Visual simulation device and method for gas-water flow behavior in micro-fracture of deep coal reservoir

Abstract

The invention belongs to the technical field of deep coal bed gas development, and particularly relates to a visual simulation device and method for gas and water flow behaviors in deep coal reservoir microfracture.The device comprises a transparent high-temperature and high-pressure experiment cavity used for containing a sample; the outlet end of the gas-water injection-output system is communicated with the inlet end of the transparent high-temperature and high-pressure experiment cavity, and the inlet end of the gas-water injection-output system is communicated with the outlet end of the transparent high-temperature and high-pressure experiment cavity; the temperature and pressure control system is arranged in the transparent high-temperature and high-pressure experiment cavity and used for controlling the temperature and pressure of the transparent high-temperature and high-pressure experiment cavity; and the external visual equipment is positioned on the outer side of the transparent high-temperature and high-pressure experiment cavity, faces the sample, and is used for observing and recording the flowing behavior of gas and water in the sample. The invention further discloses a using method of the device. According to the invention, the real migration process of gas and water in the microfissure can be observed and monitored in real time.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep coalbed methane development, and in particular relates to a device and method for visually simulating gas-water flow behavior in micro-cracks of deep coal reservoirs. Background Art

[0002] Deep coalbed methane resources are large in volume and highly reliable. Large-scale and effective development is an important guarantee for the continuous increase in oil and gas reserves and production and the "carbon reduction" of the coal industry. The gas and water content and flow distribution in deep coal seams determine the state of the gas reservoir. Accurately describing the microscopic occurrence characteristics of gas and water flow under deep conditions is an important prerequisite for the efficient development of coalbed methane resources. Although some seepage simulation devices have been proposed in the prior art, these devices still have the following problems for coalbed methane:

[0003] Traditional experiments cannot visualize gas-water flow behavior: The current coal pillar experimental method cannot directly observe the gas-water migration process inside the micro-cracks of the coal reservoir, and lacks real-time dynamic visualization observation methods. Traditional experiments rely on the overall properties of coal samples and ignore the influence of micro-crack structure, resulting in a one-sided understanding of gas-water flow behavior and unable to accurately reveal the actual characteristics of gas-water flow and its interaction with the micro-crack structure of coal rock.

[0004] Lack of verification of high temperature and high pressure experimental conditions: Although current numerical simulation studies can predict gas-water flow behavior, most simulations lack experimental verification, especially under high temperature and high pressure environments. The gas-water flow in deep coal reservoirs is affected by multiple factors such as temperature, pressure, and coal microcrack morphology. Existing experiments cannot effectively simulate the real conditions of deep coal seams, resulting in deviations in simulation results, which in turn affects the accurate prediction of coalbed methane resource development and recovery rate.

[0005] The artificial simulation materials are significantly different from natural coal and rock: the artificial simulation materials widely used in current experiments cannot accurately restore the physical and chemical properties of coal seams under high temperature and high pressure conditions, especially in terms of wettability, microcrack development, and gas-water flow mechanism of coal and rock. When using these simulation materials for gas-water flow experiments, the actual laws of coalbed gas and water flow cannot be accurately reproduced, which limits the applicability and reliability of experimental data.

[0006] The experimental device is complex to operate and has insufficient control accuracy: The existing deep coal reservoir gas-water flow experimental device is relatively complex in operation and control, especially in the temperature and pressure control system and gas-water flow observation, which have certain operational difficulties and technical bottlenecks. The temperature and pressure control accuracy of the existing equipment under high temperature and high pressure conditions is low, and it is impossible to accurately simulate and stably maintain the gas-water flow environment in deep coal seams, resulting in pressure fluctuations and data instability during the experiment, affecting the repeatability and scientificity of the experimental results.

[0007] Therefore, we propose a device and method for visual simulation of gas-water flow behavior in micro-fractures of deep coal reservoirs. Summary of the invention

[0008] The purpose of the present invention is to provide a device and method for visually simulating the flow behavior of gas and water in micro-cracks of deep coal reservoirs to solve the above problems.

