CN112485281B - Method for dynamically measuring gas hydrate saturation and permeability in porous medium - Google Patents
Method for dynamically measuring gas hydrate saturation and permeability in porous medium Download PDFInfo
- Publication number
- CN112485281B CN112485281B CN202011117140.9A CN202011117140A CN112485281B CN 112485281 B CN112485281 B CN 112485281B CN 202011117140 A CN202011117140 A CN 202011117140A CN 112485281 B CN112485281 B CN 112485281B
- Authority
- CN
- China
- Prior art keywords
- hydrate
- pressure
- saturation
- gas
- confining pressure
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- NMJORVOYSJLJGU-UHFFFAOYSA-N methane clathrate Chemical compound C.C.C.C.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O NMJORVOYSJLJGU-UHFFFAOYSA-N 0.000 title claims abstract description 82
- 238000000034 method Methods 0.000 title claims abstract description 41
- 230000035699 permeability Effects 0.000 title claims abstract description 40
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 50
- 239000007788 liquid Substances 0.000 claims abstract description 43
- 238000001228 spectrum Methods 0.000 claims abstract description 19
- 239000000463 material Substances 0.000 claims abstract description 16
- 239000011148 porous material Substances 0.000 claims description 24
- 239000011435 rock Substances 0.000 claims description 24
- 239000004696 Poly ether ether ketone Substances 0.000 claims description 23
- 229920002530 polyetherether ketone Polymers 0.000 claims description 23
- JUPQTSLXMOCDHR-UHFFFAOYSA-N benzene-1,4-diol;bis(4-fluorophenyl)methanone Chemical compound OC1=CC=C(O)C=C1.C1=CC(F)=CC=C1C(=O)C1=CC=C(F)C=C1 JUPQTSLXMOCDHR-UHFFFAOYSA-N 0.000 claims description 21
- 230000015572 biosynthetic process Effects 0.000 claims description 17
- 238000012544 monitoring process Methods 0.000 claims description 12
- 230000008569 process Effects 0.000 claims description 11
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 238000001816 cooling Methods 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 10
- 238000003786 synthesis reaction Methods 0.000 claims description 10
- 238000000354 decomposition reaction Methods 0.000 claims description 7
- 150000004677 hydrates Chemical class 0.000 claims description 7
- 238000002347 injection Methods 0.000 claims description 7
- 239000007924 injection Substances 0.000 claims description 7
- 239000002184 metal Substances 0.000 claims description 7
- 238000005086 pumping Methods 0.000 claims description 6
- 238000004364 calculation method Methods 0.000 claims description 5
- VTVVPPOHYJJIJR-UHFFFAOYSA-N carbon dioxide;hydrate Chemical compound O.O=C=O VTVVPPOHYJJIJR-UHFFFAOYSA-N 0.000 claims description 5
- 238000009738 saturating Methods 0.000 claims description 4
- 239000012153 distilled water Substances 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- 239000007789 gas Substances 0.000 abstract description 46
- 238000011161 development Methods 0.000 abstract description 5
- 238000002474 experimental method Methods 0.000 description 13
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
- G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
- G01N24/081—Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/30—Assessment of water resources
Landscapes
- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- General Physics & Mathematics (AREA)
- Pathology (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- High Energy & Nuclear Physics (AREA)
- Immunology (AREA)
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Dispersion Chemistry (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
Abstract
The invention relates to the technical field of natural gas hydrate reservoir development and discloses a method for dynamically measuring the saturation and permeability of gas hydrate in a porous medium, wherein a core is selected, and a hydrate generation system is designed and built and comprises a core holder in a low-field nuclear magnetic spectrometer, wherein a confining pressure cavity is formed in the core holder; adding non-magnetic confining pressure liquid into the confining pressure cavity; setting confining pressure in a confining pressure cavity and gas circuit air pressure, adjusting temperature to generate a gas hydrate, collecting a nuclear magnetic spectrum in real time, and determining a generation stage of the gas hydrate; collecting nuclear magnetic signals corresponding to the nuclear magnetic spectrogram when the saturation of the hydrate is stable, comparing the total amount of the nuclear magnetic signals when the hydrate does not exist, and converting the difference value of the nuclear magnetic signals and the total amount of the nuclear magnetic signals into the quality of the hydrate generated and consumed water; and calculating the saturation of the gas hydrate by using a material balance method, and measuring to obtain the permeability of the core containing the hydrate, which corresponds to the saturation. The method can greatly reduce the experimental steps and the time consumption while improving the accuracy of measuring the hydrate saturation.
Description
Technical Field
The invention relates to the technical field of natural gas hydrate reservoir development and research, in particular to a method for dynamically measuring the saturation and permeability of a gas hydrate in a porous medium.
Background
The natural gas hydrate has huge reserves and high energy density, and has attracted attention from all over the world in recent years. Although natural gas hydrate resources have many advantages, the development of reservoirs faces great technical problems. Because the development difficulty of the natural gas hydrate is high, the development data is insufficient at present, and an indoor experiment becomes a main research means. However, the laboratory simulation also has the problems of high requirements on temperature and pressure and the like, so that the experiments on the hydrate need pressurization and temperature reduction treatment, which brings about great troubles to a great deal of experimental work.
