Interlayer anti-interference method for coal measure gas horizontal well combined layer development drainage and mining

Abstract

The invention discloses a coal measure gas horizontal well combined layer development drainage and mining interlayer anti-interference method. The method comprises the following steps that S1, whether interlayer interference occurs or not is judged; s2, in the normal mining process of the coal series gas, that is, when no interlayer interference exists in discharge and mining, the difference value between the P < upper > and the P < lower > is smaller than the pressure difference identification standard; s3, when the P descends too fast and the reservoir pressure of the upper coal reservoir and the reservoir pressure of the lower coal reservoir are not coordinated, a double-pipe reverse lifting drainage and mining mode is adopted for drainage and mining; and S4, when P descends too fast or the upper coal reservoir is to be exposed, the reservoir pressure of the upper coal reservoir and the reservoir pressure of the lower coal reservoir are not coordinated, and a double-pipe forward lifting drainage and mining mode is adopted for drainage and mining. The method is scientific in principle, easy to implement and convenient to operate, the reservoir pressure of a single reservoir in the commingled production process of the coal-series gas horizontal well can be independently regulated and controlled, and commingled production development and drainage are under the preponderant gas production pressure; the pressure difference between the upper coal reservoir and the lower coal reservoir is regulated and controlled in real time in the discharging and mining process, so that the interlayer interference influence is reduced or eliminated, and the discharging and mining efficiency and effect of the coal series gas are improved.

Description

Technical Field

[0001] This invention belongs to the field of coalbed methane development technology, specifically relating to a method for preventing interference between production layers in horizontal wells for coalbed methane production. Background Technology

[0002] Coal-series gas, as an unconventional natural gas, is an important component of my country's clean and emerging energy sources due to its high combustion efficiency and cleanliness. my country's multi-coal-seam areas are generally characterized by numerous vertical coal seams and thin thickness. Compared to shallow coal seams, deep coal reservoirs have more complete coal body structures, higher gas content and saturation, and a coexistence of adsorbed and free gas, with a higher proportion of free gas. Therefore, deep coal-series gas wells often have higher single-well gas production. However, due to the great burial depth and complex geological structure, the construction cost of single-well projects for deep coal-series gas is high, limiting the production capacity and economic efficiency of single-seam coal-series gas extraction. Horizontal well co-production of coal-series gas in deep multi-coal-seam areas is one of the important ways to efficiently and economically develop deep coal-series gas resources.

[0003] During the combined production of deep coal-bearing gas in horizontal wells, the reservoir is prone to inter-layer interference due to differences in reservoir pressure gradient, permeability, critical desorption pressure, gas saturation, spatial superposition relationship between the surrounding rock aquifer and the coal seam, and supply. This leads to a significant decrease in the production capacity of coal-bearing gas wells.

[0004] Currently, various techniques are commonly used for horizontal well combined drainage of coal-bearing gas wells, including layered pressure-controlled combined drainage, dual-pump three-channel dual-coal-seam layered pressure-controlled drainage, and dual-casing multi-coal-seam layered pressure-controlled drainage. Layered pressure-controlled combined drainage refers to the process of lowering a four-channel packer downhole, where its sealing element expands to seal the wellbore between two coal seams. The two coal seams are isolated in two independent pressure systems. The combined drainage pump works in conjunction with multi-channel tubing, allowing gas and water from different coal reservoirs to be transported and produced through their respective drainage channels, thus achieving the purpose of layered pressure-controlled drainage. However, layered pressure-controlled combined drainage is greatly affected by the differences in the physical properties of different reservoirs and the interlayer spacing. When the critical desorption pressure of a certain coal seam is relatively low, excessively large interlayer spacing will cause severe interlayer interference, which will seriously affect the overall drainage effect. Dual-pump, three-channel, dual-coal-seam stratified pressure-controlled drainage refers to dividing the production casing into a production fluid channel, a lower coal seam gas production channel, and a tool string crossing channel using packers. This also blocks the hydraulic connection between the upper and lower coal seams, creating two dynamic fluid levels. Drainage is then carried out by a combined extraction pump consisting of two pump chambers and two suction inlets. The goal is to extract water from each coal seam during drainage, placing each seam under pressure suitable for its specific reservoir characteristics. However, dual-pump, three-channel, dual-coal-seam stratified pressure-controlled drainage places extremely high demands on drilling and completion quality and operational accuracy. The stratified pressure control relies heavily on the reliable sealing and long-term stability of specialized packers and other supporting tools. High downhole pressure, corrosive media, and coal dust abrasion can easily cause critical tool failure, leading to stratified pressure-controlled drainage failure. Double-casing multi-coal-seam stratified pressure-controlled drainage involves installing an internal casing between the production casing and the tubing. A packer isolates the coal seams from the internal casing. Water outlets are installed on additional casings at a certain distance above each coal seam, ensuring drainage of each target coal seam within its suitable pore pressure range. However, similar to double-pump, three-channel, double-coal-seam stratified pressure-controlled drainage, it demands extremely high drilling and completion quality and operational precision. Maintenance work, such as pump inspection, coal dust handling, and casing repair, is highly complex, limiting the effective production time of the drainage well and resulting in poor combined drainage performance. Therefore, to improve the drainage effect of coal-bearing gas horizontal wells in combined development and reduce the impact of inter-layer interference, it is urgent to research a method for preventing inter-layer interference in coal-bearing gas horizontal well development and drainage. This method should enable real-time control of the pressure and pressure difference between the upper and lower reservoirs during drainage, reducing inter-layer interference and achieving efficient drainage. Summary of the Invention

