A method for testing the dynamic change of leakage recharge and parameters of coalbed methane wells

Abstract

A method for testing the dynamic change of overflow recharge and parameters of coalbed methane wells includes the following steps: 1. Making the required core units and determining the experimental plan; 2. Assembling a test device for the dynamic change of overflow recharge and parameters of coalbed methane wells, which includes a gas-liquid environment simulation system, an overflow recharge test system, a high-performance computer and a recovery system; 3. Checking the air tightness; 4. Setting the initial state of the gas-liquid environment simulation system; 5. Arranging and combining each core unit into the overflow recharge test system; 6. Conducting the overflow recharge test, the high-performance computer collects the test data and processes and analyzes it to determine whether the overflow recharge occurs; 7. Recycling the experimental waste through the recovery system. The present invention can restore the in-situ reservoir conditions more realistically, and can monitor the conditions for the occurrence of overflow recharge and the changes in the overflow recharge under different states in real time, providing a theoretical basis for the study of the law of the change of overflow recharge.

Description

Technical Field

[0001] The invention relates to the technical field of coalbed methane drainage experiments, and in particular to a method for testing the overflow replenishment amount and dynamic changes of parameters of a coalbed methane well. Background Art

[0002] Coalbed methane is mainly stored in coal reservoirs in an adsorbed state. Today, surface coalbed methane development often uses drainage and pressure reduction methods to convert adsorbed methane gas in coal seams into free gas and drain it to the ground together with water. Drainage is carried out in three-dimensional space. The difference in the properties of surrounding rocks and coal seams may lead to overflow recharge during drainage. Differences and dynamic changes in the ground stress state, permeability, surrounding rock sealing performance and water content of coal reservoirs lead to changes in the amount of overflow recharge during drainage, affecting gas production.

[0003] At present, the method of testing the porosity and permeability of cores is often used. The mathematical model for identifying inter-coal seam overflow recharge is constructed by applying the seepage theory. The presence of overflow recharge is identified by combining the hydrogeological conditions and reservoir parameters, and verified by the actual drainage data of coalbed methane wells. Since the cores are disturbed and mechanically crushed during the collection process, the collected cores cannot truly reflect the actual situation of the formation in situ. At the same time, due to the constraints of experimental conditions, it is often impossible to measure the dynamic changes of the entire process of overflow recharge in real time. There are certain limitations in the understanding of overflow recharge and its impact. Alternatively, numerical simulation software is used to simulate the overflow recharge situation. Whether the simulation parameter settings can objectively and truly reflect the actual situation on site, as well as human subjectivity, may ultimately lead to a wide range of simulation results, which cannot objectively and truly reflect the actual situation. Therefore, it is urgent to develop a test method for the overflow recharge and dynamic changes of parameters of coalbed methane wells, which can monitor the interlayer overflow recharge and dynamic changes of parameters during drainage under different reservoir parameters in real time on the basis of a relatively realistic restoration of the in-situ reservoir conditions, in order to make an accurate judgment on whether overflow recharge can occur during drainage under different reservoir geological conditions, thereby guiding coalbed methane development. Summary of the invention

[0004] The purpose of the present invention is to provide a method for testing the dynamic change of overflow recharge and parameters of coalbed methane wells. The present invention can more realistically restore the in-situ reservoir conditions, and can more accurately judge whether overflow recharge can occur during drainage under conditions such as reservoir permeability, reservoir geostress state, and recharge inflow conditions. It can monitor in real time the conditions for overflow recharge and the changes in overflow recharge under different conditions, and provide a theoretical basis for the study of the changing law of overflow recharge.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for testing the dynamic change of coalbed methane well overflow replenishment and parameters, comprising the following steps:

[0007] 1. Make the required core units and determine the experimental plan;

[0008] 2. Assemble a coalbed methane well overflow supply and parameter dynamic change test device, which includes a gas-liquid environment simulation system, an overflow supply test system, a high-performance computer and a recovery system;

[0009] 3. Check the gas tightness of the coalbed methane well overflow supply and parameter dynamic change test device;

[0010] 4. Set the initial state of the gas-liquid environment simulation system;

[0011] 5. Arrange and combine the core units into the overflow recharge test system to simulate the real reservoir state, debug the high-performance computer, and make the high-performance computer start real-time recording;

[0012] 6. Conduct overflow recharge test through gas-liquid environment simulation system and overflow recharge test system. High-performance computer collects test data and processes and analyzes them to determine whether overflow recharge occurs.

[0013] 7. After the experiment, the experimental waste will be recycled through the recycling system.

[0014] The device for testing the dynamic change of overflow supply amount and parameters of coalbed methane wells also includes an upper conveying channel, a lower conveying channel and a gas-liquid recovery pipeline. The upper conveying channel and the lower conveying channel are both horizontally arranged in the left-right direction, the gas-liquid recovery pipeline is vertically arranged on the left side of the upper conveying channel and the lower conveying channel, the lower end of the gas-liquid recovery pipeline is blocked, the overflow supply test system is arranged between the upper conveying channel and the lower conveying channel, the gas-liquid output end of the gas-liquid environment simulation system is respectively connected to the right end of the upper conveying channel and the lower conveying channel, the left end of the upper conveying channel and the lower conveying channel are both connected to the gas-liquid recovery pipeline, the upper end of the gas-liquid recovery pipeline is connected to the gas-liquid inlet end of the recovery system, and a high-performance computer is respectively connected to the gas-liquid environment simulation system and the overflow supply test system signal.

