Drainage and gas production device and method for horizontal well for coalbed methane of coal mine area

Abstract

A drainage and gas production device for a horizontal well for coalbed methane of a coal mine area, the device comprising a surface horizontal well and a downhole borehole section (6), wherein a horizontal section (4) of the surface horizontal well is in communication with the downhole borehole section (6), a communication point (7) of the horizontal section (4) of the surface horizontal well and the downhole borehole section (6) is located at an end A or a middle or an end B of the horizontal section (4) of the surface horizontal well; and the other end of the downhole borehole section (6) is connected to a gas-water-slag separation device (15) located in a downhole drill site (5).

Description

A device and method for draining and producing coalbed methane from horizontal wells in coal mines Technical Field

[0001] The present invention relates to the technical field of coalbed methane development, and in particular to a drainage and gas production device and method for coalbed methane horizontal wells in coal mining areas. Background Art

[0002] Coalbed methane is primarily stored in coal seams in the form of adsorption. The principle of coalbed methane development is to reduce reservoir pressure by draining water, promoting the desorption of coalbed adsorbed gas into free gas, which is then transported to the coalbed methane wellbore through diffusion and seepage. Water is pumped to the surface by inserting a submersible pump into the wellbore, and the coalbed methane is automatically discharged from the wellhead due to its own pressure. The drainage and gas production methods vary depending on the type of coalbed methane well and the number of wellbores. An L-type horizontal well has only one wellbore, with drainage and gas production occurring in the same wellbore, and a gas-water separation device installed at the wellhead; a U-type horizontal well has two wellheads, with drainage using the vertical well and gas production using the horizontal wells; a V-type horizontal well has three wellheads, with drainage using the central vertical well and gas production using the horizontal wells on both sides.

[0003] The shortcomings of existing L-type horizontal well technology are:

[0004] 1. The cost of use is relatively high, including temporary land use, drainage pumps, pump inspection operations, electricity costs, temporary generators, surface water treatment, labor costs, etc.

[0005] 2. The time limit for temporary land use is subject to policy constraints. The production cycle of coalbed methane horizontal wells is generally 5-8 years. The "Detailed Rules for the Implementation of the Land Administration Law" stipulate that the temporary land use period for energy project construction shall not exceed 4 years. Forced pipe diameter will reduce gas production and sudden change elimination effects.

[0006] 3. Due to the large inclination of L-shaped wells, when using rod pumps for drainage, there are problems such as: 1. The pump cannot reach the bottom of the well, resulting in high pressure in the abandoned reservoir, reducing gas production and the effect of eliminating sudden changes; 2. Pipe and rod eccentric wear causes pipe leakage, increased torque, no drainage or reduced drainage volume, etc., which shortens the service life of the pump and the pump inspection cycle, causing discontinuous drainage and reservoir pollution.

[0007] 4. Using electric submersible pumps instead of rod pumps solves the problem of the pump not being able to reach the bottom of the well and the problem of eccentric wear of the pipe and rod. However, electric submersible pumps are very sensitive to coal powder, resulting in a short pump inspection cycle and a short pump service life. They are not suitable for broken, soft and loose coal seams, and the price and maintenance costs of electric submersible pumps are relatively high.

[0008] 5. Both rod pumps and electric submersible pumps require a certain degree of submergence, which results in insufficient drainage and pressure reduction, thereby reducing coalbed methane production and coal seam outburst elimination effects.

[0009] 6. The drainage pump is ineffective at carrying large particles, causing bridge plug residues, sand, and coal lumps to accumulate and compact in the wellbore, resulting in blockage. Currently, horizontal well sand bailing pumps and technology are still immature, and frequent sand bailing can cause significant and irreversible damage to the reservoir.

[0010] The existing patented technology with the publication number CN103967472B and the patent name is a method for enhanced extraction of coalbed methane by staged fracturing horizontal wells, which discloses a U-shaped well structure; and the existing patented technology with the publication number CN106640018A and the patent name is a method for extracting coalbed methane by V-shaped well groups, which discloses a V-shaped well structure. Both of the above patents solve the problems of shallow pump depth, pipe and rod wear, high abandonment pressure, and wellbore blockage by adding a vertical well specifically for drainage. However, such a setting still cannot avoid problems such as pump jamming caused by coal powder, retention of large particles, and limited temporary land use time. At the same time, the addition of a vertical well and a surface well site increases the engineering cost and the cost of use. In addition, it has poor adaptability to mountainous terrain conditions. Therefore, this application proposes a coalbed methane horizontal well drainage and gas extraction device and method in coal mining areas to solve the above-mentioned defects.

