CN113622906A - Testing device and testing method for simulating mechanical properties of marine energy soil-well interface in hydrate exploitation process - Google Patents
Testing device and testing method for simulating mechanical properties of marine energy soil-well interface in hydrate exploitation process Download PDFInfo
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- CN113622906A CN113622906A CN202110924314.0A CN202110924314A CN113622906A CN 113622906 A CN113622906 A CN 113622906A CN 202110924314 A CN202110924314 A CN 202110924314A CN 113622906 A CN113622906 A CN 113622906A
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- 238000012360 testing method Methods 0.000 title claims abstract description 55
- 238000000034 method Methods 0.000 title claims abstract description 49
- 230000008569 process Effects 0.000 title claims abstract description 45
- 239000002689 soil Substances 0.000 claims abstract description 51
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 49
- 239000007789 gas Substances 0.000 claims abstract description 48
- 239000007788 liquid Substances 0.000 claims abstract description 27
- 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 claims abstract description 27
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 25
- 238000011068 loading method Methods 0.000 claims abstract description 16
- 238000011084 recovery Methods 0.000 claims abstract description 14
- 238000010008 shearing Methods 0.000 claims abstract description 13
- 238000005065 mining Methods 0.000 claims abstract description 12
- 238000000926 separation method Methods 0.000 claims abstract description 12
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- 238000012545 processing Methods 0.000 claims abstract description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 17
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 9
- 239000000741 silica gel Substances 0.000 claims description 9
- 229910002027 silica gel Inorganic materials 0.000 claims description 9
- 230000001105 regulatory effect Effects 0.000 claims description 8
- 238000006073 displacement reaction Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 230000001276 controlling effect Effects 0.000 claims description 3
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- 239000011148 porous material Substances 0.000 claims description 2
- 238000007789 sealing Methods 0.000 claims description 2
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- 230000015572 biosynthetic process Effects 0.000 abstract description 7
- 238000003786 synthesis reaction Methods 0.000 abstract description 7
- 238000011160 research Methods 0.000 description 8
- 238000002347 injection Methods 0.000 description 5
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
- E21B49/001—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells specially adapted for underwater installations
Abstract
The invention belongs to the field of mechanical testing of ocean energy soil exploitation, and particularly relates to a testing device and a testing method for simulating mechanical characteristics of an ocean energy soil-well interface in a hydrate exploitation process. The testing device comprises a triaxial pressure chamber, a stress loading system, an air supply pressurization system, a water bath water tank, a soil-well interface sample, a back pressure valve, a gas-liquid separation recovery system and a data acquisition system; the stress loading system is connected with the triaxial pressure chamber to realize loading in different stress modes; the gas supply pressurization system is connected with the triaxial pressure chamber, provides a gas source and controls the application of gas pressure to generate a hydrate; the water bath water tank system seamlessly surrounds the triaxial pressure chamber and controls the indoor temperature; the mining well interface is spliced with a soil body sample and is installed in a triaxial pressure chamber, and the mechanical characteristics of the soil-well interface in the mining process are simulated; the data transmission acquisition processor is respectively connected with the triaxial pressure chamber, the high-pressure pump, the confining pressure loader, the axial pressure loader, the water bath water tank and the back pressure valve, and is used for acquiring test data at regular time and storing and processing the test data. The method realizes the synthesis of the soil containing the natural gas hydrate, controls the time of high-temperature low-pressure decomposition of the hydrate, and can accurately test the shearing characteristic between the marine energy soil and the well interface in the hydrate exploitation process.
Description
Technical Field
The invention belongs to the field of mechanical testing of ocean energy soil exploitation, and particularly relates to a testing device and a testing method for simulating mechanical properties of an ocean energy soil-well interface in a hydrate exploitation process.
