CA2881763C - System and method for recovering bitumen from a bitumen reserve using electromagnetic heating - Google Patents

Abstract

A system and method are provided for recovering bitumen from a bitumen reserve. The system and method operate to recover a bitumen containing fluid from a pay region in the bitumen reserve via gravity drainage, by heating the bitumen in the pay region using at least one electromagnetic antenna that extends into the pay region from below, from a tunnel excavated into a formation that at least in part underlies the pay region.

Description

SYSTEM AND METHOD FOR RECOVERING BITUMEN FROM A BITUMEN RESERVE
USING ELECTROMAGNETIC HEATING
TECHNICAL FIELD
[0001] The following relates to systems and methods for recovering bitumen from a bitumen reserve using electromagnetic heating.
DESCRIPTION OF THE RELATED ART

[0002] Bitumen is known to be considerably viscous and does not flow like conventional crude oil, and can be present in an oil sand reservoir. As such, bitumen is recovered using what are considered non-conventional methods. For example, bitumen reserves are typically extracted from a geographical area using either surface mining techniques, wherein overburden is removed to access the underlying pay (e.g., oil sand ore-containing bitumen) and transported to an extraction facility; or using in situ techniques, wherein subsurface formations (containing the pay) are heated such that the bitumen is caused to flow into one or more wells drilled into the pay while leaving formation rock in the reservoir in place. Both surface mining and in situ processes produce a bitumen product that is subsequently sent to an upgrading and refining facility, to be refined into one or more petroleum products, such as gasoline and jet fuel.
Bitumen reserves that are too deep to feasibly permit bitumen recovery by mining techniques are typically accessed by drilling wellbores into the hydrocarbon bearing formation (i.e. the pay) and implementing an in situ technology. There are various in situ technologies available, such as steam driven based techniques, e.g., Steam Assisted Gravity Drainage (SAGD), Cyclic Steam Stimulation (CSS), etc. SAGD and CSS typically require horizontally oriented wells that are drilled directionally from surface and production equipment located at a surface site.

[0003] For some bitumen reserves, steam driven techniques can be considered less desirable or less economical.
SUMMARY

[0004] In one aspect, there is provided a method for recovering bitumen from a bitumen reserve. The method comprises recovering a bitumen containing fluid from a pay region in the bitumen reserve via gravity drainage, by heating the bitumen in the pay region using at least one electromagnetic antenna that extends into the pay region from below from a tunnel excavated into a formation that at least in part underlies the pay region.

22681130.1 . .

[0005] In another aspect, there is provided a system for recovering bitumen from a bitumen reserve. The system comprises a tunnel excavated into a formation from ground level that at least in part underlies a pay region in the bitumen reserve, at least one electromagnetic (EM) antenna extending into the pay region from the tunnel below the pay region, at least one EM
transmitter for powering the at least one EM antenna, and at least one production apparatus configured to recover a bitumen containing fluid from the pay region via gravity drainage.

[0006] In yet another aspect, the tunnel extends from the formation to surface and is sized to accommodate equipment configured to drill a well bore into which the at least one electromagnetic antenna is positioned.

[0007] In yet another aspect, the tunnel extends from the formation to surface and is sized to accommodate equipment configured to drill a well bore into which a producer well extending into the pay region near the at least one electromagnetic antenna is positioned.

[0008] In yet another aspect, the tunnel extends from the formation to surface and is sized to accommodate equipment configured to drill a well bore into which a solvent injector is positioned.
BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Embodiments will now be described by way of example only with reference to the appended drawings wherein:

[0010] FIG. 1(a) is a cross-sectional elevation view of an electromagnetic (EM) in situ gravity drainage system deployed in a tunnel below a bitumen reservoir with a producer well drilled into the bitumen reservoir;

[0011] FIG. 1(b) is a cross-sectional elevation view of an EM in situ gravity drainage system deployed in a tunnel below a bitumen reservoir with a producer well installed in the tunnel;

[0012] FIG. 1(c) is a cross-sectional elevation view of an EM in situ gravity drainage system deployed in a tunnel below a bitumen reservoir with producer wells used in both the bitumen reserve and the tunnel;

[0013] FIG. 1(d) is a cross-sectional elevation view of an EM in situ gravity drainage system deployed in a tunnel below a bitumen reservoir and having additional solvent injection wells;

22681130.1 ,

[0014] FIG. 2(a) is a cross-sectional end view of a tunnel with a substantially vertically oriented EM antenna;
[0016] FIG. 2(b) is a cross-sectional end view of a tunnel with multiple EM antennas drilled from below at different angles with respect to vertical;
[0016] FIG. 3(a) is a cross-sectional elevation view of a horizontally oriented tunnel;
[0017] FIG. 3(b) is a cross-sectional elevation view of a tunnel configured to follow a contour defined by the interface between a bitumen reservoir and an underlying formation into which the tunnel is excavated;
[0018] FIG. 3(c) is a cross-sectional elevation view of a sinkhole in the pay targeted by EM
antennas extending from a tunnel below the sinkhole;
[0019] FIG. 4(a) is a schematic plan view of a network of tunnels for deploying an EM in situ gravity drainage system below a bitumen reservoir;
[0020] FIG. 4(b) is another schematic plan view of a network of tunnels for deploying an EM in situ gravity drainage system below a bitumen reservoir;
[0021] FIG. 4(c) is yet another schematic plan view of a network of tunnels for deploying an EM in situ gravity drainage system below a bitumen reservoir;
[0022] FIG. 4(d) is yet another schematic plan view of a network of tunnels for deploying an EM in situ gravity drainage system below a bitumen reservoir;
[0023] FIG. 5(a) is a cross-sectional elevation view of an access tunnel for an EM in situ gravity drainage system deployed in a tunnel below a bitumen reservoir;
[0024] FIG. 5(b) is a cross-sectional elevation view of an access shaft for an EM in situ gravity drainage system deployed in a tunnel below a bitumen reservoir;
[0025] FIG. 5(c) is a cross-sectional elevation view of an EM in situ gravity drainage system deployed in a tunnel below a bitumen reservoir, wherein the tunnel is accessed from a naturally occurring outcrop or a surface mine;
[0026] FIG. 6 is an enlarged cross-sectional elevation view of an EM
antenna and a dedicated EM transmitter;
[0027] FIG. 7 is an enlarged cross-sectional elevation view of portion of an array of EM
antennas powered by a shared EM transmitter;