[0011] Summary of the Invention

[0012] The technical problem to be solved by the present invention is: how to solve the problems existing in the current coalbed methane production, such as insufficient formation pressure reduction, wellbore blockage, frequent pump inspections, discontinuous production, limited temporary land use time, and high production costs.

[0013] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0014] A coalbed methane horizontal well drainage and gas production device in a coal mining area comprises a surface horizontal well section and a downhole borehole section, wherein the surface horizontal well section and the downhole borehole section are connected, and the connection point is located at the lowest elevation of the horizontal well section, the downhole borehole is an upwardly inclined borehole with an inclination angle greater than 45° and less than 90°, and the connection point between the surface horizontal well section and the downhole borehole section is located at the A end, the middle end, or the B end of the surface horizontal well section;

[0015] The other end of the downhole drilling section is connected to a gas-water-slag separation device located in a downhole drilling site, wherein the downhole drilling site is located below the surface horizontal well section and the downhole drilling section, and the gas-water-slag separation device is connected to a downhole drainage pipeline;

[0016] The wellhead of the ground horizontal well is connected to a ground gas production device, and the outlet of the ground gas production device is connected to a gas-water-slag separation device through a ground gas transmission pipeline.

[0017] As a further solution of the present invention: the gas-water-slag separation device is also connected to an underground extraction pipeline, one end of the horizontal section of the ground horizontal well is connected to the connecting horizontal well, and perforations are opened on the connecting horizontal well, wherein the coal seam decompression desorbed gas and the coal seam goaf gas can enter the extraction pipeline through the perforations.

[0018] As a further solution of the present invention: the connecting horizontal wells include an A-end connecting horizontal well, a middle connecting horizontal well and a B-end connecting horizontal well;

[0019] When the connection point between the horizontal section of the surface horizontal well and the downhole drilling section is located at end A of the horizontal section of the surface horizontal well, the tail end of the horizontal section of the surface horizontal well is connected to end A and connected to the horizontal well;

[0020] When the connection point between the horizontal section of the surface horizontal well and the downhole drilling section is located at the middle end of the horizontal section of the surface horizontal well, the tail end of the horizontal section of the surface horizontal well is connected to the middle connecting horizontal well;

[0021] When the connection point between the horizontal section of the surface horizontal well and the downhole drilling section is located at the B end of the horizontal section of the surface horizontal well, the tail end of the horizontal section of the surface horizontal well is connected to the B end and connected to the horizontal well.

[0022] As a further solution of the present invention: an air inlet connected to the horizontal section of the ground horizontal well is opened at the bottom of the ground gas production device, and a gas solenoid valve is also provided at the air inlet. A ground air outlet is opened at the other end of the ground gas production device, wherein an electric air regulating valve and an electronic gas flow meter are provided at the ground air outlet, and an electronic pressure gauge is also provided on the ground gas production device.

[0023] As a further solution of the present invention: a water-slag separation chamber is opened on the inner side of the gas-water-slag separation device, wherein the bottom of the water-slag separation chamber is connected with the underground drilling section through an inlet, and an air outlet and a water outlet are opened on one side of the gas-water-slag separation device, wherein the water outlet is connected with the underground drainage pipeline, and a slag discharge port is opened at the bottom of the water-slag separation chamber.

[0024] As a further solution of the present invention: an electronic water pressure gauge and a main solenoid valve are provided at the inlet; a gas solenoid valve and an electronic gas flowmeter are provided at the air outlet; a water solenoid valve and a second electronic water flowmeter are provided at the water outlet; and a slag discharge solenoid valve is provided at the slag discharge port.

[0025] As a further solution of the present invention: a filter mesh port is provided inside the air-water-slag separation device and above the water-slag separation chamber, wherein an electric oil nozzle is provided above the filter mesh port, and an air-water separation chamber is provided inside the air-water-slag separation device and above the water-slag separation chamber.

[0026] The present application also discloses a method for using a coal mine gas horizontal well drainage gas production device, comprising the following steps:

[0027] S1. Open the main solenoid valve, and the return fluid enters the gas-water-slag separation device from the drill hole. It first enters the water-slag separation chamber at the bottom of the device, and is separated by gravity and the filter screen.

