Test system for testing and analyzing desorption / adsorption gas pressure of in-situ reservoir core

Abstract

A test system for testing and analyzing the desorption / adsorption gas pressure of an in-situ reservoir core, comprising an adsorption / desorption apparatus, a gas injection apparatus, a vacuum pumping apparatus, and a desorption measurement apparatus. The adsorption / desorption apparatus comprises a coal sample tank (20), and the adsorption / desorption apparatus further comprises a volume-variable diffusion unit (10). The volume-variable diffusion unit (10) comprises a diffusion tank (14), a hollow centralizing cylinder (15), and a driving mechanism (17) arranged at a bottom end of the centralizing cylinder (15). A diffusion cavity (141) is provided in the diffusion tank (14), the diffusion cavity (141) being in communication with the interior of the centralizing cylinder (15). A plunger (16) is provided in the centralizing cylinder (15), a top end of the plunger (16) extends into the diffusion cavity (141), and the driving mechanism is used for driving the plunger (16) to move up and down in the centralizing cylinder (16) and the diffusion cavity (141). According to the technical solution, the process of a space in which a coal sample is located expanding when the coal sample is put into a coring device during coring can be simulated, thereby ensuring the accuracy of in-situ reservoir gas pressure measurement.

Description

A test system for testing and analyzing desorption gas pressure of in-situ reservoir core TECHNICAL FIELD

[0001] The present application relates to a test system, in particular to a test system for testing and analyzing desorption gas pressure of in-situ reservoir core. BACKGROUND

[0002] With the rapid development of the world economy, the resources in the shallow part of the earth are gradually exhausted, and the resource development gradually moves to the deep part of the earth. At present, the in-situ reservoir mining such as coal mining has a depth of 1500 meters, non-ferrous metal mining has a depth of more than 4350 meters, and oil and gas resource mining has a depth of 7500 meters. Deep mining will become the norm in resource development. Exploring and developing deep in-situ rock mechanics theory and testing technology is an important basis for realizing deep mining. Taking coal mining as an example, a test system is generally built to simulate the process of putting coal samples in the in-situ coal seam into a coring device during the coal mining process. Through experimental methods, the coal samples are subjected to adsorption and desorption experiments to determine the desorption amount of the coal samples. The desorption amount data is analyzed and based on the in-situ reservoir gas pressure calculation method, so that the in-situ coal seam gas pressure can be determined. Through the determination of the in-situ coal seam gas pressure, the prevention and treatment of gas accidents can be effectively realized, and the safety of the coal mining process can be ensured.

[0003] The existing test system generally includes an adsorption and desorption device, a gas injection device, a vacuum pumping device and a desorption measuring device. The adsorption and desorption device generally includes a coal sample tank. The volume in the coal sample tank is generally constant and cannot be changed. The process that the space volume of the coal sample becomes larger when the coal sample is put into the coring device during the coring process is not considered. The influence of the expansion of the space volume of the coal sample on the gas desorption of the coal sample is ignored, so that the adsorption amount and the desorption amount obtained cannot restore the real gas desorption situation, and the accurate determination of the in-situ coal seam gas pressure is affected. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the present application provides a test system for testing and analyzing desorption gas pressure of in-situ reservoir core. The space expansion process of the coal sample when the coal sample is put into the coring device during the coring process is simulated, and the accuracy of the determination of the in-situ reservoir gas pressure is ensured.

[0005] The technical scheme adopted by the present application to solve its technical problems is:

[0006] The utility model provides a kind of test system for testing and analyzing in-situ reservoir core desorption gas pressure, including adsorption and desorption device, gas injection device, vacuum pumping device and desorption measurement device, the adsorption and desorption device includes coal sample jar, the adsorption and desorption device further includes variable volume diffusion unit, the variable volume diffusion unit includes diffusion jar, hollow centralizer and the drive mechanism arranged at the bottom end of the centralizer, diffusion chamber is equipped in the diffusion jar, and the diffusion chamber is communicated with the inside of the centralizer, plunger is equipped in the centralizer, the top end of the plunger extends into the diffusion chamber, and the drive mechanism is used to drive the plunger to move up and down in the centralizer and diffusion chamber;The diffusion jar is connected with first connecting pipeline, second connecting pipeline and third connecting pipeline, and the first connecting pipeline, second connecting pipeline and third connecting pipeline are communicated with the diffusion chamber, the first connecting pipeline is connected with the gas injection device, the second connecting pipeline is connected with the vacuum pumping device, the third connecting pipeline is connected with the coal sample jar, the coal sample jar is connected with fourth connecting pipeline, and the third connecting pipeline and fourth connecting pipeline are communicated with the inside of the coal sample jar, the fourth connecting pipeline is used to be connected with the desorption measurement device, first switch valve, first pressure sensor are equipped on the first connecting pipeline in the direction close to the diffusion jar in sequence, second switch valve is equipped on the second connecting pipeline, third switch valve and second pressure sensor are equipped on the third connecting pipeline in the direction close to the coal sample jar in sequence.

[0007] As a preferred technical scheme, the drive mechanism includes a drive motor, a speed reducer and a connecting seat, the connecting seat is arranged at the bottom end of the centralizer, the speed reducer is arranged at the bottom end of the connecting seat, the drive motor is arranged at the bottom end of the speed reducer, the output shaft of the drive motor is connected with the input end of the speed reducer, the connecting seat is provided with a connecting shaft, the bottom end of the connecting shaft is connected with the output end of the speed reducer, the plunger is provided with a receiving cavity, the bottom end of the plunger is provided with a plunger opening communicated with the receiving cavity, the centralizer is provided with a lead screw, the top end of the lead screw is connected with the top end of the connecting shaft, the lead screw penetrates through the plunger opening and extends into the receiving cavity, and the lead screw is threadedly connected with a nut, the nut is located between the connecting seat and the plunger, and the top end of the nut is arranged in the plunger opening.

[0008] Preferably, the diffusion tank is externally sleeved with a first water jacket and a first heat preservation sleeve in sequence, a first heat preservation cavity is formed between the inner wall of the first water jacket and the diffusion tank, the outer wall of the first water jacket is provided with a first water inlet joint and a first water outlet joint, the first water inlet joint and the first water outlet joint are both in communication with the first heat preservation cavity, the outer wall of the first heat preservation sleeve is provided with a first avoiding hole for avoiding the first water inlet joint and a second avoiding hole for avoiding the first water outlet joint, and the first water inlet joint and the first water outlet joint are respectively used for being connected with a constant temperature water bath system.

[0009] Preferably, the gas injection device comprises a carbon dioxide gas cylinder, a first gas injection pipeline connected with the carbon dioxide gas cylinder, the first gas injection pipeline connected with the first connecting pipeline, a fourth switch valve, a first pressure reducing valve, a first pressure gauge, a fifth switch valve, a first flow controller, a first check valve and a sixth switch valve arranged on the first gas injection pipeline in sequence along the direction close to the diffusion tank, a methane gas cylinder, a second gas injection pipeline connected with the methane gas cylinder, the second gas injection pipeline connected with the first connecting pipeline, a seventh switch valve, a second pressure reducing valve, a second pressure gauge, an eighth switch valve, a second flow controller, a second check valve and a ninth switch valve arranged on the second gas injection pipeline in sequence along the direction close to the diffusion tank, a nitrogen gas cylinder, a third gas injection pipeline connected with the nitrogen gas cylinder, the third gas injection pipeline connected with the first connecting pipeline, a tenth switch valve, a third pressure reducing valve, a third pressure gauge, an eleventh switch valve, a third flow controller, a third check valve and a twelfth switch valve arranged on the third gas injection pipeline in sequence along the direction close to the diffusion tank, and a helium gas cylinder, a fourth gas injection pipeline connected with the helium gas cylinder, the fourth gas injection pipeline connected with the first connecting pipeline, and a thirteenth switch valve arranged on the fourth gas injection pipeline.

[0010] Preferably, the vacuumizing device comprises a vacuum pump and a vacuum tank, the vacuum pump is connected with a first vacuum pipeline, the first vacuum pipeline is connected with the vacuum tank, the vacuum tank is connected with a second vacuum pipeline, and the second vacuum pipeline is connected with the second connecting pipeline.

[0011] Preferably, the test system further comprises a gas drainage measuring device, a water injection device and a pressure boosting device, the fourth connecting pipeline is used for being connected with the gas drainage measuring device, the coal sample tank is connected with a first water inlet pipeline, the first water inlet pipeline is in communication with the inside of the coal sample tank, the first water inlet pipeline is connected with the water injection device, and the pressure boosting device is connected with the first connecting pipeline.