In core experiments in unconventional oil fields, low-field nuclear magnetic technology has been widely used for quantitatively monitoring the water content in pores and the variation of water. The low-field nuclear magnetic technology has the advantages of being capable of measuring water signals in different states in real time through the opaque holder, and can be well applied to monitoring the water signal variation quantity accompanying the synthesis and decomposition process of the natural gas hydrate in the rock core in real time. The traditional calculation of the hydrate saturation depends on the conversion of the initial water saturation of the rock core to the water saturation of the hydrate before the hydrate generation experiment, so that in each experiment, once the water saturation of the rock core is determined, only one water saturation can be obtained, correspondingly, if the permeability corresponding to a plurality of hydrate saturations needs to be measured, the experiment needs to be carried out for many times, and the permeability is measured on the basis of the obtained hydrate saturations.
Disclosure of Invention
The invention aims to provide a method for dynamically measuring the saturation and permeability of a gas hydrate in a porous medium aiming at the technical problems in the prior art, so that the test precision is improved, the experimental steps are greatly simplified, and the experimental time is shortened.
In order to solve the problems proposed above, the technical scheme adopted by the invention is as follows:
a method for dynamically monitoring and determining the saturation of gas hydrates in a porous medium comprises the following specific steps:
selecting a rock core, drying the rock core and saturating distilled water;
designing and building a hydrate generation system, wherein the hydrate generation system comprises a non-magnetic core holder connected with a low-field nuclear magnetic spectrometer, and a confining pressure cavity is formed in the non-magnetic core holder;
adding confining pressure liquid into the confining pressure cavity, and adding gas into the pores of the rock core;
setting confining pressure in a confining pressure cavity and air pressure in a pore, adjusting temperature to generate a gas hydrate, acquiring a nuclear magnetic spectrum on a nuclear magnetic spectrometer in real time, and determining a generation stage of the gas hydrate;
monitoring by a nuclear magnetic spectrometer, and waiting for the saturation of the gas hydrate to be stable;
collecting nuclear magnetic signals on a corresponding nuclear magnetic spectrogram under the conditions of stable confining pressure and air pressure, comparing the total amount of the nuclear magnetic signals without hydrates, and converting the difference value of the nuclear magnetic signals with the total amount of the nuclear magnetic signals without hydrates into the quality of hydrate generation consumption water;
calculating the saturation of the gas hydrate by a material balance method according to the mass of the consumed water;
measuring the permeability of the core containing the hydrate corresponding to the saturation;
and repeatedly acquiring and calculating by changing confining pressure and air pressure to obtain saturation and permeability data meeting the requirements.
Further, the calculation of the gas hydrate saturation by using the material balance method comprises the following steps:
when the saturation of the hydrate is stable, the mass of the gas hydrate is mhThen, the following is obtained according to the material balance equation formed by the gas hydrate and the corresponding relation between the quantity and the mass of the material:
thus obtaining: m ish＝{(18n+Ym)×ΔmH2O}/(18n) ①
Wherein Y is the molar mass of the gas X participating in the formation of the hydrate, and X is the gas participating in the reaction; n and m are respectively the proportion of water molecules and gas molecules participating in the reaction; Δ mH2OThe mass of water consumed for reaction is calculated according to the variation of a nuclear magnetic spectrum;
the volume of the gas hydrate generated is calculated by equation (ii):
Vh＝mh/ρ h ②
where rhohDensity as pure gas hydrate;
gas hydrate saturation ShCalculating by formula (c):
Sh＝Vh/Vpore ③
in the formula VporeThe core pore volume.
Further, the hydrate generation system comprises a non-magnetic core holder arranged in the nuclear magnetic spectrometer, an inlet of the non-magnetic core holder is connected with an air source, and a first stop valve and a first pressure sensor are arranged between the non-magnetic core holder and the gas source; the outlet of the non-magnetic core holder is connected with a back pressure valve, the back pressure valve is controlled to be opened and closed by a back pressure liquid injection pump for providing back pressure, a third stop valve is arranged between the back pressure valve and the back pressure valve, and a second pressure sensor is further arranged between the outlet of the non-magnetic core holder and the back pressure valve; the back pressure valve is also connected with a gas flowmeter.
The confining pressure liquid pressurizing pump is connected with the second stop valve and then connected with the non-magnetic core holder and is used for injecting confining pressure liquid to provide required confining pressure; one end of the confining pressure liquid cooling box is also connected with an inlet of the confining pressure cavity of the non-magnetic core holder, and the other end of the confining pressure liquid cooling box is connected with a confining pressure circulating pump and then is connected with an outlet of the confining pressure cavity of the non-magnetic core holder; and the outlet of the confining pressure cavity of the non-magnetic core holder is also connected with a temperature sensor.
Further, a computer system is adopted to be respectively connected with the first pressure sensor, the second pressure sensor, the temperature sensor, the nuclear magnetic spectrometer and the gas flowmeter.
Further, a drying bottle is arranged between the backpressure valve and the gas flowmeter.
Further, the core holder comprises a core, a PEEK confining pressure cylinder, PEEK filling plungers, a heat-shrinkable sleeve and metal plugs, wherein the core is packaged between the two PEEK filling plungers through the heat-shrinkable sleeve, the PEEK filling plungers and the core are integrally inserted into the PEEK confining pressure cylinder, and the metal plugs are arranged at two ends of the PEEK confining pressure cylinder for sealing; and a cavity is formed between the PEEK confining pressure cylinder body and the thermal shrinkage sleeve and is used as a confining pressure cavity into which nonmagnetic low-temperature confining pressure liquid is pumped.