[0028] S2. Open the electric oil nozzle, and the liquid enters the gas-water separation chamber from the water-slag separation chamber. Due to the sudden drop in pressure, the coalbed methane dissolved in the water is precipitated;

[0029] S3, open the second gas solenoid valve, and the precipitated coalbed methane enters the extraction pipeline under the action of negative pressure;

[0030] S4. Open the water solenoid valve and water enters the drainage pipe under the action of gravity;

[0031] S5. When the wellhead casing pressure is lifted and gas production begins, the gas solenoid valve 1 is opened, and the coalbed methane enters the surface gas pipeline under the action of pressure and buoyancy;

[0032] S6. Analyze the changing patterns of the electronic air pressure gauge, electronic air flow meter, electronic water pressure gauge, and electronic water flow meter in real time, and adjust the production speed by adjusting the opening of the electric air regulating valve and electric oil nozzle;

[0033] S7. When slag discharge is required, first close the gas solenoid valve 1, gas solenoid valve 2, water solenoid valve, electric oil nozzle and main solenoid valve in sequence, and open the slag discharge solenoid valve to discharge the slag;

[0034] S8. After the slag discharge is completed, immediately close the slag discharge solenoid valve, then open the gas solenoid valve 1, gas solenoid valve 2, water solenoid valve, electric oil nozzle and main solenoid valve in sequence to resume normal water discharge and gas production operations.

[0035] As a further solution of the present invention: after the drainage and gas production is completed, the underground orifice is directly connected to the extraction pipeline. During mining at the working face, the unloading gas from the coal seam at the working face and the gas in the goaf enter the extraction pipeline through the perforations, realizing dual use of one well.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The underground drilling section of the present invention is connected with the lowest elevation of the horizontal wellbore on the ground, and the gravity of solid waste such as water, sand, coal powder and bridge plug residue is automatically discharged downward from the underground drilling site, and the gas, water and slag are directly separated by the gas-water-slag separation device in the underground drilling site, and the automatic separation can be completed in the tunnel; the pressure and buoyancy of the gas are fully utilized to automatically discharge upward from the wellhead, and the discharge of the gas is controlled by the ground gas production device. The present invention eliminates the ground well drainage pump, eliminates the reservoir damage caused by pump inspection / pump replacement operations and production stoppages, and truly realizes continuous drainage; eliminates the ground well drainage pump, so that the lowest liquid level is not affected by the position and submergence of the pump, and the formation pressure can be reduced to the theoretical minimum value, thereby realizing maximum extraction and coal seam outburst elimination; water carries sand powder and is discharged from the lower orifice by its own gravity, has the function of automatically cleaning the wellbore, and keeps the wellbore clean; greatly reduces temporary land use, labor and drainage costs;

[0038] Second, the present invention can realize the collection and transmission of surface casing pressure, surface gas flow, downhole flow pressure, downhole water flow, and slag discharge information, can realize automatic control of the opening of the surface electric gas regulating valve and downhole drainage electric oil nozzle, can realize automatic control of the opening and closing of the surface gas solenoid valve, downhole main solenoid valve, slag discharge solenoid valve, drainage solenoid valve, and air extraction solenoid valve, thereby realizing intelligent management of production operations;

[0039] 3. The present invention uses a horizontal well for dual purposes, extracting gas from the goaf during mining, thus saving gas extraction costs at the working face.

[0040] Fourth, the present invention determines the horizontal well trajectory and well type based on the distribution of coal seams in the target block of the mine, ground construction conditions and the location of the mine roadway. The horizontal well includes a horizontal section and a drilled section. The connection point between the horizontal section and the drilled section is located at the lowest elevation of the horizontal section of the horizontal well. The horizontal well types include A-end connection type, middle connection type and B-end connection type. By setting a variety of connection positions, users can choose;

[0041] 5. When the wellbore needs to be cleaned, the present invention can realize large-volume continuous water injection to clean the wellbore. By controlling the balance between the water injection volume of the surface well and the water discharge volume of the downhole borehole, the formation pressure is guaranteed to be constant, which protects the reservoir and makes the wellbore cleaning cleaner. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG1 is a plan view of a drainage and gas production device for a coalbed methane horizontal well in a coal mine according to an embodiment of the present invention;

[0043] FIG2 is a schematic diagram of a horizontal section of a surface horizontal well and an end A of a downhole drilling section connected in accordance with an embodiment of the present invention;

[0044] FIG3 is a schematic diagram of a horizontal section of a surface horizontal well and a middle end of a downhole drilling section connected in an embodiment of the present invention;

[0045] FIG4 is a schematic diagram of a horizontal section of a surface horizontal well and a downhole drilling section B connected to each other according to an embodiment of the present invention;