Background
The natural gas hydrate is a novel clean energy, and has abundant hydrate resources in the east sea, the south sea and the adjacent sea areas of China according to estimation of the national resource ministry. Natural gas hydrates are usually formed in loose sediments in shallow deep water overburden layers, have the characteristics of poor cementation and low strength, and can generate a phenomenon of weakening an earth-well interface in the process of deep sea exploitation: softening a soil-structure interface of the natural gas hydrate coating under the action of the cyclic load of the uplift structure; under the action of deep seawater power, liquefaction can occur on the soil-well interface; the phase change of the natural gas hydrate at the soil-well interface can be caused by multi-process coupling (deformation process, chemical process, seepage process, heat conduction and the like) in the exploitation process. Weakening of the soil-well structure interface can cause instability of the foundation of the exploitation platform, and seriously endangers the exploitation safety of the natural gas hydrate. However, the existing research on the natural gas hydrate only focuses on productivity evaluation and the mechanical characteristics of the deposit, and the interaction between the soil body and the well interface in the hydrate exploitation process is neglected. Therefore, the research on the mechanical properties of the marine energy soil-well interface containing the natural gas hydrate in the process of exploiting the hydrate has important significance for exploiting the hydrate.
The mechanical property of the ocean energy soil is one of the key points in the current research, and the simulation experiment between the soil-well structure interfaces containing the natural gas hydrate is less. The gas hydrate injection synthesis and direct shear test system is developed in the Weekly and the like in the research and application of a gas hydrate injection synthesis and direct shear test system, the system comprises a hydrate injection synthesis subsystem and a hydrate-containing soil low-temperature high-pressure direct shear subsystem, the hydrate injection synthesis system consists of a gas supply module, a water supply module, a temperature control module and a reaction kettle module, and a hydrate injection synthesis device can quickly synthesize hydrate by injecting water mist and reacting the water mist with gas in a high-pressure low-temperature environment, so that the supporting body type gas hydrate can be quickly and efficiently prepared by the method. The direct shear test system consists of a gas supply module, a stress loading module, a temperature control module and a data acquisition module, and can realize direct shear tests of cementing type and filling type hydrates by applying axial pressure by a constant-speed constant-pressure pump. Compared with a triaxial shear test, the direct shear test is more convenient and time-saving, and can quickly obtain the mechanical parameters of the sediment. However, the system can not simulate different working conditions of hydrate exploitation and can not simulate the mechanical characteristics between hydrate deposits and the structural interface of the exploitation well in the hydrate exploitation process.
On the basis of referring to the relevant natural gas hydrate test research data at home and abroad, the existing hydrate test device is considered to have certain limitations. At present, most of the mechanical property test researches of natural gas hydrate-containing soil at home and abroad are developed by a triaxial test based on indoor natural gas hydrate synthesis, and the simulation experiment of the natural gas hydrate-containing soil-well structure interface is only rarely reported in public by simulating various properties of the natural gas hydrate-containing soil under different geological conditions (confining pressure, air pressure, temperature and the like) and in different mining modes. At present, the research on the mechanical properties of the soil-structure surface is mostly carried out by a direct shear apparatus, and the exploitation process of the natural gas hydrate cannot be simulated. The invention provides a device and a method for testing the mechanical properties of a marine energy soil-well interface in the process of simulating hydrate exploitation, which are improved on the basis of the existing hydrate testing equipment and combined with the traditional direct shear test. The device can be used for preparing the soil containing the natural gas hydrate and carrying out a conventional mechanical test on the soil containing the natural gas hydrate under a high-pressure low-temperature environment, can control the decomposition time of the hydrate, simulate the influence of the hydrate exploitation process on the mechanical properties of hydrate sediments, simulate the shearing process of an earth-well interface in the hydrate exploitation process and provide a good test technical support for researching the earth-structure plane weakening behavior in the hydrate exploitation process.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a testing device and a testing method for simulating the mechanical properties of an ocean energy soil-well interface in the process of exploiting a hydrate. The device can test the shear mechanical property of the marine energy soil-well interface in the hydrate exploitation process, and the shear mechanical property is displayed by using the data acquisition system, so that the operation is simple and the result is reliable.