And further, opening a first stop valve and a second stop valve, respectively adding confining pressure liquid and gas into the confining pressure cavity and the core hole through a confining pressure liquid pressurizing pump and a gas source, and setting confining pressure and gas pressure.
Further, setting inlet pressure in the core hole, adjusting confining pressure, keeping the pressure difference between the confining pressure and the average air pressure unchanged, opening a third stop valve, pumping back pressure liquid through a back pressure liquid injection pump, and opening the back pressure valve to release pressure; and acquiring the gas flow of an outlet through a computer system and a gas flowmeter, and calculating the permeability according to the gas flow by using a gas Darcy formula.
Compared with the prior art, the invention has the beneficial effects that:
the method is combined with a real-time monitoring system of a low-field nuclear magnetic spectrum, the saturation of the generated gas hydrate can be accurately measured on the premise of no damage to a test sample, repeated pressure rise and pressure reduction can be carried out under the condition of not disassembling an experimental instrument, the saturation of hydrates under the condition of multiple groups of pressure is obtained, the traditional step of building a primary instrument is simplified, the step of obtaining a gas hydrate saturation experiment corresponding to a group of initial water saturation by saturating the primary sample is simplified, the testing precision is improved, the experiment step is greatly simplified, and the experiment time is shortened.
Drawings
FIG. 1 is a flow chart of the method for dynamically determining gas hydrate saturation and permeability in a porous medium according to the present invention.
FIG. 2 is a schematic diagram of a hydrate formation system according to the present invention.
FIG. 3 is a schematic diagram of the structure of the non-magnetic core holder of the present invention.
Description of reference numerals: 1-air source, 2-core holder, 3-nuclear magnetic spectrometer, 4-computer system, 5-confining pressure circulating pump, 6-confining pressure liquid cooling box, 7-confining pressure liquid pressurizing pump, 8-backpressure valve, 9-drying bottle, 10-gas flowmeter, 11-backpressure liquid injection pump, 121-first stop valve, 122-second stop valve, 123-third stop valve, 131-first pressure sensor, 132-second pressure sensor, 14-temperature sensor, 100-core (core cavity), 200-PEEK confining pressure cylinder, 300-PEEK filling plunger, 400-thermal shrinkage sleeve and 500-metal plug.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Referring to fig. 1, the present invention provides a method for dynamically determining the saturation and permeability of gas hydrate in a porous medium, which comprises the following specific steps:
step S1: selecting a rock core, drying the rock core and saturating the rock core with distilled water.
Step S2: designing and building a hydrate generation system according to the selected core, wherein the hydrate generation system comprises a core holder connected with a low-field nuclear magnetic spectrometer, and a confining pressure cavity is formed in the core holder.
Step S3: and adding confining pressure liquid into the confining pressure cavity, and adding gas into the pores of the core.
Step S4: setting the confining pressure in the confining pressure cavity and the air pressure in the pores, adjusting the temperature to generate the gas hydrate, acquiring a nuclear magnetic spectrum on a nuclear magnetic spectrometer in real time, and determining the generation stage of the gas hydrate.
In step S4, a nuclear magnetic spectrum is acquired in real time to determine the generation stage of the gas hydrate in the core, and the nuclear magnetic spectrum of the water signal is used to determine the water content in the core due to the consumption of the water content accompanied by the formation of the gas hydrate, so that the generation stage of the hydrate can be reflected. In the initial stage of the experiment, the nuclear magnetic spectrum can be selected to be collected every 1 to 2 hours, and when the nuclear magnetic signal quantity changes to be smaller, the nuclear magnetic spectrum can be collected once in 10 minutes instead.
Step S5: monitoring by a nuclear magnetic spectrometer, waiting for the saturation of the gas hydrate to be stable, judging whether the gas hydrate is stable, and if not, continuing to wait; if so, the next step is performed.
In step S5, it is observed and waited that the hydrate saturation under a certain specific confining pressure and air pressure is stable, and after at least 4 hours, a nuclear magnetic spectrum of the core at that time is collected to obtain a nuclear magnetic signal. Due to the influence of capillary force, the gas hydrate saturation degree which can be generated in the rock core is different under different ambient pressure and air pressure conditions, and in order to determine the hydrate saturation degree corresponding to the pressure condition, the nuclear magnetic spectrum of the rock core needs to be collected in real time to observe the water content in the rock core. It cannot be determined that the gas hydrate saturation in the core 100 reaches a plateau at this pressure condition until the water content is substantially stable.
Step S6: and when the saturation of the hydrate is stable, acquiring nuclear magnetic signals on a corresponding nuclear magnetic spectrogram under the conditions of confining pressure and air pressure, comparing the total amount of the nuclear magnetic signals in the absence of the hydrate, and converting the difference value of the nuclear magnetic signals and the total amount of the nuclear magnetic signals into the quality of the hydrate generated and consumed water.
Step S7: the calculation of the gas hydrate saturation is performed by a mass balance method, depending on the mass of water consumed.
Step S8: and measuring the permeability of the core containing the hydrate corresponding to the saturation.