[0046] FIG5 is a schematic structural diagram of a surface wellhead gas production device according to an embodiment of the present invention;

[0047] FIG6 is a schematic structural diagram of a gas-water-slag separation device at a downhole borehole according to an embodiment of the present invention;

[0048] FIG7 is a schematic diagram of a dual-purpose working face with pressure relief for negative pressure gas extraction according to an embodiment of the present invention;

[0049] FIG8 is a first construction step for connecting the end of a horizontal well to a downhole drilling site according to an embodiment of the present invention;

[0050] FIG9 is a second construction step for connecting the end of a horizontal well to a downhole drilling site according to an embodiment of the present invention;

[0051] Explanation of reference numerals: 1, mining area; 2, underground rock tunnel; 3, surface well site; 4, horizontal section of surface horizontal well; 5, underground drilling site; 6, underground drilling section; 7, connection point; 7-1, A-end connection point; 7-2, middle connection point; 7-3, B-end connection point; 8, coal seam elevation contour line; 9, A-end connection horizontal well; 10, middle connection horizontal well; 11, B-end connection horizontal well; 12, underground extraction pipeline; 13, well Drainage pipeline; 14. Ground gas extraction device; 14-1. Air inlet; 14-2. Gas solenoid valve 1; 14-3. Electronic pressure gauge; 14-4. Electric gas regulating valve; 14-5. Electronic gas flow meter 1; 14-6. Ground gas outlet; 15. Gas-water-slag separation device; 15-1. Inlet; 15-2. Connecting pipe; 15-3. Electronic water pressure gauge; 15-4. Main solenoid valve; 15-5. Water-slag separation chamber; 15 -6, slag discharge port; 15-7, slag discharge solenoid valve; 15-8, filter screen port; 15-9, electric oil nozzle; 15-10, gas-water separation chamber; 15-11, annular partition; 15-12, gas outlet; 15-13, gas solenoid valve 2; 15-14, electronic gas flowmeter 2; 15-15, water outlet; 15-16, water solenoid valve; 15-17, electronic water flowmeter; 15-18, support leg; 16, Return air tunnel in the mining area; 17. Track tunnel in the mining area; 18. Working face; 19. Return air chute; 20. Track chute; 21. Goaf; 22. Perforation hole; 23. Monitoring host; 24. Mine industrial Ethernet ring network; 25. Data receiver; 26. Orifice rotary blowout preventer; 27. Drill pipe; 28. Magnetic rotary transmitter short circuit 1; 29. ​​Crawler; 30. Magnetic probe tube 1; 31. Magnetic rotary transmitter short circuit 2; 32. Magnetic probe tube 2. DETAILED DESCRIPTION

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0053] Example 1

[0054] Referring to Figures 1, 2, 3 and 4, a coalbed methane horizontal well drainage and gas production device in a coal mine area has two entrances and exits. The surface wellhead is a reservoir fracturing transformation channel and a gas production channel, and the downhole orifice is a discharge channel for water, fracturing sand, coal powder, solid residue, etc.; wherein the coalbed methane horizontal well drainage and gas production device in a coal mine area includes a surface horizontal well and a downhole drilling section 6, wherein the downhole drilling section 6 is connected to the horizontal section 4 of the surface horizontal well, and the downhole drilling section 6 is an upward inclined borehole, and the inclination angle is preferably greater than 45° and less than 90° to avoid steps; and the connection point between the horizontal well horizontal section 4 and the downhole drilling section 6 is located at the lowest elevation of the horizontal section of the horizontal well (as shown in Figures 2, 3 and 4). According to the position of the connection point, It can be divided into three well types. When the connection point is at the target point A of the horizontal well, it is the connection point 7-1 at the A end (front end of the horizontal well); when the connection point is in the middle of the horizontal well, it is the middle connection point 7-2; when the connection point is at the target point B of the horizontal well, it is the connection point 7-3 at the B end (rear end of the horizontal well). At this time, the coalbed methane horizontal well has an overall "ㄣ"-shaped structure; the connection point should be selected at a location where the formation is stable and the cementing quality is good, and avoid the casing coupling and casing stabilizer. It should be noted that the specific location of the connection point depends on the actual situation of the coal seam on site. This application provides a variety of different methods for reference.