[0012] As a preferred technical scheme, the coal sample jar comprises a jar body, a T-shaped sealing upper cover and a T-shaped sealing lower cover, the top end and the bottom end of the jar body are respectively provided with a first opening and a second opening, the first opening and the second opening are in communication with the inside of the jar body, the horizontal part of the sealing upper cover is detachably arranged at the top end of the jar body, the vertical part of the sealing upper cover is inserted into the first opening, the third connecting pipeline is connected with the horizontal part of the sealing upper cover, the horizontal part and the vertical part of the sealing upper cover are provided with a first flow channel, the first flow channel is in communication with the third connecting pipeline and the inside of the jar body respectively, the horizontal part of the sealing upper cover is connected with the fourth connecting pipeline, the horizontal part and the vertical part of the sealing upper cover are provided with a second flow channel, the second flow channel is in communication with the fourth connecting pipeline and the inside of the jar body respectively, the horizontal part of the sealing lower cover is detachably arranged at the bottom end of the jar body, the vertical part of the sealing lower cover is inserted into the second opening, the horizontal part of the sealing lower cover is connected with the first water inlet pipeline, the horizontal part and the vertical part of the sealing lower cover are provided with a third flow channel, and the third flow channel is in communication with the first water inlet pipeline and the inside of the jar body respectively.

[0013] As a preferred technical scheme, the outside of the jar body is sequentially sleeved with a second water jacket and a second heat preservation sleeve, a second heat preservation cavity is formed between the inner wall of the second water jacket and the jar body, the outer wall of the second water jacket is provided with a second water inlet connector and a second water outlet connector, the second water inlet connector and the second water outlet connector are in communication with the second heat preservation cavity, the outer wall of the second heat preservation sleeve is provided with a first through hole for avoiding the second water inlet connector and a second through hole for avoiding the second water outlet connector, and the first water inlet connector and the first water outlet connector are respectively used for being connected with a constant temperature water bath system.

[0014] As a preferred technical scheme, the desorption measuring device comprises a gas chromatograph, at least three collection bags and a flow divider, the flow divider is connected with a fifth connecting pipeline, the fourth connecting pipeline is connected with a first conversion joint, the fifth connecting pipeline is connected with a second conversion joint, the first conversion joint is used for being connected with the second conversion joint, the collection bags are respectively connected with a sixth connecting pipeline and a seventh connecting pipeline, the sixth connecting pipeline is connected with the flow divider, the seventh connecting pipeline is connected with the gas chromatograph, a back pressure valve is arranged on the fourth connecting pipeline, an adjusting valve, a constant container and a fourteenth switch valve are sequentially arranged on the fifth connecting pipeline in the direction close to the flow divider; the gas drainage measuring device comprises a first container, a second container and a weighing device, a sealing head is inserted into an opening at the top end of the first container, one end of an exhaust pipeline is connected with a third conversion joint, the first conversion joint is used for being connected with the third conversion joint, the other end of the exhaust pipeline penetrates through a first through hole of the sealing head and extends into the first container, one end of a drainage pipeline penetrates through a second through hole of the sealing head and extends into the first container, the other end of the drainage pipeline is used for being inserted into the second container, and the second container is arranged on the weighing device.

[0015] As a preferred technical scheme, the water injection device comprises a first constant-speed constant-pressure pump, the first constant-speed constant-pressure pump is connected with a second water inlet pipeline, the second water inlet pipeline is connected with the first water inlet pipeline, and a water inlet valve is arranged on the second water inlet pipeline; the pressure boosting device comprises a second constant-speed constant-pressure pump, the second constant-speed constant-pressure pump is connected with the first connecting pipeline through a communication pipeline, the communication pipeline is located between the gas injection device and the first switch valve, and a fifteenth switch valve is arranged on the communication pipeline.

[0016] The beneficial effects of the present application are as follows: the variable volume diffusion unit is arranged, the plunger is driven to move downwards to different positions in the diffusion cavity and the righting cylinder by the driving mechanism of the variable volume diffusion unit, so that the volume of the diffusion cavity can be expanded, the process of expanding the space of the coal sample when the coal sample is placed into the corer in the coring process can be simulated, the real situation of gas adsorption and desorption of the coal sample in the field coring process is further restored, the accuracy of the obtained adsorption amount and desorption amount is ensured, and the accuracy of the in-situ reservoir gas pressure measurement is ensured. The in-situ reservoir gas pressure data measured is analyzed, so that the change rule of the in-situ reservoir gas pressure can be explored. BRIEF DESCRIPTION OF DRAWINGS

[0017] FIG. 1 is a structural schematic view of a test system for testing and analyzing in-situ reservoir core desorption gas pressure according to an embodiment of the present application;

[0018] FIG. 2 is a structural schematic view of a variable volume diffusion unit of an adsorption and desorption device of the test system shown in FIG. 1;

[0019] Fig. 3 is a top view of the variable volume diffusion unit shown in Fig. 2;

[0020] Fig. 4 is a cross-sectional view of the variable volume diffusion unit shown in Fig. 2 at A-A;

[0021] Fig. 5 is a cross-sectional view of the variable volume diffusion unit shown in Fig. 2 at B-B;

[0022] Fig. 6 is a structural view of a coal sample tank of the adsorption and desorption device of the test system shown in Fig. 1;

[0023] Fig. 7 is a cross-sectional view of the coal sample tank shown in Fig. 6. DETAILED DESCRIPTION

[0024] The concept, specific structure and generated technical effects of the present application will be described clearly and completely in combination with the embodiments and the drawings, so as to fully understand the purpose, features and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application. In addition, all the coupling / connection relations involved in the patent do not mean that the components are directly connected, but means that a better coupling structure can be formed by adding or reducing coupling accessories according to the specific implementation. The technical features in the present application can be combined interactively without conflict.

[0025] Please refer to Fig. 1, an embodiment of the present application provides a test system for testing and analyzing in-situ reservoir core desorption gas pressure, which comprises an adsorption and desorption device, a gas injection device, a vacuum pumping device, a desorption measurement device, a gas drainage measurement device, a water injection device and a pressure boosting device.

[0026] The adsorption and desorption device comprises a variable volume diffusion unit 10 and a coal sample tank 20.

[0027] In combination with Figs. 2 to 5, the variable volume diffusion unit 10 comprises a diffusion tank 14, a hollow centralizer 15 and a driving mechanism 17 arranged at the bottom end of the centralizer 15.

[0028] The diffusion tank 14 is provided with a diffusion cavity 141, which is in communication with the inside of the centralizing cylinder 15. The centralizing cylinder 15 is provided with a plunger 16, the top end of which extends into the diffusion cavity 141. A driving mechanism 17 is used to drive the plunger 16 to move up and down in the centralizing cylinder 15 and the diffusion cavity 141, so as to reduce or expand the volume of the diffusion cavity 141, and by expanding the volume of the diffusion cavity 141, the process of simulating the space expansion of the coal sample when placed in the corer during coring can be realized. The diffusion tank 14 is connected with a first connecting pipeline 11, a second connecting pipeline 12 and a third connecting pipeline 13. The first connecting pipeline 11, the second connecting pipeline 12 and the third connecting pipeline 13 are all in communication with the diffusion cavity 141. The first connecting pipeline 11 is connected with a gas injection device, the second connecting pipeline 12 is connected with a vacuum pumping device, and the third connecting pipeline 13 is connected with a coal sample tank 20. The third connecting pipeline 13 is in communication with the inside of the coal sample tank 20. The first connecting pipeline 12 is provided with a first switch valve 111 and a first pressure sensor 112 in sequence along the direction close to the diffusion tank 14. The first pressure sensor 112 is used to detect the pressure in the diffusion cavity 141. The second connecting pipeline 12 is provided with a second switch valve 121. The third connecting pipeline 13 is provided with a third switch valve 131 and a second pressure sensor 132 in sequence along the direction close to the coal sample tank 20. The second pressure sensor 132 is used to detect the pressure in the coal sample tank 20.

[0029] In the embodiment, the outside of the diffusion tank 14 is sequentially sleeved with a first water jacket 144 and a first heat preservation sleeve 145 which plays a heat preservation role. The inner wall of the first water jacket 144 and the diffusion tank 14 form a first heat preservation cavity 146. The outer wall of the first water jacket 141 is provided with a first water inlet joint 1441 and a first water outlet joint 1442, both of which are in communication with the first heat preservation cavity 146. The outer wall of the first heat preservation sleeve 145 is provided with a first avoiding hole 1451 for avoiding the first water inlet joint 1441 and a second avoiding hole 1452 for avoiding the first water outlet joint 1442. The first water inlet joint 1441 and the first water outlet joint 1442 are respectively used to be connected with a constant temperature water bath system. In actual application, hot water can be delivered into the first heat preservation cavity 146 through the first water inlet joint 1441 by the constant temperature water bath system, and then backflows to the constant temperature water bath system through the first water outlet joint 1442, so as to provide a water bath constant temperature environment for the diffusion tank 14, so as to simulate the environmental temperature of the coal sample as the temperature of the in-situ reservoir, for example, 26℃.