[0005] This invention addresses the problem of difficulty in controlling the pressure and pressure difference between different coal-bearing reservoirs during the development and drainage of coal-bearing gas horizontal wells, resulting in poor drainage performance and easy inter-layer interference. By developing a method to prevent inter-layer interference during the development and drainage of coal-bearing gas horizontal wells, this invention enables real-time control of the pressure and pressure difference between the upper and lower reservoirs during the drainage process through "forward drainage" and "reverse drainage," reducing the impact of inter-layer interference and achieving efficient drainage.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preventing interference between layers in the development and drainage of coal-bearing gas horizontal wells, comprising the following steps: S1. During the extraction of coalbed methane from adjacent upper and lower coal seams, the reservoir pressure P of the upper coal seam is monitored in real time. 上 and the reservoir pressure P of the lower coal seam 下 The pressure signal is transmitted to the control system, which has a built-in criterion for detecting inter-layer interference, via P. 上 and P 下 The difference is compared with the pressure difference identification standard to determine whether inter-layer interference has occurred; S2. During normal coalbed methane extraction, i.e., when there is no inter-layer interference during drainage, P 上 and P 下 The difference is less than the pressure difference identification standard; S3, when P 下 If the pressure drops too quickly, the reservoir pressures of the upper and lower coal seams become uncoordinated, and a dual-pipe reverse lifting drainage mode is adopted for drainage. S4, when P 上 When the descent is too rapid or the upper coal reservoir is about to be exposed, the reservoir pressures of the upper and lower coal reservoirs are not coordinated, and a dual-pipe positive lifting drainage mode is adopted for drainage.

[0007] An upper horizontal well is drilled in the upper coal reservoir, and a lower horizontal well is drilled in the lower coal reservoir. One end of the upper horizontal well is connected to the lower end of the vertical shaft through an upper arc-shaped shaft passage, and one end of the lower horizontal well is connected to the lower end of the vertical shaft through a lower arc-shaped shaft passage. The vertical shaft is equipped with a cementing casing, an outer tube inside the cementing casing, a central tube inside the outer tube, and a sucker rod and a tubular pump inside the central tube. The lower end of the sucker rod is connected to the power input end of the tubular pump. An outer annular cavity is formed between the cementing casing and the outer tube, and an inner annular cavity is formed between the outer tube and the central tube. A first through hole is drilled on the outer tube wall near the tubular pump to connect the outer annular cavity and the inner annular cavity. A second through hole is drilled on the central tube wall near the tubular pump to connect the inner annular cavity and the inner cavity of the central tube. The lower end of the central tube is connected to the upper horizontal well through an upper arc-shaped pipe passing through the upper arc-shaped shaft passage, and the lower end of the outer tube is connected to the lower horizontal well through a lower arc-shaped pipe passing through the lower arc-shaped shaft passage.

[0008] The central tube contains a first-stage air lift valve, a second-stage air lift valve, and a third-stage air lift valve arranged sequentially from top to bottom above the tubular pump.