[0055] It should be noted that the ground horizontal well has an "L"-shaped structure, including a vertical section and a horizontal section, wherein the vertical section of the ground horizontal well is connected to the ground well site 3 and is connected to the ground gas production device 14 on the ground well site 3, while the horizontal section of the ground horizontal well is connected to the downhole drilling section 6, and the other end of the downhole drilling section 6 is connected to the gas-water-slag separation device 15 set in the downhole drilling site (tunnel) 5, wherein the gas outlet of the gas-water-slag separation device 15 is connected to the downhole extraction pipeline 12, and the drainage outlet of the gas-water-slag separation device 15 is connected to the downhole drainage pipeline 13.

[0056] Furthermore, the underground drilling site (tunnel) 5 is located below the underground drilling section 6, and the elevation of the underground drilling site (tunnel) 5 is lower than the elevation of the connecting point between the horizontal section 4 of the ground horizontal well and the underground drilling section 6, wherein the tunnel is located outside the influence range of the fracturing cracks of the ground horizontal well, the tunnel surrounding rock is stable and there is no structure around the tunnel, and reinforcement is carried out within a certain range around the drilling opening position of the underground tunnel of the mine. Generally, the tunnel reinforcement range is not less than 20m, and the reinforcement methods include but are not limited to anchor reinforcement, anchor cable reinforcement, bracket reinforcement, U-shaped steel reinforcement, grouting reinforcement, etc.

[0057] Furthermore, the drilling trajectory of the downhole drilling section 6 remains smooth, and the hole inclination gradually increases to avoid steps, preferably greater than 45° and less than 90°; the larger the inclination angle, the more beneficial it is for water drainage and slag removal. When the well inclination is 90 degrees, the slag removal effect is best.

[0058] 2, 3, 4 and 5, the surface gas extraction device 14 and the gas-water-slag separation device 15 are connected to the monitoring host through the mine industrial Ethernet ring network communication, which is used to guide the completion of coalbed methane drainage and gas extraction automatic control to form a closed loop.

[0059] Further, referring to Figure 5, an air inlet 14-1 connected to the horizontal section 4 of the ground horizontal well is provided at the bottom of the ground gas production device 14, and a gas solenoid valve 14-2 is also provided at the air inlet 14-1. A ground air outlet 14-6 is provided at the other end of the ground gas production device 14, wherein an electric air regulating valve 14-4 and an electronic gas flow meter 14-5 are provided at the ground air outlet 14-6. An electronic pressure gauge 14-3 is also provided on the ground gas production device 14. When in use, the gas collected from the ground horizontal well can enter from the air inlet 14-1 and then be discharged under the control of the gas solenoid valve 14-2 and the electric air regulating valve 14-4. During the process, the gas pressure and gas flow can be monitored by the electronic pressure gauge 14-3 and the electronic gas flow meter 14-5, and the casing pressure and gas flow data of the ground horizontal well can be obtained in real time, and automatic control of the switch and opening can be realized.

[0060] 6 , a water-slag separation chamber 15-5 is provided inside the gas-water-slag separation device 15, wherein the bottom of the water-slag separation chamber 15-5 is connected to the downhole drilling section 6 via an inlet 15-1. An air outlet 15-12 and a water outlet 15-15 are provided on one side of the gas-water-slag separation device 15, wherein the water outlet 15-15 is connected to the downhole drainage pipeline 13. A slag discharge port 15-6 is provided at the bottom of the water-slag separation chamber 15-5.

[0061] Furthermore, an electronic water pressure gauge 15-3 and a main solenoid valve 15-4 are provided at the inlet 15-1; a gas solenoid valve 15-13 and an electronic gas flow meter 15-14 are provided at the gas outlet 15-12; a water solenoid valve 15-16 and an electronic water flow meter 15-17 are provided at the water outlet 15-15; a slag discharge solenoid valve 15-7 is provided at the slag discharge port 15-6; an electronic water pressure gauge 15-3 and a main solenoid valve 15-4 are installed at the inlet 15-1 of the gas-water-slag separation device 15 15-4, can obtain the bottom hole flow pressure at any time and realize automatic switch control; a slag discharge solenoid valve 15-7 is set at the slag discharge port 15-6 at the bottom of the water-slag separation chamber 15-5; an electronic gas flow meter 15-14 and a gas solenoid valve 15-13 are installed at the gas outlet 15-12 to monitor the gas flow and control the gas flow rate; an electronic water flow meter 15-17 and a water solenoid valve 15-16 are installed at the water outlet 15-15 to monitor the water flow and control the water flow rate.