[0030] In this embodiment, the diffusion tank 14 includes a diffusion tank body 142 and a plug 143. The diffusion tank body 142 is provided with the diffusion cavity 141 described above, the top end of the diffusion tank body 142 is provided with a top end opening, the bottom end of the diffusion tank body 142 is provided with a bottom end opening, and the top end opening and the bottom end opening are both in communication with the diffusion cavity 141. The bottom end opening is in communication with the interior of the centralizing cylinder 15, so that the diffusion cavity 141 is in communication with the interior of the centralizing cylinder 15 through the bottom end opening. The plug 143 has a T-shaped cross section, the horizontal part 143a of the plug 143 is arranged at the top end of the diffusion tank body 142 by a plug fastener such as a screw or the like, and the vertical part 143b of the plug 143 is inserted into the top end opening. The top end of the horizontal part 143a of the plug 143 is provided with a first interface 1431 and a second interface 1432, the horizontal part 143a and the vertical part 143b of the plug 143 are provided with a first channel 1434 in communication with the first interface 1431 and a second channel 1435 in communication with the second interface 1432, and the first channel 1434 and the second channel 1435 are both in communication with the diffusion cavity 141. The first interface 1431 is provided with a first connector (not shown in the figure), the first connector is connected with a branch pipe, the branch pipe is connected with the first connecting pipeline 11 and the second connecting pipeline 12 described above, the first connector is in communication with the first channel 1434 and the branch pipe respectively, and the branch pipe is in communication with the first connecting pipeline 11 and the second connecting pipeline 12 respectively. The second interface 1432 is provided with a second connector (not shown in the figure), the second connector is connected with the third connecting pipeline 13 described above, and the second connector is in communication with the second channel 1435 and the third connecting pipeline 13 respectively. The first water jacket 144 and the first heat preservation sleeve 145 are sequentially arranged outside the diffusion tank body 142.

[0031] The first sealing ring 1436 is arranged between the vertical part 143b of the plug 143 and the inner wall of the diffusion cavity 141, and the first sealing ring 1436 plays a sealing role to avoid gas leakage.

[0032] The inner wall of the bottom end of the diffusion cavity 141 and the inner wall of the bottom end opening are provided with a plurality of second sealing rings 1411, the plurality of second sealing rings 1411 are sequentially arranged from top to bottom, and the number of the second sealing rings 1411 can be set according to actual conditions. The second sealing rings 1411 are arranged around the outer periphery of the plunger 16. The second sealing rings 1411 play a sealing role to avoid gas leakage.

[0033] The driving mechanism 17 comprises a driving motor 171, a speed reducer 172 and a connecting base 173. The connecting base 173 is arranged at the bottom end of the centralizer 15. In the embodiment, the top end of the connecting base 173 is inserted into the centralizer 15, and the outer periphery of the connecting base 173 is formed with an annular mounting table 1731. The mounting table 1731 is arranged at the bottom end of the centralizer 15 by mounting table fasteners such as screws. The speed reducer 172 is arranged at the bottom end of the connecting base 173. The driving motor 171 is arranged at the bottom end of the speed reducer 172. The output shaft of the driving motor 171 is connected with the input end of the speed reducer 172. A connecting shaft 1721 is arranged in the connecting base 173, and the bottom end of the connecting shaft 1721 is connected with the output end of the speed reducer 172. The plunger 16 is provided with a receiving cavity 161, and the bottom end of the plunger 16 is provided with a plunger opening which is in communication with the receiving cavity 161. The centralizer 15 is provided with a lead screw 18, the bottom end of the lead screw 18 is connected with the top end of the connecting shaft 1721, the top end of the lead screw 18 penetrates through the plunger opening and extends into the receiving cavity 161, and the lead screw 18 is threadedly connected with a nut 19 which is located between the connecting base 173 and the plunger 16, and the top end of the nut 19 is arranged in the plunger opening. The driving motor 171 is used to drive the connecting shaft 1721 to rotate through the speed reducer 172, so as to drive the lead screw 18 to rotate. The rotation of the lead screw 18 drives the nut 19 to move up and down, so as to drive the plunger 16 to move up and down.

[0034] In the embodiment, the top end of the connecting shaft 1721 is provided with a groove, the bottom end of the lead screw 18 is matched with the groove, the outer periphery of the lead screw 18 is formed with an annular mounting portion 181, and the mounting portion 181 is arranged at the top end of the connecting shaft 1721 by mounting portion fasteners such as screws.

[0035] The connecting base 173 is provided with a rotating bearing 1722 which is sleeved on the outer periphery of the top end of the connecting shaft 1721. The rotating bearing 1722 provides support for the rotation of the connecting shaft 1721.

[0036] The outer periphery of the nut 19 is formed with an annular boss 191, and the outer peripheral surface of the boss 191 is provided with two mounting members 192 which are symmetric about the center of the boss 191. The outer wall of the centralizing cylinder 15 is provided with two through grooves 151 corresponding to the two mounting members 192 respectively, and the two through grooves 151 are both in communication with the inside of the centralizing cylinder 15, and the length direction of the through groove 151 is the same as the height direction of the centralizing cylinder 15. The two mounting members 192 are partially accommodated in the two through grooves 151 respectively, and the outer periphery of the mounting member 192 is sleeved with a bearing 193 which is matched with the corresponding through groove 151. The up-and-down movement of the nut 19 can drive the up-and-down movement of the two mounting members 192 and the bearings 193 on the outer periphery of the mounting members 192. The mounting members 192 and the bearings 193 arranged thereon play a guiding role in the up-and-down movement of the nut 19, and thus play a guiding role in the up-and-down movement of the plunger 16, so as to improve the stability of the movement of the plunger 16. The mounting member 192 is, for example, a screw.

[0037] It can be understood that in other embodiments, the number of mounting members 192 can also be, for example, three, four, etc., which can be set according to actual conditions.

[0038] Both the rotating bearing 1722 and the bearing 193 are deep groove ball bearings.

[0039] The coal sample tank 20 is connected with a fourth connecting pipeline 21 and a first water inlet pipeline 22, and the fourth connecting pipeline 21 and the first water inlet pipeline 22 are both in communication with the inside of the coal sample tank 20. The fourth connecting pipeline 21 is used to be connected with a desorption measurement device or a gas drainage measurement device, and a back pressure valve 211 is arranged on the fourth connecting pipeline 21, which is used to control the flow of gas.

[0040] In combination with FIGS. 6 and 7, in the present embodiment, the coal sample tank 20 is used to contain coal samples. The coal sample tank 20 includes a hollow tank body 23, a sealing upper cover 24 and a sealing lower cover 25. The sealing upper cover 24 and the sealing lower cover 25 are respectively detachably arranged at the top end and the bottom end of the tank body 23.

[0041] Specifically, the cross-sectional shape of the sealing upper cover 24 is T-shaped, the vertical part 24b of the sealing upper cover 24 is inserted into the tank body 23, the top end of the tank body 23 is provided with a first mounting hole, the horizontal part 24a of the sealing upper cover 24 is provided with a second mounting hole corresponding to the first mounting hole, and a first fastener 241 such as a screw is mounted in the first mounting hole and the second mounting hole. By disassembling the first fastener 241, the sealing upper cover 24 can be disassembled. The number of the first mounting hole, the second mounting hole and the first fastener 241 can be set according to actual conditions. The cross-sectional shape of the sealing lower cover 25 is T-shaped, the vertical part 25b of the sealing lower cover 25 is inserted into the tank body 23, the bottom end of the tank body 23 is provided with a third mounting hole, the horizontal part 25a of the sealing lower cover 25 is provided with a fourth mounting hole corresponding to the third mounting hole, and a second fastener 251 such as a screw is mounted in the third mounting hole and the fourth mounting hole. By disassembling the second fastener 251, the sealing lower cover 25 can be disassembled. The number of the third mounting hole, the fourth mounting hole and the second fastener 251 can be set according to actual conditions.

[0042] The third connecting pipeline 13 is connected with the sealing upper cover 24, and the sealing upper cover 24 is connected with the fourth connecting pipeline 21. Specifically, the side wall of the horizontal part 24a of the sealing upper cover 24 is provided with a first connecting port 242 and a second connecting port 244, and the horizontal part 24a and the vertical part 24b of the sealing upper cover 24 are provided with a first flow channel 243 communicating with the first connecting port 242 and a second flow channel 245 communicating with the second connecting port 244. The first flow channel 243 and the second flow channel 245 both communicate with the inside of the tank body 23. The first connecting port 242 is provided with a third connector (not shown in the figure), the third connecting pipeline 13 is connected with the third connector, and the third connector respectively communicates with the third connecting pipeline 13 and the first flow channel 243. The second connecting port 244 is provided with a fourth connector (not shown in the figure), the fourth connector is connected with the fourth connecting pipeline 21, and the fourth connector respectively communicates with the fourth connecting pipeline 21 and the second flow channel 245.