Step S9: judging whether enough saturation and permeability data are acquired, if not, changing the confining pressure and the gas pressure to promote the synthesis or decomposition of the gas hydrate, and returning to the step S4; if yes, the process is finished.
In step S7, the gas hydrate saturation is calculated by a material balance method, which includes the following steps:
when the hydrate saturation is stable, the mass of gas hydrate generated in the rock core under the pressure condition is mhThen, the following is obtained according to the material balance equation formed by the gas hydrate and the corresponding relation between the quantity and the mass of the material:
thus obtaining: m ish＝{(18n+Ym)×ΔmH2O}/(18n) ①
Wherein Y is the molar mass (mol/g) of the gas X participating in the hydrate formation, and X is a gas participating in the reaction, such as CH4、CO2Etc.; n and m are water molecules and gas molecules respectively participating in reactionThe mixture ratio is that the n and m values of different gases are different; Δ mH2OThe mass (g) of water consumed for the reaction is calculated from the amount of change in the nuclear magnetic spectrum.
The volume of the gas hydrate generated is calculated by equation (ii):
Vh＝mh/ρ h ②
where rhohDensity (g/cm) of pure gas hydrate3)。
Gas hydrate saturation ShCan be calculated by formula (c):
Sh＝Vh/Vpore ③
in the formula VporeCore pore volume (ml).
Further, referring to fig. 2, the hydrate generating system includes a non-magnetic core holder 2 and a nuclear magnetic spectrometer 3, and the non-magnetic core holder 2 is disposed in the nuclear magnetic spectrometer 3 and used for generating and decomposing hydrates. An inlet of the non-magnetic core holder 2 is connected with an air source 1, and a first stop valve 121 and a first pressure sensor 131 are arranged between the non-magnetic core holder and the air source 1 and used for providing and adjusting air pressure.
The outlet of the non-magnetic core holder 2 is connected with a back pressure valve 8, the back pressure valve 8 is controlled to be opened and closed by a back pressure liquid injection pump 11 for providing back pressure, a third stop valve 123 is arranged between the back pressure valve 8 and the back pressure valve 8, a second pressure sensor 132 is further arranged between the outlet of the non-magnetic core holder 2 and the back pressure valve 8, and the back pressure valve 8 is further connected with a gas flowmeter 10.
And the confining pressure liquid pressurizing pump 7 is connected with the non-magnetic core holder 2 after being connected with the second stop valve 122 and is used for injecting confining pressure liquid to provide and adjust required confining pressure. One end of the confining pressure liquid cooling box 6 is also connected with an inlet of the confining pressure cavity of the non-magnetic core holder 2, and the other end of the confining pressure liquid cooling box is connected with an outlet of the non-magnetic core holder 2 after being connected with the confining pressure circulating pump 5. And the outlet of the confining pressure cavity of the non-magnetic core holder 2 is also connected with a temperature sensor 14. The confining pressure circulating pump 5 is used for enabling confining pressure liquid to continuously circulate in the pipeline, taking away the temperature in real time, ensuring that the rock core is kept in a stable low-temperature environment, and cooling the non-magnetic confining pressure liquid in the confining pressure pipeline through the confining pressure liquid cooling box 6, so that the working reliability and stability of the hydrate generation system are ensured, and the test precision of the experiment is reliably ensured.
Further, the computer system 4 is respectively connected to the first pressure sensor 131, the second pressure sensor 132, the temperature sensor 14, the nuclear magnetic spectrometer 3 and the gas flowmeter 10, and can acquire a pressure signal, a temperature signal, a nuclear magnetic signal and a gas flow rate in the confining pressure cavity in real time.
Further, a drying bottle 9 is arranged between the back pressure valve 8 and the gas flowmeter 10, so that discharged outlet gas passes through the drying bottle 9, the gas passing through the gas flowmeter 10 is completely dried, the gas flowmeter 10 cannot be damaged, and the reliability of an experiment is ensured.
Further, referring to fig. 3, the nonmagnetic core holder comprises a core 100, a PEEK confining pressure cylinder 200, PEEK filling plungers 300, a heat shrinkable sleeve 400 and a metal plug 500, wherein the core 100 is encapsulated between the two PEEK filling plungers 300 through the heat shrinkable sleeve 400, the PEEK filling plungers 300 and the core 100 are integrally inserted into the PEEK confining pressure cylinder 200, and the metal plugs 500 are arranged at two ends of the PEEK confining pressure cylinder 200 for sealing. A cavity is formed between the PEEK confining pressure cylinder body 200 and the thermal shrinkage sleeve 400 and can be used as a confining pressure cavity for pumping non-magnetic low-temperature confining pressure liquid. By adopting the non-magnetic core holder, the completeness and the closure of the thermal shrinkable sleeve 400 can be ensured, and sufficient gas pressure can be provided for the core 100, so that the confining pressure in the whole experimental process is greater than the air pressure, and gas hydrate can be generated more reliably.
The process of the present invention is further illustrated by the following specific examples.
The method for dynamically determining the saturation and permeability of the gas hydrate in the porous medium provided by the embodiment comprises the following steps:
step 100: and selecting the water-containing siltstone core, drying the water-containing siltstone core in a drying box for more than 48 hours, and adding low-pressure saturated distilled water for 2-4 hours to obtain a partially saturated water sample.
