Multi-layer stacked thin coal seam coalbed methane commingling production experimental device and method

Abstract

The invention relates to the technical field of coalbed methane development engineering, and discloses a multi-layer stacked thin coal seam coalbed methane commingling production experimental device and method.The multi-layer stacked thin coal seam coalbed methane commingling production experimental device comprises a pressure cavity, coal rock physical models are arranged in the pressure cavity in the axial direction, and every two adjacent coal rock physical models are communicated; the fluid injection system comprises a plurality of fluid injection pieces, and the plurality of fluid injection pieces are respectively communicated with one ends of the plurality of coal rock physical models and are used for injecting fluid into the coal rock physical models; the fluid metering system comprises a plurality of metering pieces, the plurality of metering pieces are respectively communicated with the other ends of the plurality of coal rock physical models, and the plurality of metering pieces are communicated with one another; the processing system comprises a control and data analysis system and a signal acquisition and processing device, and the coal rock physical model, the fluid injection part, the metering part and the control and data analysis system are electrically connected with the signal acquisition and processing device. According to the method, the output characteristics of the multi-layer commingled production coal bed gas of the multi-layer stacked thin coal seam can be realized, and interlayer fluid channeling and fluid and pressure distribution rules can be quantitatively represented.

Description

Technical Field

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

[0002] As a clean and efficient energy source, coalbed methane has received widespread attention and attention. In southern Sichuan, my country, there are multiple layers of superimposed coal seams, among which coalbed methane reserves are rich and have great development potential. However, due to the relatively thin coal seams, the traditional single coal seam independent development method often leads to low production of coalbed methane wells, and the overall development effect is not ideal. Multi-layer combined mining technology can effectively improve the mining efficiency and development effect of coalbed methane in multiple layers of superimposed thin 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 commingled 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 commingled mining technology. In order to optimize the multi-layer commingled mining process, it is first necessary to conduct in-depth research and clarify the interlayer crossflow mechanism, the migration law of fluids within the layers, and the production characteristics of coalbed methane in the commingled 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 on the interlayer crossflow mechanism, the migration law of intralayer fluids, and the production characteristics of coalbed methane in the process of multi-layer combined mining of coalbed methane in multiple layers of superimposed thin coal seams. The existing physical simulation models of coalbed methane in multi-coal seams are mostly coal rocks placed in a clamp, and their shape and size are quite different from those of real coal seams; in addition, the existing physical models of multi-layer combined mining cannot simulate the characteristics of interlayer fluid crossflow in the far well area and the wellbore section; there is a lack of effective means to detect the migration of fluids in the coal seams and the dynamic distribution of pressure during combined mining. In short, there is currently a lack of equipment for simulating the process of coalbed methane in multi-layer combined mining of multiple layers of superimposed thin coal seams, and it is impossible to quantitatively study the interlayer crossflow mechanism, the migration law of intralayer fluids, and the production characteristics of coalbed methane.

[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 object, the present invention provides the following solution: The present invention provides a multi-layer stacked thin coal seam coalbed methane combined production experimental device, comprising:

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

[0009] A fluid injection system, comprising a plurality of fluid injection members, wherein the plurality of fluid injection members are respectively connected to one end of the plurality of coal-rock physical models, and are used to inject fluid into the coal-rock physical models;

[0010] A fluid metering system, comprising a plurality of metering components, wherein the plurality of metering components are respectively connected to the other ends of the plurality of coal-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 device 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 two adjacent 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 with the first metal pipe, the output port is connected with 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 with 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 end of the resin layer along the axial direction, and a plurality of pressure sensors are fixedly connected to the bottom end 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, pressure flow meters are installed on the third metal pipe and the fourth metal pipe, and the pressure flow meters are connected to the signal acquisition and processing device through wires.

[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] A coal-bed methane commingling experimental method for multi-layered thin coal seams comprises the following steps:

[0021] Injecting hydraulic oil into the pressure chamber so that the pressure in the pressure chamber reaches a 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 the fluid output data by the measuring element;

[0024] After the test is finished, 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 a coalbed methane co-production experimental device and method for 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 the metering parts, and the data are collected by the signal acquisition and processing device. The various components and data are controlled and analyzed by the 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 of multiple coal seams. At the same time, the simulation of interlayer fluid crossflow under the condition of multi-layer coal seam connection can be realized, and the simulation of interlayer fluid crossflow through the wellbore can be realized, and the control and measurement of crossflow can be realized. The present invention can realize the coalbed methane production characteristics of 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 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:

[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 structure of the coal rock plate of the present invention;

[0031] Figure 4 It is a 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 / pressure relief port; 18. pump body. DETAILED DESCRIPTION

[0033] 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.

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

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

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

[0038] A fluid metering system, comprising a plurality of metering components, wherein the plurality of metering components are respectively connected to the other ends of the plurality of coal-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, the pressure cavity 1 is used to place the coal-rock physical model 4, and to provide overburden pressure for the coal-rock physical model 4 by injecting hydraulic oil. The pressure cavity 1 is mainly composed of a cavity and a cavity cover, and the cavity is reinforced and sealed by reinforcing screws and sealing strips. The internal dimensions of the cavity are 40*40*40cm, and the cavity wall thickness is 3cm.

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

[0042] According to a further optimized solution, the fluid injection component includes an intermediate container 7 and an injection pump 8. Two cavities are arranged in the intermediate container 7. 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 to inject the experimental fluid into the coal-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 component is used to collect liquid and gas from the output port 44 on each coal-rock physical model 4, and the liquid is left in the gas-liquid separator 10, and the flow data of the output gas is monitored by the gas flow meter 12.

[0046] A further optimization scheme is provided, in which the coal-rock physical model 4 includes a coal-rock plate 41, which 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, the output port 44 is connected to the 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.

