A multi-layered thin coal seam coalbed methane combined production experimental device and method

Abstract

The present invention relates to the technical field of coalbed methane development engineering, and discloses a coalbed methane combined production experimental device and method for multiple layers of stacked thin coal seams, comprising a pressure chamber, wherein a coal rock physical model is axially arranged in the pressure chamber, and adjacent coal rock physical models are connected; a fluid injection system, comprising a plurality of fluid injection parts, which are respectively connected to one end of the coal rock physical models and used to inject fluid into the coal rock physical models; a fluid metering system, comprising a plurality of metering parts, which are respectively connected to the other end of the coal rock physical models and are connected to each other; a processing system, comprising a control and data analysis system and a signal acquisition and processing device, wherein the coal rock physical model, the fluid injection part, the metering part and the control and data analysis system are respectively electrically connected to the signal acquisition and processing device. The present invention can realize the coalbed methane production characteristics of multiple layers of stacked thin coal seams, and quantitatively characterize the interlayer crossflow and the fluid and pressure distribution laws.

Description

Technical Field

[0001] The present invention relates to the technical field of coalbed methane development engineering, in particular to a coalbed methane combined production experimental device and method for multiple layers of stacked thin coal seams. Background Art

[0002] Coalbed methane (CBM) has garnered widespread attention and recognition as a clean and efficient energy source. Southern Sichuan, my country, boasts abundant CBM reserves and significant development potential, thanks to its multi-layered, overlapping coal seams. However, due to the relatively thin coal seams, traditional independent development of each seam often results in low CBM production from individual wells, resulting in unsatisfactory overall development results. Multi-layer commingled production technology can effectively improve the efficiency and effectiveness of CBM extraction in these thin, overlapping coal seams.

[0003] In southern Sichuan, the distance between coal seams is small, and some of them have a certain degree of connectivity and share the same pressure system. However, there are significant differences in key physical parameters such as permeability and gas content of each coal seam. This leads to the problem of interlayer interference being particularly prominent during the implementation of multi-layer combined mining. Especially during fracturing operations, cracks may communicate with adjacent coal seams, thereby causing interlayer crossflow, which not only increases the uncertainty of coalbed methane production, but also brings additional challenges to the design of multi-layer combined mining technology. In order to optimize the multi-layer combined mining technology, it is first necessary to conduct in-depth research and clarify the interlayer crossflow mechanism, the migration law of the fluid within the layer, and the production characteristics of coalbed methane in the combined mining process of multiple superimposed coal seams. Based on the in-depth analysis of these key factors, a scientific basis can be provided for process design, thereby effectively avoiding interlayer interference and optimizing the development strategy of coalbed methane.

[0004] However, there are few reports on quantitative research into the interlayer crossflow mechanism, intralayer fluid migration patterns, and coalbed methane production characteristics during multi-layer commingled mining of multiple thin coal seams. Existing physical simulation models for multi-layer commingled mining of coalbed methane mostly use coal rock placed in a holder, whose shape and size differ significantly from those of actual coal seams. Furthermore, existing multi-layer commingled mining physical models cannot simulate the characteristics of interlayer fluid crossflow in areas far from the wellbore and in the wellbore section. Furthermore, there is a lack of effective means to monitor the fluid migration and dynamic pressure distribution patterns within the coal seams during commingled mining. In short, there is currently a lack of equipment to simulate the coalbed methane process in multi-layer commingled mining of multiple thin coal seams, making it impossible to quantitatively study the interlayer crossflow mechanism, intralayer fluid migration patterns, and coalbed methane production characteristics.

[0005] Therefore, there is an urgent need for a multi-layer stacked thin coal seam coalbed methane combined production experimental device and method to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a multi-layer stacked thin coal seam coalbed methane combined production experimental device and method to solve the problems existing in the above-mentioned prior art.

[0007] To achieve the above-mentioned object, the present invention provides the following solution: The present invention provides a multi-layer stacked thin coal seam coalbed methane commingling experimental device, comprising:

[0008] A pressure chamber, wherein a plurality of support nets are fixedly connected in the axial direction of the pressure chamber through a support frame, and coal and rock physical models are arranged on the support nets, and adjacent two coal and rock physical models are connected;

[0009] a fluid injection system comprising a plurality of fluid injection members, each of which is connected to one end of each of the coal and rock physical models, and is used to inject fluid into the coal and rock physical models;

[0010] A fluid metering system includes a plurality of metering components, wherein the plurality of metering components are respectively connected to the other ends of the plurality of coal and rock physical models, and the plurality of metering components are connected to each other;

[0011] The processing system includes a control and data analysis system and a signal acquisition and processing device. The coal-rock physical model, the fluid injection, the metering element and the control and data analysis system are electrically connected to the signal acquisition and processing device respectively.