22681130.1 [0028] FIG. 8 is a schematic illustration of a phased array wavefront generated using an array of EM antennas;
[0029] FIG. 9 is a schematic diagram of an array of EM antennas deployed in multiple tunnels;
[0030] FIG. 10 is a flowchart illustrating operations performed in controlling a distributed array of EM antennas;
[0031] FIG. 11(a) is an enlarged cross-sectional view illustrating gravity drainage through an antenna well into a tunnel-deployed collector;
[0032] FIG. 11(b) is an enlarged cross-sectional view illustrating an antenna well configured to support both an EM antenna and solvent injection apparatus;
[0033] FIG. 12(a) is a cross-sectional elevation view illustrating an implementation for a producer well drilled from surface; and [0034] FIG. 12(b) is a cross-sectional elevation view illustrating another implementation for a producer well drilled from surface.
DETAILED DESCRIPTION
[0035] In the following, there is provided a system and method of recovering bitumen from a bitumen reserve. The system and method operate to recover a bitumen containing fluid from a pay region in the bitumen reserve via gravity drainage, by heating the bitumen in the pay region using at least one electromagnetic antenna that extends into the pay region from below, from a tunnel excavated into a formation that at least in part underlies the pay region.
[0036] In an implementation of the system and method, the electromagnetic antennas can be operated to produce radio frequency (RF) signals that penetrate the pay region to heat the bitumen. Solvent can also be injected subsequent to heating the pay region using such RF
signals. In at least some implementations, the bitumen containing fluid is recovered using a producer well drilled into the pay region near the at least one electromagnetic antenna, wherein the producer well configured to produce the bitumen containing fluid to surface. The bitumen containing fluid can also (or alternatively) be recovered using other production apparatus, such as a collector located in the tunnel, the collector being fluidly connected to the pay region.

22681130.1 [0037] Each electromagnetic antenna can be powered by a dedicated electromagnetic transmitter, or an array having a plurality of electromagnetic antennas are powered by a common electromagnetic transmitter.
[0038] In at least some implementations the tunnel is part of a network of tunnels. Such a network of tunnels can be implemented in various configurations as will be explained in greater detail below.
[0039] The use of electromagnetic heating (such as RF heating) rather than conductive electrical heating avoids the creation of a temperature gradient away from the heat source, while reducing the temperature required at the source to generate enough heat at further distances from the heat source. The use of electromagnetic heating can be advantageously combined with solvent injection to reduce or eliminate the need to heat the solvent prior to injection in order to mobilize the bitumen at lower temperatures than alternative in situ bitumen recovery techniques such as steam-based SAGD and CSS. Moreover, by having electromagnetic antennas extending into the pay from below via one or more tunnels, the footprint required at surface can be reduced, when compared to drilling into the pay from above.
Also, abandonment of the tunnels post-production requires only backfilling of the tunnels. The equipment used for bitumen recovery, including the antennas, transmitters, etc. are located away from inclement weather thus reducing maintenance costs and disruptions due to such weather.
[0040] Turning now to the figures, FIG. 1(a) illustrates a bitumen reserve, hereinafter referred to as the "pay 10"; which is accessed for in situ bitumen recovery using a tunnel 12 excavated into a formation that at least partially underlies the pay 10, hereinafter referred to as the "underlying formation 14". In the example shown in FIG. 1(a), the pay 10 itself underlies a layer of overburden 16 between the pay 10 and the surface 18.
[0041] The tunnel 12 facilitates the installation of a series of EM
antennas 20 by drilling antenna wells 21 into the pay 10, from the tunnel 12, which is below the pay 10. The EM
antennas 20 are powered in order to emit EM signals 22 into the pay 10 to increase the temperature of bitumen 24 in the pay 10 and thereby decrease the viscosity of the bitumen and/or to stimulate the bitumen for a solvent injection process. The bitumen is therefore mobilized at least in part by the EM signals 22, causing a bitumen containing fluid 24 to flow under the influence of gravity towards the tunnel 14.