[0009] To achieve the above object, the present invention provides the following solutions:

[0010] A visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs, comprising:

[0011] Transparent high temperature and high pressure experimental chamber, used to place samples;

[0012] A gas-water injection-output system, wherein the outlet of the gas-water injection-output system is connected to the inlet of the transparent high-temperature and high-pressure experimental cavity, and the inlet of the gas-water injection-output system is connected to the outlet of the transparent high-temperature and high-pressure experimental cavity;

[0013] A temperature and pressure control system is arranged in the transparent high-temperature and high-pressure experimental cavity, and the temperature and pressure control system is used to control the temperature and pressure of the transparent high-temperature and high-pressure experimental cavity;

[0014] The external visualization device is located outside the transparent high-temperature and high-pressure experimental cavity. The external visualization device is arranged toward the sample and is used to observe and record the flow behavior of air and water in the sample.

[0015] Optionally, the transparent high temperature and high pressure experimental chamber comprises:

[0016] An intermediate cabin, wherein a placement plate is coaxially fixedly connected in the intermediate cabin, the placement plate is used to place the sample, a pressure plate is coaxially fixedly connected on the placement plate, and the sample is located between the placement plate and the pressure plate;

[0017] An upper cover is coaxially fixed to the top of the intermediate cabin, and a high temperature and high pressure resistant transparent glass is axially connected to the middle of the upper cover;

[0018] A lower cover is coaxially fixed to the bottom of the intermediate cabin, and another high temperature and high pressure resistant transparent glass is axially connected to the middle of the lower cover;

[0019] The upper cover, the lower cover and the inner wall of the intermediate cabin together form a reaction kettle;

[0020] The sample is placed in the reaction vessel.

[0021] The upper cover, the lower cover and the middle cabin body are all circumferentially provided with screw holes for bolts to pass through, and the upper cover, the lower cover and the middle cabin body are fastened together by bolts.

[0022] The placing plate and the pressure plate are both circumferentially provided with another screw hole for bolts to pass through. After the sample is placed on the placing plate and the pressure plate covers the sample, the placing plate and the pressure plate are fixed by bolts.

[0023] Optionally, the gas-water injection-production system includes:

[0024] An injection system, used for gas and liquid injection, wherein the outlet of the injection system is connected to the inlet of the reactor;

[0025] The output system is used for gas and liquid recovery, and the inlet end of the output system is connected with the outlet end of the reactor.

[0026] Optionally, the injection system comprises:

[0027] An injection hole is provided on the placement plate, the injection hole is connected to a gas-liquid injection part, and the injection hole is connected to the sample;

[0028] The gas-liquid injection part comprises an intermediate container and a gas booster pump, and the liquid outlet end of the intermediate container and the gas outlet end of the gas booster pump are simultaneously connected to the inlet end of the injection hole;

[0029] A piston is slidably arranged in the intermediate container, and the piston divides the intermediate container into a dyeing water tank containing dyed formation water and a squeezing water tank, the dyeing water tank is connected to the injection hole, and the squeezing water tank is connected to a horizontal flow pump, and the horizontal flow pump injects water into the squeezing water tank to push the piston to move the dyed formation water in the dyeing water tank toward the injection hole;

[0030] The air inlet end of the gas booster pump is connected with the air outlet end of the gas cylinder.

[0031] Optionally, the output system includes:

[0032] A back pressure valve, the inlet end of which is connected to an output hole, the output hole is arranged on the placement plate, and the output hole is connected to the sample;

[0033] The outlet end of the back-pressure valve is connected to a waste liquid collection bottle for recovering waste liquid and a back-pressure pump for maintaining stable air pressure in the reactor, and the inlet end of the back-pressure pump is connected to a pressure gauge for detecting air pressure.

[0034] Optionally, the temperature and pressure control system includes:

[0035] A heating device, coaxially arranged on the inner wall of the reactor, the heating device is electrically connected to a thermometer, and the thermometer is used to record the temperature in the reactor;

[0036] A constant speed and constant pressure pump is connected to the reaction kettle, and the constant speed and constant pressure pump is used to apply confining pressure to the sample.

[0037] Optionally, the external visualization device includes:

[0038] A device support, on which the intermediate cabin is rotatably arranged;

[0039] A video microscope is used to film the air-water flow behavior in the sample.

[0040] The two sides of the middle part of the intermediate cabin are respectively fixed with a cavity rotating shaft, and the cavity rotating shaft is rotatably connected with a fixing buckle, and the fixing buckle is fixed to the device bracket.

[0041] The video microscope is electrically connected to a computer via a data connection line, and the computer is electrically connected to the horizontal flow pump, the thermometer, the temperature increasing device, and the constant speed and constant pressure pump via another data connection line.