In order to achieve the above object, the solution adopted by the present invention is as follows:
a testing device for simulating mechanical properties of a marine energy soil-well interface in a hydrate exploitation process comprises: the device comprises a triaxial pressure chamber, an axial pressure loader, a confining pressure loader, an air supply and pressure regulation system, a water bath water tank, a back pressure valve, a gas-liquid separation and recovery device and a data transmission and acquisition processor. The maximum axial load that the device can provide is 1500kN, and maximum confined pressure is 60MPa, and the range of applying of atmospheric pressure is 0 ~ 20MPa, and the control range of temperature is-30 ~ 99.9 ℃. Wherein: the gas supply pressure regulating system, the confining pressure loader and the axial pressure loader are respectively connected with the triaxial pressure chamber, so that gas pressure application, loading in different stress modes and different stress paths are realized; the backpressure valve can control the decomposition of hydrate; the water bath water tank seamlessly surrounds the triaxial pressure chamber to realize the control of test temperature; the mining well interface is spliced with a soil body sample and is installed in a triaxial pressure chamber, and the mechanical characteristics of the soil-well interface in the mining process are simulated; the data transmission acquisition processor is respectively connected with the triaxial pressure chamber, the air supply pressure regulating system, the confining pressure loader, the axial pressure loader, the water bath water tank and the back pressure valve, and is used for acquiring test data at regular time and storing and processing the test data.
Compared with the prior art, the invention has the following beneficial effects:
1. the soil body sample containing the natural gas hydrate can be stably generated, and the mechanical property test research of the soil-well interface in the hydrate mining process can be realized;
2. the temperature rise and pressure reduction decomposition of the hydrate in different decomposition time can be considered, and the influence of different mining working conditions on the mechanical characteristics of the soil-well interface can be simulated by pressure reduction or temperature rise independently;
3. the upper base and the lower base are composed of an L-shaped steel block with holes and soft silica gel with holes, so that gas-liquid flow is ensured, natural gas hydrate is generated and decomposed smoothly, and meanwhile, axial pressure is transmitted to a sample soil body and a well interface respectively, so that mutual shearing between the soil-well interface is realized;
4. the data are automatically acquired and calculated, so that the data acquisition precision is high, the automation degree is high, and the manual error is reduced;
drawings
FIG. 1 is a schematic structural diagram of a soil-well interface mechanical property testing device in a process of simulating hydrate exploitation;
FIG. 2 is a schematic diagram of upper/lower cushion blocks and soil-well interface samples of a soil-well interface mechanical property testing device in the process of simulating hydrate exploitation;
FIG. 3 is a schematic diagram of a gas-liquid separation and recovery device in a soil-well interface mechanical property testing device in a simulated hydrate exploitation process.
In the figure: 1. the device comprises a triaxial pressure chamber, 2, an axial pressure loader, 3, a confining pressure loader, 4, a soil-well interface sample, 5, an air supply and pressure regulation system, 6, a water bath water tank, 7, a back pressure valve, 8, a gas-liquid separation and recovery device, 9 and a data acquisition system.
Detailed Description
As shown in fig. 1, the testing device for simulating the mechanical properties of the marine energy soil-well interface in the hydrate exploitation process comprises: the device comprises a triaxial pressure chamber 1, an axial pressure loader 2, a confining pressure loader 3, a soil-well interface shear sample 4, an air supply and pressure regulation system 5, a water bath water tank 6, a back pressure valve 7, a gas-liquid separation and recovery device 8 and a data acquisition system 9; wherein: the stress loading systems 2 and 3 are connected with the triaxial pressure chamber 1 to realize loading in different stress modes; the gas supply and pressure regulation system 5 is connected with the triaxial pressure chamber 1, provides a gas source and controls gas to apply pressure; the water bath water tank 6 seamlessly surrounds the triaxial pressure chamber 1, and the temperature in the confining pressure chamber is controlled to realize stable generation of the hydrate or heating decomposition of the hydrate; the soil-well interface sample 4 is arranged in the triaxial pressure chamber 1 and simulates the mutual shearing action of the soil-well interface caused by mining; the backpressure valve 7 is connected with the triaxial pressure chamber 1, and the hydrate decomposition is controlled by adjusting the pressure of the backpressure valve; the gas-liquid separation and recovery device 8 is connected with the back pressure valve 7 and is used for metering and recovering gas and liquid; the data acquisition system 9 acquires test data at regular time and stores and processes the test data.