22681130.1 . .
[0042] In EM heating, one or more antennas 20 are inserted into the bitumen reserve, and a power transmitter 40, 50 (see also FIGS. 6 and 7) is used to power the antennas 20, which induces an EM field through the pay 10. The absorbed EM energy heats the water and oil/bitumen within the pay 10, thereby resulting in flow of the hydrocarbon material. A producer well 26 is then used to withdraw the mobilized as outlined above.
[0043] EM heating uses one or more of three energy forms: electric currents, electric fields, and magnetic fields at radio frequencies (i.e. RF energy). Depending on operating parameters, the heating mechanism can be resistive by Joule effect or dielectric by molecular moment.
Resistive heating by Joule effect is often described as electric heating, where electric current flows through a resistive material, and dielectric heating occurs where polar molecules, such as water, change orientation when immersed in an electric field as is known in the art. Magnetic fields also heat electrically conductive materials through the formation of eddy currents, which in turn heat resistively. Thus magnetic fields can provide resistive heating without conductive electrode contact.
[0044] EM heating can use electrically conductive antennas 20 to function as heating applicators, e.g., dipole antennas. The antenna 20 is a passive device that converts applied electrical current into oscillating electromagnetic fields, and electrical currents in the target material, without having to heat the structure to a specific threshold level.
[0045] Antennas 20, including antennas 20 for EM heat application as described herein, can provide multiple field zones which are determined by the radius from the antenna r and the electrical wavelength A (lambda). Susceptors are materials that heat in the presence of RF
energies. Salt water is a particularly good susceptor for EM heating; it can respond to all three RF energies: electric currents, electric fields, and magnetic fields. Oil sands and heavy oil formations commonly contain connate liquid water and salt in sufficient quantities to serve as an EM heating susceptor. "connate" refers to liquid trapped in the pores of the oil sand formation.
[0046] As bitumen becomes mobile at or below the boiling point of water at reservoir conditions, liquid water may be a used as an EM heating susceptor during bitumen extraction, permitting well stimulation by the application of RF energy. In general, EM
heating has superior penetration and heating rate compared to conductive heating in hydrocarbon formations. EM
heating can also have properties of thermal regulation because steam is not an EM heating susceptor. In other words, once the water is heated sufficiently to vaporize, it is no longer 22681130.1 electrically conductive and is not further heated to any substantial degree by continued application of electrical energy.
[0047] In one implementation, a horizontally drilled producer well 26 recovers the bitumen containing fluid 24, which can be pumped or otherwise transported to surface for subsequent processing, e.g., using a pump 27 as shown in FIG. 1(a). The horizontally drilled producer well 26 can be inclined in order to have enough of a slope to allow bitumen to drain towards the pump 27.
[0048] As illustrated in FIG. 1(b), the mobilized bitumen containing fluid 24 can also be collected within the tunnel 12 using a pipe or other collection mechanism, hereinafter referred to as a "collector 28". The collector 28 is installed in the tunnel 12 and configured to permit the bitumen containing fluid 24 to be recovered through the base portion of the antenna wells 100 as discussed in greater detail below.
[0049] It can be appreciated that the bitumen containing fluid 24 can also be recovered using both an inclined horizontally drilled producer well 26 and a collector 28 located in the tunnel 12, as illustrated in FIG. 1(c). As such, the bitumen containing fluid 24 can be recovered and produced to surface 18 using one or more "production apparatuses", which can include one or more producer wells 26, one or more collectors 28, or both. It can also be appreciated that other types of production apparatus are possible, e.g., any well or passage providing fluid communication with the pay 10 to permit gravity drainage into the production apparatus.
[0050] In addition to using EM signals 22 to mobilize the bitumen, solvent can also be injected into the pay 10, e.g., subsequent to applying EM heating, similar to the Enhanced Solvent Extraction Incorporating Electromagnetic Heating (ESEIEH) advance oil recovery technique, described in U.S. Patent No. 8,616,273. Solvent can be used to mobile the bitumen at lower temperatures than, for example, steam-based heating techniques.
[0051] In the ESEIEH process, RF heating can be used to heat the pay 10 prior to solvent injection. When the pay 10 reaches the desired temperature within a desired region, an appropriate solvent is then injected into the pay 10. The solvent partially mixes with the bitumen and further reduces its viscosity and partially displaces the hot-diluted bitumen towards the producer well 26. The choice of solvent can be similar to existing solvent injection processes.
The RE-induced heating (or other EM heating) initially heats connate water and bitumen near the RE antennas 20. Water and the heated bitumen drain to the producer well 26 creating a flow 22681130.1 pathway. The flow pathway thus created is then used as the primary conduit to inject a solvent from an appropriate well (e.g., the antenna well 21, a separate injector well 29 (see FIG. 1(d)), or both).
[0052] The RF heating is applied so as to maintain the reservoir temperature at a level that is sufficient to allow efficient application of a solvent extraction process.
For example, the reservoir can be maintained at a temperature of 40-70 C. The temperature can be maintained at least in the vicinity of the injected solvent, which dissolves the partially heated bitumen. The solvent/bitumen mixture then drains towards the producer well 26.
[0053] In the solvent injection phase, a solvent vapor comes into contact with bitumen and through diffusion it creates a mobile, dilute bitumen stream which in turn drains towards a producer well 26 via gravity drainage. However, directional RF-induced EM
heating (e.g., as described herein and shown by way of example in FIG. 8) can be used to provide the initial energy to quickly and efficiently heat the bitumen, reducing viscosity by several orders of magnitude while simultaneously increasing the solvent diffusion within the bitumen, while the solvent mixing provides additional oil viscosity reduction to generate threshold and higher commercial rates. Alkanes such as ethane, propane, butane, pentane, etc., or any mixture of these alkanes can be used. Other suitable solvents include, without limitation: naphtha, toluene, xylene, benzene, diesel, natural gas, etc.
[0054] In any of the configurations shown in FIGS. 1(a) to 1(c), the antenna wells 21 can be configured to incorporate solvent injectors 29 (see also FIG. 11(b)). In other implementations, one or more solvent injectors 29 can also be drilled into separate wells located anywhere in the pay 10, as shown in FIG. 1(d).
[0055] The EM antennas 20 are drilled into the pay 10 from below, via access provided by the tunnel 12. The EM antennas 20 can be substantially vertically oriented as shown in FIG.
2(a), or can be drilled at an angle to vertical as shown in FIG. 2(b). Such angled EM antennas 20 can be used to target particular portions of the pay 10, to avoid geological obstructions, etc.
[0056] The EM antennas 20 can be configured to transmit various types of EM
signals 22, for example, electric currents, electric fields, and magnetic fields at radio frequencies or microwave frequencies. The type of EM signals 22 used can affect the number of, and spacing between the EM antennas 20. That is, the depth of penetration of the particular EM signals 22 can require greater or fewer EM antennas 20 to target a bitumen reserve of a particular size.