[0042] Optionally, the sample includes:

[0043] Columnar coal sample;

[0044] An epoxy resin shell is wrapped around the outside of the columnar coal sample, and the epoxy resin shell is open;

[0045] A PET film covering the open portion of the epoxy resin shell;

[0046] The placement plate is sealed at the open end of the epoxy resin shell, and the injection hole and the output hole are connected to the columnar coal sample through the PET film.

[0047] Optionally, sealing rings are sleeved on the outer sides of the injection hole and the output hole; another sealing ring is sleeved between the upper cover and the middle cabin body, and between the lower cover and the middle cabin body.

[0048] A method for using a visualization simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs, using the visualization simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs, comprising the following steps:

[0049] preparing the sample;

[0050] Installing the sample in the transparent high-temperature and high-pressure experimental chamber;

[0051] Starting the gas-water injection-output system, and injecting water and gas into the sample in sequence through the gas-water injection-output system;

[0052] Starting the temperature and pressure control system to make the transparent high-temperature and high-pressure experimental cavity reach a specified temperature and pressure;

[0053] The gas-water flow behaviors of gas and water in the sample under specified temperature and pressure conditions are photographed by external visualization equipment.

[0054] Compared with the prior art, the present invention has the following advantages and technical effects:

[0055] When in use, first prepare the sample; install the sample in a transparent high-temperature and high-pressure experimental cavity; start the gas-water injection-output system, and inject water and gas into the sample through the gas-water injection-output system; start the temperature and pressure control system to make the transparent high-temperature and high-pressure experimental cavity reach the specified temperature and pressure; use an external visualization device to shoot the gas-water flow behavior of gas and water in the sample under the specified temperature and pressure conditions. The present invention sets the test cavity as a transparent high-temperature and high-pressure experimental cavity, and by combining with an external visualization device, it can directly and clearly capture the gas-water flow behavior in the micro-cracks of deep coal reservoirs. This innovative method overcomes the defects of traditional coal pillar experiments that the real migration process of coalbed gas and water in micro-cracks cannot be observed and the scale of the cracks is large. It can truly restore the gas-water migration environment of deep coal seams under experimental conditions. Through the temperature and pressure control system, it can accurately control various influencing factors (such as pressure, temperature, gas flow, water flow rate, etc.) during the experiment, and monitor the gas-water flow process in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative labor:

[0057] Figure 1 This is a schematic diagram of a device for simulating gas-water flow behavior in micro-cracks of deep coal reservoirs according to the present invention;

[0058] Figure 2 It is a top view of the internal structure of the experimental cavity of the present invention;

[0059] Figure 3 It is a side view of the experimental cavity of the present invention;

[0060] Figure 4 The structure diagram of the experimental cavity rotating bracket of the present invention

[0061] Figure 5 Schematic diagram of the pressure plate of the present invention

[0062] Figure 6 This is a schematic diagram of crack distribution simulated by laser etching of the present invention;

[0063] Figure 7 A schematic diagram of making a sample for the present invention;

[0064] Among them, 1. horizontal flow pump; 2. intermediate container; 3. dyed formation water; 4. thermometer; 5. screw hole; 6. reactor; 7. injection hole; 8. high temperature and high pressure resistant transparent glass; 9. heating device; 10. output hole; 11. back pressure valve; 12. pressure gauge; 13. constant speed and constant pressure pump; 14. waste liquid collection bottle; 15. back pressure pump; 16. gas booster pump; 17. gas cylinder; 18. computer; 19. data connection line; 20. video microscope; 21. sealing ring; 22. placement plate; 23. pressure plate; 24. device bracket; 25. cavity rotating shaft; 26. fixing buckle; 27. PET film; 28. epoxy resin shell; 29. ​​columnar coal sample. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0067] Reference Figures 1 to 7 The present invention discloses a visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs, comprising:

[0068] Transparent high temperature and high pressure experimental chamber, used to place samples;

[0069] A gas-water injection-output system, wherein the outlet of the gas-water injection-output system is connected to the inlet of the transparent high-temperature and high-pressure experimental cavity, and the inlet of the gas-water injection-output system is connected to the outlet of the transparent high-temperature and high-pressure experimental cavity;

[0070] A temperature and pressure control system is arranged in the transparent high-temperature and high-pressure experimental cavity, and the temperature and pressure control system is used to control the temperature and pressure of the transparent high-temperature and high-pressure experimental cavity;

[0071] The external visualization device is located outside the transparent high-temperature and high-pressure experimental chamber. The external visualization device is set toward the sample and is used to observe and record the gas-water flow behavior in the sample.

