

41. The method of claim 1, wherein the product gas comprises from about 20% to about 30% by mole methane.

42. The method of claim 1, wherein the product gas comprises from about 40% to about 50% by mole hydrogen.

43. The method of claim 1, wherein the product gas comprises a mole ratio of hydrogen to carbon dioxide of about 15:1.

44. The method of claim 1, wherein the laser head has a longitudinal axis, and the heating is performed 360° radially outward relative to the longitudinal axis.

45. A method of producing a product gas from a mass of carbonaceous material, wherein the carbonaceous material includes a pyrolysis chamber within the mass and defined by surrounding portions of the carbonaceous material, the method comprising: inserting a laser head into the pyrolysis chamber, wherein the laser head is configured to output and direct laser energy to the surrounding portions of the carbonaceous material; while the laser head is present within the pyrolysis chamber, irradiating multiple regions of the carbonaceous material with multiple laser beams emitted from the laser head so as to sustain, at the multiple regions, a desired pyrolysis state that produces the product gas from the carbonaceous material; and extracting the product gas from the mass of carbonaceous material.

46. The method of claim 45, wherein irradiating multiple regions of the carbonaceous material includes irradiating the multiple regions so that the multiple regions are substantially contiguous with one another.

47. The method of claim 45, wherein irradiating multiple regions of the carbonaceous material includes irradiating the multiple regions so that ones of the multiple regions overlap with one another.

48. The method of claim 45, wherein irradiating multiple regions of the carbonaceous material includes scanning one or more laser beams over each of the multiple regions.

49. The method of claim 45, wherein irradiating multiple regions of the carbonaceous material includes irradiating the multiple regions so as to control a transverse cross-sectional shape of the pyrolysis chamber.

50. The method of claim 45, wherein the carbonaceous material is in situ within a geological formation, and the pyrolysis chamber is manmade chamber within the geological formation.

51. The method of claim 50, wherein the pyrolysis chamber comprises an induced fissure within the geological formation.

52. The method of claim 50, wherein the pyrolysis chamber comprises an elongate bore formed within the geological formation.

53. The method of claim 52, wherein the elongate bore is a lateral bore extending from a primary bore.

54. The method of claim 45, wherein the laser energy is provided via one or more laser beams, and heating the target portion includes scanning the one or more laser beams on the target portion of the carbonaceous material.

55. The method of claim 45, wherein the laser head has a length and a plurality of laser-beam outputs spaced from one another along the length of the laser head, and each laser-beam output is configured to output a corresponding laser beam for providing a portion of the laser energy to the target portion of the carbonaceous material.

56. The method of claim 55, wherein each laser-beam output is a scanning-type output.

57. The method of claim 56, wherein each laser-beam output includes one or more movable reflective and/or refractive elements.

58. The method of claim 57, wherein the target portion of the carbonaceous material extends in a direction parallel to the length of the laser head, and the method further comprises controlling the scanning-type outputs so as to provide a laser-power density that is substantially uniform across the target portion along the length of the laser head.

59. The method of claim 45, further comprising establishing a pyrolysis zone within the carbonaceous material surrounding the pyrolysis chamber, and continuing to heat the target portion until all of the carbonaceous material within the pyrolysis zone has been pyrolyzed.

60. The method of claim 45, wherein the carbonaceous material comprises oil shale.

61. The method of claim 45, wherein the carbonaceous material comprises coal.

62. The method of claim 45, wherein the laser head is present at a first end of an optic-fiber cable, and the method includes using multiple laser-beam generators to input laser energy into the optic-fiber cable at a second end opposite the first end.

63. The method of claim 62, wherein the optic-fiber cable contains multiple fiber bundles, and each of the multiple fiber bundles receives laser energy from a corresponding one of the multiple laser-beam generators.

64. The method of claim 63, wherein the laser head is partitioned into multiple laser-emitting sections, each of the multiple laser-emitting sections receiving laser energy from a corresponding one of the multiple laser bundles.

65. The method of claim 45, wherein the laser head is connected to a tether, and extracting the product gas includes extracting the product gas via a passageway of the tether.

66. The method of claim 45, further comprising providing an oxidant to the pyrolysis chamber.

67. The method of claim 66, wherein the laser head is connected to a tether, and providing an oxidant includes providing the oxidant via a passageway of the tether.

68. The method of claim 45, further comprising heating the target portion with a non-laser heat source.

69. The method of claim 68, wherein heating the target portion includes heating the target portion with steam.

70. The method of claim 69, wherein the laser head is connected to a tether, and heating the target portion with steam includes providing the steam via a passageway in the tether.

71. The method of claim 68, wherein the non -laser heat source includes a heating element integrated with the laser head.

72. The method of claim 45, wherein the pyrolysis chamber has a length, and heating the surrounding portions of the carbonaceous material is performed while moving the laser head along the length of the pyrolysis chamber.