[0062] Furthermore, a filter mesh port 15-8 is provided inside the air-water-slag separation device 15 and above the water-slag separation chamber 15-5, wherein an electric oil nozzle 15-9 is provided above the filter mesh port 15-8, and an air-water separation chamber 15-10 is provided inside the air-water-slag separation device 15 and above the water-slag separation chamber 15-5, and an electric oil nozzle 15-9 is provided at the liquid outlet at the top of the water-slag separation chamber 15-5, which can realize automatic control of the switch and opening.

[0063] It should be noted that the return fluid enters the water-slag separation chamber 15-5 at the bottom of the gas-water-slag separation device 15 through the device inlet 15-1, the slag settles at the bottom of the separation chamber, and the water enters the gas-water separation chamber 15-10 through the electric oil nozzle. The water pressure is reduced, causing the coalbed methane dissolved in the water to precipitate and convert into free gas. The free gas enters the underground extraction pipeline 12 from the gas outlet 15-12 at the top of the device, and the water enters the underground drainage pipeline 13 from the water outlet 15-15.

[0064] An annular partition 15-11 is provided in the gas-water separation chamber 15-10. When the liquid level exceeds the annular partition 15-11, water enters the water outlet 15-15, preventing the dissolved gas from directly entering the drainage pipe 13 and causing an air hammer effect before it can be precipitated.

[0065] The automatic slag discharge process is as follows: First, close the gas solenoid valve 15-13, water solenoid valve 15-16, electric nozzle 15-9, and main solenoid valve 15-4 in sequence, then open the slag discharge solenoid valve 15-7 to discharge the slag. After slag discharge is completed, immediately close the slag discharge solenoid valve 15-7, then open the gas solenoid valve 15-13, water solenoid valve 15-16, electric nozzle 15-9, and main solenoid valve 15-4 in sequence to resume normal drainage. When formation pressure depletes in the late stages of production, formation water production is minimal or even intermittent. At this time, the surface wellhead can be sealed, and the surface well site gas production pipeline can be removed. Only downhole drilling can be used for water drainage, slag removal, and gas production. When gas production is also very low, intermittent production can be adopted.

[0066] Example 2

[0067] 1 and 7 , based on Example 1, when the ground horizontal well is located at the top / bottom of the coal seam, the horizontal section 4 of the ground horizontal well and the downhole drilling section 6 can be used as a pressure relief gas extraction pipeline for the working face goaf 21, achieving dual uses of one well. Coalbed methane is pre-extracted before the working face is mined to eliminate the danger of coal seam gas outburst; when the working face is mined, free gas in the goaf is extracted to reduce the gas concentration of the working face; that is, one end of the horizontal section 4 of the ground horizontal well is connected to a connecting horizontal well, and a perforation hole 22 is opened on the connecting horizontal well, wherein the coal seam pressure relief desorption gas and the coal seam goaf gas can enter the extraction pipeline 12 through the perforation hole 22.

[0068] It should be noted that the installation steps of the gas extraction pipeline are as follows: connect one end of the underground drilling section 6 to the underground extraction pipeline 12, and the coal seam decompression desorbed gas and the coal seam goaf gas enter through the perforations 22 on the connected horizontal well, and then enter the underground extraction pipeline 12 through the horizontal section 4 of the ground horizontal well and the underground drilling section 6. Among them, the mining area return air tunnel 16, the mining area track tunnel 17, the return air chute 19, and the track chute 20 shown in Figure 7 are all commonly used tunnels in coal mines. This application can use these tunnels to construct underground drilling.

[0069] Example 3

[0070] This application takes the connection between the end of a horizontal well and the downhole drilling site as an example, that is, when the connection point is at the horizontal well target point B, the B end (the back end of the horizontal well) is connected to point 7-3. The construction steps of the horizontal well are as follows. According to the different construction sequences of the surface horizontal well and the downhole drilling, the present invention discloses two construction methods, of which the first construction steps are as follows: (refer to Figure 8)

[0071] A1. Determine the trajectory of the "ㄣ"-shaped horizontal well based on the distribution of coal seams in the target block of the mine, ground construction conditions, and underground tunnel locations;

[0072] A2. Complete the ground horizontal well drilling construction;

[0073] A3. Reinforce the tunnel at the location of the underground drilling opening;

[0074] A4. Connect a magnetic rotary transmitter short circuit to the front end of the drill pipe of the directional drill rig. Set up a data receiver in the drilling site. Run a magnetic probe outside the horizontal well docking point. The magnetic probe is connected to the ground monitoring host via a cable. The monitoring host and receiver are connected via the mine industrial Ethernet ring network.