[0012] Preferably, the fluid injection component includes an intermediate container and an injection pump, and two cavities are provided in the intermediate container, and the two cavities are respectively filled with water and methane. One end of the two cavities is connected to the injection pump through a first metal pipe, and the other end of the two cavities is connected to the coal rock physical model through the first metal pipe.

[0013] Preferably, the metering component includes a back-pressure pump and a gas-liquid separator, the back-pressure pump is connected to the coal-rock physical model through a second metal pipe, a back-pressure valve is installed on the second metal pipe, the back-pressure valve is connected to the gas-liquid separator, a gas flow meter is provided on the gas-liquid separator, several of the gas flow meters are respectively connected to the signal acquisition and processing device through wires, and adjacent two second metal pipes are connected through a fourth metal pipe.

[0014] Preferably, the coal rock physical model includes a coal rock plate, which is wrapped with a resin layer, and an injection port and an output port are respectively provided at both ends of the coal rock plate, the injection port is connected to the first metal pipe, and the output port is connected to the second metal pipe, and a crossflow port is provided on one side of the bottom end of the coal rock plate, and the crossflow port is connected to the adjacent coal rock plate through a third metal pipe.

[0015] Preferably, a plurality of drill holes are opened on the coal rock slab, and the plurality of drill holes are distributed in an array.

[0016] Preferably, a plurality of resistance sensors are fixedly connected to the top of the resin layer along the axial direction, and a plurality of pressure sensors are fixedly connected to the bottom of the resin layer along the axial direction. The resistance sensors and the pressure sensors are respectively connected to the signal acquisition and processing device through wires.

[0017] Preferably, the third metal pipe and the fourth metal pipe are both installed with a pressure flow meter, and the pressure flow meter is connected to the signal acquisition and processing device through a wire.

[0018] Preferably, valves are installed on the first metal pipe, the second metal pipe, the third metal pipe and the fourth metal pipe.

[0019] Preferably, a pressurization / pressure relief port is provided at the bottom end of the pressure chamber, and a pump body is fixedly connected to the pressurization / pressure relief port.

[0020] An experimental method for coalbed methane commingling production in multiple stacked thin coal seams comprises the following steps:

[0021] injecting hydraulic oil into the pressure chamber to make the pressure in the pressure chamber reach the designed value;

[0022] injecting fluid into the coal-rock physical model through the fluid injection member, so that the coal seam fully absorbs the fluid;

[0023] Measuring and recording fluid output data by the measuring element;

[0024] After the test is completed, the hydraulic oil in the pressure chamber is drained.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] The present invention provides an experimental device and method for coalbed methane co-production in multi-layered thin coal seams. Several coal rock physical models are placed on several support nets respectively, and fluid is injected into the coal rock physical models through injection parts. The outflowing liquid and gas data are measured by a metering part, and the data is collected by a signal acquisition and processing device. The various components and data are controlled and analyzed by a control and data analysis system. Based on the coal seam pressure system and reservoir distribution characteristics, several connected coal rock physical models are set to simulate the coalbed methane co-production process in multi-layered coal seams. At the same time, it can also realize the simulation of interlayer fluid crossflow under the condition of multi-layer coal seam connectivity, and can also realize the simulation of interlayer fluid crossflow through the wellbore, and can realize the control and measurement of crossflow. The present invention can realize the coalbed methane production characteristics of multi-layered co-production in multi-layered thin coal seams, quantitatively characterize the interlayer crossflow and the fluid and pressure distribution laws, and provide a reliable means for the design of coalbed methane multi-layer co-production development schemes in multi-layered thin coal seams and the research on reducing interlayer interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work.