[0009] The lower horizontal well is equipped with a system for real-time monitoring of P. 下 The downpressure sensor is connected to the wellhead control system via a downpressure cable passing through the outer annular cavity; a device for real-time monitoring of P is installed in the upper horizontal well. 上 The upper pressure sensor is connected to the well control system via an upper pressure cable that passes through the outer annular cavity.

[0010] The specific criteria for identifying inter-layer interference in step S1 are as follows: In the formula: The reservoir pressure difference in the commingled reservoir is expressed in MPa. Surface tension, N / m; R is the contact angle, °; R is the diameter of the interlayer fluid transport channel, m; The interlayer spacing is in meters (m). Let be the fluid transport velocity, in m / s, where the minimum value is t is the sampling time, in seconds; is the reservoir pressure of the lower coal seam, in MPa; Re is the Reynolds number, dimensionless. For fluid density, kg / m³ 3 g is the acceleration due to gravity.

[0011] The specific process of the dual-tube reverse lift drainage in step S3 is as follows: Gas is injected downwards from the upper port of the inner annular cavity, causing the liquid level in the inner annular cavity to drop. Since the outer tube has a first through-hole connecting the outer and inner annular cavities, and the central tube has a second through-hole connecting the inner annular cavity and the central tube cavity, the liquid in the inner annular cavity enters the outer annular cavity through the first through-hole and simultaneously enters the central tube through the second through-hole. Driven by the sucker rod, the tubular pump inside the central tube pumps the liquid upwards through the central tube to the surface, causing the liquid level in the outer annular cavity to rise. Coal-based gas is discharged upwards through the outer annular cavity. Since the liquid inside the inner annular cavity mainly comes from the lower horizontal well of the lower coal reservoir, the high-pressure gas injected into the inner annular cavity from the wellhead increases or inhibits the decrease in reservoir pressure in the lower coal reservoir. The tubular pump mainly pumps out the liquid from the upper horizontal well in the upper coal reservoir, thereby accelerating the drainage and depressurization of the upper coal reservoir. When P is monitored... 上 and P 下 When the pressure is balanced, gas is no longer injected into the inner annular cavity, and the central pipe and outer pipe simultaneously discharge liquid upwards, thereby achieving balanced drainage of the upper and lower coal reservoirs.

[0012] The specific process of dual-pipe reverse lift drainage in step S4 is as follows: Gas is injected downwards from the upper end of the central pipe, causing the liquid level inside the central pipe to drop. Simultaneously, the gas pressure drives one, two, or three of the first-stage, second-stage, and third-stage gas lift valves to close, thereby preventing the central pipe from draining liquid upwards and inhibiting the rapid drainage of the upper horizontal well in the upper coal reservoir connected to the central pipe. Since the outer pipe has a first through-hole connecting the outer annular cavity and the inner annular cavity, and the central pipe has a second through-hole connecting the inner annular cavity and the inner cavity of the central pipe... Under the action of the tubular pump, the inner annular cavity becomes the only drainage channel. The lower end of the outer pipe is connected to the lower horizontal well of the lower coal reservoir. The liquid discharged upward from the inner annular cavity is mainly from the lower coal reservoir, while the coalbed methane is still discharged upward through the outer annular cavity. The liquid inside the central pipe mainly comes from the upper horizontal well of the upper coal reservoir. Therefore, the high-pressure gas injected into the central pipe from the wellhead increases or inhibits the decrease in reservoir pressure in the upper coal reservoir. The tubular pump mainly pumps out the liquid from the lower horizontal well in the lower coal reservoir, thereby accelerating the drainage and depressurization of the lower coal reservoir. When P is monitored... 上 and P 下 When the pressure is balanced, gas is no longer injected into the central pipe, and liquid is discharged upwards from both the central and outer pipes, thereby achieving balanced drainage of the upper and lower coal reservoirs.

[0013] The working principle of this invention, employing the above technical solution, is as follows: Deep coalbed methane exists primarily in coal-bearing reservoirs in two forms: adsorbed gas and free gas. As free gas is produced from the reservoir, deep coalbed methane drainage rapidly enters a gas-liquid two-phase flow stage. The discharge of this two-phase fluid triggers a comprehensive pressure reduction mode combining "drainage pressure reduction" and "venting pressure reduction." When the coal reservoir pressure reaches below the critical desorption pressure, the adsorbed coalbed methane first desorbs from the coal surface into free gas, then diffuses and migrates through the micropores of the coal to the fracture system, and finally flows into the wellbore and is extracted to the surface via seepage.