[0015] A first stop valve is arranged at the left end of the upper conveying channel, a second stop valve is arranged at the left end of the lower conveying channel, and a third stop valve is arranged in the middle of the gas-liquid recovery pipeline.

[0016] The gas-liquid environment simulation system includes a first gas-liquid delivery system and a second gas-liquid delivery system, and the gas-liquid output ends of the first gas-liquid delivery system and the second gas-liquid delivery system are respectively connected to the left ends of the upper delivery channel and the lower delivery channel;

[0017] The first gas-liquid delivery system comprises a first high-pressure methane gas cylinder, a first water tank, a first two-phase flow delivery pipeline, a first constant speed constant pressure pump and a second constant speed constant pressure pump, the gas outlet end of the first high-pressure methane gas cylinder is connected to the first gas delivery pipeline, the liquid outlet end of the first water tank is connected to the first liquid delivery pipeline, the liquid outlet end of the first liquid delivery pipeline and the gas outlet end of the first gas delivery pipeline are connected to the gas-liquid inlet end of the first two-phase flow delivery pipeline through a tee, the gas-liquid output end of the first two-phase flow delivery pipeline is connected to the right end of the upper delivery channel, the first constant speed constant pressure pump is arranged on the first gas delivery pipeline, and the second constant speed constant pressure pump is arranged on the first liquid delivery pipeline;

[0018] The second gas-liquid delivery system includes a second high-pressure methane gas cylinder, a second water tank, a second two-phase flow delivery pipeline, a third constant speed constant pressure pump and a fourth constant speed constant pressure pump. The gas outlet end of the second high-pressure methane gas cylinder is connected to the second gas delivery pipeline, the liquid outlet end of the second water tank is connected to the second liquid delivery pipeline, the liquid outlet end of the second liquid delivery pipeline and the gas outlet end of the second gas delivery pipeline are connected to the gas-liquid inlet end of the second two-phase flow delivery pipeline through a tee, the gas-liquid output end of the second two-phase flow delivery pipeline is connected to the right end of the lower delivery channel, the third constant speed constant pressure pump is arranged on the second gas delivery pipeline, the fourth constant speed constant pressure pump is arranged on the fourth liquid delivery pipeline, and the high-performance computer is respectively connected to the signals of the first constant speed constant pressure pump, the second constant speed constant pressure pump, the third constant speed constant pressure pump and the fourth constant speed constant pressure pump.

[0019] The overflow supply test system includes several inter-coalbed reservoir channels. The upper conveying channel, the lower conveying channel, the gas-liquid recovery pipeline and the inter-coalbed reservoir channel are all circular pipes. Each inter-coalbed reservoir channel is arranged at intervals on the left and right and vertically connected between the upper conveying channel and the lower conveying channel to simulate the coalbed methane well body structure of combined layer drainage. Each inter-coalbed reservoir channel is provided with N layers of upper and lower spaced support layers. Each support layer divides the inner cavity of the corresponding inter-coalbed reservoir channel into N+1 compartments. Each support layer includes several support plates. The circumferential array of each support plate is arranged on the corresponding On the inner wall of the inter-coal seam reservoir channel, each cabin is provided with a core unit supported on corresponding support plates, the top and bottom of the core unit are provided with mass flow controllers, the mass flow controllers are connected to a display via a signal cable, and a detachable side panel is provided on the front side of each inter-coal seam reservoir channel. A confining pressure simulation system for applying confining pressure on the four sides of a corresponding core unit is installed at the corresponding cabin positions around each inter-coal seam reservoir channel, and a high-performance computer is respectively connected to the signals of each mass flow controller, each display and each confining pressure simulation system.

[0020] A confining pressure simulation system located on the right side of the corresponding inter-coal seam reservoir channel includes a confining pressure pump and four pressure transmission rods. The confining pressure pump is arranged on the right side of the corresponding inter-coal seam reservoir channel through a bracket and corresponds to the corresponding cabin on the left and right. The four pressure transmission rods are horizontally arranged in the left and right directions and are arranged between the confining pressure pump and the corresponding inter-coal seam reservoir channel at intervals up and down. The left ends of the four pressure transmission rods penetrate the right side wall of the corresponding inter-coal seam reservoir channel and extend into the corresponding cabin. The left ends of the four pressure transmission rods are fixedly installed with pressure blocks, which are horizontally arranged in the front-back direction. A stress sensor is arranged on the left side of the pressure block. The four pressure blocks are arranged in an upper and lower stacking manner, and the left sides of the four pressure blocks tightly cover the right side of the corresponding core unit. The confining pressure pump is connected to the right ends of the four pressure transmission rods through hydraulic pipelines, and a pressure cut-off valve is arranged on the hydraulic pipeline. A high-performance computer is respectively connected to the confining pressure pump and the stress sensor signals.

[0021] The recovery system includes a gas-liquid separator, a liquid collecting tank and a gas collecting bottle. The upper end of the gas-liquid recovery pipeline is connected to the gas-liquid inlet end of the gas-liquid separator through a third two-phase flow conveying pipeline, the liquid outlet end of the gas-liquid separator is connected to the liquid inlet end of the liquid collecting tank through a liquid collecting pipeline, and the gas outlet end of the gas-liquid separator is connected to the gas inlet end of the gas collecting bottle through a gas collecting pipeline.

[0022] Step (I) is as follows: before the experiment begins, the required core units are first produced. The core units include all possible reservoir lithologies existing between coal seams: mudstone, sandy mudstone, siltstone, fine-grained sandstone, medium-grained sandstone, coarse-grained sandstone, shale and limestone. Then the types of gas and liquid required for the experiment and the required state of the reservoir are determined. At the same time, the initial state and experimental state of the gas-liquid environment simulation system are determined and formulated, such as environmental pressure, fluid flow rate, and fluid flow rate.

