A non-stop production, pressure-stabilizing pumping and washing system and method for coalbed methane wells

Abstract

The present invention relates to the field of coalbed methane development technology, and in particular to a non-stop production stabilizing pressure well washing system during the drainage and extraction process of coalbed methane wells. A non-stop production stabilizing pressure pumping and washing system for coalbed methane wells, comprising: a plunger pump, an oil pipe, and an extraction pump; the oil pipe and the extraction pump are lowered into the wellbore, and the oil pipe is connected to the oil casing annulus through the bottom suction port; the oil pipe is provided with a three-way structure at the part above the well; the pumping and washing fluid is pressurized by the plunger pump and injected into the oil casing annulus through the safety valve. Under a certain working system of the extraction pump, the pumping and washing fluid enters the oil pipe through the suction port, washes the coal powder and mud sand in the extraction pump and the oil pipe, and is discharged to the ground through the second interface of the three-way structure. The plunger pump has a pressurizing effect, and continuously injects the pumping and washing fluid on the ground into the oil casing annulus. By increasing the flow rate of the pumping and washing fluid and increasing the flow rate of the pumping and washing fluid, the purpose of flushing the solid phase in the extraction pump and the oil pipe and avoiding pump jamming is achieved. The present invention does not require special well column coordination, reducing safety risks.

Description

Technical Field

[0001] The present invention relates to the technical field of coalbed methane development, and in particular to a non-stop pressure-stabilizing pumping and washing system and method during the drainage and production of a coalbed methane well. Background Art

[0002] During the development of coalbed methane, a large amount of coal powder will be produced due to the grinding of drill tools, flushing of fracturing fluid and grinding of fracturing proppants. During the subsequent drainage, these coal powders will be carried into the wellbore along with the output of water and gas, and finally enter the pump barrel and oil pipe. When the coal powder reaches a certain amount, it will cause the pump to get stuck and production to stop.

[0003] ZL201210026646.8 discloses a method for continuously pumping and washing the drainage well during coalbed methane extraction. In this method, the well-washing pipe string is continuously pumped into the underground casing of the coalbed methane drainage well, and the drainage pipe string is lowered into the oil pipe. Well-washing water is pumped into the annular space between the casing and the oil pipe, and the well-washing water washes the adhered coal powder and continues to carry the coal powder upward to reach the ground drainage pipeline. The well-washing pipe string used in this scheme is relatively complex, and the complex structure of the well-washing pipe string is prone to frequent safety accidents underground, and the investment cost and maintenance cost are relatively high. In addition, if the coalbed methane well is stuck, the coalbed methane extraction equipment is already in a shutdown state. This method cannot solve the problem of pump sticking in the shutdown state. The conventional solution to the problem of pump sticking in coalbed methane wells is usually to pull up the pipe string to check the pump. It is necessary to mobilize a professional well repair team to perform on-site well repair operations. Before the operation, the coalbed methane well needs to be slowly depressurized for half a month or even longer. This will not only cause the cracks in the coalbed methane reservoir to close to varying degrees, thereby affecting the permeability of the coal reservoir and thus the production capacity of the coalbed methane well, but also the discontinuous drainage caused by depressurization will make it take a long time for the coalbed methane well production capacity to recover. Summary of the invention

[0004] The purpose of the present invention is to provide a non-stop pressure-stabilizing pumping and washing system and method for coal-bed methane wells with large amounts of coal dust, which can clean the coal dust in the tubular pump. At the same time, for coal-bed methane wells with stuck pumps, a pumping and washing method is provided to solve the problem of stuck pumps without requiring well repair work or lifting the drainage and production pipe string.

[0005] A technical solution of the present invention is: a non-stop production, pressure-stabilizing and pumping system for coalbed methane wells, which comprises: a plunger pump, an oil pipe and a pumping pump.

[0006] The oil pipe and the extraction pump are lowered into the wellbore, and an oil-casing annulus is formed between the oil pipe and the casing in the wellbore. The oil pipe is connected with the oil-casing annulus through the bottom suction port; a three-way structure is provided on the part of the oil pipe located above the well; the first interface of the three-way structure is connected to the oil pipe; the output end of the power device above the well is connected to the extraction pump in the oil pipe through the third interface of the three-way structure.

[0007] After being pressurized by the plunger pump, the pumping fluid is injected into the annulus of the oil casing through the safety valve. Under a certain working system of the pumping pump, the pumping fluid enters the oil pipe through the suction port, flushes the coal powder and mud in the pump and the oil pipe, and is discharged to the ground through the second interface of the three-way structure.