[0072] When in use, first prepare the sample; install the sample in a transparent high-temperature and high-pressure experimental cavity; start the gas-water injection-output system, and inject water and gas into the sample through the gas-water injection-output system; start the temperature and pressure control system to make the transparent high-temperature and high-pressure experimental cavity reach the specified temperature and pressure; use an external visualization device to shoot the gas-water flow behavior of gas and water in the sample under the specified temperature and pressure conditions. The present invention sets the test cavity as a transparent high-temperature and high-pressure experimental cavity, and by combining with an external visualization device, it can directly and clearly capture the gas-water flow behavior in the micro-cracks of deep coal reservoirs. This innovative method overcomes the defects of traditional coal pillar experiments that the real migration process of coalbed gas and water in micro-cracks cannot be observed and the scale of the cracks is large. It can truly restore the gas-water migration environment of deep coal seams under experimental conditions. Through the temperature and pressure control system, it can accurately control various influencing factors (such as pressure, temperature, gas flow, water flow rate, etc.) during the experiment, and monitor the gas-water flow process in real time.

[0073] As an optional implementation, the transparent high temperature and high pressure experimental chamber includes:

[0074] An intermediate cabin, in which a placing plate 22 is coaxially fixedly connected, the placing plate 22 is used to place the sample, a pressure plate 23 is coaxially fixedly connected to the placing plate 22, and the sample is located between the placing plate 22 and the pressure plate 23;

[0075] The upper cover is coaxially fixed to the top of the middle cabin, and a high temperature and high pressure resistant transparent glass 8 is axially connected to the middle of the upper cover;

[0076] The lower cover is coaxially fixed to the bottom of the middle cabin, and another high temperature and high pressure resistant transparent glass 8 is axially connected to the middle of the lower cover;

[0077] The upper cover, the lower cover and the inner wall of the middle cabin together form a reaction kettle 6;

[0078] The sample is placed in the reaction vessel 6.

[0079] The upper cover, the lower cover and the middle cabin body are all circumferentially provided with screw holes 5 for the bolts to pass through, and the upper cover, the lower cover and the middle cabin body are fastened together by bolts.

[0080] The placing plate 22 and the pressure plate 23 are both circumferentially provided with another screw hole 5 for bolts to pass through. After the sample is placed on the placing plate 22 and the pressure plate 23 covers the top of the sample, the placing plate 22 and the pressure plate 23 are fixed by bolts.

[0081] As an optional embodiment, the gas-water injection-production system includes:

[0082] An injection system, used for gas and liquid injection, wherein the outlet of the injection system is connected to the inlet of the reaction kettle 6;

[0083] The output system is used for gas and liquid recovery, and the inlet end of the output system is connected to the outlet end of the reactor 6.

[0084] As an optional embodiment, the injection system includes:

[0085] The injection hole 7 is provided on the placement plate 22, the injection hole 7 is connected with the gas-liquid injection part, and the injection hole 7 is connected with the sample;

[0086] The gas-liquid injection part includes an intermediate container 2 and a gas booster pump 16, and the liquid outlet end of the intermediate container 2 and the gas outlet end of the gas booster pump 16 are simultaneously connected to the inlet end of the injection hole 7;

[0087] A piston is slidably arranged in the intermediate container 2, and the piston divides the intermediate container 2 into a dyeing water tank containing dyeing formation water 3 and a squeezing water tank. The dyeing water tank is connected to the injection hole 7, and the squeezing water tank is connected to the advection pump 1. The advection pump 1 injects water into the squeezing water tank to push the piston to move the dyeing formation water 3 in the dyeing water tank toward the injection hole 7.

[0088] The air inlet end of the gas booster pump 16 is connected to the air outlet end of the gas cylinder 17 .

[0089] As an optional implementation, the output system includes:

[0090] The inlet end of the back pressure valve 11 is connected with an output hole 10, and the output hole 10 is arranged on the placement plate 22, and the output hole 10 is connected with the sample;

[0091] The outlet of the back pressure valve 11 is connected to a waste liquid collection bottle 14 for recovering waste liquid and a back pressure pump 15 for maintaining the air pressure in the reactor 6. The inlet of the back pressure pump 15 is connected to a pressure gauge 12 for detecting the air pressure.