The gas supply pressure regulating system 5 comprises a methane gas cylinder 51, a pressure regulating valve 52, a pressure gauge 53 and a gas valve 54. Wherein the pressure regulating valve 52 is connected with a methane gas bottle 51 to set the pressure of the buffer container, the pressure gauge 53 is used for measuring the gas pressure, and the gas valve 54 controls the gas input.
The water bath water tank 6 seamlessly surrounds the triaxial pressure chamber 1, and the thermometer 61 can measure the internal temperature of the triaxial pressure chamber 1, so that the accurate control of the temperature is ensured.
The back pressure valve 7 is connected with the sample through the lower cushion block 12, when the air pressure inside the sample is higher than the preset pressure of the back pressure valve 7, the gas is discharged through the back pressure valve 7 until the air pressure reaches the preset pressure, and the pressure of the back pressure valve 7 is set to realize controllable decomposition of the hydrate. The pressure gauge 71 is used for measuring the gas outlet pressure in the pipeline; and a gas-liquid valve 72 for controlling gas-liquid output.
As shown in fig. 2, the triaxial cell 1 is provided with a lower cushion block 12, an upper base of an earth-well interface sample (an L-shaped steel block with holes 43 and a semicircular soft silica gel with holes 44), a semicircular soil body sample 41, a well interface 42 and an upper base of an earth-well interface sample (an L-shaped steel block with holes 43 and a semicircular soft silica gel with holes 44) from bottom to top. The upper mat 11 is connected to the air supply and pressure regulation system 5 through a line 55. The lower pad 12 is connected to a back pressure valve via a line 73. The L-shaped perforated steel block 43 is uniformly provided with circular holes 432 with the diameter of 1mm, the inner layer and the outer layer are uniformly distributed, and the circular holes 432 penetrate through the whole L-shaped perforated steel block 43. The porous soft silica gel 44 is provided with 4 circular holes 441 with the diameter of 3mm and the centers of the circular holes correspond to the centers of the circular holes on the inner layer of the L-shaped porous steel block 43. The upper surface of the L-shaped perforated steel block 43 is provided with a groove 431 with the depth of 0.5mm, which is beneficial to the circulation of methane gas.
The soil-well interface sample 4 is 100mm high and 50mm in diameter; the semi-cylindrical soil sample 41 has the same size as the well interface 42, and has a diameter of 50mm and a height of 60 mm. The outer side of the soil-well interface sample 4 is wrapped with a thermal shrinkage rubber sleeve, and the upper end and the lower end of the thermal shrinkage rubber sleeve are respectively connected with an upper cushion block 11 and a lower cushion block 12 to ensure the sealing of the sample; in addition, the two axial sides of the thermal shrinkage rubber sleeve are provided with an axial strain sensor 45 and an axial displacement sensor 46, and the middle part of the outer surface is provided with an annular strain sensor 47.
The L-shaped perforated steel block 43 has high rigidity and is used for transferring axial pressure applied by the axial pressure loading system 2 to the semi-cylindrical soil sample 41 and the well interface 42 so as to realize mutual shearing between the soil sample and the well interface; the rigidity of the semicircular porous soft silica gel 44 is extremely low, mutual dislocation during shearing of a soil-well interface is not influenced, and the same confining pressure value in the thermal shrinkage rubber sleeve and the inside of the triaxial pressure chamber 1 in the test process can be kept.