22681130.1 , The following examples illustrate the use of RF antennas 20 and RF signals 22, however, it can be appreciated that the principles described herein can be implemented using other types of EM
antennas 20 and EM signals 22.
[0057] When a producer well 26 is used, after determining the access location for the producer well 26 (or producer wells 26 for multiple tunnels 12), and determining where the one or more producer wells 26 will be located relative to the RF antennas 20 (e.g., by conducting typical computer simulations using geological and reservoir data), the corresponding access locations are prepared for drilling, including providing infrastructure for water and electricity, as is known in the art. A drilling rig is then installed at the location of the producer well 26 (e.g., inside the tunnel 12 when the producer well 26 begins in the tunnel 12 as shown in FIGS. 1(a), 1(c), 1(d), 5(a), 5(b), and 5(c)) and drilling commences subject to requisite inspections. The drilling phase includes steps of drilling, then running and cementing new casing, which are repeated until the drill bit reaches the desired well length by adding new drill pipe as the well lengthens. The access location is also prepared for pumping drilling fluid through the interior of the drill pipe, which circulates through the drill bit, and returns via the annulus between the pipe and the borehole to be cleaned (i.e. processed to remove drilled particles) and cleaned fluid pumped back down the drill pipe. It can be appreciated that measurement while drilling (MWD) technologies and bends can be utilized to steer the bit and the producer wells 26 in a particular direction. When the drilling is completed and deemed to be ready for production, casing is installed, which extends from the entry of the borehole to the end of the wells 26 and is cemented in place. Alternatively, the pay section of the well can be lined with a slotted liner or other form of sand control that is not cemented into place. The liner can also utilize packers and inflow or injection control devices (ICDs) that divide the producer wells 26 into segments. The drilling rig can then be moved and used to drill the next well 26 at the same or a different access location.
[0058] Drilling equipment is used to drill the producer wells 26. After drilling the wells 26, the pump 27 or production equipment 110 (see FIGS. 9(a) and 9(b)) is installed in one or more production facilities for recovering bitumen. Completing a particular well for production can involve several steps, as is known in the art. For example, a service rig is moved into location and used to perform a cleanout trip to the total length of the well to ensure that there is no cement or debris left inside the production casing. Alternatively, the well can be completed by the drilling rig after the production casing cement has hardened. To allow mobilized bitumen 22681130.1 containing fluid 24 to flow into the producer well 26, perforating is performed to create holes through the casing and cement, which can be performed before or after production tubing is installed in the wells 26. Alternatively, the pay section of the well can be lined with a slotted liner or other form of sand control that is not cemented in place. The liner can utilize packers and inflow or ICDs that divide the injector or production wells into segments.
The production tubing is then installed using the service rig. In addition to production tubing, the operator may install downhole instrumentation that can include temperature sensors, pressure sensors or fiber optic cable. Once the tubing has been landed, a wellhead is installed over the production casing.
[0059] The antenna wells 21 can be drilled in a similar manner, particularly when bitumen containing fluid 24 is to be recovered using a collector 28. It can be appreciated that other drilling techniques can also be used, for example, rock bolt installation methods employed in the mining industry.
[0060] The tunnel 12 can be excavated using earth boring equipment, drilling equipment, or any other suitable excavation equipment. For example, conventional tunnel boring equipment used in the mining and construction industries is suitable for excavating the tunnels 12. As shown in FIG. 3(a), the tunnel 12 can be excavated to be substantially level and horizontal with relatively longer or shorter antennas 20 used depending on the distance between the tunnel 12 and the pay 10. The tunnels 12 can also be excavated in order to, at least in part, follow a contour defined by the interface between the pay 10 and the underlying formation 14, as shown in FIG. 3(b). In this way, gaps between the tunnel 12 and the pay 10 can be shortened in at least some areas along the tunnel 12. The tunnel 12 is therefore, in general, horizontally oriented although portions of the tunnel 12 can include an incline or slope.
[0061] Referring to FIG. 3(c), it can be appreciated that since the RE
antennas 20 are drilled into the pay 10 from below, sinkholes 29 or other dips in the formation 14 (e.g., Karst hole) containing recoverable bitumen can be more easily accessed when compared to other in situ techniques such as SAGD where the producer wells are drilled from surface and generally extend horizontally above the interface between the pay 10 and the underlying formation 14, which may leave pay 10 stranded within the sinkhole or dip. In the present example, RE
antennas 20 drilled into the sinkhole 29 can mobilize the bitumen and recover bitumen containing fluid 24 from that area of the pay 10, via gravity drainage.