[0092] As an optional implementation, the temperature and pressure control system includes:

[0093] A heating device 9 is coaxially arranged on the inner wall of the reaction kettle 6. The heating device 9 is electrically connected to a thermometer 4, and the thermometer 4 is used to record the temperature in the reaction kettle 6;

[0094] The constant speed and constant pressure pump 13 is connected to the reaction kettle 6 and is used to apply a confining pressure to the sample.

[0095] As an optional implementation, the external visualization device includes:

[0096] A device support 24, on which the intermediate cabin is rotatably disposed;

[0097] The video microscope 20 is used to photograph the flow behavior of air and water in the sample.

[0098] The cavity rotating shaft 25 is fixedly connected to both sides of the middle part of the intermediate cabin respectively. The cavity rotating shaft 25 is rotatably connected to a fixing buckle 26 , and the fixing buckle 26 is fixedly connected to the device bracket 24 .

[0099] The video microscope 20 is electrically connected to the computer 18 via a data connection line 19 , and the computer 18 is electrically connected to the horizontal flow pump 1 , the thermometer 4 , the temperature increasing device 9 , and the constant speed and pressure pump 13 via another data connection line 19 .

[0100] As an optional embodiment, the sample includes:

[0101] Columnar coal sample 29;

[0102] An epoxy resin shell 28 is wrapped around the outer side of the columnar coal sample 29, and the epoxy resin shell 28 is open;

[0103] PET film 27, covering the open part of epoxy resin shell 28;

[0104] The placement plate 22 is sealed and arranged at the open end of the epoxy resin shell 28 , and the injection hole 7 and the output hole 10 are connected with the columnar coal sample 29 through the PET film 27 .

[0105] As an optional embodiment, a sealing ring 21 is sleeved on the outside of the injection hole 7 and the output hole 10; another sealing ring 21 is sleeved between the upper cover and the middle cabin body, and between the lower cover and the middle cabin body.

[0106] The device includes a transparent high-temperature and high-pressure experimental chamber, a gas-water injection-output system, a temperature and pressure control system and external visualization equipment.

[0107] The transparent high-temperature and high-pressure experimental chamber includes an upper and lower sealing layer and an intermediate cabin. A high-temperature and high-pressure transparent glass 8 is arranged in the middle of the upper and lower sealing layers for subsequent observation of the gas-water flow behavior. Six screw holes 5 are arranged in the upper and lower sealing layers for connecting the intermediate cabin. The upper and lower sealing layers seal the intermediate cabin through a sealing ring 21 to form a reactor 6. A sample placement tray 22 is placed inside the reactor for later coal sample experiments.

[0108] The gas-water injection-output system includes an injection system, an output system and experimental coal samples. The injection system mainly includes an injection hole 7, an intermediate container 2, a horizontal flow pump 1, a gas cylinder 17 and a gas booster pump 16, and the output system includes a back pressure valve 11, a pressure gauge 12, a waste liquid collection bottle 14 and a back pressure pump 15. The injection hole 7 and the output hole 10 are located on the sample placement plate 22, and the corresponding holes of the prepared samples are turned upside down on the placement plate 22, and the samples are fixed with a pressure plate 23; another sealing ring 21 is arranged above the injection hole 7 and the output hole 10 in the sample placement plate to prevent the water in the reactor 6 from flowing into the micro-cracks of the coal sample; the injection hole 7 is connected to the upper end of the intermediate container 2 through a pipeline, and there is a piston in the intermediate container 2, and the lower end of the intermediate container 2 is connected to the horizontal flow pump 1; the horizontal flow pump 1 drives the piston to pump dyed formation water 3 into the injection hole 7 by injecting pure water under pressure; A dye is added to the dyed formation water 3 to facilitate real-time observation of the flow behavior of the formation water; on the other hand, the injection hole 7 is connected to the gas cylinder 17 through a pipeline, and the pipeline is pressurized and injected by a gas booster pump 16 to control the gas flow injection; the output hole 10 in the reactor 6 is connected to the outer waste liquid collection bottle 14 through a part of the back pressure valve 11, which is used to collect the output water during the experiment; the back pressure valve 11 is connected to the pressure gauge 12 and the back pressure pump 15 to control the outlet pressure to prevent pressure relief during the experiment and maintain pressure stability.