[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 of 20*20*5cm in size 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 of 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 a crossflow interface is buried, and resin is poured in to fix it. A total of twenty holes 46 of 4*5 are evenly drilled on the top of the coal rock plate 41, with a hole depth of 1cm and a diameter of 0.5cm, of which 5 holes are along the injection-output port direction, and a resistance sensor 13 is buried in the hole, and resin is poured in to fix it. Similarly, twenty holes 46 are evenly drilled at the same position below the coal rock plate, with a hole depth of 1cm and a diameter of 0.3cm. A pressure sensor 14 is buried in the hole, and resin is poured in to fix it. After drying in a dry and ventilated place for 24 hours, it is placed in a customized mold and resin is poured on the coal rock plate 41 as a whole. After being placed in a dry and ventilated place to dry for 48 hours, the outer resin shell of the coal rock is 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, and realize quantitative monitoring of fluid migration and pressure distribution.

[0051] To further optimize the solution, a pressure flow meter 15 is installed on 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 optimization scheme, 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 designed value. After the test is completed, the hydraulic oil in the pressure chamber 1 is discharged through the pump body 18.

[0055] A coal-bed methane commingling experimental method for multi-layered 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 designed 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 designed 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 are opened respectively, the back pressure at the outlet end is adjusted to atmospheric pressure, and two PV (pore volumes) of brine are injected into the coal-rock through the injection pump 8. Then, CH4 is injected to displace the brine. After that, the back pressure valve is adjusted to the reservoir pressure, and CH4 is continuously injected for 72 hours to allow the coal seam to fully absorb CH4.

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

[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 valve 16 at the outlet end, adjust the back pressure to the design value, and start the multi-layer combined production stage simulation experiment until the outlet no longer produces gas. Record the resistance, pressure value, and interlayer crossflow flow at each position in the coal-rock physical model 4 throughout the process, and measure the fluid output data. Use the software to draw real-time dynamic diagrams of resistance and pressure distribution, and draw gas-liquid production curves;

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

[0063] After the experiment is over, all passage valves 16 are closed, the pressurization / 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", "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.

[0065] 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 multi-layered 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), a coal-rock physical model (4) is arranged on the support net (3), and two adjacent coal-rock physical models (4) are connected; A fluid injection system, comprising a plurality of fluid injection components, wherein the plurality of fluid injection components are respectively connected to one end of the plurality of coal-rock physical models (4) and are used to inject fluid into the coal-rock physical models (4); A fluid metering system, comprising a plurality of metering components, wherein the plurality of metering components are respectively connected to the other ends of the plurality of coal-rock physical models (4), and the plurality of metering components are connected to each other; The processing system comprises 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, the metering element and the control and data analysis system (5) are respectively electrically connected to the signal acquisition and processing device (6).

2. The multi-layered thin coal seam coalbed methane combined production experimental device according to claim 1 is characterized by: The fluid injection component comprises an intermediate container (7) and an injection pump (8), wherein two cavities are arranged in the intermediate container (7), wherein the two cavities are respectively filled with water and methane, wherein one end of the two cavities is connected to the injection pump (8) via a first metal pipe, and the other end of the two cavities is connected to the coal-rock physical model (4) via the first metal pipe.

3. The multi-layered thin coal seam coalbed methane combined production experimental device according to claim 2 is characterized by: The metering component comprises 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) via 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); a plurality of the gas flow meters (12) are respectively connected to the signal acquisition and processing device (6) via wires; and two adjacent second metal pipes are connected via a fourth metal pipe.

4. The multi-layered thin coal seam coalbed methane commingling experimental device according to claim 3 is characterized by: The coal-rock physical model (4) comprises a coal-rock plate (41), the coal-rock plate (41) being wrapped with a resin layer (42), an injection port (43) and an output port (44) being respectively arranged at both ends of the coal-rock plate (41), the injection port (43) being connected to the first metal pipe, the output port (44) being connected to the second metal pipe, a crossflow port (45) being arranged on one side of the bottom end of the coal-rock plate (41), the crossflow port (45) being connected to the adjacent coal-rock plate (41) through a third metal pipe.

5. The multi-layered thin coal seam coalbed methane combined production experimental device according to claim 4 is characterized by: The coal rock plate (41) is provided with a plurality of drill holes (46), and the plurality of drill holes (46) are distributed in an array.

6. The multi-layered thin coal seam coalbed methane combined production experimental device according to claim 5 is characterized by: A plurality of resistance sensors (13) are fixedly connected along the axial direction at the top end of the resin layer (42), and a plurality of pressure sensors (14) are fixedly connected along the axial direction at the bottom end of the resin layer (42). The resistance sensors (13) and the pressure sensors (14) are respectively connected to the signal acquisition and processing device (6) via wires.

7. The multi-layered thin coal seam coalbed methane combined production experimental device according to claim 4 is characterized by: The third metal pipe and the fourth metal pipe are both installed with a pressure flow meter (15), and the pressure flow meter (15) is connected to the signal acquisition and processing device (6) through a wire.

8. The multi-layered thin coal seam coalbed methane combined production experimental device according to claim 7 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.

9. The multi-layered thin coal seam coalbed methane commingling experimental device according to claim 1 is characterized by: The bottom end of the pressure chamber (1) is provided with a pressurization / pressure relief port (17), and a pump body (18) is fixedly connected to the pressurization / pressure relief port (17).

10. A method for combined production of coalbed methane in multi-layered thin coal seams, applicable to the device for combined production of coalbed methane in multi-layered 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 the fluid output data by the measuring element; After the test is finished, the hydraulic oil in the pressure chamber (1) is drained.

Images