[0023] Step (iii) is specifically as follows: close the first stop valve and the second stop valve, start the first constant speed constant pressure pump, and the gas in the first high-pressure methane cylinder is transported to the upper transport channel through the first constant speed constant pressure pump via the first gas transport pipeline and the first two-phase flow transport pipeline, and the pressure in the pipeline is monitored in real time by the first constant speed constant pressure pump. When the pressure is displayed as 2MPa, close the first constant speed constant pressure pump and stop injecting gas. After a period of time, observe whether the pressure display of the third constant speed constant pressure pump is consistent with the pressure display of the first constant speed constant pressure pump to detect the air tightness of the overall device;

[0024] Step (iv) is specifically as follows: start the first constant speed and constant pressure pump, the second constant speed and constant pressure pump, the third constant speed and constant pressure pump and the fourth constant speed and constant pressure pump, then the first high-pressure methane cylinder delivers gas to the first two-phase flow delivery pipeline through the first constant speed and constant pressure pump and the first gas delivery pipeline, the first water tank delivers liquid to the first two-phase flow delivery pipeline through the second constant speed and constant pressure pump and the first liquid delivery pipeline, and then the first two-phase flow delivery pipeline delivers the gas-liquid mixed fluid to the upper delivery channel to simulate the replenishment inflow environment, and similarly, the second high-pressure methane cylinder delivers gas to the second two-phase flow delivery pipeline through the third constant speed and constant pressure pump and the second gas delivery pipeline. The gas is transported in the two-phase flow transport pipeline, and the second water tank transports liquid to the second two-phase flow transport pipeline through the fourth constant speed and constant pressure pump and the second liquid transport pipeline, and then the second two-phase flow transport pipeline transports the gas-liquid mixed fluid to the lower transport channel to simulate the coal seam environment during coalbed methane extraction; the first constant speed and constant pressure pump, the second constant speed and constant pressure pump, the third constant speed and constant pressure pump and the fourth constant speed and constant pressure pump are adjusted to adjust the initial gas-liquid flow rate injected into the upper transport channel and the lower transport channel, and the gas-liquid injection is continuously performed until the initial state of the gas-liquid environment simulation system determined in the experimental plan is reached.

[0025] Step (V) is specifically as follows: by studying the actual reservoir state, the prepared core units are arranged and combined according to the actual situation, the lithology of the inter-coal seam reservoir is simulated under the actual situation, the side plates at the front side of each inter-coal seam reservoir channel are opened, and the assembled core units are placed into the corresponding inter-coal seam reservoir channel at one time, so that each core unit is supported on the corresponding supporting plates respectively, and then each side plate is installed, and then the corresponding confining pressure pumps are started, and the corresponding pressure transmission rods are adjusted through the pressure stop valves to change the confining pressure of the core unit under different gradients in the corresponding inter-coal seam reservoir channel. Each core unit can be set to four confining pressure states, thereby better simulating the reservoir stress state under the actual state. At the same time, the confining pressure can also change the permeability of the core unit, debug the high-performance computer, open the adjustment interface, and select the file saving location, so that the high-performance computer starts real-time recording. The high-performance computer records the stress state of each core unit in real time through each stress sensor.

[0026] Step (six) is specifically as follows: by regulating the first constant speed constant pressure pump, the second constant speed constant pressure pump, the third constant speed constant pressure pump and the fourth constant speed constant pressure pump, respectively changing the experimental conditions in the upper conveying channel and the lower conveying channel: environmental pressure, fluid flow rate, fluid flow rate, so as to simulate the replenishment inflow environment under different conditions and the coal seam environment during the coalbed methane drainage process, each mass flow controller measures the mass of the gas-liquid fluid flowing through to obtain the gas-liquid fluid flow rate and flow rate, each display displays the flow data measured by the corresponding mass flow controller, stipulates that the flow rate of the gas-liquid fluid from top to bottom is displayed as positive, and the high-performance computer records the flow data measured by each mass flow controller in real time. The high-performance computer analyzes the basic data of each core unit, the stress state of each core unit and the recorded flow data measured by each mass flow controller, so as to monitor the conditions for the occurrence of overflow replenishment and the changes in the overflow replenishment amount under different conditions in real time, and provide a theoretical basis for the study of the law of the change of overflow replenishment amount;

[0027] Step (seven) is specifically as follows: after the experiment is over, the first stop valve, the second stop valve and the third stop valve are opened to allow the gas-liquid mixed fluid in the upper conveying channel and the lower conveying channel to enter the gas-liquid separator through the gas-liquid recovery pipeline and the third two-phase flow conveying pipeline, the gas-liquid mixed fluid is separated in the gas-liquid separator, the separated gas enters the gas collection bottle through the gas collection pipeline, and the separated liquid enters the liquid collection tank through the liquid collection pipeline, thereby completing the recovery of the experimental waste.

[0028] Compared with the prior art, the present invention has outstanding substantial features and significant progress. Specifically, the present invention can more realistically restore the in-situ reservoir conditions, and can more accurately determine whether overflow recharge can occur during drainage under conditions such as reservoir permeability, reservoir geostress state, and recharge inflow conditions. It can monitor in real time the conditions for overflow recharge and the changes in overflow recharge amounts under different conditions, providing a theoretical basis for the study of the changing laws of overflow recharge amounts. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of a device for testing the overflow replenishment amount and dynamic change of parameters of a coalbed methane well according to the present invention.