[0109] The preparation method of the experimental sample includes using a wire cutting instrument to make a columnar coal sample 29 with a diameter of 25 mm and a height of 10 mm, using a cylindrical mold to cast a 5 mm thick epoxy resin shell 28 around and on the bottom, using sandpaper of different meshes and polishing liquid to make the wall relatively smooth, using CT to scan the sample, extracting one of the fracture development profiles, using CAD software instructions to depict the fracture development pattern and the positions of the injection hole 7 and the output hole 10, using laser etching technology to depict the microcrack development characteristics on the coal sample, treating the generated coal powder with alcohol, and then using 5 layers of 0.1 mm PET film 27 to bond with the coal rock to make the required experimental sample.

[0110] The temperature and pressure control system mainly includes a heating device 9, a thermometer 4, and a constant speed and pressure pump 13. The wall of the reactor 6 is provided with a heating device 9, and the temperature change inside the cabin can be displayed and recorded with the help of the thermometer 4; a pressurizing hole is provided in the experimental cabin, and a constant speed and pressure pump 13 is used to set the flow rate, flow pressure, water injection and pressure control;

[0111] The external visualization equipment includes a video microscope 20, a device bracket 24, a cavity rotating shaft 25, a fixing buckle 26, and a computer 18. The video microscope 20 is placed directly above the experimental cabin to visualize the flow behavior of air and water; the intermediate container 2 is connected to the outer device bracket 24 through the cavity rotating shaft 25, which is used to flip the experimental cavity and observe the flow behavior of air and water in the experimental sample; the cavity rotating shaft 25 is connected to the outer device bracket 24 through the fixing buckle 26; the temperature and pressure control system, video microscope 20, and advection pump 1 of this equipment are all connected to the computer 18 through the data connection line 19 for subsequent data processing.

[0112] A method for using a visualization simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs, using the visualization simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs, comprising the following steps:

[0113] Prepare the test specimen;

[0114] The sample is installed in a transparent high temperature and high pressure test chamber;

[0115] Start the gas-water injection-output system, and inject water and gas into the sample in sequence through the gas-water injection-output system;

[0116] Start the temperature and pressure control system to make the transparent high temperature and high pressure experimental chamber reach the specified temperature and pressure;

[0117] The gas-water flow behavior of gas and water in the sample under specified temperature and pressure conditions is captured by external visualization equipment.

[0118] The above method specifically comprises the following steps:

[0119] Step 1: Select a coal sample with a complete coal structure and no obvious defects, and use a wire cutting instrument to prepare a columnar coal sample 29 with a diameter of 25 mm and a height of 10 mm. Use a cylindrical mold to cast a 5 mm thick epoxy resin shell 28 around the coal sample and on the bottom to ensure that the coal sample is fixed and increase the stability of the sample. Use sandpaper and polishing liquid of different mesh sizes to grind and polish the coal surface on the top of the sample and the epoxy resin shell 28 to ensure that the surface is relatively smooth and suitable for subsequent experiments;

[0120] Step 2: Use CT scanning to reconstruct the coal sample, extract the fracture development profile, and use CAD software to draw the fracture development pattern and the positions of the injection hole 7 and the output hole 10, and use laser etching technology to depict the micro-crack development characteristics on the surface of the coal sample. Use alcohol to wipe and treat the coal powder on the surface of the coal sample, and then use 5 layers of 0.1mm thick PET film 27 to bond with the coal rock surface to obtain the experimental sample;

[0121] Step 3: Place the prepared sample upside down on the placement plate 22, press the back of the sample tightly with the pressing plate 23, and fix the sample with screws to ensure that the sample is stable and does not move;

[0122] Step 4: Tighten the upper and lower sealing layers to ensure that the seal is intact, rotate the cabin of the simulation device so that the lower sealing layer faces upward, and align the fracture surface with the video microscope 20. Debug the video microscope 20 to ensure that the fracture surface is clearly displayed to facilitate subsequent observation of the gas-water flow behavior in the microcracks;

[0123] Step 5: Inject dyed formation water 3 into the upper part of the intermediate container, start the horizontal flow pump 1, inject dyed formation water 3 into the micro-cracks in the coal sample, and after confirming that the water flow is completely injected through the video microscope 20, close the valve;

[0124] Step 6: Start the constant speed and constant pressure pump 13, and maintain constant pressure by injecting pure water into the reactor 6 to simulate the in-situ stress conditions of the deep coal seam. When the pressure of the constant speed and constant pressure pump 13 reaches the set value, close the valve and stop the constant speed and constant pressure pump 13.