[0014] The "pressure-differential drainage" technology employs a drainage tool structure consisting of an outer pipe (drainage tubing) with a built-in central pipe (small-diameter tubing string) and multi-stage gas lift valves for combined layer drainage. During the drainage process, the drainage flow pressure of the upper and lower coal reservoirs is adjusted by regulating the drainage method of the central pipe. When the reservoir pressure gradient of the upper coal reservoir is low, the central pipe is adjusted to reduce the drainage pressure drop of the upper coal reservoir through forward gas injection (dual-pipe forward lifting drainage); conversely, the central pipe is adjusted to enhance the drainage pressure reduction of the upper coal reservoir through reverse fluid production (dual-pipe reverse lifting drainage). The key to implementing this technology is controlling the pressure difference between the upper and lower coal reservoirs during combined drainage, reducing the impact of inter-layer interference, and maintaining a reasonable pressure difference between the two reservoirs. The advantage of this technology is that it allows for real-time regulation of the pressure difference between the upper and lower coal reservoirs during the drainage process to reduce the impact of inter-layer interference.

[0015] The fundamental cause of inter-layer interference in horizontal coal-bearing gas wells is the pressure mismatch between adjacent coal seams. Therefore, the main driving force for fluid migration during inter-layer interference is the pressure difference between adjacent reservoirs. As drainage progresses, the reservoir pressures of the upper and lower reservoirs gradually decrease. The reservoir pressure P of the upper coal seam can be obtained using upper and lower pressure sensors. 上 and the reservoir pressure P of the lower coal seam 下 .

[0016] The present invention has the following beneficial effects: The principle of the present invention is scientific, easy to implement and convenient to operate. It can independently control the reservoir pressure of a single reservoir during the syngas production process of horizontal wells, so that the syngas development and drainage are at the dominant gas production pressure. By adjusting the pressure difference between the upper and lower coal reservoirs in real time during the drainage process, the influence of inter-layer interference is reduced or eliminated, thereby improving the efficiency and effect of coal gas drainage. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of a dual-tube reverse lifting extraction system; Figure 3 This is a schematic diagram of a dual-tube forward lifting extraction system. Detailed Implementation

[0018] like Figures 1-3 As shown, the present invention provides a method for preventing interference between layers during the development and drainage of coal-bearing gas horizontal wells, comprising the following steps: S1. During the coalbed methane extraction process of adjacent upper coalbed mound 1 and lower coalbed mound 2, the reservoir pressure P of upper coalbed mound 1 is monitored in real time. 上 The reservoir pressure P of the lower coal reservoir 2 下 The pressure signal is transmitted to the control system, which has a built-in criterion for detecting inter-layer interference, via P. 上 and P 下 The difference between the pressure difference and the identification standard P 标 In comparison, determine whether interlayer interference has occurred; S2. During normal coalbed methane extraction, i.e., when there is no inter-layer interference during drainage, P 上 and P 下 The difference is less than the pressure difference identification standard P 标 ; S3, when P 下 The pressure drop is too rapid, and the reservoir pressures of the upper coal seam 1 and the lower coal seam 2 are not coordinated, i.e., P 上 and P 下 The difference is greater than or equal to P 标 The extraction process is carried out using a dual-tube reverse extraction mode. S4, when P 上When the descent is too rapid or when the upper coal reservoir 1 is about to be exposed, i.e., P 上 and P 下 The difference is greater than or equal to P 标 The reservoir pressures of the upper coal reservoir 1 and the lower coal reservoir 2 are not coordinated, so a dual-pipe positive lifting drainage mode is adopted for drainage.