[0030] Figure 2 It is a structural schematic diagram of the confining pressure simulation system of the present invention. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are further described below with reference to the accompanying drawings.

[0032] like Figure 1 and Figure 2 As shown, a method for testing the dynamic change of coalbed methane well overflow supply and parameters includes the following steps:

[0033] 1. Make the required core unit 1 and determine the experimental plan;

[0034] 2. Assemble a coalbed methane well overflow supply and parameter dynamic change test device, which includes a gas-liquid environment simulation system, an overflow supply test system, a high-performance computer 2 and a recovery system;

[0035] 3. Check the gas tightness of the coalbed methane well overflow supply and parameter dynamic change test device;

[0036] 4. Set the initial state of the gas-liquid environment simulation system;

[0037] 5. Arrange and combine the core units 1 and place them into the overflow recharge test system to simulate the real reservoir state, debug the high performance computer 2, and make the high performance computer 2 start real-time recording;

[0038] 6. Conduct overflow replenishment test through gas-liquid environment simulation system and overflow replenishment test system, and high performance computer 2 collects test data and processes and analyzes it to determine whether overflow replenishment occurs;

[0039] 7. After the experiment, the experimental waste will be recycled through the recycling system.

[0040] The coalbed methane well overflow supply amount and parameter dynamic change test device also includes an upper conveying channel 3, a lower conveying channel 4 and a gas-liquid recovery pipeline 5. The upper conveying channel 3 and the lower conveying channel 4 are both horizontally arranged in the left-right direction, the gas-liquid recovery pipeline 5 is vertically arranged on the left side of the upper conveying channel 3 and the lower conveying channel 4, the lower end of the gas-liquid recovery pipeline 5 is blocked, the overflow supply test system is arranged between the upper conveying channel 3 and the lower conveying channel 4, the gas-liquid output end of the gas-liquid environment simulation system is respectively connected to the right end of the upper conveying channel 3 and the lower conveying channel 4, the left end of the upper conveying channel 3 and the lower conveying channel 4 are both connected to the gas-liquid recovery pipeline 5, the upper end of the gas-liquid recovery pipeline 5 is connected to the gas-liquid inlet end of the recovery system, and the high-performance computer 2 is respectively connected to the gas-liquid environment simulation system and the overflow supply test system signal.

[0041] A first stop valve 6 is provided at the left end of the upper conveying channel 3 , a second stop valve 7 is provided at the left end of the lower conveying channel 4 , and a third stop valve 8 is provided in the middle of the gas-liquid recovery pipeline 5 .

[0042] The gas-liquid environment simulation system includes a first gas-liquid delivery system and a second gas-liquid delivery system, and the gas-liquid output ends of the first gas-liquid delivery system and the second gas-liquid delivery system are respectively connected to the left ends of the upper delivery channel 3 and the lower delivery channel 4;

[0043] The first gas-liquid delivery system includes a first high-pressure methane gas cylinder 9, a first water tank 10, a first two-phase flow delivery pipeline 11, a first constant speed constant pressure pump 12 and a second constant speed constant pressure pump 13, the gas outlet end of the first high-pressure methane gas cylinder 9 is connected to the first gas delivery pipeline 14, the liquid outlet end of the first water tank 10 is connected to the first liquid delivery pipeline 15, the liquid outlet end of the first liquid delivery pipeline 15 and the gas outlet end of the first gas delivery pipeline 14 are connected to the gas-liquid inlet end of the first two-phase flow delivery pipeline 11 through a tee, the gas-liquid output end of the first two-phase flow delivery pipeline 11 is connected to the right end of the upper delivery channel 3, the first constant speed constant pressure pump 12 is arranged on the first gas delivery pipeline 14, and the second constant speed constant pressure pump 13 is arranged on the first liquid delivery pipeline 15;

[0044] The second gas-liquid delivery system includes a second high-pressure methane gas cylinder 16, a second water tank 17, a second two-phase flow delivery pipeline 18, a third constant speed constant pressure pump 19 and a fourth constant speed constant pressure pump 20. The gas outlet end of the second high-pressure methane gas cylinder 16 is connected to the second gas delivery pipeline 21, the liquid outlet end of the second water tank 17 is connected to the second liquid delivery pipeline 22, the liquid outlet end of the second liquid delivery pipeline 22 and the gas outlet end of the second gas delivery pipeline 21 are connected to the gas-liquid inlet end of the second two-phase flow delivery pipeline 18 through a tee, the gas-liquid output end of the second two-phase flow delivery pipeline 18 is connected to the right end of the lower delivery channel 4, the third constant speed constant pressure pump 19 is arranged on the second gas delivery pipeline 21, the fourth constant speed constant pressure pump 20 is arranged on the fourth liquid delivery pipeline, and the high-performance computer 2 is respectively connected to the first constant speed constant pressure pump 12, the second constant speed constant pressure pump 13, the third constant speed constant pressure pump 19 and the fourth constant speed constant pressure pump 20.