[0125] Step 7: Check the air tightness of the system to ensure there is no leakage. If the air tightness of the system is good, you can proceed to the next step;

[0126] Step 8: Adjust the back pressure pump 15 and the back pressure valve 11, set the back pressure to the pressure of the backflow formation water of the coalbed methane reservoir, and ensure that the back pressure system can accurately control the pressure change during the experiment;

[0127] Step nine: Start the video microscope 20 and the gas cylinder 17, and pressurize the gas through the gas booster pump 16, inject the gas into the injection hole 7, displace the formation water, and record the gas-water flow behavior during the gas displacement process in real time through the video microscope 20, especially the gas-water displacement in the microcracks and the movement trajectory under different microcrack modes;

[0128] Step 10: After the entire displacement process is completed, turn off the gas booster pump 16 and the video microscope 20. According to the experimental design, observe and record the gas-water flow behavior and change characteristics under different microcrack combination modes under different pressure and temperature conditions in the deep.

[0129] Compared with the prior art, the present invention has the following advantages and technical effects:

[0130] ① Combination of transparent experimental chamber and video microscope: The present invention adopts transparent experimental chamber and video microscope observation technology, and the use of laser etching technology reduces the scale of the crack to the nanometer scale. This technological innovation can directly and clearly capture the gas and water flow behavior in the micro-cracks of deep coal reservoirs. This innovative method overcomes the defects of traditional coal pillar experiments that cannot observe the real migration process of coalbed gas and water in micro-cracks and the large scale of the cracks, which is a major breakthrough in existing technologies.

[0131] ② Simulate the real deep coal seam gas and water migration conditions: Compared with the existing technology, the present invention can truly restore the gas and water migration environment of deep coal seams under experimental conditions by combining high temperature and high pressure control system, actual coal rock samples, and considering the actual development morphology of coal rock components, coal body wettability and microcracks. This innovative design of simulated experimental conditions not only improves the reliability of experimental data, but also fills the gap of lack of experimental verification in existing numerical simulation research.

[0132] ③ Multi-factor control and precise monitoring: The present invention integrates a temperature and pressure control system, a gas-water injection-output system, a back pressure control system and a video microscope monitoring system, which can accurately control a variety of influencing factors (such as pressure, temperature, gas flow rate, water flow rate, etc.) during the experiment, and monitor the gas-water flow process in real time. This technical solution that combines high-precision experimental control with real-time data monitoring allows researchers to observe and record the flow behavior of coalbed methane and water under a variety of environmental conditions, thereby effectively improving the repeatability and scientificity of the experiment. At the same time, the experimental design is compact and highly integrated, which can simplify the operation process. Through simple operations, complex experimental processes can be completed, allowing researchers to more efficiently carry out research on the flow behavior of gas and water in deep coal reservoirs.

[0133] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0134] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs, characterized in that: include: Transparent high temperature and high pressure experimental chamber, used to place samples; A gas-water injection-output system, wherein the outlet of the gas-water injection-output system is connected to the inlet of the transparent high-temperature and high-pressure experimental cavity, and the inlet of the gas-water injection-output system is connected to the outlet of the transparent high-temperature and high-pressure experimental cavity; A temperature and pressure control system is arranged in the transparent high-temperature and high-pressure experimental cavity, and the temperature and pressure control system is used to control the temperature and pressure of the transparent high-temperature and high-pressure experimental cavity; The external visualization device is located outside the transparent high-temperature and high-pressure experimental cavity. The external visualization device is arranged toward the sample and is used to observe and record the flow behavior of air and water in the sample.