22681130.1 . .
[0062] The RF antennas 20 can be deployed in multiple tunnels 12, creating a network 30 of RF antennas 20. There are numerous implementations for the network of tunnels 30, several of which are illustrated in FIGS. 4(a) through 4(d).
[0063] Referring to FIG. 4(a), a particularly convenient configuration for the network of tunnels 30 when using conventional boring equipment is shown. In the implementation shown in FIG. 4(a), a continuous tunnel 12 is excavated downwardly at an incline into the underlying formation 14 and extending into the underlying formation 14 in a serpentine pattern. The tunnel 12 can then be excavated upwardly back to surface 12 to provide egress, e.g., to meet safety requirements.
[0064] FIG. 4(a) illustrates an example of a tunnel network 30 configured in a serpentine pattern using a continuous tunnel 12. The tunnel 12 includes a first tunnel segment 12a, a second tunnel segment 12b, a third tunnel segment 12c, a fourth tunnel segment 12d, and a fifth tunnel segment 12e, which are connected to each other using a first bend 36a between the first and second tunnel segments 12a, 12b; a second bend 36b between the second and third tunnel segments 12b, 12c; a third bend 36c between the third and fourth tunnel segments 12c, 12d; and a fourth bend 36d between the fourth and fifth tunnel segments 12d, 12e.
[0065] In the implementation shown in FIG. 4(a), an ingress surface access location 32a connects the tunnel network 30 to surface 18 via an entry tunnel 34. Also, an egress surface access location 32b connects the tunnel network 30 to surface 18 via an exit tunnel 35. The entry and exit tunnels 34, 35 can be configured in various ways. For example, one or more of the entry and exit tunnels 34, 35 can be an inclined or sloped tunnel extending from the surface access location 32a, 32b down to particular segments of the tunnel network 30.
The surface access locations 32 and entry and exit tunnels 34, 35 can be sized to permit machinery to be transported and/or driven down into and/or out of the tunnel network 30, e.g., to facilitate installation, operation, and maintenance of the RF antennas 20 (only one antenna 20 being labeled in FIG. 4(a) for ease of illustration), and to permit personnel to enter and exit the tunnel network 30.
[0066] Various other tunnel network implementations are possible.
For example, as shown in FIG. 4(b), a grid-like pattern can be employed for the tunnel network 30 in which the tunnel segments 12a-12e are connected at both ends by access tunnels 38a, 38b rather than bends 36 between adjacent segments. As illustrated in FIG. 4(b), the ingress and egress surface access locations 32a, 32b can be located in any desired position relative to the tunnel network 22681130.1 , , 30 such that the entry and exit tunnels 34a, 34b provide a connection between the tunnel network 30 and surface 18.
[0067] Another implementation is shown in FIG. 4(c), wherein a single access tunnel 38 in the underlying formation 14 is used to provide access to the tunnel segments 12a-12e, such that the tunnel segments 12a-12e are effectively individual tunnels extending from the access tunnel 36. In yet another implementation shown in FIG. 4(d), a discontinuous tunnel network 30 is created, in which multiple individual tunnels 12 are configured to have dedicated ingress and egress surface access locations 32a, 32b and corresponding entry and exit tunnels 34, 35; and a multi-segment continuous sub-network is provided using a first tunnel segment 12a and a second tunnel segment 12b connected by a bend 36. It can be appreciated that the example shown in FIG. 4(d) illustrates that any combination of tunnel patterns and configurations are possible within the principles discussed herein, and can therefore accommodate various surface access and underground constraints.
[0068] It can be appreciated that the number of tunnels (and/or tunnel segments) 12 and the particular implementations shown in FIGS. 4(a) to 4(d) are illustrative only and various other configurations are possible to accommodate different applications and/or locations. For example, a single ingress surface access location 32a and a single egress surface access location 32b can be used along with at least one access tunnel 38 or bend 36 (connecting the tunnels 12 or tunnel segments 12a, 12b, etc.) to minimize the surface footprint, whereas multiple ingress surface access locations 32a and/or multiple egress surface access locations 32b can also be used to accommodate other constraints such as geological or surface space constraints.
[0069] The ingress and egress surface access locations 32a, 32b and entry and exit tunnels 34, 35, can be configured in various ways in order to provide access to the tunnel network 30 from surface 18. For example, as shown in FIG. 5(a), an inclined or sloped entry tunnel 34 can be created by boring downwardly with a gradual slope towards the underlying formation 14 at which point the horizontally oriented tunnel 12 (or tunnel segment) commences.
By providing a gradual sloped entry tunnel 34 as shown in FIG. 5(a), machinery, equipment, vehicles, and personnel can drive or be driven into and out of the tunnel network 30. The mobilized bitumen containing fluid 24 recovered by the producer well 26 can also be pumped out through the entry tunnel 34 to surface by installing a pump 27 and outlet pipes 39 to 22681130.1 transport the bitumen containing fluid 24 to surface 18. It can be appreciated that a similar configuration can be used with the egress surface access location 32b and exit tunnel 35.
[0070] FIG. 5(b) illustrates another implementation for providing an entry tunnel 34 and ingress surface access location 32a, wherein the entry tunnel 34 is provided using a vertically drilled shaft, similar to a mine shaft. The vertically drilled shaft can be equipped with a lift or other elevation equipment to enable drilling equipment such as a drilling rig to be transported below surface. As illustrated in FIG. 5(b), the bitumen containing fluid 24 recovered by the producer well 26 can be transported to surface 18 via the entry tunnel 34.
[0071] FIG. 5(c) illustrates yet another implementation for providing access to a tunnel network 30. In the example configuration shown in FIG. 5(c), a tunnel 12 is excavated into the underlying formation 14 from a naturally occurring outcrop or other exposure of the underlying formation 14 such as from a surface mine. In the implementation illustrated in FIG. 5(c), the outlet pipes 39 from the pump 27 can be configured to extend towards the outcrop or other exposure in order to be transported for subsequent processing. Likewise, the surface access location 32a in this example is located along a bank of the outcrop or other exposure and extends directly into the underlying formation 14.
[0072] The RF antennas 20 can be powered using various configurations. FIG.