[0019] An upper horizontal well 3 is drilled in the upper coal reservoir 1, and a lower horizontal well 4 is drilled in the lower coal reservoir 2. One end of the upper horizontal well 3 is connected to the lower end of the vertical shaft 6 through an upper arc-shaped shaft 5, and one end of the lower horizontal well 4 is connected to the lower end of the vertical shaft 6 through a lower arc-shaped shaft 7. The vertical shaft 6 is equipped with a cementing casing 8, an outer tube 9 is installed inside the cementing casing 8, a central tube 10 is installed inside the outer tube 9, and a sucker rod 11 and a tubular pump 12 are installed inside the central tube 10. The lower end of the sucker rod 11 is connected to the power input end of the tubular pump 12. An outer annular cavity 13 is formed between the cementing casing 8 and the outer tube 9. An inner annular cavity 14 is formed between the outer tube 9 and the central tube 10. A first through hole 15 is provided on the wall of the outer tube 9 near the tubular pump 12 to connect the outer annular cavity 13 and the inner annular cavity 14. A second through hole 16 is provided on the wall of the central tube 10 near the tubular pump 12 to connect the inner annular cavity 14 and the inner cavity of the central tube 10. The lower end of the central tube 10 is connected to the upper horizontal well 3 through the upper arc-shaped tube 17 passing through the upper arc-shaped well passage 5. The lower end of the outer tube 9 is connected to the lower horizontal well 4 through the lower arc-shaped tube 18 passing through the lower arc-shaped well passage 7.

[0020] The central tube 10 is equipped with a first-stage air lift valve 19, a second-stage air lift valve 20, and a third-stage air lift valve 21, arranged sequentially from top to bottom above the tubular pump 12.

[0021] The lower horizontal well 4 is equipped with a system for real-time monitoring of P. 下 The downpressure sensor 25 is connected to the well control system via a downpressure cable 22 passing through the outer annular cavity 13; the upper horizontal well 3 is equipped with a device for real-time monitoring of P. 上 The upper pressure sensor 23 is connected to the well control system via an upper pressure cable 24 passing through the outer annular cavity 13.

[0022] The specific criteria for identifying inter-layer interference in step S1 are as follows: In the formula: The reservoir pressure difference in the commingled reservoir is expressed in MPa. Surface tension, N / m; R is the contact angle, °; R is the diameter of the interlayer fluid transport channel, m; The interlayer spacing is in meters (m). Let be the fluid transport velocity, in m / s, where the minimum value is t is the sampling time, in seconds; is the reservoir pressure of the lower coal seam, in MPa; Re is the Reynolds number, dimensionless. For fluid density, kg / m³ 3 g is the acceleration due to gravity.

[0023] The specific process of the dual-tube reverse lifting and extraction in step S3 is as follows: air is injected downwards from the upper port of the inner annular cavity 14, causing the liquid level in the inner annular cavity 14 to drop. Since the outer tube 9 has a first through hole 15 connecting the outer annular cavity 13 and the inner annular cavity 14, and the central tube 10 has a second through hole 16 connecting the inner annular cavity 14 and the inner cavity of the central tube 10, the liquid in the inner annular cavity 14 enters the outer annular cavity 13 through the first through hole 15 and simultaneously enters the interior of the central tube 10 through the second through hole 16. The interior of the central tube 10 is equipped with... Driven by the sucker rod 11, the tubular pump 12 pumps the liquid upwards to the surface through the central pipe 10. The liquid level in the outer annular cavity 13 rises, and the coalbed methane is discharged upwards through the outer annular cavity 13. Since the liquid inside the inner annular cavity 14 mainly comes from the lower horizontal well 4 of the lower coal reservoir 2, the high-pressure gas injected into the inner annular cavity 14 from the wellhead increases or inhibits the decrease in reservoir pressure of the lower coal reservoir 2. The tubular pump 12 mainly pumps and discharges the liquid from the upper horizontal well 3 in the upper coal reservoir 1, thereby accelerating the drainage and pressure reduction of the upper coal reservoir 1. When P is monitored... 上 and P 下 When the pressure is balanced, gas is no longer injected into the inner annular cavity 14, and the central pipe 10 and the outer pipe 9 simultaneously discharge liquid upwards, thereby achieving balanced drainage of the upper and lower coal reservoirs 2.