[0075] A5. During downhole drilling, magnetic rotation data is collected and the relative position between the drill bit and the connection point is analyzed. The data is transmitted in real time to a receiver at the downhole drilling site via industrial Ethernet. Directional drilling of the downhole drilling tool face is adjusted in real time based on the relative position data until a connection is made.

[0076] A6. Run a drillable bridge plug from the horizontal well to the designed docking point;

[0077] A7. Drilling and cementing casing in the well;

[0078] A8. Casing and cementing are performed in the main borehole of the horizontal well, and staged fracturing is performed;

[0079] A9. Drill holes in the butt joint section from downhole, and drill floating collars, float shoes, and drillable bridge plugs from the horizontal well to achieve secondary connectivity.

[0080] A10. Automatically drain water from the underground borehole and automatically extract gas from the surface wellhead, realizing automatic drainage and production without a pump.

[0081] The second construction method is as follows: Method 2 is to first construct an underground borehole, and then construct a ground horizontal well to connect it (see Figure 9):

[0082] B1. Determine the trajectory of the "ㄣ"-shaped horizontal well based on the distribution of coal seams in the target area of ​​the mine, ground construction conditions, and underground tunnel locations;

[0083] B2. First, reinforce the tunnel at the location of the underground drilling opening;

[0084] B3: Use a directional drill to drill downhole, cement the well with casing after drilling, then expand the hole and create a cavity in the target layer of the horizontal well. After the cavity is created, install a pressure gauge and a rotary blowout preventer at the hole mouth;

[0085] B4. When constructing a horizontal well on the ground, when drilling to 120m from the target docking point, the drill is pulled out and a magnetic transmitter is installed. A data receiver is set up at the well site. A magnetic probe is lowered into the hole at the location of the hole. The magnetic probe is connected to the monitoring host via a cable. The monitoring host and the receiver are connected via the mine industrial Ethernet ring network.

[0086] B5. Continuing construction of the surface horizontal well, the downhole monitoring host collects magnetic rotation data and analyzes the relative position of the drill bit and the connection point. This data is transmitted in real time to a surface well site receiver via industrial Ethernet. Directional drilling of the tool face is adjusted in real time based on the relative position data until a connection is achieved.

[0087] B6. Run a drillable bridge plug from the horizontal well to the docking point;

[0088] B7. Casing cementing in horizontal wells and performing staged fracturing;

[0089] B8. Drill the floating collar, float shoe, and drillable bridge plug from the horizontal well to achieve secondary connectivity;

[0090] B9. Automatically drain water from the underground borehole and automatically extract gas from the surface wellhead, realizing automatic drainage and production without a pump.

[0091] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A coal mine area coal bed methane horizontal well drainage gas production device, comprising a ground horizontal well and an underground drilling section (6), characterized in that: The horizontal section (4) of the ground horizontal well is connected to the downhole drilling section (6), and the connection point is located at the lowest elevation of the horizontal section of the horizontal well. The downhole drilling section (6) is an upward inclined borehole with an inclination angle greater than 45° and less than 90°. The connection point between the horizontal section (4) of the ground horizontal well and the downhole drilling section (6) is located at the A end, the middle end or the B end of the horizontal section of the ground horizontal well; The other end of the downhole drilling section (6) is connected to a gas-water-slag separation device (15) located in a downhole drilling site (5), wherein the downhole drilling site (5) is located below the ground horizontal well section (4) and the downhole drilling section (6), and the gas-water-slag separation device (15) is connected to a downhole drainage pipeline (13); The orifice of the ground horizontal well section (4) is connected to a ground gas extraction device (14) located in an underground drilling site (5). The underground drilling site (5) is located below the ground horizontal well section (4) and the underground drilling section (6). The ground gas extraction device (14) and the gas-water-slag separation device (15) are both connected to a monitoring host via a mine industrial Ethernet ring network communication.

2. A coal mine area coalbed methane horizontal well drainage gas production device according to claim 1, characterized in that: The gas-water-slag separation device (15) is also connected to an underground extraction pipeline (12), and one end of the horizontal section (4) of the ground horizontal well is connected to the connected horizontal well. The connected horizontal well is provided with a perforation hole (22), wherein gas desorbed by coal seam pressure relief and gas in the coal seam goaf can enter the extraction pipeline (12) through the perforation hole (22).