Step 200: designing and building a hydrate generation system, wherein the hydrate generation system comprises a non-magnetic core holder 2 connected with a low-field nuclear magnetic spectrometer 3, and a confining pressure cavity is formed in the non-magnetic core holder 2.
Step 300: and opening the second stop valve 122, pumping low-temperature non-magnetic fluorinated liquid into the confining pressure cavity through the confining pressure liquid pressurizing pump 7, and opening the first stop valve 121 and the gas source 1 to add carbon dioxide gas into the pores of the core.
Step 400: the confining pressure and the air pressure in the confining pressure cavity are set through the confining pressure liquid pressurizing pump 7 and the air source 1, the temperature is adjusted on a setting panel of the confining pressure liquid cooling box 6, methane hydrate is generated, a computer system 4 collects a nuclear magnetic spectrum on a nuclear magnetic spectrometer in real time, and the generation stage of the methane hydrate in the rock core is determined.
In the above, the confining pressure in the confining pressure cavity is adjusted by pumping or sucking confining pressure liquid by the confining pressure pump 7, the first stop valve 121 and the pressure reducing valve of the gas source 1 are opened to adjust the gas pressure, the confining pressure is ensured to be greater than the gas pressure in the experimental process, and the confining pressure and the gas pressure are collected by the first pressure sensor 131; the set temperature and pressure reach the hydrate generating condition and are acquired by the temperature sensor 14.
Step 500: and monitoring by a nuclear magnetic spectrometer, waiting for the saturation of the gas hydrate to be stable, and judging whether the gas hydrate is stable.
In the step, after the collected hydrate is generated under the conditions of the confining pressure of 4.0MPa and the air pressure of 3.57MPa, the nuclear magnetic signal quantity is monitored until the water content is stable after the saturation degree of the carbon dioxide hydrate is basically stable under the pressure condition.
Step 600: and (3) acquiring a corresponding nuclear magnetic spectrum when the saturation of the hydrate is stable, and comparing the total nuclear magnetic signal amount in the absence of the hydrate, wherein the nuclear magnetic signal of 1596.368p.u. is reduced in the synthesis of the hydrate, so that 1.097g of water is consumed in the generation of the hydrate.
Step 700: under the pressure condition, the hydrate mass in the core can be calculated according to the mass of consumed water and a material balance equation and a derivative formula (phi):
mh＝{(44+5.75×18)×1.097}/(5.75×18)＝1.563g ①
wherein 44 is the molar mass (mol/g) involved in carbon dioxide; 5.75 is the proportion of water molecules combined by one molecule of carbon dioxide.
The volume of the generated gas hydrate is calculated by the formula (II):
Vh＝mh/ρh＝1.699cm 3 ②
in the formula, ρhDensity of pure carbon dioxide hydrate, 0.92g/cm3。
Gas hydrate saturation ShCan be calculated by formula (c):
Sh＝Vh/Vpore＝63.17％ ③
in the formula, VporeThe core pore volume was 2.69 ml.
That is, the sandstone was found to have a hydrate saturation of 63.17% at an average pressure of 3.08 MPa.
Step 800: and measuring the permeability of the core containing the hydrate corresponding to the saturation, specifically:
keeping the first stop valve 121 and the second stop valve 122 open, setting the pressure in the core hole and adjusting the confining pressure at any time, keeping the pressure difference between the confining pressure and the average air pressure stable, keeping the inlet pressure of the non-magnetic core holder 2 still at 3.57MPa, opening the third stop valve 123, pumping back pressure liquid through the back pressure liquid injection pump 11, enabling the back pressure valve 8 to open for pressure relief, discharging the gas at the outlet of the core holder 2, reducing the pressure to 2.597MPa, and acquiring the pressure through the second pressure sensor 132. The gas flow at the outlet is collected by the computer system 4 and the gas flowmeter 10, and the permeability can be calculated by using a gas Darcy formula after the stable gas flow is obtained.
Step 900: judging whether enough saturation and permeability data are acquired, if not, changing the confining pressure and the gas pressure to promote the synthesis or decomposition of the gas hydrate, and repeating the process; if yes, the process is finished.
If not, continuously changing the confining pressure and the gas pressure to promote the synthesis or decomposition of the gas hydrate, wherein the processes are respectively as follows:
(1) keeping the first stop valve 121 and the second stop valve 122 open, setting the pressure in the core hole and adjusting the confining pressure at any time to keep the pressure difference between the confining pressure and the average air pressure stable, opening the third stop valve 123 to reduce the pressure of the core holder 2 until the inlet pressure of the core holder 2 is reduced to 2.54MPa and the outlet pressure is reduced to 2.395MPa, keeping the confining pressure to 3.5MPa, and monitoring the nuclear magnetic signal quantity until the water content is stable after waiting for the carbon dioxide hydrate saturation under the new pressure condition to be basically stable.
And acquiring a nuclear magnetic spectrum corresponding to the stable hydrate saturation in the rock core, and comparing the total nuclear magnetic signal amount in the absence of the hydrate, wherein the nuclear magnetic signal of 1280.774p.u. is reduced in the synthesis of the hydrate, so that 0.880g of water is consumed in the generation of the hydrate.