[0043] The sealing lower cover 25 is connected with the first water inlet pipeline 22. Specifically, the side wall of the horizontal part 25a of the sealing lower cover 25 is provided with a third connecting port 252, and the horizontal part 25a and the vertical part 25b of the sealing lower cover 25 are provided with a third flow channel 253 communicating with the third connecting port 252. The third flow channel 253 communicates with the inside of the tank body 23. The third connecting port 252 is provided with a fifth connector (not shown in the figure), the fifth connector is connected with the first water inlet pipeline 22, and the fifth connector respectively communicates with the third flow channel 253 and the first water inlet pipeline 22.

[0044] The vertical part 24b of the sealing upper cover 24 and the inner wall of the tank body 23 are provided with a third sealing ring 246, and the vertical part 25b of the sealing lower cover 25 and the inner wall of the tank body 23 are provided with a fourth sealing ring 254. The third sealing ring 246 and the fourth sealing ring 254 are provided to seal and avoid gas leakage.

[0045] The outer part of the tank body 23 is sequentially sleeved with a second water jacket 232 and a second heat preservation sleeve 233 for heat preservation. The inner wall of the second water jacket 232 and the tank body 23 form a second heat preservation cavity 234. The outer wall of the second water jacket 232 is provided with a second water inlet connector 2321 and a second water outlet connector 2322, both of which are in communication with the second heat preservation cavity 234. The outer wall of the second heat preservation sleeve 233 is provided with a first through hole 2331 for avoiding the second water inlet connector 2321 and a second through hole for avoiding the second water outlet connector 2322. The second water inlet connector 2321 and the second water outlet connector 2322 are respectively used for connecting with a constant temperature water bath system. In actual application, hot water can be delivered into the second heat preservation cavity 234 through the second water inlet connector 2321 by the constant temperature water bath system, and then flows back to the constant temperature water bath system through the second water outlet connector 2322, so as to provide a water bath constant temperature environment for the coal sample tank 20, so as to simulate the temperature of the environment in which the coal sample is located as the temperature of the in-situ reservoir.

[0046] The gas injection device includes a carbon dioxide gas cylinder 32, a methane gas cylinder 33, a nitrogen gas cylinder 34 and a helium gas cylinder 31.

[0047] The carbon dioxide gas cylinder 32 is connected with a first gas injection pipeline 321, and the first gas injection pipeline 321 is connected with the first connecting pipeline 11. Carbon dioxide gas can be injected into the tank body 23 of the coal sample tank 20 through the diffusion cavity 141 of the carbon dioxide gas cylinder 32, that is, the carbon dioxide gas first enters the diffusion cavity 141 through the first gas injection pipeline 321 and the first connecting pipeline 11, and then enters the tank body 23 through the third connecting pipeline 13. The first gas injection pipeline 321 is sequentially provided with a fourth switch valve 322, a first pressure reducing valve 323, a first pressure gauge 324, a fifth switch valve 325, a first flow controller 326, a first check valve 327 and a sixth switch valve 328 in the direction close to the diffusion tank 14. The first pressure reducing valve 323 is used for reducing the pressure of the carbon dioxide gas. The first pressure gauge 324 is used for detecting the pressure in the first gas injection pipeline 321. The first flow controller 326 is used for controlling the flow of the carbon dioxide gas. The first check valve 327 is used for preventing the gas from flowing back to the carbon dioxide gas cylinder 32.

[0048] The methane gas cylinder 33 is connected with a second gas injection pipeline 331, and the second gas injection pipeline 331 is connected with the first connecting pipeline 11. The methane gas cylinder 33 can inject methane gas into the tank body 23 of the coal sample tank 20 through the diffusion cavity 141, that is, the methane gas first enters into the diffusion cavity 141 through the second gas injection pipeline 331 and the first connecting pipeline 11, and then enters into the tank body 23 through the third connecting pipeline 13. The second gas injection pipeline 331 is sequentially provided with a seventh switch valve 332, a second pressure reducing valve 333, a second pressure gauge 334, an eighth switch valve 335, a second flow controller 336, a second check valve 337 and a ninth switch valve 338 in the direction close to the diffusion tank 14. The second pressure reducing valve 333 is used for reducing the pressure of the methane gas. The second pressure gauge 334 is used for detecting the pressure in the second gas injection pipeline 331. The second flow controller 336 is used for controlling the flow of the methane gas. The second check valve 337 is used for preventing the gas from flowing back into the methane gas cylinder 33.

[0049] The nitrogen gas cylinder 34 is connected with a third gas injection pipeline 341, and the third gas injection pipeline 341 is connected with the first connecting pipeline 11. The nitrogen gas cylinder 34 can inject nitrogen gas into the tank body 23 of the coal sample tank 20 through the diffusion cavity 141, that is, the nitrogen gas first enters into the diffusion cavity 141 through the third gas injection pipeline 341 and the first connecting pipeline 11, and then enters into the tank body 23 through the third connecting pipeline 13. The third gas injection pipeline 341 is sequentially provided with a tenth switch valve 342, a third pressure reducing valve 343, a third pressure gauge 344, an eleventh switch valve 345, a third flow controller 346, a third check valve 347 and a twelfth switch valve 348 in the direction close to the diffusion tank 14. The third pressure reducing valve 343 is used for reducing the pressure of the nitrogen gas. The third pressure gauge 344 is used for detecting the pressure in the third gas injection pipeline 341. The third flow controller 346 is used for controlling the flow of the nitrogen gas. The third check valve 347 is used for preventing the gas from flowing back into the nitrogen gas cylinder 34.

[0050] The helium gas cylinder 31 is connected with a fourth gas injection pipeline 311, and the fourth gas injection pipeline 311 is connected with the first connecting pipeline 11. The helium gas cylinder 31 can inject helium gas into the diffusion cavity 141 and the tank body 23 of the coal sample tank 20, so that the diffusion tank 14 and the coal sample tank 20 can be detected for air tightness. The fourth gas injection pipeline 311 is provided with a thirteenth switch valve 312. That is, the helium gas first enters into the diffusion cavity 141 through the fourth gas injection pipeline 311 and the first connecting pipeline 11, so that the diffusion tank 14 can be detected for air tightness. After the third switch valve 131 is opened, the helium gas can enter into the tank body 23 through the third connecting pipeline 13, so that the coal sample tank 20 can be detected for air tightness.

[0051] The vacuumizing device comprises a vacuum pump 41 and a vacuum tank 42. The vacuum pump 41 is connected with a first vacuum pipeline 411, and the first vacuum pipeline 411 is connected with the vacuum tank 42. The vacuum tank 42 is connected with a second vacuum pipeline 421, and the second vacuum pipeline 421 is connected with the second connecting pipeline 12.

[0052] The desorption measuring device comprises a gas chromatograph 51, three collecting bags 52 and a flow divider 53. The flow divider 53 is connected with a fifth connecting pipeline 531. The fourth connecting pipeline 21 is connected with a first switching joint, and the fifth connecting pipeline 531 is connected with a second switching joint. The first switching joint is used for being connected with the second switching joint. The collecting bags 52 are respectively connected with a sixth connecting pipeline 521 and a seventh connecting pipeline 522. The sixth connecting pipeline 521 is connected with the flow divider 53, and the seventh connecting pipeline 522 is connected with the gas chromatograph 51. The fifth connecting pipeline 531 is sequentially provided with an adjusting valve 511, a constant volume container 512 and a fourteenth switching valve 513 in the direction close to the flow divider 53. The adjusting valve 511 is used for adjusting the pressure of the gas. The flow divider 53 is a structure in the prior art. The flow divider 53 is used for sequentially dividing the gas into the three collecting bags 52. The three collecting bags 52 are respectively used for outputting the gas to the gas chromatograph 51, so that the relative volume fraction of each gas component can be calculated by the gas chromatograph 51. The constant volume container 512 is used for buffering the gas of a fixed volume.

[0053] It can be understood that the number of the collecting bags 52 can also be other numbers, for example, four, five and the like, which can be set according to actual conditions.

[0054] The gas drainage measuring device comprises a first container 61, a second container 62 and a weighing device 63. A sealing head is inserted into the opening at the top end of the first container 61. One end of an exhaust pipeline 64 is connected with a third switching joint, and the first switching joint is used for being connected with the third switching joint. The other end of the exhaust pipeline 64 penetrates through a first through hole of the sealing head and extends into the first container 61. One end of a drainage pipeline 65 penetrates through a second through hole of the sealing head and extends into the first container 61. The other end of the drainage pipeline 65 is used for being inserted into the second container 62, and the second container 62 is placed on the weighing device 63. In actual application, the first container 61 is used for containing a liquid such as water. The other end of the exhaust pipeline 64 is located above the liquid surface, and one end of the drainage pipeline 65 is located below the liquid surface. The second container 62 is weighed by the weighing device 63 to obtain the original weight of the second container 62. After the gas enters the first container 61 through the exhaust pipeline 64, the pressure in the first container 61 increases, so that the water in the first container 61 can be drained into the second container 62 through the drainage pipeline 65. At this time, the second container 65 can be weighed again by the weighing device 63. The weight obtained by the weighing this time is subtracted from the original weight of the second container 62, so that the weight of the water drained into the second container 62 can be obtained. The weight of the water is the volume of the gas entering the first container 61.