[0008] In the technology of the above scheme, further, the pumping and washing system also includes: a water reservoir for storing the pumping and washing liquid; the water reservoir is connected to the inlet of the plunger pump through a water inlet pipeline, and a filter is provided on the water inlet pipeline.

[0009] In the above technical solution, further, a first flow meter and a first pressure gauge are provided at the outlet of the plunger pump, and the outlet of the plunger pump is connected to the safety valve through the extraction and washing pipeline. The first flow meter and the first pressure gauge are used to display the pressure and flow of the extraction and washing liquid at the outlet of the plunger pump.

[0010] In the above technical solution, a throttling pipeline is further provided at the outlet of the plunger pump, one end of the throttling pipeline is connected to the pumping and washing pipeline through a water diverting valve, and the other end is connected to the water inlet pipeline between the plunger pump inlet and the filter. The water diverting valve is used to divert the pumping and washing liquid at the outlet of the plunger pump. When the flow rate of the pumping and washing liquid at the outlet of the plunger pump is greater than the actual flow rate required for well washing, a part of the pumping and washing liquid is diverted to the inlet of the plunger pump through the throttling pipeline again by adjusting the opening of the water diverting valve for recycling.

[0011] In the above technical solution, a second flow meter, a second pressure gauge and a check valve are further provided between the extraction and washing pipeline and the safety valve. The second flow meter and the second pressure gauge are used to display the flow rate and pressure of the extraction and washing liquid in the extraction and washing pipeline respectively, and the check valve is used to prevent the extraction and washing liquid from flowing back.

[0012] In the technology of the above scheme, further, a water level gauge is provided in the water reservoir. When the water level is displayed to be too low, the water reservoir should be supplemented with pumping liquid in time.

[0013] In the technical aspect of the above solution, further, the plunger pump is powered by electricity from a power distribution cabinet.

[0014] In the above technical solution, further, the frequency of the plunger pump motor can be adjusted. By adjusting the frequency of the plunger pump motor, the flow rate and flow rate of the washing liquid can be further regulated.

[0015] On the basis of the above scheme, further, in order to realize automatic control, the pumping and washing system also includes: a diagnostic monitoring device; the diagnostic monitoring device establishes a signal connection with the water level meter, the first flow meter, the first pressure gauge, the second flow meter, and the second pressure gauge, which are respectively used to collect the water level in the reservoir, the flow and pressure at the outlet of the plunger pump, and the pressure in the pumping and washing pipeline; the diagnostic monitoring device establishes a signal connection with the motor in the plunger pump and the water diversion valve, and makes a comprehensive judgment based on the above collected information, thereby adjusting the frequency of the plunger pump motor and the opening of the water diversion valve.

[0016] Furthermore, the pumping and washing system also includes: a remote client; the remote client establishes a signal connection with the diagnostic monitoring device, can synchronously view the collected information obtained by the diagnostic monitoring device, and the remote client can adjust the frequency of the plunger pump motor and the opening of the water diversion valve through the diagnostic monitoring device.

[0017] Another technical solution of the present invention is: a method for pumping and washing coalbed methane wells without stopping production and stabilizing pressure, which is based on the above-mentioned coalbed methane wells without stopping production and stabilizing pressure pumping and washing system, and includes the following steps:

[0018] A. Install the extraction and washing system;

[0019] B. Turn on the plunger pump. Under the action of the plunger pump, the washing liquid is injected into the annulus of the casing;

[0020] C. For a coalbed methane well that is operating normally, start the extraction pump and continue to inject the extraction fluid until the extraction fluid is discharged to the ground from the second interface of the three-way structure;

[0021] D. Adjust the flow rate and flow rate of the injected pumping and washing fluid to wash the inner wall of the pumping pump and the oil pipe. The washing time should be greater than 30 minutes;

[0022] E. Turn off the extraction pump and use the plunger pump to pressurize and wash the pump. The pumping pressure of the plunger pump should be 2-3MPa higher than the wellhead casing pressure, and the pump flushing time should be more than 30 minutes;

[0023] F. Repeat steps D and E until the washing liquid discharged from the ground is clear and free of impurities;

[0024] G. Shut down the extraction and cleaning system and dismantle it.

[0025] On the basis of the above scheme, for coalbed methane wells with stuck pumps, a pressurization and unblocking step is performed between steps B and C, namely: the injection pressure of the plunger pump is made 2-3MPa higher than the wellhead casing pressure, and if the pump cannot be unstuck after continuous pressurization for 5 minutes, continue to pressurize by 2MPa until the pump is unstuck; when the pumping fluid is discharged to the ground from the second interface of the three-way structure, reduce the pump pressure to 0MPa.