The hydrate mass in the core under the pressure condition can be calculated according to a material balance equation and a derivative formula (phi) of the mass of consumed water:
mh＝{(44+5.75×18)×0.880}/(5.75×18)＝1.254g ①
the volume of the generated gas hydrate is calculated by the formula (II):
Vh＝mh/ρh＝1.363cm 3 ②
gas hydrate saturation ShCalculated by formula (c):
Sh＝Vh/Vpore＝50.67％ ③
that is, the sandstone was found to have a hydrate saturation of 50.67% at an average pressure of 2.54 MPa.
And measuring the permeability of the corresponding core containing the hydrate by the computer system 4 according to the hydrate saturation.
(2) Keeping the first stop valve 121 and the second stop valve 122 open, setting the inlet pressure in the core hole and adjusting the confining pressure at any time, keeping the pressure difference between the confining pressure and the average air pressure stable, opening the third stop valve 123 to reduce the pressure of the nonmagnetic core holder 2 until the inlet pressure of the nonmagnetic core holder 2 is reduced to 2.44MPa, the outlet pressure is reduced to 2.390MPa, keeping the confining pressure to 3.4MPa, and monitoring the nuclear magnetic signal quantity until the water content is stable after waiting for the carbon dioxide hydrate saturation under the new pressure condition to be basically stable.
And acquiring a nuclear magnetic spectrum corresponding to the stable hydrate saturation in the rock core, and comparing the total nuclear magnetic signal amount in the absence of the hydrate, wherein the nuclear magnetic signal of 934.019p.u. is reduced in the synthesis of the hydrate, so that 0.641g of water is consumed in the generation of the hydrate.
The hydrate mass in the core under the pressure condition can be calculated according to a material balance equation and a derivative formula (phi) of the mass of consumed water:
mh＝{(44+5.75×18)×0.641}/(5.75×18)＝0.914g ①
the volume of the generated gas hydrate is calculated by the formula (II):
Vh＝mh/ρh＝0.994cm 3 ②
gas hydrate saturation ShCalculated by formula (c):
Sh＝Vh/Vpore＝36.95％ ③
that is, the saturation of hydrate in the sandstone was 36.95% at an average pressure of 2.46 MPa.
And measuring the permeability of the corresponding core containing the hydrate by the computer system 4 according to the hydrate saturation.
In the above steps, the synthesis or decomposition of the hydrate is promoted by changing the air pressure and the confining pressure for many times, the nuclear magnetic signal of the core at the moment is collected after the hydrate saturation is stable, the hydrate saturation is calculated, and the permeability corresponding to the saturation is measured. After the saturation and permeability of the core hydrate under a group of specific confining pressure and air pressure conditions are collected, the experimental instrument is not required to be disassembled, the cores with different water saturation degrees are prepared again, a new saturation state of the gas hydrate can be obtained only by changing the confining pressure and the air pressure again, and the corresponding permeability after the state is changed can be measured. After a set of hydrate saturation data is collected, the pressure condition can be changed for many times until the experimental requirements are met.
According to the method for dynamically measuring the saturation and permeability of the gas hydrate in the porous medium, provided by the invention, through matching with a nuclear magnetic experiment, after the change rule of the water content in the porous medium is obtained, the mass of the hydrate existing in the porous medium can be calculated in real time according to a material balance method, and the accurate numerical value of the saturation of the hydrate can be obtained by combining with the porosity information of a sample, so that the real-time monitoring of the saturation of the hydrate is realized, and the stability of the saturation of the hydrate in the experimental process is ensured. Therefore, the method provided by the invention does not depend on the conversion of the initial water saturation of the rock core to the hydrate saturation, can obtain a plurality of groups of hydrate saturation numerical values under the condition of not disassembling a test device, improves the test precision, can directly measure and obtain the permeability corresponding to the hydrate saturation by using the instrument after obtaining a hydrate saturation state each time, and also greatly simplifies the experimental steps and shortens the experimental time.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (8)
1. A method for dynamically measuring the saturation and permeability of gas hydrate in a porous medium is characterized in that: the method comprises the following specific steps:
selecting a rock core, drying the rock core and saturating distilled water;
designing and building a hydrate generation system, wherein the hydrate generation system comprises a core holder connected with a low-field nuclear magnetic spectrometer, and a confining pressure cavity is formed in the core holder;
adding confining pressure liquid into the confining pressure cavity, and adding gas into the pores of the rock core;
setting confining pressure in a confining pressure cavity and air pressure in a pore, adjusting temperature to generate a gas hydrate, acquiring a nuclear magnetic spectrum on a nuclear magnetic spectrometer in real time, and determining a generation stage of the gas hydrate;
monitoring by a nuclear magnetic spectrometer, and waiting for the saturation of the gas hydrate to be stable;
collecting nuclear magnetic signals on a corresponding nuclear magnetic spectrogram in a stable state, comparing the total amount of the nuclear magnetic signals in the absence of hydrates, and converting the difference value of the nuclear magnetic signals and the total amount of the nuclear magnetic signals into the quality of water consumed by generating the hydrates;
calculating the saturation of the gas hydrate by a material balance method according to the mass of the consumed water;
measuring the permeability of the core containing the hydrate corresponding to the saturation;
changing confining pressure and air pressure to repeatedly acquire and calculate to obtain saturation and permeability data meeting the requirements;
wherein, the repeated collection and calculation of the confining pressure and the air pressure to obtain the saturation and the permeability data meeting the requirement comprises the following steps: judging whether enough saturation and permeability data are acquired, if not, changing the confining pressure and the gas pressure to promote the synthesis or decomposition of the gas hydrate, and repeating the process; if yes, ending;
wherein the changing of the confining pressure and the gas pressure promotes the synthesis or decomposition of the gas hydrate, and the repeating of the process comprises the following steps:
without changing the structure of the hydrate formation system, removing the core from a core holder of the hydrate formation system to re-prepare cores of different water saturations; resetting the pressure in the pores of the rock core, and adjusting the confining pressure at any time to keep the pressure difference between the confining pressure and the average air pressure stable;
after the saturation of the carbon dioxide hydrate is stable under the new pressure condition, monitoring the nuclear magnetic signal quantity until the water content is stable;
collecting a nuclear magnetic spectrum corresponding to the stable saturation of the gas hydrate in the rock core, comparing the total nuclear magnetic signal amount without the hydrate, and converting to obtain the quality of the generated and consumed water of the hydrate;
calculating to obtain the saturation of the gas hydrate;
and measuring the permeability of the core containing the hydrate corresponding to the saturation.