[0055] In the embodiment, the first conversion joint is a male joint, and the second conversion joint and the third conversion joint are female joints.

[0056] The water injection device comprises a first constant-speed constant-pressure pump 71, and the first constant-speed constant-pressure pump 71 is connected with a second water inlet pipeline 711, and the second water inlet pipeline 711 is connected with the first water inlet pipeline 22. The second water inlet pipeline 711 is provided with a water inlet valve (not shown in the figure). The first constant-speed constant-pressure pump 71 is used for injecting water into the tank body 23 of the coal sample tank 20 in a constant-speed constant-pressure mode, so that the in-situ reservoir environment can be simulated, and the accuracy of gas pressure measurement can be ensured.

[0057] The pressurizing device comprises a second constant-speed constant-pressure pump 81, and the second constant-speed constant-pressure pump 81 is connected with the first connecting pipeline 11 through a communication pipeline 811. The communication pipeline 811 is located between the gas injection device and the first switch valve 111, and the communication pipeline 811 is provided with a fifteenth switch valve 812. The second constant-speed constant-pressure pump 81 is used for compressing gas to realize pressurization of the gas.

[0058] All the switch valves in the application are ball valves.

[0059] Through the above structure, the experimental steps for determining the in-situ reservoir gas pressure by using single-component gas in the application are as follows:

[0060] In the initial state, the distance between the top end of the plunger 16 and the bottom end of the vertical part 143b of the plug 143 is, for example, 14.6 mm, and the plunger 16 is in the lowest position shown in FIGS. 4 and 5. At this time, the distance between the top end of the plunger 16 and the bottom end of the vertical part 143b of the plug 143 is, for example, 100 mm, the height in the tank body 23 is also 100 mm, the inner diameter of the diffusion cavity 141 and the inner diameter of the tank body 23 are, for example, 30 mm, and the first conversion joint is not connected with the second conversion joint and the third conversion joint:

[0061] S1, air tightness detection: close the fourth switch valve 322, the first pressure reducing valve 323, the fifth switch valve 325, the first flow controller 326, the first check valve 327, the sixth switch valve 328, the seventh switch valve 332, the second pressure reducing valve 333, the eighth switch valve 335, the second flow controller 336, the second check valve 337, the ninth switch valve 338, the tenth switch valve 342, the third pressure reducing valve 343, the eleventh switch valve 345, the third flow controller 346, the third check valve 347, the twelfth switch valve 348, the back pressure valve 211, the second switch valve 121, the water inlet valve, the third switch valve 131 and the fifteenth switch valve 312, open the thirteenth switch valve 312 and the first switch valve 111, so that helium gas in the helium gas cylinder 31 can be injected into the diffusion chamber 141, for example, above 1 MPa (mega pascal), then close the thirteenth switch valve 312 and the first switch valve 111, detect the pressure in the diffusion chamber 141 by the first pressure sensor 112, if the pressure does not change within 12 hours, it indicates that the air tightness of the diffusion tank 14 is good. Then open the third switch valve 131, at this time the helium gas in the diffusion chamber 141 can enter the tank body 23 of the coal sample tank 20, detect the pressure in the tank body 23 by the second pressure sensor 132, if the pressure does not change within 12 hours, it indicates that the air tightness of the coal sample tank 20 is good.

[0062] S2, vacuumizing: remove the sealing upper cover 24 from the tank body 23, put the coal sample into the tank body 23, then reinstall the sealing upper cover 24 on the tank body 23. Then open the second switch valve 121, start the vacuum pump 41 to vacuumize the vacuum tank 42, so that the interior of the diffusion chamber 141 and the tank body 23 can be vacuumized, the vacuumizing time is for example 8 hours, after completion, close the second switch valve 121 and the third switch valve 131.

[0063] S3, empty volume calibration: open the thirteenth switch valve 312 and the first switch valve 111, so that helium gas can be injected into the diffusion cavity 141 through the helium gas cylinder 31, the pressure in the diffusion cavity 141 is detected by the first pressure sensor 112, if the pressure does not change within 20 minutes, it indicates that the pressure in the diffusion cavity 141 is stable, at this time the stable pressure in the diffusion cavity 141 is recorded as P1, then the thirteenth switch valve 312 and the first switch valve 111 are closed and the third switch valve 131 is opened, so that the helium gas in the diffusion cavity 141 can enter the tank body 23, at this time the coal sample adsorbs the helium gas, the pressure in the tank body 23 is detected by the second pressure sensor 132, if there is no pressure change within 20 minutes, it indicates that the coal sample no longer adsorbs the helium gas, at this time the pressure in the tank body 23 is stable, and the stable pressure in the tank body 23 is P2, then the third switch valve 131 is closed, according to the ideal gas state equation PV=nRT (P is the pressure, V is the volume, T is the temperature, n is the amount of substance of gas, and R is the molar gas constant), the empty volume in the tank body 23 can be calculated, the specific calculation is as follows:

[0064] Since the total amount of helium gas is constant, according to the ideal gas state equation, the calculation formula of the empty volume in the tank body 23 can be obtained: P1V1=P2(V1+V2), V1 is the volume of the diffusion cavity 141, V2 is the empty volume in the tank body 23, wherein V1=π(r 2 )*h, r=30 / 2mm, h is 14.6mm, so the volume V1 of the diffusion cavity 141 can be calculated, then the empty volume V2 in the tank body 23 can be calculated according to the calculation formula.

[0065] S4, gas adsorption: open the back pressure valve 211, the helium gas in the tank body 23 can be discharged through the first conversion joint, then close the back pressure valve 211 and open the second switch valve 121 and the third switch valve 131, start the vacuum pump 41 to vacuumize the vacuum tank 42, so as to realize the vacuumization of the inside of the tank body 23 and the diffusion cavity 141, the vacuumization time is for example 8 hours, after completion, close the second switch valve 121. Then open the first switch valve 111, the fourth switch valve 322, the first pressure reducing valve 323, the fifth switch valve 325, the first flow controller 326, the first check valve 327 and the sixth switch valve 328, so that a certain amount of carbon dioxide gas can be injected into the tank body 23 through the diffusion cavity 141 from the carbon dioxide gas cylinder 32, the amount of carbon dioxide gas injection can be set according to the actual situation. Then close the first switch valve 111, the fourth switch valve 322, the first pressure reducing valve 323, the fifth switch valve 325, the first flow controller 326, the first check valve 327 and the sixth switch valve 328, the coal sample in the tank body 23 starts to adsorb carbon dioxide, the pressure in the tank body 23 at this time is detected by the second pressure sensor 132, if the pressure does not change for 3 hours continuously and the adsorption time reaches for example 8 hours, it is considered that the tank body 23 has reached adsorption equilibrium, at this time the pressure in the tank body 23 is recorded as P3, according to the pressure P3 and the empty volume V2 in the tank body 23, the adsorption amount of carbon dioxide can be calculated, the specific calculation is as follows:

[0066] The adsorption amount is represented by V 吸附 , the injection amount is represented by V 注入 , and the free amount is represented by V 游离 , V 游离 The following calculation formula (I) can be used to calculate:

[0067] Wherein, n is the amount of substance of carbon dioxide gas, the unit is mol (mol); V M is the molar volume, the molar volume is a fixed value, for example 22.4 L / mol (liter / mol); Z is the gas compression factor, R is the constant 8.314; T is the temperature, the temperature is 26℃, P is the pressure P3, V 自由 is the empty volume V2.

[0068] The injection amount is the injection amount of carbon dioxide gas, the injection amount is known, so the adsorption amount of carbon dioxide can be calculated.

[0069] S5, expansion, to simulate the process of expanding the space in which the coal sample is placed in the corer during coring: first, drive the plunger 16 downward by driving mechanism 17, so that the plunger 16 is lowered by, for example, 5 mm, at which time the volume in the diffusion chamber 141 is expanded, the pressure in the tank 23 is lowered, and the coal sample begins to desorb, and the pressure in the tank 23 at this time is recorded by the second pressure sensor 132, if the pressure does not change for 3 hours and the desorption time reaches, for example, 8 hours, it is considered that the desorption equilibrium in the tank 23 has been reached, at which time the pressure in the tank 23 is P4, and the desorption amount of carbon dioxide can be calculated according to the pressure P4, the empty volume V2 of the tank 23, and the amount of carbon dioxide adsorbed calculated in step S4, which is calculated as follows:

[0070] Desorption amount = adsorption amount - adsorption amount after expansion, the desorption amount is represented by V 解吸 , the adsorption amount is the aforementioned V 吸 附 , and the adsorption amount after expansion is represented by V 扩容吸附 .