[0028] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of the coal rock physical model of the present invention;

[0030] Figure 3 This is a schematic diagram of the coal rock plate structure of the present invention;

[0031] Figure 4 Schematic diagram of the internal structure of the pressure chamber of the present invention;

[0032] Among them, 1. Pressure chamber; 2. Support frame; 3. Support net; 4. Coal rock physical model; 41. Coal rock plate; 42. Resin layer; 43. Injection port; 44. Output port; 45. Crossflow port; 46. Drilling hole; 5. Control and data analysis system; 6. Signal acquisition and processing device; 7. Intermediate container; 8. Injection pump; 9. Back pressure pump; 10. Gas-liquid separator; 11. Back pressure valve; 12. Gas flow meter; 13. Resistance sensor; 14. Pressure sensor; 15. Pressure flow meter; 16. Valve; 17. Pressurization / depressurization port; 18. Pump body. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0034] 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.

[0035] Reference Figures 1-4 The present invention provides a multi-layer stacked thin coal seam coalbed methane combined production experimental device, comprising:

[0036] A pressure chamber 1, wherein a plurality of support nets 3 are fixedly connected in the axial direction through a support frame 2, and coal and rock physical models 4 are arranged on the support nets 3, and adjacent coal and rock physical models 4 are connected;

[0037] A fluid injection system includes a plurality of fluid injection members, each of which is connected to one end of the plurality of coal and rock physical models 4 and is used to inject fluid into the coal and rock physical models 4;

[0038] The fluid metering system includes a plurality of metering components, each of which is connected to the other end of the plurality of coal and rock physical models 4, and the plurality of metering components are connected to each other;

[0039] The processing system includes a control and data analysis system 5 and a signal acquisition and processing device 6. The coal-rock physical model 4, the fluid injection, the metering element and the control and data analysis system 5 are electrically connected to the signal acquisition and processing device 6 respectively.

[0040] In one embodiment of the present invention, a pressure chamber 1 is used to house a coal and rock physics model 4 and to provide overburden pressure to the model by injecting hydraulic oil. The pressure chamber 1 primarily consists of a chamber body and a chamber cover, which are reinforced and sealed using screws and sealing strips. The chamber has internal dimensions of 40 x 40 x 40 cm, and a wall thickness of 3 cm.

[0041] The control and data analysis system 5, consisting of a signal transmission line, a computer and corresponding software, controls the operation of the pump, monitors resistance and pressure data, and records and analyzes fluid injection, interlayer crossflow and fluid output parameters.

[0042] To further optimize the solution, the fluid injection component includes an intermediate container 7 and an injection pump 8. Two cavities are provided in the intermediate container 7, and the two cavities are respectively filled with water and methane. One end of the two cavities is connected to the injection pump 8 through a first metal pipe, and the other end of the two cavities is connected to the coal-rock physical model 4 through the first metal pipe.

[0043] In one embodiment of the present invention, the intermediate container 7 is filled with fluids such as water and methane. The intermediate container 7 and the injection pump 8 constitute an injection system, which injects the experimental fluid into the coal and rock physical model 4 at a certain speed and pressure.

[0044] To further optimize the solution, the metering parts include a back-pressure pump 9 and a gas-liquid separator 10. The back-pressure pump 9 is connected to the coal-rock physical model 4 through a second metal pipe. A back-pressure valve 11 is installed on the second metal pipe. The back-pressure valve 11 is connected to the gas-liquid separator 10. A gas flow meter 12 is provided on the gas-liquid separator 10. Several gas flow meters 12 are respectively connected to the signal acquisition and processing device 6 through wires, and two adjacent second metal pipes are connected through a fourth metal pipe.

[0045] In one embodiment of the present invention, the metering element is used to collect liquid and gas from the output port 44 of each coal-rock physical model 4 , leaving liquid in the gas-liquid separator 10 , and monitoring the flow data of the output gas through the gas flow meter 12 .

[0046] Further optimization scheme, the coal rock physical model 4 includes a coal rock plate 41, the coal rock plate 41 is wrapped with a resin layer 42, and an injection port 43 and an output port 44 are respectively provided at both ends of the coal rock plate 41. The injection port 43 is connected to the first metal pipe, and the output port 44 is connected to the second metal pipe. A crossflow port 45 is provided on one side of the bottom end of the coal rock plate 41, and the crossflow port 45 is connected to the adjacent coal rock plate 41 through a third metal pipe.

[0047] According to a further optimization scheme, a plurality of drill holes 46 are opened on the coal rock plate 41, and the plurality of drill holes 46 are distributed in an array.