illustrates one configuration in which an RF antenna 20 is powered by a dedicated RF
transmitter 40 located in the tunnel 12 near the RF antenna 20 which it is powering. The RF
transmitter 40 is configured to operate a single RF antenna 20 at a particular frequency.
[0073] The particular frequency applied can vary depending on the conductivity of the media within a particular hydrocarbon formation, however, signals with frequencies between about 0 to 500 Hz and including direct current (DC) are contemplated to heat a typical formation through electric currents in at least one implementation.
[0074] A frequency signal is applied to the RF antennas 20, which is sufficient to heat the hydrocarbon formation through electric fields, magnetic fields, or both. It can be appreciated that once the water near the applicator is nearly or completely desiccated, applying a different frequency signal can provide more efficient penetration of heat the formation.
The frequencies necessary to produce heating through electric fields varies depending on a number of factors, such as the dielectric permittivity of the hydrocarbon formation, however, frequencies between 22681130.1 . .
about 30 MHz and about 24 GHz are contemplated to heat a typical hydrocarbon formation through electric fields in another implementation.
[0075] The frequencies to produce heating through magnetic fields can vary depending on a number of factors, such as the conductivity of the hydrocarbon formation, however, frequencies between about 500 Hz and about 1 MHz are contemplated to heat a typical hydrocarbon formation through magnetic fields in another implementation.
Relatively lower frequencies (e.g., lower than about 1 kHz) can provide greater heat penetration while the relatively higher frequencies (e.g., higher than about 1 kHz) can allow higher power application as the load resistance increases. The optimal frequency can relate to the electrical conductivity of the formation, thus the frequency ranges provided are listed as examples and can be different for different formations. The formation penetration is related to the radio frequency skin depth at radio frequencies. For example, signals greater than about 500 Hz are contemplated to heat a hydrocarbon formation through electric fields, magnetic fields, or both. Thus, by changing the frequency, the formation can be further heated without conductive electrical contact with the hydrocarbon formation.
[0076] At some frequencies, the hydrocarbon formation can be simultaneously heated by a combination of types of RF energy. For example, the hydrocarbon formation can be simultaneously heated using a combination of electric currents and electric fields, electric fields and magnetic fields, electric currents and magnetic fields, or electric currents, electric fields, and magnetic fields. A change in frequency can also provide additional benefits as the heating pattern can be varied to more efficiently heat a particular formation. For example, the signal applied can be configured to provide enhanced heating along the boundary conditions between the pay 10 and the overburden 16 and underlying formation 14, and this can increase convection in the pay 18. As the desiccated zone expands, the electromagnetic heating achieves deeper penetration within the reservoir. The frequency can be adjusted to optimize RF
penetration depth and the power is selected to establish the desired size of the desiccated zone and thus establish the region of heating within the pay 10. Such considerations can be factored in when determining the number and spacing of the RF antennas 20 and the tunnel pattern within a tunnel network 30.
[0077] In another configuration shown in FIG. 7, a relatively higher power RF transmitter 50 is used to power a distributed array of a plurality of RF antennas 20. In the example shown in FIG. 7, a first RF antenna 20a, a second RF antenna 20b and so forth are powered by the 22681130.1 single RF transmitter 50, which is configured to operate the multiple RF
antennas 20 in the array. It can be appreciated that an array of antennas 20 powered by a single RF transmitter 50 can be located in the same tunnel 12 or be distributed within multiple tunnels 12 of the tunnel network 30.
[0078] An array of RF antennas 20 can be operated as a phased array as shown in FIG. 8, wherein each of the RF antennas 20a-20e is pulsed separately. As is known in the art, a phased array is an array of antennas in which the relative phases of the respective signals powering the antennas are varied in such a way that the effective radiation pattern of the array is compounded in a desired direction and suppressed in undesired directions.
As such, a distributed array of RF antennas 20 used in the tunnel network 30 can be controlled to direct the EM signals 22 towards or away from particular portions of the pay 10.
Beamforming can be implemented for directional signal transmission using either time domain beamformers in which time delays are used, or frequency domain beamformers in which multiple frequency bins or spatial frequencies are used.
[0079] As shown in FIG. 8, the rightmost RF antenna 20e is pulsed first, and emits an energy wave 22e that begins to spread first. Accordingly, the next RF antenna 20d to be pulsed emits an energy wave 22d that is smaller than the first energy wave 22e due to the delay between pulses. The process continues for the other RF antennas 20c, 20b, and 20a until all elements have been pulsed. The multiple EM energy waves 22a-22e add up to a single wave front 52 travelling at a particular angle. That is, the beam angle can be controlled by controlling the pulse timings of the RF transmitter 50 applied to the individual RF
antennas 20a-20e.
[0080] It can be appreciated that the RF antennas 20 can also be configured to receive RF
signals. For example, EM signals 22 emitted from one RF antenna 20 can be detected using another RF antenna 20 to perform diagnostic checks and/or optimizations on the control of an array of RF antennas 20. In an implementation, array tuning can also be performed, wherein the performance of an RF signal in a particular portion of the pay 10 can be detected in order to perform modifications to the array control scheme being employed, e.g., to perform beamforming as shown in FIG. 8 in order to avoid geological obstacles, or to adjust the power or frequency to achieve better performance in that area of the pay 10.
[0081] FIG. 9 illustrates an example of an electrical schematic diagram for powering an array of RF antennas 20. The RF antennas 20 in this example are dipole RF
antennas 20 and the array of RF antennas 20 are distributed in a first tunnel 12a and a second tunnel 12b.

- 15 22681130.1 [0082] The first tunnel 12a includes a first RF transmitter 50a that powers a plurality of RF
antennas 20 over a first power line 60a, using a series of one or more splitters 62. In this example implementation, the first RF transmitter 50a and each RF antenna 20 in the first tunnel 12a can be selectively controlled (i.e. turned "ON" or "OFF" or pulsed) using a first controller 64a, via a series of switches 66 controlled using a first control line 68a. In this way, while the first RF transmitter 50a operates to generate RF signals to provide RF signals 22 into the pay via the RF antennas 20, the first controller 64a can selectively target different areas of the pay 10 by turning ON or OFF selected ones of the RF antennas 20 using the respective switches 66 or by pulsing the RF antennas 20 as shown in FIG. 8 to direct the wave front 52 in a particular direction.
[0083] The second tunnel 12b similarly includes a second RF transmitter 50b that powers a plurality of RF antennas 20 in the second tunnel 12b over a second power line 60b, using a series of one or more splitters 62. The second RF transmitter 50b and each RF
antenna 20 in the second tunnel 12b is also selectively controlled using a second controller 64b, via a series of switches 66 controlled using a second control line 68b. It can be appreciated that, as illustrated using dashed lines in FIG. 9, a single controller 64 and a single RF
transmitter 50 can also be configured to control RF antennas 20 in both the first tunnel 12a and second tunnel 12b by way of inter-tunnel power and control lines, collectively identified using numeral 70. As such, the provision of separate transmitters 50 and controllers 64 is illustrative only and various configurations are possible. For example, due to space and/or distance related constraints, some tunnels 12 can be operated using dedicated RF transmitters 40 with other tunnels 12 being wholly or at least in part being operated using shared or common RF
transmitters 50 and/or controllers 64 located in outside of that tunnel 12. The control lines 68 and other communication connections shown in FIG. 9 can be implemented using wired, wireless or a combination of wired and wireless technologies. Also, the control lines 68 can also be used to operate one or more of the RF antennas 20 as a receiver antenna, wherein the controllers 64 can analyze and, if necessary, optimize further control of the array of RF
antennas 20.
[0084] FIG. 10 illustrates an example of a set of operations that are performed in controlling an array of RF antennas 20. At step 70 the controller 64 controls operation of at least one RF transmitter 50, e.g., by providing operating parameters such as power level, frequency, etc. At step 72 the controller 64 determines a control instruction, e.g., by receiving an input from a surface computer or operator in the tunnel 12 to selectively control at least one