[0071] The adsorption amount after expansion (V 扩容吸附 ) = injection amount (V 注入 ) - free amount (V 游离 ), V 游离 can be obtained according to the calculation method of step S4, wherein V 自由 in step S4 = empty volume V2 + expansion volume V 扩容 , V 扩容 = π(r 2 ) * h, r = 30 / 2 mm, and h is 5 mm, so the expansion volume V 扩容 can be calculated, the injection amount is the injection amount of carbon dioxide gas, which is known, so the adsorption amount after expansion can be calculated, and thus the desorption amount of carbon dioxide can be obtained.

[0072] S6, exhaust collection: close the regulating valve 511, the constant volume container 512, and the fourteenth on-off valve 513, connect the first conversion joint with the second conversion joint, then open the back pressure valve 211, the regulating valve 511, the constant volume container 512, and the fourteenth on-off valve 513, the gas in the tank 23 first enters the constant volume container 512 for buffering, then is shunted by the flow divider 53 to the first collection bag 52, then the gas in the tank 23 continues to enter the constant volume container 512 for buffering, then is continuously shunted by the flow divider 53 to the second collection bag 52, then the gas in the tank 23 continues to enter the constant volume container 512 for buffering, then is continuously shunted by the flow divider 53 to the third collection bag 52, and then the gas is input to the gas chromatograph 51 through the three collection bags 52, and the relative volume fraction of each gas component can be calculated by the gas chromatograph 51.

[0073] S7, repeating the experiment of steps S1-S6, for example, four times, wherein each time the position of the plunger 16 in step S5 is changed, for example, the first time the plunger 16 is driven to descend 10 mm by the driving mechanism 17, the second time the plunger 16 is driven to descend 15 mm by the driving mechanism 17, the third time the plunger 16 is driven to descend 20 mm by the driving mechanism 17, and the fourth time the plunger 16 is driven to descend 25 mm by the driving mechanism 17. Thus, five different volumes of the desorbed carbon dioxide can be obtained according to five experiments.

[0074] Then, the experiment of steps S1-S7 is repeated by using methane instead of carbon dioxide, thus the desorbed volumes of methane in five different volumes can be obtained. Then, the experiment of steps S1-S7 is repeated by using nitrogen instead of carbon dioxide, thus the desorbed volumes of nitrogen in five different volumes can be obtained.

[0075] Each of the obtained desorbed volume data is analyzed, and the in-situ reservoir gas pressure is determined based on the in-situ reservoir gas pressure calculation method (which is known and not described here). According to the determined in-situ reservoir gas pressure data, the in-situ reservoir gas pressure change rule can be obtained.

[0076] In the above steps, step S6 can be replaced by step S8, S7: exhaust gas collection: connecting the first conversion joint with the third conversion joint, then opening the back pressure valve 211, the gas in the tank body 23 can enter the first container 61 through the exhaust gas pipeline 64, the pressure in the first container 61 increases, thus the water in the first container 61 can be discharged into the second container 62 through the water discharge pipeline 65, at this time the second container 62 can be weighed by the weighing device 63, the weight of this time is subtracted from the original weight of the second container 62, thus the weight of the water discharged into the second container 62 can be obtained, which is the volume of the gas entering the first container 61.

[0077] In the above steps, in step S4, if the carbon dioxide gas injected into the tank 23 needs to be pressurized, the fifteenth switch valve 812, the fourth switch valve 322, the first pressure reducing valve 323, the fifth switch valve 325, the first flow controller 326, the first check valve 327 and the sixth switch valve 328 are opened, the first switch valve 111 is closed, the carbon dioxide gas bottle 32 can inject the carbon dioxide gas with a predetermined pressure value into the second constant speed and constant pressure pump 81, so that the carbon dioxide gas can be pressurized by the second constant speed and constant pressure pump 81, then the fourth switch valve 322, the first pressure reducing valve 323, the fifth switch valve 325, the first flow controller 326, the first check valve 327 and the sixth switch valve 328 are closed, and the first switch valve 111 is opened. The pressurized carbon dioxide gas can be injected into the tank 23 by the second constant speed and constant pressure pump 81, and after completion, the fifteenth switch valve 812 is closed, and the coal sample in the tank 23 starts to adsorb carbon dioxide. If water needs to be injected into the tank 23, after step S4, step S41 is performed: the water inlet valve is opened, 3-6 milliliters of water is injected into the tank 23 by the first constant speed and constant pressure pump 71, and after completion, the water inlet valve is closed, and then step S5 is performed. By pressurizing the gas injected into the tank 23 and injecting water into the tank 23, the original reservoir environment can be simulated to ensure the accuracy of the gas pressure measurement.

[0078] In the above steps, the coal sample can be a coal sample containing water, and the water content of the coal sample is, for example, 2%, 4%, 6%, 8%, etc. This can realize the adsorption and desorption experiment of the coal sample containing water.

[0079] The experimental steps for measuring the in-situ reservoir gas pressure by using multi-component gas are as follows:

[0080] In the initial state, the distance between the top end of the plunger 16 and the bottom end of the vertical part 143b of the plug 143 is, for example, 14.6 millimeters, and the plunger 16 is in the lowest position as shown in FIGS. 4 and 5. At this time, the distance between the top end of the plunger 16 and the bottom end of the vertical part 143b of the plug 143 is, for example, 100 millimeters, the height in the tank 23 is also 100 millimeters, the inner diameter of the diffusion chamber 141 and the inner diameter of the tank 23 are, for example, 30 millimeters, and the first conversion joint and the second conversion joint, the third conversion joint are not connected.

[0081] S11, gas tightness detection: this step is the same as step S1.

[0082] S12, vacuumizing: this step is the same as step S2.

[0083] S13, empty volume calibration: this step is the same as step S3.

[0084] S14, gas adsorption: open the back pressure valve 211, helium gas in the tank 23 can be discharged through the first conversion joint, then close the back pressure valve 211 and open the second switch valve 121, the third switch valve 131, start the vacuum pump 41 to vacuumize the vacuum tank 42, so as to realize vacuumizing the inside of the tank 23 and the diffusion cavity 141, the vacuumizing time is for example 8 hours, after completion, close the second switch valve 121. Then open the first switch valve 111, the fourth switch valve 322, the first pressure reducing valve 323, the fifth switch valve 325, the first flow controller 326, the first check valve 327 and the sixth switch valve 328, so that a certain amount of carbon dioxide gas can be injected into the tank 23 through the diffusion cavity 141 from the carbon dioxide cylinder 32, the carbon dioxide gas accounts for 10% of the total amount of injected gas. Then close the fourth switch valve 322, the first pressure reducing valve 323, the fifth switch valve 325, the first flow controller 326, the first check valve 327 and the sixth switch valve 328 and open the seventh switch valve 332, the second pressure reducing valve 333, the eighth switch valve 335, the second flow controller 336, the second check valve 337 and the ninth switch valve 338, so that a certain amount of methane gas can be injected into the tank 23 through the diffusion cavity 141 from the methane cylinder 33, the methane gas accounts for 70% of the total amount of injected gas. Then close the seventh switch valve 332, the second pressure reducing valve 333, the eighth switch valve 335, the second flow controller 336, the second check valve 337 and the ninth switch valve 338 and open the tenth switch valve 342, the third pressure reducing valve 343, the eleventh switch valve 345, the third flow controller 346, the third check valve 347 and the twelfth switch valve 348, so that a certain amount of nitrogen gas can be injected into the tank 23 through the diffusion cavity 141 from the nitrogen cylinder 34, the nitrogen gas accounts for 20% of the total amount of injected gas. Then close the first switch valve 111, the tenth switch valve 342, the third pressure reducing valve 343, the eleventh switch valve 345, the third flow controller 346, the third check valve 347 and the twelfth switch valve 348, the coal sample in the tank 23 starts to adsorb carbon dioxide, methane and nitrogen, the pressure in the tank 23 is detected by the second pressure sensor 132, if the pressure does not change for 3 hours continuously and the adsorption time reaches for example 8 hours, it is considered that the tank 23 has reached adsorption equilibrium, the pressure in the tank 23 at this time is recorded as P5.

