Coal measure gas horizontal well combined layer development and drainage device with interlayer anti-interference function

Abstract

The utility model discloses a coal measure gas horizontal well combined layer development drainage and production device with interlayer anti -interference function, including shaft, upper horizontal well and lower horizontal well, and the shaft is equipped with well cementing casing pipe, is equipped with outer tube in well cementing casing pipe, is equipped with central tube in outer tube, is equipped with sucker rod and tubular pump in central tube, and the outer annular cavity is formed between well cementing casing pipe and outer tube, and the inner annular cavity is formed between outer tube and central tube, and the first through -hole for communicating the outer annular cavity and the inner annular cavity is set up on the outer tube wall at the place near tubular pump, and the second through -hole for communicating the inner annular cavity and the central tube inner chamber is set up on the central tube wall at the place near tubular pump. The utility model is easy to implement, and the operation is convenient, can independently regulate and control single reservoir reservoir pressure in the combined production process of coal measure gas horizontal well, makes the combined layer development drainage and production be in the advantageous gas production pressure, through the differential pressure reduction or elimination of interlayer interference influence of real -time regulation and control of upper coal reservoir and lower coal reservoir in the drainage and production process, improves coal measure gas drainage and production efficiency and effect.

Description

Technical Field

[0001] This utility model belongs to the field of coalbed methane development technology, specifically relating to a coalbed methane horizontal well combined layer development and drainage device with inter-layer anti-interference function. 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. Dual-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 dual-pump, three-channel dual-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 coal-bearing gas horizontal well combined development and drainage devices with inter-layer anti-interference functions. This would 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. Utility Model Content

[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 coal-bearing gas horizontal well development and drainage device with inter-layer anti-interference function, it is possible to achieve 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, this utility model adopts the following technical solution: a coalbed methane horizontal well combined development and drainage device with inter-layer anti-interference function, including a vertical shaft, an upper horizontal shaft, and a lower horizontal shaft. The vertical shaft is opened vertically downward from the ground. The upper horizontal shaft is opened in the upper coalbed methane reservoir, and the lower horizontal shaft is opened in the lower coalbed methane reservoir. One end of the upper horizontal shaft is connected to the lower end of the vertical shaft through an upper arc-shaped shaft passage, and one end of the lower horizontal shaft is connected to the lower end of the vertical shaft through a lower arc-shaped shaft passage. The vertical shaft is equipped with a cemented casing, an outer pipe is installed inside the cemented casing, a central pipe is installed inside the outer pipe, and a pumping device is installed inside the central pipe. The system includes a sucker rod and a tubing pump. The lower end of the sucker rod is connected to the power input end of the tubing 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 opened on the outer tube wall near the tubing pump to connect the outer annular cavity and the inner annular cavity. A second through hole is opened on the central tube wall near the tubing 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 well 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 well passage.

[0007] 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.

[0008] The lower horizontal well is equipped with a reservoir pressure P for real-time monitoring of the underlying coal seam. 下 The downpressure sensor is connected to the wellhead control system via a downpressure cable that passes through the outer annular cavity.

[0009] The upper horizontal well is equipped with a reservoir pressure P for real-time monitoring of the coal-bearing reservoir. 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 working principle of this utility model, employing the above technical solution, is as follows: Deep coalbed methane mainly exists in coal-bearing reservoirs in two forms: adsorbed gas and free gas. As free gas is produced in the reservoir, deep coalbed methane drainage rapidly enters the gas-liquid two-phase flow stage; the discharge of the gas-liquid 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 in the form of seepage.

[0011] 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.

[0012] 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 .

[0013] The present invention has the following beneficial effects: The present invention is based on a scientific principle, is easy to implement and convenient to operate, and 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

[0014] Figure 1 This is a schematic diagram of the structure of this utility model; 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 and extraction system. Detailed Implementation

[0015] like Figures 1-3As shown, the coalbed methane horizontal well combined development and drainage device with inter-layer anti-interference function of this utility model includes a vertical shaft 6, an upper horizontal shaft 3, and a lower horizontal shaft 4. The vertical shaft 6 is opened vertically downward from the ground. The upper horizontal shaft 3 is opened in the upper coal reservoir 1, and the lower horizontal shaft 4 is opened in the lower coal reservoir 2. One end of the upper horizontal shaft 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 shaft 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 cemented casing 8, an outer pipe 9 is installed inside the cemented casing 8, a central pipe 10 is installed inside the outer pipe 9, and a sucker rod 11 and a tubular pump 12 are installed inside the central pipe 10. The lower end of the sucker rod 11 is connected to... The power input end of the tubular pump 12 is connected to the outer annular cavity 13 formed between the cementing casing 8 and the outer tube 9, and the inner annular cavity 14 formed between the outer tube 9 and the central tube 10. A first through hole 15 for connecting the outer annular cavity 13 and the inner annular cavity 14 is opened on the wall of the outer tube 9 near the tubular pump 12. A second through hole 16 for connecting the inner annular cavity 14 and the inner cavity of the central tube 10 is opened on the wall of the central tube 10 near the tubular pump 12. The lower end of the central tube 10 is connected to the upper horizontal well 3 through the upper arc-shaped pipe 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 pipe 18 passing through the lower arc-shaped well passage 7.