[0045] The overflow supply test system includes a plurality of inter-coalbed reservoir channels 23, wherein the upper transport channel 3, the lower transport channel 4, the gas-liquid recovery pipeline 5 and the inter-coalbed reservoir channel 23 are all circular pipes, and each inter-coalbed reservoir channel 23 is arranged at intervals on the left and right and vertically connected between the upper transport channel 3 and the lower transport channel 4 to simulate the wellbore structure of the coalbed methane well for combined layer drainage, and each inter-coalbed reservoir channel 23 is provided with N layers of upper and lower spaced support layers, and each support layer divides the inner cavity of the corresponding inter-coalbed reservoir channel 23 into N+1 compartments, and each support layer includes a plurality of support plates 24, and each support plate 24 is arranged in a circular array in the corresponding inter-coalbed reservoir channel 23, each compartment is provided with a core unit 1 supported on the corresponding support plates 24, the top and bottom of the core unit 1 are provided with a mass flow controller 25, the mass flow controller 25 is connected to a display 27 through a signal cable 26, and the front side of each inter-coal seam reservoir channel 23 is provided with a detachable side panel (not shown in the figure), and each inter-coal seam reservoir channel 23 is surrounded by a confining pressure simulation system 39 for applying confining pressure on the four sides of a corresponding core unit 1 at the corresponding compartment position, and the high-performance computer 2 is respectively connected to the signals of each mass flow controller 25, each display 27 and each confining pressure simulation system 39.

[0046] A confining pressure simulation system 39 located on the right side of the corresponding inter-coal reservoir channel 23 includes a confining pressure pump 28 and four pressure transmission rods 29. The confining pressure pump 28 is arranged on the right side of the corresponding inter-coal reservoir channel 23 through a bracket and corresponds to the left and right sides of the corresponding cabin. The four pressure transmission rods 29 are all arranged horizontally in the left and right directions and are arranged at intervals between the confining pressure pump 28 and the corresponding inter-coal reservoir channel 23. The left ends of the four pressure transmission rods 29 penetrate the right side wall of the corresponding inter-coal reservoir channel 23 and extend into the corresponding cabin. The left ends of the four pressure transmission rods 29 are fixedly installed with pressure blocks 30, which are arranged horizontally in the front-to-back direction. A stress sensor (not shown) is arranged on the left side of the pressure block 30. The four pressure blocks 30 are arranged in an up-and-down stack, and the left sides of the four pressure blocks 30 tightly cover the right side of the corresponding core unit 1. The confining pressure pump 28 is connected to the right ends of the four pressure transmission rods 29 through a hydraulic pipeline 31, and a pressure cut-off valve 32 is arranged on the hydraulic pipeline 31. The high-performance computer 2 is respectively connected to the confining pressure pump 28 and the stress sensor signal.

[0047] The recovery system includes a gas-liquid separator 33, a liquid collecting tank 34 and a gas collecting bottle 35. The upper end of the gas-liquid recovery pipeline 5 is connected to the gas-liquid inlet end of the gas-liquid separator 33 through a third two-phase flow conveying pipeline 36, the liquid outlet end of the gas-liquid separator 33 is connected to the liquid inlet end of the liquid collecting tank 34 through a liquid collecting pipeline 37, and the gas outlet end of the gas-liquid separator 33 is connected to the gas inlet end of the gas collecting bottle 35 through a gas collecting pipeline 38.

[0048] Step (i) is as follows: before the experiment begins, the required core unit 1 is first produced. The core unit 1 includes all possible reservoir lithologies existing between coal seams: mudstone, sandy mudstone, siltstone, fine-grained sandstone, medium-grained sandstone, coarse-grained sandstone, shale and limestone. Then, the types of gas and liquid required for the experiment and the required state of the reservoir are determined. At the same time, the initial state and experimental state of the gas-liquid environment simulation system are determined and formulated, such as environmental pressure, fluid flow rate, and fluid flow rate.

[0049] Step (iii) is specifically as follows: close the first stop valve 6 and the second stop valve 7, start the first constant speed constant pressure pump 12, and the gas in the first high-pressure methane cylinder 9 is transported to the upper conveying channel 3 through the first constant speed constant pressure pump 12 via the first gas conveying pipeline 14 and the first two-phase flow conveying pipeline 11, and the pressure in the pipeline is monitored in real time by the first constant speed constant pressure pump 12. When the pressure is displayed as 2MPa, close the first constant speed constant pressure pump 12 and stop injecting gas. After a period of time, observe whether the pressure display of the third constant speed constant pressure pump 19 is consistent with the pressure display of the first constant speed constant pressure pump 12 to detect the air tightness of the overall device;

[0050] Step (iv) is specifically as follows: start the first constant speed constant pressure pump 12, the second constant speed constant pressure pump 13, the third constant speed constant pressure pump 19 and the fourth constant speed constant pressure pump 20, then the first high-pressure methane gas cylinder 9 delivers gas to the first two-phase flow delivery pipeline 11 through the first constant speed constant pressure pump 12 and the first gas delivery pipeline 14, the first water tank 10 delivers liquid to the first two-phase flow delivery pipeline 11 through the second constant speed constant pressure pump 13 and the first liquid delivery pipeline 15, and then the first two-phase flow delivery pipeline 11 delivers the gas-liquid mixed fluid to the upper delivery channel 3 to simulate the supply inflow environment. Similarly, the second high-pressure methane gas cylinder 16 delivers gas to the first two-phase flow delivery pipeline 2 through the third constant speed constant pressure pump 19 and the second gas delivery pipeline 2 1 delivers gas to the second two-phase flow delivery pipeline 18, the second water tank 17 delivers liquid to the second two-phase flow delivery pipeline 18 through the fourth constant speed constant pressure pump 20 and the second liquid delivery pipeline 22, and then the second two-phase flow delivery pipeline 18 delivers the gas-liquid mixed fluid to the lower delivery channel 4 to simulate the coal seam environment during the coal seam gas extraction process; adjust the first constant speed constant pressure pump 12, the second constant speed constant pressure pump 13, the third constant speed constant pressure pump 19 and the fourth constant speed constant pressure pump 20 to adjust the initial gas-liquid flow rate injected into the upper delivery channel 3 and the lower delivery channel 4, and continuously inject gas and liquid until the initial state of the gas-liquid environment simulation system determined in the experimental plan is reached.