2. The visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs according to claim 1 is characterized in that: The transparent high temperature and high pressure experimental chamber comprises: An intermediate cabin, wherein a placement plate (22) is coaxially fixedly connected in the intermediate cabin, the placement plate (22) is used to place the sample, a pressure plate (23) is coaxially fixedly connected to the placement plate (22), and the sample is located between the placement plate (22) and the pressure plate (23); An upper cover is coaxially fixed to the top of the intermediate cabin, and a high temperature and high pressure resistant transparent glass (8) is axially connected to the middle of the upper cover; A lower cover is coaxially fixed to the bottom of the intermediate cabin, and another high temperature and high pressure resistant transparent glass (8) is axially connected to the middle of the lower cover; The upper cover, the lower cover and the inner wall of the intermediate cabin together form a reaction kettle (6); The sample is placed in the reaction vessel (6).

3. The visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs according to claim 2, characterized in that: The gas-water injection-output system comprises: An injection system, used for gas and liquid injection, wherein the outlet of the injection system is connected to the inlet of the reactor (6); An output system is used for recovering gas and liquid, and the inlet end of the output system is connected to the outlet end of the reactor (6).

4. The visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs according to claim 3 is characterized in that: The injection system comprises: An injection hole (7) is provided on the placement plate (22), the injection hole (7) is connected to a gas-liquid injection portion, and the injection hole (7) is connected to the sample; The gas-liquid injection part comprises an intermediate container (2) and a gas booster pump (16), and the liquid outlet end of the intermediate container (2) and the gas outlet end of the gas booster pump (16) are simultaneously connected to the inlet end of the injection hole (7); A piston is slidably arranged in the intermediate container (2), and the piston divides the intermediate container (2) into a dyeing water tank containing dyed formation water (3) and a squeezing water tank. The dyeing water tank is connected to the injection hole (7), and the squeezing water tank is connected to a horizontal flow pump (1). The horizontal flow pump (1) injects water into the squeezing water tank to push the piston to move the dyed formation water (3) in the dyeing water tank toward the injection hole (7). The gas inlet end of the gas booster pump (16) is connected to the gas outlet end of the gas cylinder (17).

5. The visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs according to claim 4, characterized in that: The output system includes: A back pressure valve (11), the inlet end of which is connected to an output hole (10), the output hole (10) is arranged on the placement plate (22), and the output hole (10) is connected to the sample; The outlet end of the back-pressure valve (11) is connected to a waste liquid collection bottle (14) for recovering waste liquid and a back-pressure pump (15) for maintaining the stable air pressure in the reactor (6), and the inlet end of the back-pressure pump (15) is connected to a pressure gauge (12) for detecting air pressure.

6. The visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs according to claim 2, characterized in that: The temperature and pressure control system comprises: A temperature increasing device (9) is coaxially arranged on the inner wall of the reaction kettle (6), the temperature increasing device (9) is electrically connected to a thermometer (4), and the thermometer (4) is used to record the temperature inside the reaction kettle (6); A constant speed and constant pressure pump (13) is connected to the reaction kettle (6), and the constant speed and constant pressure pump (13) is used to apply a confining pressure to the sample.

7. The visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs according to claim 2, characterized in that: The external visualization device comprises: A device support (24), wherein the intermediate cabin is rotatably arranged on the device support (24); A video microscope (20) is used to photograph the flow behavior of air and water in the sample.

8. The visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs according to claim 5, characterized in that: The sample includes: Columnar coal sample (29); An epoxy resin shell (28) is wrapped around the outer side of the columnar coal sample (29), and the epoxy resin shell (28) is open; A PET film (27) covering the open portion of the epoxy resin shell (28); The placement plate (22) is sealed and arranged at the open portion of the epoxy resin shell (28); the injection hole (7) and the output hole (10) are connected to the columnar coal sample (29) through the PET film (27).

9. The visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs according to claim 5, characterized in that: The injection hole (7) and the output hole (10) are both sleeved with sealing rings (21); another sealing ring (21) is sleeved between the upper cover and the middle cabin body, and between the lower cover and the middle cabin body.

10. A method for using a visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs, using the visual simulation device for gas-water flow behavior in micro-cracks of deep coal reservoirs as claimed in any one of claims 1 to 9, characterized in that: The steps include: preparing the sample; Installing the sample in the transparent high-temperature and high-pressure experimental chamber; Starting the gas-water injection-output system, and injecting water and gas into the sample in sequence through the gas-water injection-output system; Starting the temperature and pressure control system to make the transparent high-temperature and high-pressure experimental cavity reach a specified temperature and pressure; The gas-water flow behaviors of gas and water in the sample under specified temperature and pressure conditions are photographed by external visualization equipment.

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