[0085] S15, volume fraction analysis of each gas component: close the regulating valve 511, the constant volume container 512, the fourteenth switch valve 513, connect the first conversion joint with the second conversion joint, then open the back pressure valve 211, the regulating valve 511, the constant volume container 512 and the fourteenth switch valve 513, the gas in the tank body 23 first enters the constant volume container 512 for buffering, then the gas is shunted to the first collection bag 52 through the flow divider 53, then the gas in the tank body 23 continues to enter the constant volume container 512 for buffering, then the gas is continuously shunted to the second collection bag 52 through the flow divider 53, then the gas in the tank body 23 continues to enter the constant volume container 512 for buffering, then the gas is continuously shunted to the third collection bag 52 through the flow divider 53, then the gas is input to the gas chromatograph 51 through the three collection bags 52, and the relative volume fraction of each gas component can be calculated through the gas chromatograph 51, and after completion, the regulating valve 511, the constant volume container 512, the fourteenth switch valve 513 and the back pressure valve 211 are closed. According to the relative volume fraction of each component gas, the pressure data of each gas can be obtained, for example, if the relative volume fractions of methane gas, carbon dioxide gas and nitrogen gas are 50%, 30% and 20% respectively, then the pressure data of methane gas is 50%*P5, the pressure data of carbon dioxide gas is 30%*P5, and the pressure data of nitrogen gas is 20%*P5.

[0086] According to the pressure of each gas, the empty volume V2 in the tank body 23 and the relative volume fraction of each gas component, the adsorption amount of each gas component can be calculated, and the specific calculation is as follows:

[0087] The methane adsorption amount is the methane injection amount minus the methane free amount, which can be calculated in the manner of step S4, the carbon dioxide adsorption amount is the carbon dioxide injection amount minus the carbon dioxide free amount, which can be calculated in the manner of step S4, and the nitrogen adsorption amount is the nitrogen injection amount minus the nitrogen free amount, which can be calculated in the manner of step S4.

[0088] S16, expansion, to simulate the process of expanding the space of the coal sample when the coal sample is placed into the corer during coring: first drive the plunger 16 to move downward by the driving mechanism 17, so that the plunger 16 is lowered by, for example, 5 mm, at this time the volume in the diffusion chamber 141 is expanded and the pressure in the tank body 23 is lowered, the coal sample begins to desorb, the pressure in the tank body 23 is detected by the second pressure sensor 132, if the pressure does not change for 3 hours continuously and the adsorption time reaches, for example, 8 hours, it is considered that the desorption equilibrium in the tank body 23 has been reached, and the pressure in the tank body 23 at this time is recorded as P6, according to the pressure P6, the empty volume V2 in the tank body and the methane adsorption amount, the carbon dioxide adsorption amount and the nitrogen adsorption amount calculated in step 15, the total desorption amount of the coal sample can be calculated, and the specific calculation is as follows:

[0089] The total desorption amount = (methane adsorption amount + carbon dioxide adsorption amount + nitrogen adsorption amount) - (expansion after methane adsorption amount + expansion after carbon dioxide adsorption amount + expansion after nitrogen adsorption amount), the expansion after methane adsorption amount, the expansion after carbon dioxide adsorption amount, and the expansion after nitrogen adsorption amount can be calculated according to the calculation method of the step S5, so the total desorption amount can be calculated.

[0090] The methane desorption amount can be obtained by subtracting the expansion after methane adsorption amount from the methane adsorption amount, the carbon dioxide desorption amount can be obtained by subtracting the expansion after carbon dioxide adsorption amount from the carbon dioxide adsorption amount, and the nitrogen desorption amount can be obtained by subtracting the expansion after nitrogen adsorption amount from the nitrogen adsorption amount.

[0091] S17, exhaust collection: connecting the first conversion joint with the third conversion joint, then opening the back pressure valve 211, the gas in the tank body 23 can enter into the first container 61 through the exhaust pipeline 64, the pressure in the first container 61 increases, so that the water in the first container 61 can be discharged into the second container 62 through the drain pipeline 65, at this time, the second container 62 can be weighed by the weighing device 63, the weight of the water discharged into the second container 62 can be obtained by subtracting the weight of the second container 62 from the weight of the second container 62, and the weight of the water is the volume of the gas entering into the first container 61. The exhaust collection of the step S17 can also be carried out by the desorption measuring device, and the specific process can be referred to the step S6.

[0092] S18, repeating the above steps S11-S17 for 4 times, for example, wherein the position of the plunger 16 is changed in each repetition, for example, in the first repetition, the plunger 16 is driven to descend 10 mm by the driving mechanism 17, in the second repetition, the plunger 16 is driven to descend 15 mm by the driving mechanism 17, in the third repetition, the plunger 16 is driven to descend 20 mm by the driving mechanism 17, and in the fourth repetition, the plunger 16 is driven to descend 25 mm by the driving mechanism 17. Thus, the total desorption amount and the desorption amounts of the methane gas, the carbon dioxide gas and the nitrogen gas under five different volumes can be obtained according to the five experiments.

[0093] Afterwards, the experimental process of the above steps S11-S18 is repeated by using methane, carbon dioxide and nitrogen with the proportions of 80%, 10%, 10% respectively instead of the above methane, carbon dioxide and nitrogen with the proportions of 70%, 10%, 20% respectively, so that the total desorption amount and the desorption amount of methane gas, the desorption amount of carbon dioxide gas and the desorption amount of nitrogen gas under five different volumes can be obtained. The experimental process of the above steps S11-S18 is repeated by using methane, carbon dioxide and nitrogen with the proportions of 70%, 20%, 10% respectively instead of the above methane, carbon dioxide and nitrogen with the proportions of 70%, 10%, 20% respectively, so that the total desorption amount and the desorption amount of methane gas, the desorption amount of carbon dioxide gas and the desorption amount of nitrogen gas under five different volumes can be obtained. The experimental process of the above steps S11-S18 is repeated by using methane, carbon dioxide and nitrogen with the proportions of 60%, 10%, 30% respectively instead of the above methane, carbon dioxide and nitrogen with the proportions of 70%, 10%, 20% respectively, so that the total desorption amount and the desorption amount of methane gas, the desorption amount of carbon dioxide gas and the desorption amount of nitrogen gas under five different volumes can be obtained. The experimental process of the above steps S11-S18 is repeated by using methane, carbon dioxide and nitrogen with the proportions of 60%, 30%, 10% respectively instead of the above methane, carbon dioxide and nitrogen with the proportions of 70%, 10%, 20% respectively, so that the total desorption amount and the desorption amount of methane gas, the desorption amount of carbon dioxide gas and the desorption amount of nitrogen gas under five different volumes can be obtained. The experimental process of the above steps S11-S18 is repeated by using methane, carbon dioxide and nitrogen with the proportions of 60%, 20%, 20% respectively instead of the above methane, carbon dioxide and nitrogen with the proportions of 70%, 10%, 20% respectively, so that the total desorption amount and the desorption amount of methane gas, the desorption amount of carbon dioxide gas and the desorption amount of nitrogen gas under five different volumes can be obtained.

[0094] Afterwards, the experimental process of the above steps S11-S18 is repeated by using methane and carbon dioxide with the proportions of 80%, 20% respectively instead of the above methane, carbon dioxide and nitrogen with the proportions of 70%, 10%, 20% respectively, so that the total desorption amount and the desorption amount of methane gas and the desorption amount of carbon dioxide gas under five different volumes can be obtained. The experimental process of the above steps S11-S18 is repeated by using methane and nitrogen with the proportions of 80%, 20% respectively instead of the above methane, carbon dioxide and nitrogen with the proportions of 70%, 10%, 20% respectively, so that the total desorption amount and the desorption amount of methane gas and the desorption amount of nitrogen gas under five different volumes can be obtained.

[0095] The desorption amount data obtained above is analyzed, and in-situ reservoir gas pressure is calculated based on an existing in-situ reservoir gas pressure calculation method (which will not be described here again), so that the in-situ reservoir gas pressure can be determined, and the determined in-situ reservoir gas pressure data is analyzed (analysis method is existing, which will not be described here again), so that the change rule of in-situ reservoir gas pressure can be explored.

[0096] The variable volume diffusion unit 10 is arranged, the plunger 16 is driven by the driving mechanism 17 of the variable volume diffusion unit 10 to move downward to different positions in the diffusion cavity 141 and the centralizing cylinder 15, so that the volume of the diffusion cavity 141 can be expanded, the process of expanding the space of the coal sample when the coal sample is put into the corer in the coring process can be simulated, the real situation of gas adsorption and desorption of the coal sample in the field coring process is further restored, the accuracy of the obtained adsorption amount and desorption amount is ensured, and the accuracy of the in-situ reservoir gas pressure measurement is ensured. And the determined in-situ reservoir gas pressure data is analyzed, so that the change rule of in-situ reservoir gas pressure can be explored. Meanwhile, the water injection device is arranged to inject water into the coal sample tank 20, and the booster device is arranged to pressurize the gas to be injected into the coal sample tank 20, so that the in-situ reservoir environment can be simulated, and the accuracy of the in-situ reservoir gas pressure measurement is further ensured.