[0024] The specific process of the dual-pipe reverse lift drainage in step S4 is as follows: gas is injected downwards from the upper port of the central pipe 10, causing the liquid level inside the central pipe 10 to drop. At the same time, the gas pressure drives one, two, or three of the first-stage gas lift valve 19, the second-stage gas lift valve 20, and the third-stage gas lift valve 21 to close, thereby preventing the central pipe 10 from draining liquid upwards and thus inhibiting the rapid drainage of liquid from the upper horizontal well 3 of the upper coal reservoir 1 connected to the central pipe 10. Since the outer pipe 9 has a first through hole 15 connecting the outer annular cavity 13 and the inner annular cavity 14, and the central pipe 10 has a second through hole 15 connecting the inner annular cavity 14 and the inner cavity of the central pipe 10, the central pipe 10 has a second through hole 15 connecting the inner annular cavity 14 and the inner cavity of the central pipe 10. Through hole 16, under the action of tubular pump 12, the inner annular cavity 14 becomes the only drainage channel. The lower end of the outer pipe 9 is connected to the lower horizontal well 4 of the lower coal reservoir 2. The liquid discharged upward from the inner annular cavity 14 is mainly from the lower coal reservoir 2, while the coal gas is still discharged upward through the outer annular cavity 13. The liquid inside the central pipe 10 mainly comes from the upper horizontal well 3 of the upper coal reservoir 1. Therefore, the high-pressure gas injected into the central pipe 10 from the wellhead increases or inhibits the decrease in reservoir pressure of the upper coal reservoir 1. The tubular pump 12 mainly pumps out the liquid in the lower horizontal well 4 of the lower coal reservoir 2, thereby accelerating the drainage and pressure reduction of the lower coal reservoir 2. When P is monitored... 上 and P 下When the pressure is balanced, gas is no longer injected into the central pipe 10, and the central pipe 10 and the outer pipe 9 simultaneously discharge liquid upwards, thereby achieving balanced drainage of the upper and lower coal reservoirs 2.

[0025] The above embodiments illustrate the basic principles and features of the present invention, but are merely preferred embodiments and are not limited to these embodiments. Those skilled in the art, inspired by this patent, can make many modifications and improvements without departing from the spirit and scope of the claims, all of which fall within the scope of protection of the present invention. Therefore, the scope of this patent and its protection should be determined by the appended claims.

Claims

1. A method for preventing interference between layers during the development and drainage of coal-bearing gas horizontal wells, characterized in that: Includes the following steps: S1. During the extraction of coalbed methane from adjacent upper and lower coal seams, the reservoir pressure P of the upper coal seam is monitored in real time. 上 and the reservoir pressure P of the lower coal seam 下 The pressure signal is transmitted to the control system, which has a built-in criterion for detecting inter-layer interference, via P. 上 and P 下 The difference is compared with the pressure difference identification standard to determine whether inter-layer interference has occurred; S2. During normal coalbed methane extraction, i.e., when there is no inter-layer interference during drainage, P 上 and P 下 The difference is less than the pressure difference identification standard; S3, when P 下 If the pressure drops too quickly, the reservoir pressures of the upper and lower coal seams become uncoordinated, and a dual-pipe reverse lifting drainage mode is adopted for drainage. S4, when P 上 When the descent is too rapid or the upper coal reservoir is about to be exposed, the reservoir pressures of the upper and lower coal reservoirs are not coordinated, and a dual-pipe positive lifting drainage mode is adopted for drainage.

2. The method for preventing interference between layers in the development and drainage of coal-bearing gas horizontal wells according to claim 1, characterized in that: An upper horizontal well is drilled in the upper coal reservoir, and a lower horizontal well is drilled in the lower coal reservoir. One end of the upper horizontal well is connected to the lower end of the vertical shaft through an upper arc-shaped shaft passage, and one end of the lower horizontal well is connected to the lower end of the vertical shaft through a lower arc-shaped shaft passage. The vertical shaft is equipped with a cementing casing, an outer tube inside the cementing casing, a central tube inside the outer tube, and a sucker rod and a tubular pump inside the central tube. The lower end of the sucker rod is connected to the power input end of the tubular pump. An outer annular cavity is formed between the cementing casing and the outer tube, and an inner annular cavity is formed between the outer tube and the central tube. A first through hole is drilled on the outer tube wall near the tubular pump to connect the outer annular cavity and the inner annular cavity. A second through hole is drilled on the central tube wall near the tubular pump to connect the inner annular cavity and the inner cavity of the central tube. The lower end of the central tube is connected to the upper horizontal well through an upper arc-shaped pipe passing through the upper arc-shaped shaft passage, and the lower end of the outer tube is connected to the lower horizontal well through a lower arc-shaped pipe passing through the lower arc-shaped shaft passage.

3. The method for preventing interference between layers in the development and drainage of coal-bearing gas horizontal wells according to claim 2, characterized in that: The central tube contains a first-stage air lift valve, a second-stage air lift valve, and a third-stage air lift valve arranged sequentially from top to bottom above the tubular pump.