- 16 22681130.1 RF antenna 20 (e.g., to turn OFF at least one RF antenna 20 in a particular location, to pulse a number of RF antennas 20 according to a beamforming scheme, etc.). At step 74 the controller 64 controls operation of at least one RF antenna 20 by operating the corresponding switch(es) 66. The process shown in FIG. 10 can repeat during operation of the array of RF antenna 20 until new instructions are determined. Also, as shown in dashed lines in FIG.
10, solvent can be injected at step 76 after at least some RF heating occurs and the solvent injection process at step 76 can occur in parallel, e.g., when different segments of the pay 10 are targeted separately. Another optional step is shown in FIG. 10, namely step 78, which uses an RF
antenna 20 as a receiver. As illustrated in FIG. 10, an RF antenna 20 which is operated by an RF transmitter 40, 50, can initiate steps of detecting and receiving signals on another of the RF
antennas 20. For example, after powering an RF antenna 20, adjacent RF
antennas 20 can be monitored for received signals in order to analyze the performance of the sending RF antenna 20.
[0085] As illustrated in FIGS. 1(b) and 1(c), the tunnel 14 can be configured to include a collector 28 for recovering bitumen containing fluid 24 via antenna wells 21.
FIG. 11(a) illustrates an antenna well 21 containing an RF antenna 20. The antenna well 21 is configured to allow bitumen containing fluid 24 to penetrate the wall thereof (e.g., via perforations) and allow the bitumen containing fluid 24 to drain into a collection area 80 under the influence of gravity and then into the collector 28 by way of fluid communication between the antenna well 21 and the collector 28. Similar to the producer well 26, the contents that drain into the collector 28 can be pumped to surface 18 for subsequent processing. In this way, mobilized bitumen containing fluid 24 near the RF antennas 20 is more easily recovered when it is mobilized such that it flows towards and into the antenna well 20. The RF transmitter 40, 50 is not shown in FIG. 11(a) for ease of illustration and can be located at or near the RF
antenna 20 or at some distance depending on whether a dedicated transmitter 40 or an array-powering RF transmitter 50 is configured for powering the particular RF antenna 20 which is shown.
[0086] FIG. 11(b) illustrates another implementation in which the antenna well 21 is sized and configured to include both an RF antenna 20 and a solvent injector 29, that is, rather than requiring a separate well to be drilled for the solvent injector 29.
Accordingly, in the implementation shown, both an EM transmitter 40, 50 and solvent injection equipment 90 are configured to be connected to the RF antenna 20 and solvent injector 29 respectively. As shown in FIG. 11(b), the solvent injector 29 is configured to inject solvent 92 through the

- 17 22681130.1 . .
antenna well 21 and into the pay 10 to further mobilize the bitumen in the pay 10, e.g., subsequent to stimulation via RF heating.
[0087] The producer well 26 can be drilled up into the pay 10 from the tunnel 12 with the production equipment 110 located within the tunnel 12 as shown in the examples described above. It can be appreciated that in order to accommodate drilling equipment such as a drilling rig, the tunnels 12 are sized accordingly. For example, it has been found that a tunnel with a height (and/or diameter) of about 10 feet to about 14 feet is suitable, although other sizes are possible according to the size of the equipment being used in the tunnel 12.
In such a configuration, the producer well 26 can be slightly inclined in order to facilitate a gravity drainage towards the pump 27. Also, the pump 27 can also be configured to direct produced bitumen containing fluid 24 into an outlet pipe 39 that is arranged to pump the produced bitumen containing fluid 24 to surface 18.
[0088] In other implementations, the producer well 26 can be provided in various different ways other than being drilled from within the tunnel 12. For example, as shown in FIG. 12(a), a SAGD-like producer well 26 can be drilled from surface down into the pay 10 to extend along the bottom of the pay 10 above the underlying formation 14 and tunnel 12. In this example, production equipment 100 is located at surface 18, similar to a SAGD or CSS
operation, and the producer well 26 that extends generally in the same direction as the tunnel 12 such that the production equipment 100 is located near the ingress surface access location 32a to minimize the footprint at surface. It can be appreciated that, as shown in FIG. 12(b), the producer well 26 can also be drilled in a direction which is generally opposite to the tunnel 12, e.g., due to space or location constraints imposed at surface 18.
[0089] It will be appreciated that any module or component exemplified herein that executes instructions can include or otherwise have access to computer readable media such as storage media, computer storage media, or data storage devices (removable and/or non-removable) such as, for example, magnetic disks, optical disks, or tape.
Computer storage media can include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Examples of computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired

-18 22681130.1 information and which can be accessed by an application, module, or both. Any such computer storage media can be part of the controller 64, RE transmitters 40, 50, or any component of or related thereto, or accessible or connectable thereto. Any application or module herein described can be implemented using computer readable/executable instructions that can be stored or otherwise held by such computer readable media.
[0090] For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.
In addition, numerous specific details are set forth in order to provide a thorough understanding of the examples described herein. However, it will be understood by those of ordinary skill in the art that the examples described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the examples described herein. Also, the description is not to be considered as limiting the scope of the examples described herein.
[0091] The examples and corresponding diagrams used herein are for illustrative purposes only. Different configurations and terminology can be used without departing from the principles expressed herein. For instance, components and modules can be added, deleted, modified, or arranged with differing connections without departing from these principles.
[0092] The steps or operations in the flow charts and diagrams described herein are just for example. There may be many variations to these steps or operations without departing from the principles discussed above. For instance, the steps may be performed in a differing order, or steps may be added, deleted, or modified.
[0093] Although the above principles have been described with reference to certain specific examples, various modifications thereof will be apparent to those skilled in the art as outlined in the appended claims.

- 19 22681130.1

Claims (50)

Claims:

1. A method for recovering bitumen from a bitumen reserve, the method comprising:
recovering a bitumen containing fluid from a pay region in the bitumen reserve via gravity drainage, by heating the bitumen in the pay region using at least one electromagnetic antenna that extends into the pay region from below from a tunnel excavated into a formation that at least in part underlies the pay region.

2. The method of claim 1, wherein the tunnel extends from the formation to surface and is sized to accommodate equipment configured to drill a well bore into which the at least one electromagnetic antenna is positioned.

3. The method of claim 1 or claim 2, wherein the tunnel extends from the formation to surface and is sized to accommodate equipment configured to drill a well bore into which a producer well extending into the pay region near the at least one electromagnetic antenna is positioned.

4. The method of claim 3, wherein the producer well is configured to produce the bitumen containing fluid to surface.

5. The method of any one of claims 1 to 4, wherein the tunnel extends from the formation to surface and is sized to accommodate equipment configured to drill a well bore into which a solvent injector is positioned.

6. The method of any one of claims 1 to 5, wherein the bitumen containing fluid is recovered using a collector located in the tunnel, the collector being fluidly connected to the pay region.