2. The method for dynamically determining gas hydrate saturation and permeability in a porous medium according to claim 1, wherein: the calculation method for the gas hydrate saturation by adopting the material balance method comprises the following steps:
when the saturation of the hydrate is stable, the mass of the gas hydrate is mhThen, the following is obtained according to the material balance equation formed by the gas hydrate and the corresponding relation between the quantity and the mass of the material:
thus obtaining: m ish＝{(18n+Ym)×ΔmH2O}/(18n) ①
Wherein Y is the molar mass of the gas X participating in the formation of the hydrate, and X is the gas participating in the reaction; n and m are respectively the proportion of water molecules and gas molecules participating in the reaction; Δ mH2OThe mass of water consumed for reaction is calculated according to the variation of a nuclear magnetic spectrum;
the volume of the gas hydrate generated is calculated by equation (ii):
Vh＝mh/ρh ②
where rhohDensity as pure gas hydrate;
gas hydrate saturation ShCalculating by formula (c):
Sh＝Vh/Vpore ③
in the formula VporeThe core pore volume.
3. The method for dynamically determining gas hydrate saturation and permeability in a porous medium according to claim 2, wherein: the hydrate generation system comprises a non-magnetic core holder arranged in a nuclear magnetic spectrometer, an inlet of the non-magnetic core holder is connected with an air source, and a first stop valve and a first pressure sensor are arranged between the non-magnetic core holder and the air source; the outlet of the non-magnetic core holder is connected with a back pressure valve, the back pressure valve is controlled to be opened and closed by a back pressure liquid injection pump for providing back pressure, a third stop valve is arranged between the back pressure valve and the back pressure valve, a second pressure sensor is further arranged between the outlet of the non-magnetic core holder and the back pressure valve, and the back pressure valve is further connected with a gas flowmeter;
the confining pressure liquid pressurizing pump is connected with the second stop valve and then connected with the non-magnetic core holder and is used for injecting confining pressure liquid to provide required confining pressure; one end of the confining pressure liquid cooling box is also connected with an inlet of the confining pressure cavity of the non-magnetic core holder, and the other end of the confining pressure liquid cooling box is connected with a confining pressure circulating pump and then is connected with an outlet of the confining pressure cavity of the non-magnetic core holder; and the outlet of the confining pressure cavity of the non-magnetic core holder is also connected with a temperature sensor.
4. The method for dynamically determining gas hydrate saturation and permeability in a porous medium according to claim 3, wherein: and the computer system is respectively connected with the first pressure sensor, the second pressure sensor, the temperature sensor, the nuclear magnetic spectrometer and the gas flowmeter.
5. The method for dynamically determining gas hydrate saturation and permeability in a porous medium according to claim 4, wherein: and a drying bottle is also arranged between the backpressure valve and the gas flowmeter.
6. The method for dynamically determining gas hydrate saturation and permeability in a porous medium according to claim 3, wherein: the nonmagnetic core holder comprises a core, a PEEK confining pressure cylinder, PEEK filling plungers, a heat-shrinkable sleeve and metal plugs, wherein the core is packaged between the two PEEK filling plungers through the heat-shrinkable sleeve, the PEEK filling plungers and the core are integrally inserted into the PEEK confining pressure cylinder, and the metal plugs are arranged at two ends of the PEEK confining pressure cylinder for sealing; and a cavity is formed between the PEEK confining pressure cylinder body and the thermal shrinkage sleeve and is used as a confining pressure cavity into which nonmagnetic low-temperature confining pressure liquid is pumped.
7. The method for dynamically determining gas hydrate saturation and permeability in a porous medium according to claim 6, wherein: and opening the first stop valve and the second stop valve, respectively adding confining pressure liquid and gas into the confining pressure cavity and the rock core pore space through a confining pressure liquid pressurizing pump and a gas source, and setting confining pressure and gas pressure.