[0051] Step (V) is specifically as follows: by studying the real reservoir state, the prepared core units 1 are arranged and combined according to the actual situation, the lithology of the inter-coal seam reservoir under the actual situation is simulated, the side panels of the front side of each inter-coal seam reservoir channel 23 are opened, and the assembled core units 1 are placed into the corresponding inter-coal seam reservoir channel 23 at one time, so that each core unit 1 is supported on the corresponding supporting plates 24 respectively, and then each side panel is installed, and then the corresponding confining pressure pumps 28 are started, and the corresponding pressure transmission rods 29 are adjusted through the pressure cut-off valves 32 to change the confining pressure of the core unit 1 under different gradients in the corresponding inter-coal seam reservoir channel 23. Each core unit 1 can be set to four confining pressure states, thereby better simulating the reservoir stress state under the real state. At the same time, the confining pressure can also change the permeability of the core unit 1, debug the high-performance computer 2, open the adjustment interface, and select the file saving location, so that the high-performance computer 2 starts real-time recording. The high-performance computer 2 records the stress state of each core unit 1 in real time through each stress sensor.

[0052] Step (six) is specifically as follows: by regulating the first constant speed constant pressure pump 12, the second constant speed constant pressure pump 13, the third constant speed constant pressure pump 19 and the fourth constant speed constant pressure pump 20, the experimental conditions in the upper conveying channel 3 and the lower conveying channel 4 are changed respectively: the environmental pressure, the fluid flow rate, the fluid flow rate, so as to simulate the supply inflow environment under different conditions and the coal seam environment in the coalbed methane drainage process, each mass flow controller 25 measures the mass of the gas-liquid fluid flowing through and then obtains the gas-liquid fluid flow rate and flow rate, each display 27 displays the flow data measured by the corresponding mass flow controller 25, and stipulates that the flow rate of the gas-liquid fluid from top to bottom is displayed as positive, the high-performance computer 2 records the flow data measured by each mass flow controller 25 in real time, and the high-performance computer 2 analyzes the basic data of each core unit 1, the stress state of each core unit 1 and the recorded flow data measured by each mass flow controller 25, so as to monitor the conditions for the occurrence of overflow replenishment and the changes in the overflow replenishment amount under different states in real time, and provide a theoretical basis for the study of the law of the change of overflow replenishment amount;

[0053] Step (seven) is specifically as follows: after the experiment is finished, the first stop valve 6, the second stop valve 7 and the third stop valve 8 are opened, so that the gas-liquid mixed fluid in the upper conveying channel 3 and the lower conveying channel 4 enters the gas-liquid separator 33 through the gas-liquid recovery pipeline 5 and the third two-phase flow conveying pipeline 36, the gas-liquid mixed fluid is separated in the gas-liquid separator 33, the separated gas enters the gas collection bottle 35 through the gas collection pipeline 38, and the separated liquid enters the liquid collection tank 34 through the liquid collection pipeline 37, thereby completing the recovery of the experimental waste.

[0054] The high performance computer 2, the first constant speed constant pressure pump 12, the second constant speed constant pressure pump 13, the third constant speed constant pressure pump 19, the fourth constant speed constant pressure pump 20, the mass flow controller 25, the display 27, the confining pressure pump 28, the pressure transmission rod 29, the stress sensor and the gas-liquid separator 33 are all conventional technologies, and the specific structure and working principle are not repeated. The high performance computer 2 is a computer used in the laboratory, and has a built-in experimental system. The control and signal transmission technologies therein are all existing technologies and do not involve new computer programs.

[0055] The present invention can more realistically restore the in-situ reservoir conditions, and can more accurately determine whether overflow recharge can occur during drainage under conditions such as reservoir permeability, reservoir geostress state, and recharge inflow conditions. It can also monitor in real time the conditions for overflow recharge and changes in overflow recharge amounts under different conditions, providing a theoretical basis for the study of the changing laws of overflow recharge amounts.

[0056] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for testing the dynamic change of leakage supply and parameters of coalbed methane wells, characterized by: The following steps are involved:

1. Make the required core units and determine the experimental plan; 2. Assemble a coalbed methane well overflow supply and parameter dynamic change test device, which includes a gas-liquid environment simulation system, an overflow supply test system, a high-performance computer and a recovery system; 3. Check the gas tightness of the coalbed methane well overflow supply and parameter dynamic change test device; 4. Set the initial state of the gas-liquid environment simulation system; 5. Arrange and combine the core units into the overflow recharge test system to simulate the real reservoir state, debug the high-performance computer, and make the high-performance computer start real-time recording; 6. Conduct overflow recharge test through gas-liquid environment simulation system and overflow recharge test system. High-performance computer collects test data and processes and analyzes them to determine whether overflow recharge occurs.