As shown in fig. 3, the gas-liquid separation and recovery device 8 includes a gas-liquid separator 81, a drying box 82, a gas flow meter 83, a gas recovery bottle 84, a liquid flow meter 85, and a liquid collection device 86. The gas-liquid separation meter 81 is connected to the back pressure valve 7 to separate a gas-liquid mixture; the liquid flows directly into the liquid recovery device 86, and the gas flows into the gas recovery device 84 through the drying box 82, and is metered. The gas flowmeter 83 records the gas production rate and the accumulated gas production rate, thereby judging the production condition of the hydrate.
The test method for simulating the mechanical properties of the ocean energy soil-well interface in the hydrate exploitation process adopts the measuring device and comprises the following steps:
1. mixing dry soil and deionized water to prepare an unsaturated semi-cylindrical soil sample with certain dry density and water content, attaching the unsaturated semi-cylindrical soil sample to a well interface, splicing the unsaturated semi-cylindrical soil sample with an upper base and a lower base, wrapping the unsaturated semi-cylindrical soil sample with a heat-shrinkable rubber sleeve, and placing the coated unsaturated semi-cylindrical soil sample in a triaxial pressure chamber;
2. applying confining pressure to a preset pressure through a stress loading system, injecting methane gas into a soil sample to the preset pressure by using a gas supply and pressure regulation system, keeping the state and ventilating for 24 hours to fill the pores of the soil with the methane gas;
3. setting the temperature of a water bath water tank, reducing the temperature in the triaxial pressure chamber to the temperature (1 ℃) required by the reaction, gradually reducing the air pressure, and starting to generate a hydrate; when the barometer shows that the air pressure is kept unchanged, the generation of the natural gas hydrate is finished;
4. soil-well interface shear tests before and after hydrate decomposition and at different decomposition times can be respectively carried out:
after the hydrate is generated, adjusting the internal confining pressure of the triaxial pressure chamber to a preset value, then slowly applying axial load through a stress loading system, respectively transmitting axial pressure to a sample soil body and a well interface through a sample base to enable the soil-well interface to generate shear, and measuring the circumferential strain data and the axial strain data (shear displacement) of the sample through a strain sensor.
After the hydrate is generated, the temperature is raised and the pressure is reduced through a water bath water tank and a back pressure valve to control the decomposition of the hydrate, gas is discharged through the back pressure valve until the air pressure in the sample reaches the preset air pressure of the back pressure valve, the controllable decomposition of the hydrate is realized, and the hydrate-containing samples with different decomposition times can be obtained by controlling the decomposition time of the hydrate; after the hydrate is decomposed for a preset time, axial load is slowly applied through a stress loading system, axial pressure is respectively transmitted to a sample soil body and a well interface through a sample base, so that shearing is generated on the soil-well interface, and annular strain data and axial strain data (shearing displacement) of the sample are measured through a strain sensor.
5. The influence of the hydrate exploitation process on the mechanical properties of the soil-well interface can be contrastively analyzed through the shear data of the soil-well interface before and after the hydrate is decomposed.
6. In addition, the conventional soil mechanical property test containing the natural gas hydrate can be carried out; and (3) replacing the soil-well interface sample with a pure soil sample with the same size, synthesizing and decomposing the hydrate according to the steps, carrying out a triaxial shear test on the soil containing the natural gas hydrate, and simulating and analyzing the mechanical property of the soil body in the hydrate mining process.