[0048] In one embodiment of the present invention, coal samples are selected from different coal seams and processed into coal rock plates 41 with a size of 20*20*5cm by wire cutting to simulate the morphology of thin coal seams. A hole with a depth of 3cm and a diameter of 0.5cm is drilled at the center position on the left and right sides of the coal rock plate 41, and the injection interface and the output interface are buried respectively, and resin is poured in to fix them. In the figure, a crossflow port 45 is drilled in the coal rock plate 41, and the crossflow interface is buried, and resin is poured in to fix it. Twenty holes 46 with a depth of 1cm and a diameter of 0.5cm are evenly drilled on the top of the coal rock plate 41, including 5 holes along the injection-output port direction. Resistance sensors 13 are buried in the holes and resin is poured in to fix them. Similarly, twenty holes 46 with a depth of 1cm and a diameter of 0.3cm are evenly drilled at the same position on the bottom of the coal rock plate. Pressure sensors 14 are buried in the holes and resin is poured in to fix them. After drying in a dry and ventilated place for 24 hours, they are placed in a customized mold and resin is poured on the entire coal rock plate 41. After being placed in a dry and ventilated place to dry for 48 hours, the outer resin shell of the coal rock was taken out and finely polished to make the thickness of the resin shell 1 cm, thereby preparing a resin-wrapped and sealed coal rock physical model 4.

[0049] According to a further optimization scheme, a plurality of resistance sensors 13 are fixedly connected to the top of the resin layer 42 along the axial direction, and a plurality of pressure sensors 14 are fixedly connected to the bottom of the resin layer 42 along the axial direction. The resistance sensors 13 and the pressure sensors 14 are respectively connected to the signal acquisition and processing device 6 through wires.

[0050] The resistance sensor 13 and the pressure sensor 14 can record the coal rock resistance and fluid pressure at different positions in the coal rock plate 41 in real time, thereby realizing quantitative monitoring of fluid migration and pressure distribution.

[0051] To further optimize the solution, a pressure flow meter 15 is installed on both the third metal pipe and the fourth metal pipe, and the pressure flow meter 15 is connected to the signal acquisition and processing device 6 through a wire.

[0052] According to a further optimized solution, valves 16 are installed on the first metal pipe, the second metal pipe, the third metal pipe and the fourth metal pipe.

[0053] According to a further optimized solution, a pressurization / pressure relief port 17 is provided at the bottom of the pressure chamber 1 , and a pump body 18 is fixedly connected to the pressurization / pressure relief port 17 .

[0054] Hydraulic oil is injected into the pressure chamber 1 through the pump body 18 to make the pressure in the chamber reach the design value. After the test is completed, the hydraulic oil in the pressure chamber 1 is discharged through the pump body 18.

[0055] An experimental method for coalbed methane commingling production in multiple stacked thin coal seams comprises the following steps:

[0056] Inject hydraulic oil into the pressure chamber 1 to make the pressure in the pressure chamber 1 reach the design value;

[0057] Nitrogen is introduced to check the overall air tightness of the device, the operating conditions of the sensor and signal transmission system are checked, and hydraulic oil is injected into the pressure chamber 1 through the pump body 18 to make the pressure in the chamber reach the design value.

[0058] Inject fluid into the coal-rock physical model 4 through the fluid injection member, so that the coal seam fully absorbs the fluid;

[0059] Several valves 16 at the injection and outlet ends of the coal rock model were opened respectively, the back pressure at the outlet end was adjusted to atmospheric pressure, and two PV (pore volumes) of brine were injected into the coal rock through the injection pump 8. Then, CH4 was injected to displace the brine. After that, the back pressure valve was adjusted to the reservoir pressure, and CH4 was continuously injected for 72 hours to allow the coal seam to fully absorb CH4.

[0060] Measure and record fluid output data through measuring components;

[0061] Close several valves 16 at the injection ports 43 of the coal-rock physical model 4, open the valves 16 connecting the interlayer pipelines at the injection and outlet ends, open the outlet valve 16, adjust the back pressure to the design value, and begin a multi-layer combined production simulation experiment until the outlet no longer produces gas. Record the resistance, pressure, and interlayer crossflow flow at each location in the coal-rock physical model 4 throughout the process, measure the fluid production data, and use software to draw real-time dynamic diagrams of the resistance and pressure distribution, as well as a gas-liquid production curve.

[0062] After the test is completed, the hydraulic oil in the pressure chamber 1 is drained.

[0063] After the experiment is finished, all passage valves 16 are closed, the pressure increase / pressure relief port 17 is opened, the hydraulic oil is discharged, and the pressure in the pressure chamber 1 is relieved.