7. After the experiment, the experimental waste will be recycled through the recycling system; The coalbed methane well overflow supply amount and parameter dynamic change test device also includes an upper conveying channel, a lower conveying channel and a gas-liquid recovery pipeline. The upper conveying channel and the lower conveying channel are both horizontally arranged in the left-right direction. The gas-liquid recovery pipeline is vertically arranged on the left side of the upper conveying channel and the lower conveying channel. The lower end of the gas-liquid recovery pipeline is blocked. The overflow supply test system is arranged between the upper conveying channel and the lower conveying channel. The gas-liquid output end of the gas-liquid environment simulation system is respectively connected to the right end of the upper conveying channel and the lower conveying channel. The left ends of the upper conveying channel and the lower conveying channel are both connected to the gas-liquid recovery pipeline. The upper end of the gas-liquid recovery pipeline is connected to the gas-liquid inlet end of the recovery system. The high-performance computer is respectively connected to the gas-liquid environment simulation system and the overflow supply test system signal. A first stop valve is provided at the left end of the upper conveying channel, a second stop valve is provided at the left end of the lower conveying channel, and a third stop valve is provided in the middle of the gas-liquid recovery pipeline; The gas-liquid environment simulation system includes a first gas-liquid delivery system and a second gas-liquid delivery system, and the gas-liquid output ends of the first gas-liquid delivery system and the second gas-liquid delivery system are respectively connected to the right ends of the upper delivery channel and the lower delivery channel; The first gas-liquid delivery system comprises a first high-pressure methane gas cylinder, a first water tank, a first two-phase flow delivery pipeline, a first constant speed constant pressure pump and a second constant speed constant pressure pump, the gas outlet end of the first high-pressure methane gas cylinder is connected to the first gas delivery pipeline, the liquid outlet end of the first water tank is connected to the first liquid delivery pipeline, the liquid outlet end of the first liquid delivery pipeline and the gas outlet end of the first gas delivery pipeline are connected to the gas-liquid inlet end of the first two-phase flow delivery pipeline through a tee, the gas-liquid output end of the first two-phase flow delivery pipeline is connected to the right end of the upper delivery channel, the first constant speed constant pressure pump is arranged on the first gas delivery pipeline, and the second constant speed constant pressure pump is arranged on the first liquid delivery pipeline; The second gas-liquid delivery system includes a second high-pressure methane gas cylinder, a second water tank, a second two-phase flow delivery pipeline, a third constant speed constant pressure pump and a fourth constant speed constant pressure pump, the gas outlet end of the second high-pressure methane gas cylinder is connected to the second gas delivery pipeline, the liquid outlet end of the second water tank is connected to the second liquid delivery pipeline, the liquid outlet end of the second liquid delivery pipeline and the gas outlet end of the second gas delivery pipeline are connected to the gas-liquid inlet end of the second two-phase flow delivery pipeline through a tee, the gas-liquid output end of the second two-phase flow delivery pipeline is connected to the right end of the lower delivery channel, the third constant speed constant pressure pump is arranged on the second gas delivery pipeline, the fourth constant speed constant pressure pump is arranged on the fourth liquid delivery pipeline, and the high-performance computer is respectively connected to the signals of the first constant speed constant pressure pump, the second constant speed constant pressure pump, the third constant speed constant pressure pump and the fourth constant speed constant pressure pump; The overflow supply test system includes several inter-coalbed reservoir channels. The upper conveying channel, the lower conveying channel, the gas-liquid recovery pipeline and the inter-coalbed reservoir channel are all circular pipes. Each inter-coalbed reservoir channel is arranged at intervals on the left and right and vertically connected between the upper conveying channel and the lower conveying channel to simulate the coalbed methane well body structure of combined layer drainage. Each inter-coalbed reservoir channel is provided with N layers of upper and lower spaced support layers. Each support layer divides the inner cavity of the corresponding inter-coalbed reservoir channel into N+1 compartments. Each support layer includes several support plates. The circumferential array of each support plate is arranged on the corresponding On the inner wall of the inter-coal seam reservoir channel, each cabin is provided with a core unit supported on corresponding support plates, the top and bottom of the core unit are provided with a mass flow controller, the mass flow controller is connected to a display through a signal cable, a detachable side panel is provided at the front side of each inter-coal seam reservoir channel, and a confining pressure simulation system that applies confining pressure on the four sides of a corresponding core unit is installed at the corresponding cabin positions around each inter-coal seam reservoir channel, and a high-performance computer is respectively connected to the signals of each mass flow controller, each display and each confining pressure simulation system; A confining pressure simulation system located on the right side of the corresponding inter-coal reservoir channel includes a confining pressure pump and four pressure transmission rods. The confining pressure pump is arranged on the right side of the corresponding inter-coal reservoir channel through a bracket and corresponds to the left and right sides of the corresponding cabin. The four pressure transmission rods are all arranged horizontally in the left and right directions and are arranged between the confining pressure pump and the corresponding inter-coal reservoir channel at intervals. The left ends of the four pressure transmission rods penetrate the right side wall of the corresponding inter-coal reservoir channel and extend into the corresponding cabin. The left ends of the four pressure transmission rods are all fixedly installed with pressure blocks, which are arranged horizontally in the front-back direction. A stress sensor is arranged on the left side of the pressure block. The four pressure blocks are arranged to overlap up and down, and the left sides of the four pressure blocks tightly cover the right side of the corresponding core unit. The confining pressure pump is connected to the right ends of the four pressure transmission rods through hydraulic pipelines, and a pressure cut-off valve is arranged on the hydraulic pipeline. A high-performance computer is respectively connected to the confining pressure pump and the stress sensor signal; The recovery system includes a gas-liquid separator, a liquid collecting tank and a gas collecting bottle. The upper end of the gas-liquid recovery pipeline is connected to the gas-liquid inlet end of the gas-liquid separator through a third two-phase flow conveying pipeline, the liquid outlet end of the gas-liquid separator is connected to the liquid inlet end of the liquid collecting tank through a liquid collecting pipeline, and the gas outlet end of the gas-liquid separator is connected to the gas inlet end of the gas collecting bottle through a gas collecting pipeline.