[0016] 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.

[0017] The lower horizontal well 4 is equipped with a reservoir pressure P for real-time monitoring of the lower coal seam 2. 下 The lower pressure sensor 25 is connected to the control system above the well via a lower pressure cable 22 passing through the outer annular cavity 13; the upper horizontal well 3 is equipped with a reservoir pressure P for real-time monitoring of the upper coal reservoir 1. 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.

[0018] The working process of this utility model specifically includes 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 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 employs a dual-tube reverse lift extraction mode. The specific process 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. Driven by the sucker rod 11, the internal tubular pump 12 pumps liquid upwards to the surface through the central pipe 10, causing the liquid level in the outer annular cavity 13 to rise, and the coalbed methane to be 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 in 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.

[0019] 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 seam 1 and the lower coal seam 2 are not coordinated, so a dual-pipe forward lift drainage mode is adopted for drainage. The specific process of dual-pipe reverse lift drainage is as follows: gas is injected downward from the upper end of the central pipe 10, the liquid level inside the central pipe 10 moves downward, and 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 upward. This suppresses the rapid drainage of 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 16 connecting the inner annular cavity 14 and the inner cavity of the central pipe 10, under the action of the 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 within the lower coal reservoir 2, while the coal-bearing 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 suppresses the pressure drop in the upper coal reservoir 1. The tubular pump 12 mainly pumps out the liquid from the lower horizontal well 4 within the lower coal reservoir 2, thereby accelerating the drainage and pressure reduction of the lower coal reservoir 2. When P is detected... 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.

[0020] The above embodiments illustrate the basic principles and features of this utility model. However, the above descriptions 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 protection scope of this utility model. Therefore, the patent and its scope of protection should be determined by the appended claims.

Claims

1. A coalbed methane horizontal well combined layer development and drainage device with inter-layer anti-interference function, characterized in that: The system includes a vertical shaft, an upper horizontal shaft, and a lower horizontal shaft. The vertical shaft is excavated vertically downwards from the ground. The upper horizontal shaft is located within the upper coal seam, and the lower horizontal shaft is located within the lower coal seam. One end of the upper horizontal shaft is connected to the lower end of the vertical shaft via an upper arc-shaped shaft passage, and one end of the lower horizontal shaft is connected to the lower end of the vertical shaft via a lower arc-shaped shaft passage. The vertical shaft is equipped with a cemented casing, inside which is an outer tube. Inside the outer tube is a central tube, and inside the central tube are a sucker rod and a tubular pump. The lower end of the sucker rod is connected to the power input end of the tubular pump. The cementing casing and the outer casing form an outer annular cavity, and the outer casing and the center casing form an inner annular cavity. A first through hole is opened on the outer casing near the tubular pump to connect the outer annular cavity and the inner annular cavity. A second through hole is opened on the center casing near the tubular pump to connect the inner annular cavity and the inner cavity of the center casing. The lower end of the center casing is connected to the upper horizontal well through an upper arc-shaped pipe passing through the upper arc-shaped well passage, and the lower end of the outer casing is connected to the lower horizontal well through a lower arc-shaped pipe passing through the lower arc-shaped well passage.

2. The coalbed methane horizontal well combined layer development and drainage device with inter-layer anti-interference function according to claim 1, 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.

3. The coalbed methane horizontal well combined layer development and drainage device with inter-layer anti-interference function according to claim 1 or 2, characterized in that: The lower horizontal well is equipped with a reservoir pressure P for real-time monitoring of the underlying coal seam. 下 The downpressure sensor is connected to the wellhead control system via a downpressure cable that passes through the outer annular cavity.

4. The coalbed methane horizontal well combined layer development and drainage device with inter-layer anti-interference function according to claim 1 or 2, characterized in that: The upper horizontal well is equipped with a reservoir pressure P for real-time monitoring of the coal-bearing reservoir. 上 The upper pressure sensor is connected to the well control system via an upper pressure cable that passes through the outer annular cavity.

Images