[0064] In the description of the present invention, it should be understood that the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0065] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A multi-layer thin coal seam coalbed methane combined production experimental device, characterized in that: include: A pressure chamber (1), wherein a plurality of support nets (3) are fixedly connected in the axial direction through a support frame (2) in the pressure chamber (1), coal and rock physical models (4) are arranged on the support nets (3), and adjacent coal and rock physical models (4) are connected; A fluid injection system comprises a plurality of fluid injection members, wherein the plurality of fluid injection members are respectively connected to one end of the plurality of coal and rock physical models (4) and are used for injecting fluid into the coal and rock physical models (4); A fluid metering system includes a plurality of metering components, wherein the plurality of metering components are respectively connected to the other end of the plurality of coal and rock physical models (4), and the plurality of metering components are connected to each other; The processing system includes a control and data analysis system (5) and a signal acquisition and processing device (6), wherein the coal-rock physical model (4), the fluid injection component, the metering component, and the control and data analysis system (5) are electrically connected to the signal acquisition and processing device (6); The coal rock physical model (4) includes a coal rock plate (41), the coal rock plate (41) is wrapped with a resin layer (42), an injection port (43) and an output port (44) are respectively provided at both ends of the coal rock plate (41), the injection port (43) is connected to a first metal pipe, the output port (44) is connected to a second metal pipe, and a crossflow port (45) is provided on one side of the bottom end of the coal rock plate (41), and the crossflow port (45) is connected to the adjacent coal rock plate (41) through a third metal pipe; A plurality of drill holes (46) are formed on the coal rock plate (41), the drill holes (46) are distributed in an array, and a resistance sensor (13) and a pressure sensor (14) are embedded in the drill holes (46); The top end of the resin layer (42) is fixedly connected to a plurality of resistance sensors (13) along the axial direction, and the bottom end of the resin layer (42) is fixedly connected to a plurality of pressure sensors (14) along the axial direction. The resistance sensors (13) and the pressure sensors (14) are respectively connected to the signal acquisition and processing device (6) through wires.

2. The multi-layer thin coal seam coalbed methane commingling experimental device according to claim 1 is characterized by: The fluid injection component includes an intermediate container (7) and an injection pump (8). Two cavities are provided in the intermediate container (7). Water and methane are respectively contained in the two cavities. One end of the two cavities is connected to the injection pump (8) through a first metal pipe, and the other end of the two cavities is connected to the coal-rock physical model (4) through the first metal pipe.

3. The multi-layered thin coal seam coalbed methane commingling experimental device according to claim 2 is characterized by: The metering component includes a back-pressure pump (9) and a gas-liquid separator (10). The back-pressure pump (9) is connected to the coal-rock physical model (4) through a second metal pipe. A back-pressure valve (11) is installed on the second metal pipe. The back-pressure valve (11) is connected to the gas-liquid separator (10). A gas flow meter (12) is provided on the gas-liquid separator (10). Several gas flow meters (12) are respectively connected to the signal acquisition and processing device (6) through wires. Two adjacent second metal pipes are connected through a fourth metal pipe.

4. The multi-layered thin coal seam coalbed methane commingling experimental device according to claim 3 is characterized by: A pressure flow meter (15) is installed on both the third metal pipe and the fourth metal pipe, and the pressure flow meter (15) is connected to the signal acquisition and processing device (6) via a wire.

5. The multi-layered thin coal seam coalbed methane commingling experimental device according to claim 4 is characterized by: Valves (16) are installed on the first metal pipe, the second metal pipe, the third metal pipe and the fourth metal pipe.

6. The multi-layer thin coal seam coalbed methane commingling experimental device according to claim 1 is characterized by: A pressure-increasing / pressure-releasing port (17) is provided at the bottom end of the pressure chamber (1), and a pump body (18) is fixedly connected to the pressure-increasing / pressure-releasing port (17).

7. A method for coalbed methane commingling production experiment in multiple layers of thin coal seams, applicable to the coalbed methane commingling production experiment device in multiple layers of thin coal seams as claimed in claim 1, characterized in that: The following steps are involved: Injecting hydraulic oil into the pressure chamber (1) so that the pressure in the pressure chamber (1) reaches a designed value; injecting fluid into the coal-rock physical model (4) through the fluid injection member, so that the coal seam fully absorbs the fluid; Measuring and recording fluid output data by the measuring element; After the test is completed, the hydraulic oil in the pressure chamber (1) is drained.

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