Claims (8)
1. A testing device for simulating mechanical properties of a marine energy soil-well interface in a hydrate exploitation process comprises: the device comprises a triaxial pressure chamber, an axial pressure loader, a confining pressure loader, an air supply and pressure regulation system, a water bath water tank, a back pressure valve, a gas-liquid separation and recovery device and a data transmission and acquisition processor. The maximum axial load that the device can provide is 1500kN, and maximum confined pressure is 60MPa, and the range of applying of atmospheric pressure is 0 ~ 20MPa, and the control range of temperature is-30 ~ 99.9 ℃. Wherein: the gas supply pressure regulating system, the confining pressure loader and the axial pressure loader are respectively connected with the triaxial pressure chamber, so that gas pressure application, loading in different stress modes and different stress paths are realized; the backpressure valve can control the decomposition of hydrate; the water bath water tank seamlessly surrounds the triaxial pressure chamber to realize the control of test temperature; the mining well interface is spliced with a soil body sample and is installed in a triaxial pressure chamber, and the mechanical characteristics of the soil-well interface in the mining process are simulated; the data transmission acquisition processor is respectively connected with the triaxial pressure chamber, the air supply pressure regulating system, the confining pressure loader, the axial pressure loader, the water bath water tank and the back pressure valve, and is used for acquiring test data at regular time and storing and processing the test data.
2. The device for simulating the mechanical property of the marine energy soil-well interface in the hydrate exploitation process, according to claim 1, is characterized in that: the triaxial pressure chamber is provided with a lower cushion block, an upper base of an earth-well interface sample (an L-shaped perforated steel block and semicircular perforated soft silica gel), a semicircular column earth body sample, a well interface and an upper base of the earth-well interface sample (an L-shaped perforated steel block and semicircular perforated soft silica gel) from bottom to top. The upper cushion block is connected with an air supply pressure regulating system through a pipeline. The lower cushion block is connected with the backpressure valve through a pipeline. L type band hole steel block evenly is equipped with inside and outside two-layer evenly distributed's diameter 1mm round hole, and the round hole runs through whole L type band hole steel block. The soft silica gel with the holes is provided with round holes with the diameter of 3mm, and the centers of the round holes correspond to the centers of the round holes in the inner layer of the L-shaped steel block with the holes. A groove with the depth of 0.5mm is formed in the upper surface of the L-shaped perforated steel block, and methane gas circulation is facilitated.
3. The device for simulating the mechanical property of the soil-well interface in the hydrate exploitation process according to the claims 1-2, wherein: the soil-well interface sample 4 is 100mm high and 50mm in diameter; the semi-cylindrical soil sample has the same size with the well interface, the diameter is 50mm, and the height is 60 mm. The outer side of the soil-well interface sample is wrapped with a thermal shrinkage rubber sleeve, and the upper end and the lower end of the thermal shrinkage rubber sleeve are respectively connected with an upper cushion and a lower cushion block to ensure the sealing of the sample; in addition, two axial strain sensors are arranged on two axial sides of the thermal shrinkage rubber sleeve, and an annular strain sensor is arranged in the middle of the outer surface of the thermal shrinkage rubber sleeve.
4. The device for simulating the mechanical property of the soil-well interface in the hydrate exploitation process according to the claims 1 to 3, wherein: the L-shaped perforated steel block has high rigidity and is used for transferring axial pressure applied by the axial pressure loading system to the semi-cylindrical soil sample and the well interface so as to realize mutual shearing between the soil sample and the well interface; the rigidity of the semicircular porous soft silica gel is extremely low, mutual dislocation during shearing of a soil-well interface is not influenced, and the confining pressure value in the thermal shrinkage rubber sleeve and the confining pressure value in the triaxial pressure chamber in the test process can be kept to be the same.
5. The device for simulating the mechanical property of the marine energy soil-well interface in the hydrate exploitation process as claimed in claims 1 to 4, wherein: the water bath water tank comprises a constant-temperature water bath and a thermometer; the water bath water tank seamlessly surrounds the triaxial pressure chamber; the temperature application range is-30 to 99.9 ℃.
6. The device for simulating the mechanical property of the soil-well interface in the hydrate exploitation process according to the claims 1 to 5, wherein: the back pressure valve is connected with the sample through the lower cushion block, the temperature rise and the pressure reduction are carried out through the water bath water tank system and the back pressure valve to control the decomposition of the hydrate, the gas is discharged through the back pressure valve until the pressure of the back pressure valve is equal to the pressure in the sample, the controllable decomposition of the hydrate is realized, the hydrate decomposition time can be controlled, and the hydrate samples with different decomposition times can be obtained.