[0026] Beneficial effects: The present invention has a simple structure, and the plunger pump has a pressurizing effect. The ground pumping fluid is continuously injected into the annulus of the oil casing. By increasing the flow rate and flow velocity of the pumping fluid, the purpose of flushing the solid phase in the pumping pump and the oil pipe and avoiding pump jamming is achieved. During the entire pumping process, the pumping equipment does not need to be shut down. By controlling the flow rate of the injected pumping fluid, the flow pressure and liquid level can be basically controlled to be stable, which minimizes the excitement of the coal seam and reduces the damage to the coal seam. The present invention does not require special wellbore tubing, reduces safety risks, and saves costs.

[0027] The present invention is equipped with a diagnostic monitoring device which can monitor the working conditions of the pipelines in the pumping and washing system, and automatically control the flow rate and flow velocity of the pumping and washing liquid according to the working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 2 This is a block diagram of the structure of embodiment 2 of the present invention.

[0030] Figure 3 The present invention is a flowchart of the method.

[0031] In the figure: 1- plunger pump, 2- casing, 3- oil pipe, 4- extraction pump, 5- three-way structure, 6- safety valve, 7- reservoir, 8- filter, 9- first flow meter, 10- first pressure gauge, 11- water diversion valve, 12- second pressure gauge, 13- check valve, 14- water level gauge, 15- power distribution cabinet, 16- diagnostic monitoring device, 17- remote client, 18- second flow meter. DETAILED DESCRIPTION

[0032] Example 1, see attached Figure 1 A non-stop pressure stabilizing pumping and washing system for a coalbed methane well comprises: a plunger pump 1, an oil pipe 3, a pumping pump 4 and a water reservoir 7.

[0033] The oil pipe 3 and the extraction pump 4 are lowered into the wellbore, and an oil-casing annulus is formed between the oil pipe 3 and the casing 2 in the wellbore. The oil pipe 3 is connected to the oil-casing annulus through the bottom suction port; the oil pipe 3 is provided with a three-way structure 5 at the part located above the well; the first interface of the three-way structure 5 is connected to the oil pipe 3; the output end of the well power device is connected to the extraction pump 4 in the oil pipe 3 through the third interface of the three-way structure 5.

[0034] The water reservoir 7 is used to store the pumping and washing liquid. The water reservoir 7 is connected to the inlet of the plunger pump 1 through the water inlet pipeline, and a filter 8 is provided on the water inlet pipeline. A water level gauge 14 is provided in the water reservoir 7. When the water level is displayed to be too low, the water reservoir 7 should be replenished with the pumping and washing liquid in time.

[0035] A first flow meter 9 and a first pressure gauge 10 are provided at the outlet of the plunger pump 1. The outlet of the plunger pump 1 is connected to the safety valve 6 through a pumping and washing pipeline. A throttling pipeline is also provided at the outlet of the plunger pump 1, one end of which is connected to the pumping and washing pipeline through a water diverter valve 11, and the other end is connected to the water inlet pipeline between the inlet of the plunger pump 1 and the filter 8.

[0036] A second flow meter 18, a second pressure gauge 12 and a check valve 13 are provided between the extraction and washing pipeline and the safety valve 6. The second flow meter 18 and the second pressure gauge 12 are used to display the flow rate and pressure of the extraction and washing liquid in the extraction and washing pipeline, respectively, and the check valve 13 is used to prevent the extraction and washing liquid from flowing back.

[0037] The plunger pump 1 is powered by the power distribution cabinet 15, and the frequency of the motor of the plunger pump 1 can be adjusted. By adjusting the frequency of the motor of the plunger pump 1, the flow rate and flow rate of the washing liquid can be further regulated.