[0097] The above is a specific description of the preferred embodiment of the present application, but the present application is not limited to the described embodiments, and those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A test system for testing desorbed gas pressure of a reservoir core in situ, comprising an adsorption-desorption device, a gas injection device, a vacuum extraction device, and a desorption measurement device, the adsorption-desorption device comprising a coal sample can, characterized in that, The adsorption and desorption device further comprises a variable volume diffusion unit, the variable volume diffusion unit comprises a diffusion tank, a hollow centralizer and a driving mechanism arranged at the bottom end of the centralizer, the diffusion tank is internally provided with a diffusion cavity, the diffusion cavity is in communication with the inside of the centralizer, the centralizer is internally provided with a plunger, the top end of the plunger extends into the diffusion cavity, and the driving mechanism is used to drive the plunger to move up and down in the centralizer and the diffusion cavity; the diffusion tank is connected with a first connecting pipeline, a second connecting pipeline and a third connecting pipeline, the first connecting pipeline, the second connecting pipeline and the third connecting pipeline are all in communication with the diffusion cavity, the first connecting pipeline is connected with the gas injection device, the second connecting pipeline is connected with the vacuum pumping device, the third connecting pipeline is connected with the coal sample tank, the coal sample tank is connected with a fourth connecting pipeline, the third connecting pipeline and the fourth connecting pipeline are both in communication with the inside of the coal sample tank, the fourth connecting pipeline is used to be connected with the desorption measurement device, a first switch valve and a first pressure sensor are sequentially arranged on the first connecting pipeline in the direction close to the diffusion tank, a second switch valve is arranged on the second connecting pipeline, and a third switch valve and a second pressure sensor are sequentially arranged on the third connecting pipeline in the direction close to the coal sample tank.

2. The test system of claim 1, wherein, The driving mechanism comprises a driving motor, a speed reducer and a connecting seat, the connecting seat is arranged at the bottom end of the centralizer, the speed reducer is arranged at the bottom end of the connecting seat, the driving motor is arranged at the bottom end of the speed reducer, the output shaft of the driving motor is connected with the input end of the speed reducer, the connecting seat is internally provided with a connecting shaft, the bottom end of the connecting shaft is connected with the output end of the speed reducer, the plunger is internally provided with a receiving cavity, the bottom end of the plunger is provided with a plunger opening in communication with the receiving cavity, the centralizer is internally provided with a lead screw, the bottom end of the lead screw is connected with the top end of the connecting shaft, the top end of the lead screw penetrates through the plunger opening and extends into the receiving cavity, and the lead screw is threadedly matched with a nut, the nut is located between the connecting seat and the plunger, and the top end of the nut is arranged in the plunger opening.

3. The test system of claim 1, wherein, The outside of the diffusion tank is sequentially sleeved with a first water jacket and a first heat preservation sleeve, a first heat preservation cavity is formed between the inner wall of the first water jacket and the diffusion tank, the outer wall of the first water jacket is provided with a first water inlet joint and a first water outlet joint, the first water inlet joint and the first water outlet joint are both in communication with the first heat preservation cavity, the outer wall of the first heat preservation sleeve is provided with a first avoiding hole for avoiding the first water inlet joint and a second avoiding hole for avoiding the first water outlet joint, and the first water inlet joint and the first water outlet joint are respectively used to be connected with a constant temperature water bath system.

4. The test system of claim 1, wherein, The gas injection device comprises: a carbon dioxide gas cylinder, the carbon dioxide gas cylinder is connected with a first gas injection pipeline, the first gas injection pipeline is connected with the first connecting pipeline, fourth, first pressure reducing, first pressure gauge, fifth, first flow controller, first one-way valve and sixth switch valves are sequentially arranged on the first gas injection pipeline in the direction close to the diffusion tank; A methane gas cylinder is connected with a second gas injection pipeline, the second gas injection pipeline is connected with the first connecting pipeline, and the second gas injection pipeline is sequentially provided with a seventh switch valve, a second pressure reducing valve, a second pressure gauge, an eighth switch valve, a second flow controller, a second check valve and a ninth switch valve along the direction close to the diffusion tank; A nitrogen gas cylinder is connected with a third gas injection pipeline, the third gas injection pipeline is connected with the first connecting pipeline, and the third gas injection pipeline is sequentially provided with a tenth switch valve, a third pressure reducing valve, a third pressure gauge, an eleventh switch valve, a third flow controller, a third check valve and a twelfth switch valve along the direction close to the diffusion tank; A helium gas cylinder is connected with a fourth gas injection pipeline, the fourth gas injection pipeline is connected with the first connecting pipeline, and the fourth gas injection pipeline is provided with a thirteenth switch valve.

5. The test system of claim 1, wherein, The vacuum device comprises a vacuum pump and a vacuum tank, the vacuum pump is connected with a first vacuum pipeline, the first vacuum pipeline is connected with the vacuum tank, the vacuum tank is connected with a second vacuum pipeline, and the second vacuum pipeline is connected with the second connecting pipeline.

6. The test system of claim 1, wherein, The test system further comprises a gas drainage measuring device, a water injection device and a pressure boosting device, the fourth connecting pipeline is used for being connected with the gas drainage measuring device, the coal sample tank is connected with a first water inlet pipeline, the first water inlet pipeline communicates with the inside of the coal sample tank, the first water inlet pipeline is connected with the water injection device, and the pressure boosting device is connected with the first connecting pipeline.

7. The test system of claim 6, wherein, The coal sample tank comprises a tank body, a T-shaped sealing upper cover and a T-shaped sealing lower cover, the top end and the bottom end of the tank body are respectively provided with a first opening and a second opening, the first opening and the second opening both communicate with the inside of the tank body, the horizontal part of the sealing upper cover is detachably arranged at the top end of the tank body, the vertical part of the sealing upper cover is inserted into the first opening, the third connecting pipeline is connected with the horizontal part of the sealing upper cover, the horizontal part and the vertical part of the sealing upper cover are provided with a first flow channel, the first flow channel respectively communicates with the third connecting pipeline and the inside of the tank body, the horizontal part of the sealing upper cover is connected with the fourth connecting pipeline, the horizontal part and the vertical part of the sealing upper cover are provided with a second flow channel, and the second flow channel respectively communicates with the fourth connecting pipeline and the inside of the tank body; the horizontal part of the sealing lower cover is detachably arranged at the bottom end of the tank body, the vertical part of the sealing lower cover is inserted into the second opening, the horizontal part of the sealing lower cover is connected with the first water inlet pipeline, the horizontal part and the vertical part of the sealing lower cover are provided with a third flow channel, and the third flow channel respectively communicates with the first water inlet pipeline and the inside of the tank body.

8. The test system of claim 7, wherein, The outer part of the tank body is sequentially sleeved with a second water jacket and a second heat preservation sleeve, a second heat preservation cavity is formed between the inner wall of the second water jacket and the tank body, the outer wall of the second water jacket is provided with a second water inlet joint and a second water outlet joint, the second water inlet joint and the second water outlet joint are both in communication with the second heat preservation cavity, the outer wall of the second heat preservation sleeve is provided with a first through hole for avoiding the second water inlet joint and a second through hole for avoiding the second water outlet joint, and the first water inlet joint and the first water outlet joint are respectively used for being connected with a constant temperature water bath system.

9. The test system of claim 6, wherein, The desorption measurement device comprises a gas chromatograph, at least three collection bags and a flow divider, the flow divider is connected with a fifth connecting pipeline, the fourth connecting pipeline is connected with a first conversion joint, the fifth connecting pipeline is connected with a second conversion joint, the first conversion joint is used for being connected with the second conversion joint, the collection bags are respectively connected with a sixth connecting pipeline and a seventh connecting pipeline, the sixth connecting pipeline is connected with the flow divider, the seventh connecting pipeline is connected with the gas chromatograph, a back pressure valve is arranged on the fourth connecting pipeline, an adjusting valve, a constant volume container and a fourteenth switch valve are sequentially arranged on the fifth connecting pipeline in the direction close to the flow divider; The air drainage measurement device comprises a first container, a second container and a weighing device, a sealing head is inserted into the opening at the top end of the first container, one end of an exhaust pipeline is connected with a third conversion joint, the first conversion joint is used for being connected with the third conversion joint, the other end of the exhaust pipeline penetrates through a first through hole of the sealing head and extends into the first container, one end of a drainage pipeline penetrates through a second through hole of the sealing head and extends into the first container, and the other end of the drainage pipeline is used for being inserted into the second container, and the second container is arranged on the weighing device.

10. The test system of claim 6, wherein, The water injection device comprises a first constant-speed constant-pressure pump, the first constant-speed constant-pressure pump is connected with a second water inlet pipeline, the second water inlet pipeline is connected with the first water inlet pipeline, and a water inlet valve is arranged on the second water inlet pipeline; the pressure increasing device comprises a second constant-speed constant-pressure pump, the second constant-speed constant-pressure pump is connected with the first connecting pipeline through a communication pipeline, the communication pipeline is located between the gas injection device and the first switch valve, and a fifteenth switch valve is arranged on the communication pipeline.

Images