73. The method of claim 45, wherein inserting the laser head into the pyrolysis chamber includes inserting the laser head via a first access well.

74. The method of claim 73, further comprising forming the pyrolysis chamber from the first access well.

75. The method of claim 73, wherein the first access well contains an insertion passageway for inserting the laser head into the ignition bore, and an extraction passageway for extracting the product gas.

76. The method of claim 73, wherein extracting the product gas is performed via a second access well.

77. The method of claim 76, wherein the first and second access wells are spaced from one another, and the pyrolysis chamber extends from the first access well to the second access well.

78. The method of claim 73, further comprising forming the first access well.

79. The method of claim 78, further comprising forming the second access well.

80. The method of claim 79, further comprising forming the pyrolysis chamber to connect the first access well with the second access well.

81. The method of claim 45, wherein the desired pyrolysis state occurs when the target zone has a reaction temperature in a range of about 600°C to about 1200°C.

82. The method of claim 45, wherein the desired pyrolysis state occurs when the target zone has a reaction temperature in a range of about 600°C to about 800°C.

83. The method of claim 45, wherein the product gas comprises from about 1% to about 10% by mole carbon dioxide.

84. The method of claim 45, wherein the product gas comprises from about 1% to about 10% by mole carbon monoxide.

85. The method of claim 45, wherein the product gas comprises from about 20% to about 30% by mole methane.

86. The method of claim 45, wherein the product gas comprises from about 40% to about 50% by mole hydrogen.

87. The method of claim 45, wherein the product gas comprises a mole ratio of hydrogen to carbon dioxide of about 15:1.

88. The method of claim 45, wherein the laser head has a longitudinal axis, and the heating is performed 360° radially outward relative to the longitudinal axis.

89. A laser-head assembly for gasifying a carbonaceous material that defines a pyrolysis chamber formed therein when the laser head is located in the pyrolysis chamber, the pyrolysis chamber having a first longitudinal axis, the laser-head assembly comprising: a laser head having a length and a second longitudinal axis along the length that is designed to be substantially parallel to the first longitudinal axis of the pyrolysis chamber when the laser-head assembly is present in the pyrolysis chamber, the laser head including: a plurality of laser outputs distributed in a circumferential direction at least partway around the laser head for delivering laser energy to portions of the carbonaceous material.

90. The laser-head assembly of claim 89, wherein the plurality of laser outputs is further distributed along the length of the laser head.

91. The laser-head assembly of claim 89, wherein the plurality of laser outputs are distributed 360° around the laser head.

92. The laser-head assembly of claim 89, further comprising a plurality of sensing elements for sensing one or more conditions of pyrolysis caused by heating the carbonaceous material using the laser outputs.

93. The laser-head assembly of claim 89, further comprising at least one gas-collection port for collecting a product gas formed by gasifying the carbonaceous material.

94. The laser-head assembly of claim 89, further comprising at least one gas-output port for providing at least one gas to the pyrolysis chamber.

95. The laser-head assembly of claim 89, wherein the laser head is flexible along its length and includes means for making the laser head flexible.

96. The laser-head assembly of claim 89, further comprising a laser-head support, wherein the laser head cantilevers from the laser-head support.

97. The laser-head assembly of claim 89, further comprising a stabilizing system for stabilizing the laser head within the pyrolysis chamber.

98. The laser-head assembly of claim 89, further comprising a traction system for moving the laser head within the pyrolysis chamber.

99. The laser-head assembly of claim 89, wherein the laser outputs comprise lensing for outputting laser energy from a fiber-optic cable.

100. The laser-head assembly of claim 89, wherein the laser outputs comprise solid state lasers.

101. A laser-based gasification system tuned and configured for producing a product gas from a mass of carbonaceous material via a pyrolysis chamber within the mass and having walls defined by surrounding portions of the carbonaceous materials, the laser-based gasification system comprising: a laser head having a plurality of laser outputs; one or more lasers for providing the laser energy to the laser outputs of the laser head; and a control system configured to control the laser energy output by the laser outputs so as to pyrolyze the carbonaceous material consistently throughout the pyrolysis chamber so as to produce a desired product gas.

102. The laser-based gasification system of claim 101, where the laser head is a laser head according to any one of claims 89 through 100.

103. A product gas composition produced by a process comprising: inserting a laser head into pyrolysis chamber formed in a mass of carbonaceous material, wherein the pyrolysis chamber is defined by surrounding portions of the carbonaceous material; and when the laser head is located in the pyrolysis chamber, heating the surrounding portions of the carbonaceous material with energy emitted from the laser head so as to produce the product gas composition from the carbonaceous material; wherein the product gas composition so produced comprises from about 1% to about 10% by mole carbon dioxide, from about 1% to about 10% by mole carbon monoxide, from about 20% to about 30% by mole methane, and from about 40% to about 50% by mole hydrogen.

104. The product gas composition of claim 103, having a mole ratio of hydrogen to carbon dioxide of about 15:1.