[0038] The working process of this system is:

[0039] The wash fluid in the water reservoir 7 is filtered by the filter 8 and then pressurized by the plunger pump 1. The first flow meter 9 and the first pressure gauge 10 display the pressure and flow of the wash fluid at the outlet of the plunger pump 1. The water diverter valve 11 is used to divert the wash fluid at the outlet of the plunger pump 1. When the flow of the wash fluid at the outlet of the plunger pump 1 is greater than the flow actually required for well washing, a part of the wash fluid is diverted to the inlet of the plunger pump 1 through the throttling pipeline by adjusting the opening of the water diverter valve 11 for recycling. After the pumping liquid is pressurized by the plunger pump 1, it is injected into the annulus of the oil casing through the safety valve 6. The second flow meter 18 and the second pressure gauge 12 are used to display the flow rate and pressure of the pumping liquid in the pumping pipeline respectively; under a certain working system of the pumping pump 4, the pumping liquid enters the oil pipe 3 through the suction port to flush the coal powder and mud sand in the pumping pump 4 and the oil pipe 3; by adjusting the frequency of the plunger pump 1 and the opening of the water diversion valve 11, the flow rate and flow rate of the pumping liquid are increased, so as to strengthen the flushing of the pumping pump 4 and the inner wall of the oil pipe 3 and avoid pump jam. Finally, the pumping liquid carrying coal powder and mud sand is discharged to the ground through the second interface of the three-way structure 5.

[0040] During the well washing process, if the pumping and washing pipeline leaks or the pipeline bursts due to pressure differential, the pumping and washing pipeline can be closed in time through the safety valve 6.

[0041] Example 2, see attached Figure 2On the basis of Example 1, in order to realize automatic control, the pumping and washing system also includes: a diagnostic monitoring device 16; the diagnostic monitoring device 16 establishes a signal connection with the water level meter 14, the first flow meter 9, the first pressure gauge 10, the second flow meter 18, and the second pressure gauge 12, and is respectively used to collect the water level in the reservoir 7, the flow rate and pressure at the outlet of the plunger pump 1, and the pressure in the pumping and washing pipeline; the diagnostic monitoring device 15 establishes a signal connection with the motor in the plunger pump 1 and the water diversion valve 11, and makes a comprehensive judgment based on the above-mentioned collected information, thereby adjusting the frequency of the motor of the plunger pump 1 and the opening of the water diversion valve 11.

[0042] Furthermore, the pumping and washing system also includes: a remote client 17; the remote client 17 establishes a signal connection with the diagnostic monitoring device 16, can synchronously view the collected information obtained by the diagnostic monitoring device 16, and the remote client 17 can adjust the frequency of the plunger pump 1 motor and the opening of the water diversion valve 11 through the diagnostic monitoring device 16.

[0043] Example 3, see attached Figure 3 A method for stabilizing pressure and pumping without stopping production of a coalbed methane well, based on the system for stabilizing pressure and pumping without stopping production of a coalbed methane well described in Example 1 or 2, comprises the following steps:

[0044] A. Install the extraction and washing system;

[0045] B. Start the plunger pump 1. Under the action of the plunger pump 1, the washing liquid in the water reservoir 7 is filtered and then injected into the annulus of the oil casing;

[0046] C. For a coalbed methane well that is operating normally, start the extraction pump 4 and continue to inject the extraction fluid until the extraction fluid is discharged to the ground from the second interface of the three-way structure 5;

[0047] D. By reading the first flow meter 9, the first pressure gauge 10, the second flow meter 18, and the second pressure gauge 12, the frequency of the plunger pump 1 and the opening of the water diversion valve 11 are adjusted, and then the flow rate and flow velocity of the injected pumping and washing liquid are adjusted to wash the inner wall of the pumping pump 4 and the oil pipe 3, and the washing time is greater than 30 minutes;

[0048] E. Turn off the extraction pump 4 and use the plunger pump 1 to pressurize and wash the pump. The pumping pressure of the plunger pump 1 should be 2-3MPa higher than the wellhead casing pressure, and the pump flushing time should be more than 30min;

[0049] F. Repeat steps D and E until the washing liquid discharged from the ground is clear and free of impurities;

[0050] G. Shut down the extraction and cleaning system and dismantle it.

[0051] For coalbed methane wells with stuck pumps, a pressurization and unblocking step is performed between steps B and C, namely: the pumping pressure of the plunger pump 1 is made 2-3 MPa higher than the wellhead casing pressure. If the pump cannot be unstuck after continuous pressurization for 5 minutes, continue to pressurize by 2 MPa until the pump is unstuck; when the pumping and washing fluid is discharged to the ground from the second interface of the three-way structure 5, the pump pressure is reduced to 0 MPa.