4. The method for preventing interference between layers in the development and drainage of coal-bearing gas horizontal wells according to claim 3, characterized in that: The lower horizontal well is equipped with a system for real-time monitoring of P. 下 The downpressure sensor is connected to the wellhead control system via a downpressure cable passing through the outer annular cavity; a device for real-time monitoring of P is installed in the upper horizontal well. 上 The upper pressure sensor is connected to the well control system via an upper pressure cable that passes through the outer annular cavity.

5. The method for preventing interference between layers in the development and drainage of coal-bearing gas horizontal wells according to claim 4, characterized in that: The specific criteria for identifying inter-layer interference in step S1 are as follows: In the formula: The reservoir pressure difference in the commingled reservoir is expressed in MPa. Surface tension, N / m; R is the contact angle, °; R is the diameter of the interlayer fluid transport channel, m; The interlayer spacing is in meters (m). Let be the fluid transport velocity, in m / s, where the minimum value is t is the sampling time, in seconds; is the reservoir pressure of the lower coal seam, in MPa; Re is the Reynolds number, dimensionless. For fluid density, kg / m³ 3 g is the acceleration due to gravity.

6. The method for preventing interference between layers in the development and drainage of coal-bearing gas horizontal wells according to claim 5, characterized in that: The specific process of the dual-tube reverse lift drainage in step S3 is as follows: Gas is injected downwards from the upper port of the inner annular cavity, causing the liquid level in the inner annular cavity to drop. Since the outer tube has a first through-hole connecting the outer and inner annular cavities, and the central tube has a second through-hole connecting the inner annular cavity and the central tube cavity, the liquid in the inner annular cavity enters the outer annular cavity through the first through-hole and simultaneously enters the central tube through the second through-hole. Driven by the sucker rod, the tubular pump inside the central tube pumps the liquid upwards through the central tube to the surface, causing the liquid level in the outer annular cavity to rise. Coal-based gas is discharged upwards through the outer annular cavity. Since the liquid inside the inner annular cavity mainly comes from the lower horizontal well of the lower coal reservoir, the high-pressure gas injected into the inner annular cavity from the wellhead increases or inhibits the decrease in reservoir pressure in the lower coal reservoir. The tubular pump mainly pumps out the liquid from the upper horizontal well in the upper coal reservoir, thereby accelerating the drainage and depressurization of the upper coal reservoir. When P is monitored... 上 and P 下 When the pressure is balanced, gas is no longer injected into the inner annular cavity, and the central pipe and outer pipe simultaneously discharge liquid upwards, thereby achieving balanced drainage of the upper and lower coal reservoirs.

7. The method for preventing interference between layers in the development and drainage of coal-bearing gas horizontal wells according to claim 5, characterized in that: The specific process of dual-pipe reverse lift drainage in step S4 is as follows: Gas is injected downwards from the upper end of the central pipe, causing the liquid level inside the central pipe to drop. Simultaneously, the gas pressure drives one, two, or three of the first-stage, second-stage, and third-stage gas lift valves to close, thereby preventing the central pipe from draining liquid upwards and inhibiting the rapid drainage of the upper horizontal well in the upper coal reservoir connected to the central pipe. Since the outer pipe has a first through-hole connecting the outer annular cavity and the inner annular cavity, and the central pipe has a second through-hole connecting the inner annular cavity and the inner cavity of the central pipe... Under the action of the tubular pump, the inner annular cavity becomes the only drainage channel. The lower end of the outer pipe is connected to the lower horizontal well of the lower coal reservoir. The liquid discharged upward from the inner annular cavity is mainly from the lower coal reservoir, while the coalbed methane is still discharged upward through the outer annular cavity. The liquid inside the central pipe mainly comes from the upper horizontal well of the upper coal reservoir. Therefore, the high-pressure gas injected into the central pipe from the wellhead increases or inhibits the decrease in reservoir pressure in the upper coal reservoir. The tubular pump mainly pumps out the liquid from the lower horizontal well in the lower coal reservoir, thereby accelerating the drainage and depressurization of the lower coal reservoir. When P is monitored... 上 and P 下 When the pressure is balanced, gas is no longer injected into the central pipe, and liquid is discharged upwards from both the central and outer pipes, thereby achieving balanced drainage of the upper and lower coal reservoirs.

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