8. The method for dynamically determining gas hydrate saturation and permeability in a porous medium according to claim 7, wherein: setting inlet pressure in the core hole, adjusting confining pressure, keeping the pressure difference between the confining pressure and the average air pressure unchanged, opening a third stop valve, pumping back pressure liquid through a back pressure liquid injection pump, and opening the back pressure valve to release pressure; and acquiring the gas flow of an outlet through a computer system and a gas flowmeter, and calculating the permeability according to the gas flow by using a gas Darcy formula.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011117140.9A CN112485281B (en) | 2020-10-19 | 2020-10-19 | Method for dynamically measuring gas hydrate saturation and permeability in porous medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011117140.9A CN112485281B (en) | 2020-10-19 | 2020-10-19 | Method for dynamically measuring gas hydrate saturation and permeability in porous medium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN112485281A CN112485281A (en) | 2021-03-12 |
| CN112485281B true CN112485281B (en) | 2022-04-01 |
Family
ID=74926630
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202011117140.9A Active CN112485281B (en) | 2020-10-19 | 2020-10-19 | Method for dynamically measuring gas hydrate saturation and permeability in porous medium |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112485281B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114577837A (en) * | 2022-02-21 | 2022-06-03 | 中国石油大学(华东) | Device and experimental method for evaluating pore throat structure and permeability of carbon dioxide sequestration and displacement |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111220639A (en) * | 2018-11-26 | 2020-06-02 | 中国石油天然气股份有限公司 | Method and device for determining gas saturation of rock core during gas flooding based on nuclear magnetic resonance |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8185314B2 (en) * | 2007-02-13 | 2012-05-22 | Schlumberger Technology Corporation | Method and system for determining dynamic permeability of gas hydrate saturated formations |
| CN104390902B (en) * | 2014-11-20 | 2017-01-25 | 大连理工大学 | Method for analyzing pore distribution of sediment by virtue of saturation change of gas hydrate |
| CN111220522A (en) * | 2019-10-28 | 2020-06-02 | 中国石油大学(华东) | Core scale logging calculation method for hydrate saturation of high-argillaceous fine-grained sediment |
-
2020
- 2020-10-19 CN CN202011117140.9A patent/CN112485281B/en active Active
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111220639A (en) * | 2018-11-26 | 2020-06-02 | 中国石油天然气股份有限公司 | Method and device for determining gas saturation of rock core during gas flooding based on nuclear magnetic resonance |
Also Published As
| Publication number | Publication date |
|---|---|
| CN112485281A (en) | 2021-03-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN206410978U (en) | A kind of tight rock gas phase relative permeability measurement apparatus | |
| CN106383221B (en) | A kind of reservoir stress sensitive experiment test method and device | |
| CN106153662A (en) | The measuring method of rock core stress sensitivity | |
| CN109470616B (en) | Multifunctional seepage testing system for rock | |
| CN109682850B (en) | Nuclear magnetic resonance testing device for online imbibition experiment and experiment method | |
| CN210834567U (en) | Shale mixes wettability experiment testing arrangement | |
| CN113075102B (en) | Method for establishing mathematical model of relation between spontaneous imbibition amount of porous medium and time | |
| CN113431537B (en) | Unsteady variable-flow-rate large-scale rock core water flooding gas relative permeability testing method | |
| CN113358683B (en) | Water flooding experimental device and method for researching core end face effect | |
| CN112485281B (en) | Method for dynamically measuring gas hydrate saturation and permeability in porous medium | |
| CN111220640B (en) | Experimental method for evaluating different flow modes of gas in dense porous medium | |
| CN115266800A (en) | Condensate oil saturation testing method based on two-dimensional nuclear magnetic resonance | |
| CN110967364A (en) | Combined water injection huff and puff experimental device and method for nuclear magnetic resonance | |
| CN112505298B (en) | In-situ test method for compact oil gas storage and production performance parameters | |
| CN115479964A (en) | Physical simulation method for flowback after lamination of compact oil storage layer | |
| CN115420766B (en) | Based on T 2 Method for measuring distribution of residual oil in sandstone water injection oil extraction by spectrum analysis | |
| CN211426392U (en) | High-temperature high-pressure gas mixing experimental device | |
| CN108956422A (en) | A kind of porosity experimental measurement method of compact reservoir | |
| CN111426617B (en) | Quantitative prediction method for porosity of dense reservoir of land lake basin under geological conditions | |
| CN109298008B (en) | Method, device and system for analyzing oil-water content in porous medium displacement process | |
| Wu et al. | Research on Adsorption and Desorption Characteristics of Gas in Coal Rock Based on Nuclear Magnetic Resonance Technology | |
| CN114382460B (en) | Logging evaluation method and device for low-permeability and tight gas reservoir water outlet result | |
| CN118393115B (en) | Method for determining compact gas filling lower limit based on high-pressure mercury injection and filling simulation | |
| CN116660306B (en) | Experimental method for measuring shale gas content based on plunger samples and crushed samples | |
| CN214749620U (en) | Multifunctional compact rock core gas displacement device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CB03 | Change of inventor or designer information |
Inventor after: Yao Yanbin Inventor after: Lei Xin Inventor after: Liu Dameng Inventor after: Luo Wanjing Inventor after: Wen Zhiang Inventor after: Cai Yidong Inventor before: Lei Xin Inventor before: Yao Yanbin Inventor before: Liu Dameng Inventor before: Luo Wanjing Inventor before: Wen Zhiang Inventor before: Cai Yidong |
|
| CB03 | Change of inventor or designer information |