[0052] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for pumping and washing coalbed methane wells without stopping production and stabilizing pressure, based on a system for pumping and washing coalbed methane wells without stopping production and stabilizing pressure, the system comprising a plunger pump (1), an oil pipe (3) and a pumping pump (4); characterized in that: The oil pipe (3) and the extraction pump (4) are lowered into the wellbore, an oil-casing annulus is formed between the oil pipe (3) and the casing (2) in the wellbore, and the oil pipe (3) is connected to the oil-casing annulus through a bottom suction port; the oil pipe (3) is provided with a three-way structure (5) at the part located above the well; a first interface of the three-way structure (5) is connected to the oil pipe (3); and an output end of an above-the-well power device is connected to the extraction pump (4) in the oil pipe (3) through a third interface of the three-way structure (5); After the pumping fluid is pressurized by the plunger pump (1), it is injected into the annulus of the oil casing through the safety valve (6); under a certain working system of the pumping pump (4), the pumping fluid enters the oil pipe (3) through the suction port, washes the coal powder and mud sand in the pumping pump (4) and the oil pipe (3), and is discharged to the ground through the second interface of the three-way structure (5); The pumping and washing system further comprises: a water reservoir (7), wherein a water level gauge (14) is provided in the water reservoir (7); the water reservoir (7) is connected to the inlet of the plunger pump (1) via a water inlet pipeline, and a filter (8) is provided on the water inlet pipeline; Wherein, a first flow meter (9) and a first pressure gauge (10) are provided at the outlet of the plunger pump (1), and the outlet of the plunger pump (1) is connected to the safety valve (6) via a pumping and flushing pipeline; A throttling pipeline is also provided at the outlet of the plunger pump (1), one end of the throttling pipeline is connected to the extraction and washing pipeline via a water diverter valve (11), and the other end is connected to the water inlet pipeline between the inlet of the plunger pump (1) and the filter (8); Wherein, a second flow meter (18), a second pressure gauge (12) and a check valve (13) are provided between the extraction and flushing pipeline and the safety valve (6); The plunger pump (1) is powered by a power distribution cabinet (15), and the frequency of the motor of the plunger pump (1) is adjustable; The pumping and washing system further comprises: a diagnostic monitoring device (16); the diagnostic monitoring device (16) establishes signal connections with the water level meter (14), the first flow meter (9), the first pressure gauge (10), the second flow meter (18), and the second pressure gauge (12), and is used to collect information about the water level in the water reservoir (7), the flow rate and pressure at the outlet of the plunger pump (1), and the pressure in the pumping and washing pipeline; the diagnostic monitoring device (16) establishes signal connections with the motor in the plunger pump (1) and the water diversion valve (11), and the diagnostic monitoring device (16) makes a comprehensive judgment based on the collected information about the water level in the water reservoir (7), the flow rate and pressure at the outlet of the plunger pump (1), and the pressure in the pumping and washing pipeline, thereby adjusting the frequency of the motor of the plunger pump (1) and the opening of the water diversion valve (11); The pumping and washing system further comprises: a remote client (17); the remote client (17) establishes a signal connection with the diagnostic monitoring device (16) and is capable of synchronously viewing the collected information obtained by the diagnostic monitoring device (16); and the remote client (17) is capable of adjusting the frequency of the motor of the plunger pump (1) and the opening of the water diversion valve (11) through the diagnostic monitoring device (16); The method for stabilizing pressure and pumping without stopping production of coalbed methane wells comprises the following steps: A. Install the extraction and washing system; B. turning on the plunger pump (1), and under the action of the plunger pump (1), the pumping fluid is injected into the annulus of the casing; C. For a coalbed methane well that is operating normally, start the extraction pump (4) and continue to inject the extraction fluid until the extraction fluid is discharged from the second interface of the three-way structure (5) to the ground; D. adjusting the flow rate and flow rate of the injected pumping and washing fluid to wash the inner wall of the pumping pump (4) and the oil pipe (3), wherein the washing time is greater than 30 minutes; E. Turn off the extraction pump (4), and use the plunger pump (1) to perform pressure flushing. The pumping pressure of the plunger pump (1) should be 2-3 MPa higher than the wellhead casing pressure, and the flushing time should be greater than 30 minutes; F. Repeat steps D and E until the extraction liquid discharged from the ground is clear and free of impurities; G. Shut down the extraction and cleaning system and dismantle it.

2. A method for pumping and flushing a coalbed methane well without stopping production as claimed in claim 1, characterized in that: For a coalbed methane well with a stuck pump, a pressurization and unblocking step is performed between steps B and C, namely: the pumping pressure of the plunger pump (1) is set to be 2-3 MPa higher than the wellhead casing pressure, and if the pump cannot be unblocked after continuous pressurization for 5 minutes, the pressurization is continued by 2 MPa until the pump is unblocked; when the pumping and washing fluid is discharged from the second interface of the three-way structure (5) to the ground, the pump pressure is reduced to 0 MPa.

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