7. The method of claim 6, wherein the collector is fluidly connected to the pay region via at least one wellbore extending into the pay region from the tunnel.

8. The method of claim 7, wherein the at least one wellbore contains the at least one antenna.

9. The method of claim 1, further comprising injecting solvent into the pay region using at least one solvent injector.

10. The method of claim 9, wherein the at least one solvent injector is situated within at least one wellbore extending into the pay region from the tunnel.

11. The method of claim 10, wherein the at least one wellbore extending into the pay region from the tunnel contains the at least one antenna and the at least one solvent injector.

12. The method of claim 10, wherein the at least one wellbore extending into the pay region from the tunnel contains the at least one solvent injector and wherein at least one additional wellbore contains the at least one antenna.

13. The method of any one of claims 4 to 12, further comprising transporting the bitumen containing fluid to surface.

14. The method of any one of claims 1 to 13, further comprising operating at least one electromagnetic transmitter to heat the pay region using the at least one electromagnetic antenna.

15. The method of claim 14, wherein each electromagnetic antenna is powered by a dedicated electromagnetic transmitter.

16. The method of claim 14, wherein a plurality of electromagnetic antennas are powered by a common electromagnetic transmitter.

17. The method of any one of claims 1 to 16, wherein a surface access location provides access to an entry tunnel extending from surface to the tunnel.

18. The method of any one of claims 1, 2 or 5 to 17, wherein a producer well configured to produce the bitumen containing fluid to surface is drilled from surface.

19. The method of claim 3 or claim 4, wherein the producer well is at least partially inclined to facilitate gravity drainage to a pump located in the tunnel.

20. The method of any one of claims 1 to 19, wherein the tunnel is part of a network of tunnels.

21. The method of any one of claims 1 to 20, wherein a plurality of electromagnetic antennas are powered as a phased array to direct an energy wavefront towards a particular portion of the pay region.

22. The method of any one of claims 1 to 21, further comprising controlling the at least one electromagnetic antenna using a controller connected to the at least one electromagnetic antenna via a control line.

23. The method of any one of claims 1 to 22, wherein the at least one electromagnetic antenna is operated to produce a radio frequency signal.

24. The method of any one of claims 1 to 23, further comprising receiving an electromagnetic signal at one of the at least one electromagnetic antennas, wherein the received electromagnetic signal originates from another of the at least one electromagnetic antenna.

25. The method of claim 24, further comprising controlling operation of the at least one electromagnetic antenna according to data obtained from the received electromagnetic signal.

26. A system for recovering bitumen from a bitumen reserve, the system comprising:
a tunnel excavated into a formation from ground level that at least in part underlies a pay region in the bitumen reserve;

at least one electromagnetic (EM) antenna extending into the pay region from the tunnel below the pay region;
at least one EM transmitter for powering the at least one EM antenna; and at least one production apparatus configured to recover a bitumen containing fluid from the pay region via gravity drainage.

27. The system of claim 26, wherein the tunnel is sized to accommodate equipment configured to drill a well bore into which the at least one electromagnetic antenna is positioned.

28. The system of claim 26 or claim 27, wherein the tunnel is sized to accommodate equipment configured to drill a well bore into which a producer well extending into the pay region near the at least one electromagnetic antenna is positioned.

29. The system of claim 28, wherein the producer well is configured for recovering the bitumen containing fluid and producing the bitumen containing fluid to surface.

30. The system of any one of claims 26 to 29, wherein the tunnel is sized to accommodate equipment configured to drill a well bore into which a solvent injector is positioned.

31. The system of any one of claims 26 to 30, wherein the at least one production apparatus comprises a collector located in the tunnel, the collector being fluidly connected to the pay region to recover the bitumen containing fluid.

32. The system of claim 31, wherein the collector is fluidly connected to the pay region via at least one wellbore extending into the pay region from the tunnel.

33. The system of claim 32, wherein the at least one wellbore contains the at least one antenna.

34. The system of claim 26, further comprising at least one solvent injector configured for injecting solvent into the pay region.

35. The system of claim 34, wherein the at least one solvent injector is situated within at least one wellbore extending into the pay region from the tunnel.

36. The system of claim 35, wherein the at least one wellbore extending into the pay region from the tunnel contains the at least one antenna and the at least one solvent injector.

37. The system of claim 35, wherein the at least one wellbore extending into the pay region from the tunnel contains the at least one solvent injector and wherein at least one additional wellbore contains the at least one antenna.

38. The system of any one of claims 29 to 37, further comprising a pump for transporting the bitumen containing fluid to surface.

39. The system of any one of claims 26 to 38, further comprising at least one electromagnetic transmitter for powering the at least one electromagnetic antenna.

40. The system of claim 39, wherein each electromagnetic antenna is powered by a dedicated electromagnetic transmitter.

41. The system of claim 39, wherein a plurality of electromagnetic antennas are powered by a common electromagnetic transmitter.

42. The system of any one of claims 26 to 41, wherein a surface access location provides access to an entry tunnel extending from surface to the tunnel.

43. The system of any one of claims 26, 27, or 29 to 42, wherein a producer well configured to produce the bitumen containing fluid to surface is drilled from surface.

44. The system of claim 28 or claim 29, wherein the producer well is at least partially inclined to facilitate gravity drainage into a pump located in the tunnel.

45. The system of any one of claims 26 to 44, wherein the tunnel is part of a network of tunnels.

46. The system of any one of claims 26 to 45, wherein a plurality of electromagnetic antennas are configured to be powered as a phased array to direct an energy wavefront towards a particular portion of the pay region.

47. The system of any one of claims 26 to 46, further comprising a controller connected to the at least one electromagnetic antenna via a control line for controlling the at least one electromagnetic antenna.

48. The system of any one of claims 26 to 47, wherein the at least one electromagnetic antenna is operated to produce a radio frequency signal.

49. The system of any one of claims 26 to 48, further configured for receiving an electromagnetic signal at one of the at least one electromagnetic antennas, wherein the received electromagnetic signal originates from another of the at least one electromagnetic antennas.

50. The system of claim 49, further configured for controlling the at least one electromagnetic antennas according to data obtained from the received electromagnetic signal.