7. The device for simulating the mechanical property of the soil-well interface in the hydrate exploitation process according to the claims 1 to 6, wherein: the gas-liquid separation and recovery device comprises a gas-liquid separation meter, a gas flowmeter, a liquid flowmeter, a drying box, a gas collecting bottle and a liquid collecting device. The gas-liquid separation meter is connected with the back pressure valve to separate the gas-liquid mixture; the liquid directly flows into the liquid recovery device, and the gas flows into the gas recovery device through the drying box and is metered. And the gas flowmeter records the gas production rate and the accumulated gas production rate, so as to judge the exploitation condition of the hydrate.
8. The device for simulating the mechanical property of the soil-well interface in the hydrate exploitation process, according to the claims 1 to 7, is characterized by comprising the following steps:
(1) mixing dry soil and deionized water to prepare an unsaturated semi-cylindrical soil sample with certain dry density and water content, attaching the unsaturated semi-cylindrical soil sample to a well interface, splicing the unsaturated semi-cylindrical soil sample with an upper base and a lower base, wrapping the unsaturated semi-cylindrical soil sample with a heat-shrinkable rubber sleeve, and placing the coated unsaturated semi-cylindrical soil sample in a triaxial pressure chamber;
(2) applying confining pressure to a preset pressure through a stress loading system, injecting methane gas into a soil sample to the preset pressure by using a gas supply pressurization system, keeping the state and ventilating for 24 hours to fill the pores of the soil with the methane gas;
(3) setting the temperature of a water bath water tank, reducing the temperature in the triaxial pressure chamber to the temperature (1 ℃) required by the reaction, gradually reducing the air pressure, and starting to generate a hydrate; when the barometer shows that the air pressure is kept unchanged, the generation of the natural gas hydrate is finished;
(4) and soil-well interface shear tests before and after hydrate decomposition and at different decomposition times can be respectively carried out:
after the hydrate is generated, adjusting the internal confining pressure of the triaxial pressure chamber to a preset value, then slowly applying axial load through a stress loading system, respectively transmitting axial pressure to a sample soil body and a well interface through a sample base to enable the soil-well interface to generate shear, and measuring the circumferential strain data and the axial strain data (shear displacement) of the sample through a strain sensor.
After the hydrate is generated, the temperature is raised and the pressure is reduced through a water bath water tank and a back pressure valve to control the decomposition of the hydrate, gas is discharged through the back pressure valve until the air pressure in the sample reaches the preset air pressure of the back pressure valve, the controllable decomposition of the hydrate is realized, and the hydrate-containing samples with different decomposition times can be obtained by controlling the decomposition time of the hydrate; after the hydrate is decomposed for a preset time, axial load is slowly applied through a stress loading system, axial pressure is respectively transmitted to a sample soil body and a well interface through a sample base, so that shearing is generated on the soil-well interface, and annular strain data and axial strain data (shearing displacement) of the sample are measured through a strain sensor.
(5) And the influence of the hydrate exploitation process on the mechanical properties of the soil-well interface can be contrastively analyzed through the shearing data of the soil-well interface before and after the hydrate is decomposed.
(6) In addition, the conventional soil mechanical property test containing the natural gas hydrate can be carried out; and (3) replacing the soil-well interface sample with a pure soil sample with the same size, synthesizing and decomposing the hydrate according to the steps, carrying out a triaxial shear test on the soil containing the natural gas hydrate, and simulating and analyzing the mechanical property of the soil body in the hydrate mining process.
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| CN114837626A (en) * | 2022-03-29 | 2022-08-02 | 哈尔滨工程大学 | Device and method for replacing natural gas hydrate with stress-controllable carbon dioxide |
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