2. The method for testing the leakage replenishment amount and dynamic change of parameters of coalbed methane wells according to claim 1 is characterized in that: Step (I) is as follows: before the experiment begins, the required core units are first produced. The core units include all possible reservoir lithologies existing between coal seams: mudstone, sandy mudstone, siltstone, fine-grained sandstone, medium-grained sandstone, coarse-grained sandstone, shale and limestone. Then the types of gas and liquid required for the experiment and the required state of the reservoir are determined. At the same time, the initial state and experimental state of the gas-liquid environment simulation system are determined and formulated: environmental pressure, fluid flow rate and fluid flow rate; Step (iii) is specifically as follows: close the first stop valve and the second stop valve, start the first constant speed constant pressure pump, and the gas in the first high-pressure methane cylinder is transported to the upper transport channel through the first constant speed constant pressure pump via the first gas transport pipeline and the first two-phase flow transport pipeline, and the pressure in the pipeline is monitored in real time by the first constant speed constant pressure pump. When the pressure is displayed as 2MPa, close the first constant speed constant pressure pump and stop injecting gas. After a period of time, observe whether the pressure display of the third constant speed constant pressure pump is consistent with the pressure display of the first constant speed constant pressure pump to detect the air tightness of the overall device; Step (iv) is specifically as follows: start the first constant speed and constant pressure pump, the second constant speed and constant pressure pump, the third constant speed and constant pressure pump and the fourth constant speed and constant pressure pump, then the first high-pressure methane cylinder delivers gas to the first two-phase flow delivery pipeline through the first constant speed and constant pressure pump and the first gas delivery pipeline, the first water tank delivers liquid to the first two-phase flow delivery pipeline through the second constant speed and constant pressure pump and the first liquid delivery pipeline, and then the first two-phase flow delivery pipeline delivers the gas-liquid mixed fluid to the upper delivery channel to simulate the replenishment inflow environment, and similarly, the second high-pressure methane cylinder delivers gas to the second two-phase flow delivery pipeline through the third constant speed and constant pressure pump and the second gas delivery pipeline. The gas is transported in the two-phase flow transport pipeline, and the second water tank transports liquid to the second two-phase flow transport pipeline through the fourth constant speed and constant pressure pump and the second liquid transport pipeline, and then the second two-phase flow transport pipeline transports the gas-liquid mixed fluid to the lower transport channel to simulate the coal seam environment during coalbed methane extraction; the first constant speed and constant pressure pump, the second constant speed and constant pressure pump, the third constant speed and constant pressure pump and the fourth constant speed and constant pressure pump are adjusted to adjust the initial gas-liquid flow rate injected into the upper transport channel and the lower transport channel, and the gas-liquid injection is continuously performed until the initial state of the gas-liquid environment simulation system determined in the experimental plan is reached.

3. The method for testing the leakage replenishment amount and dynamic change of parameters of coalbed methane wells according to claim 1 is characterized in that: Step (V) is specifically as follows: by studying the actual reservoir state, the prepared core units are arranged and combined according to the actual situation, the lithology of the inter-coal seam reservoir is simulated under the actual situation, the side plates at the front side of each inter-coal seam reservoir channel are opened, and the assembled core units are placed into the corresponding inter-coal seam reservoir channel at one time, so that each core unit is supported on the corresponding supporting plates respectively, and then each side plate is installed, and then the corresponding confining pressure pumps are started, and the corresponding pressure transmission rods are adjusted through the pressure stop valves to change the confining pressure of the core unit under different gradients in the corresponding inter-coal seam reservoir channel. Each core unit can be set to four confining pressure states, thereby better simulating the reservoir stress state under the actual state. At the same time, the confining pressure can also change the permeability of the core unit, debug the high-performance computer, open the adjustment interface, and select the file saving location, so that the high-performance computer starts real-time recording. The high-performance computer records the stress state of each core unit in real time through each stress sensor.

4. The method for testing the leakage replenishment amount and dynamic change of parameters of coalbed methane wells according to claim 1 is characterized in that: Step (six) is specifically as follows: by regulating the first constant speed constant pressure pump, the second constant speed constant pressure pump, the third constant speed constant pressure pump and the fourth constant speed constant pressure pump, respectively changing the experimental conditions in the upper conveying channel and the lower conveying channel: environmental pressure, fluid flow rate and fluid flow rate, so as to simulate the replenishment inflow environment under different conditions and the coal seam environment during the coalbed methane drainage process, each mass flow controller measures the mass of the gas-liquid fluid flowing through to obtain the gas-liquid fluid flow rate and flow rate, each display displays the flow data measured by the corresponding mass flow controller, stipulates that the flow rate of the gas-liquid fluid from top to bottom is displayed as positive, and the high-performance computer records the flow data measured by each mass flow controller in real time. The high-performance computer analyzes the basic data of each core unit, the stress state of each core unit and the recorded flow data measured by each mass flow controller, so as to monitor the conditions for the occurrence of overflow replenishment and the changes in the overflow replenishment amount under different conditions in real time, and provide a theoretical basis for the study of the law of the change of overflow replenishment amount; Step (seven) is specifically as follows: after the experiment is over, the first stop valve, the second stop valve and the third stop valve are opened to allow the gas-liquid mixed fluid in the upper conveying channel and the lower conveying channel to enter the gas-liquid separator through the gas-liquid recovery pipeline and the third two-phase flow conveying pipeline, the gas-liquid mixed fluid is separated in the gas-liquid separator, the separated gas enters the gas collection bottle through the gas collection pipeline, and the separated liquid enters the liquid collection tank through the liquid collection pipeline, thereby completing the recovery of the experimental waste.

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