3. A coal mine area coalbed methane horizontal well drainage gas production device according to claim 2, characterized in that: The connecting horizontal wells include an A-end connecting horizontal well (9), an intermediate connecting horizontal well (10) and a B-end connecting horizontal well (11); When the connection point between the horizontal section (4) of the ground horizontal well and the downhole drilling section (6) is located at the A end of the horizontal section of the ground horizontal well, the tail end of the horizontal section (4) of the ground horizontal well is connected to the A end and connected to the horizontal well (9); When the connection point between the horizontal section (4) of the ground horizontal well and the downhole drilling section (6) is located at the middle end of the horizontal section of the ground horizontal well, the tail end of the horizontal section (4) of the ground horizontal well is connected to the middle connecting horizontal well (10); When the connection point between the horizontal section (4) of the ground horizontal well and the downhole drilling section (6) is located at the B end of the horizontal section of the ground horizontal well, the tail end of the horizontal section (4) of the ground horizontal well is connected to the B end and connected to the horizontal well (11).

4. The coal mine area coal bed methane horizontal well drainage gas production device according to claim 1, characterized in that: The bottom of the surface gas extraction device (14) is provided with an air inlet (14-1) connected to the horizontal section (4) of the surface horizontal well, and a gas solenoid valve (14-2) is also provided at the air inlet (14-1). The other end of the surface gas extraction device (14) is provided with a surface gas outlet (14-6), wherein an electric gas regulating valve (14-4) and an electronic gas flow meter (14-5) are provided at the surface gas outlet (14-6). The surface gas extraction device (14) is also provided with an electronic barometer (14-3).

5. The drainage and gas production device for coalbed methane horizontal wells in coal mining areas according to claim 1 is characterized by: A water-slag separation chamber (15-5) is provided on the inner side of the gas-water-slag separation device (15), wherein the bottom of the water-slag separation chamber (15-5) is connected to the underground drilling section (6) through the inlet (15-1); a gas outlet (15-12) and a water outlet (15-15) are provided on one side of the gas-water-slag separation device (15), wherein the water outlet (15-15) is connected to the underground drainage pipeline (13); and a slag discharge port (15-6) is provided at the bottom of the water-slag separation chamber (15-5).

6. A coal mine area coal bed methane horizontal well drainage gas production device according to claim 5, characterized in that: The inlet (15-1) is provided with an electronic water pressure gauge (15-3) and a main electromagnetic valve (15-4); the gas outlet (15-12) is provided with a second gas electromagnetic valve (15-13) and a second electronic gas flow meter (15-14); the water outlet (15-15) is provided with a water electromagnetic valve (15-16) and an electronic water flow meter (15-17); and the slag discharge port (15-6) is provided with a slag discharge electromagnetic valve (15-7).

7. The device for draining and producing coalbed methane from a horizontal well in a coal mine according to claim 5, characterized in that: A filter mesh opening (15-8) is also provided inside the gas-water-slag separation device (15) and located above the water-slag separation chamber (15-5), wherein an electric oil nozzle (15-9) is provided above the filter mesh opening (15-8), and a gas-water separation chamber (15-10) is also provided inside the gas-water-slag separation device (15) and located above the water-slag separation chamber (15-5).

8. A method for drainage and gas production using a drainage and gas production device for coalbed methane horizontal wells in a coal mine area according to any one of claims 1 to 7, characterized in that: The steps include: S1. Open the main solenoid valve, and the return fluid enters the gas-water-slag separation device from the drill hole, first entering the water-slag separation chamber at the bottom of the device, and realizes water-slag separation through gravity separation and filter screen; S2. Open the electric oil nozzle, and the liquid enters the gas-water separation chamber from the water-slag separation chamber. Due to the sudden decrease in pressure, the coalbed methane dissolved in the water is precipitated; S3, open the second gas solenoid valve, and the precipitated coalbed methane enters the extraction pipeline under the action of negative pressure; S4, open the water solenoid valve, and water enters the drainage pipe under the action of gravity; S5. When the wellhead starts to produce gas after the casing pressure is lifted, the gas solenoid valve 1 is opened, and the coalbed methane enters the ground gas pipeline under the action of pressure and buoyancy; S6. Analyze the changing rules of the electronic air pressure meter, electronic air flow meter, electronic water pressure meter, and electronic water flow meter in real time, and adjust the production speed by adjusting the opening of the electric air regulating valve and the electric oil nozzle; S7. When slag discharge is required, first close the gas solenoid valve 1, gas solenoid valve 2, water solenoid valve, electric oil nozzle and main solenoid valve in sequence, and open the slag discharge solenoid valve to discharge slag; S8. After the slag discharge is completed, immediately close the slag discharge solenoid valve, and then open the gas solenoid valve 1, gas solenoid valve 2, water solenoid valve, electric oil nozzle and main solenoid valve in sequence to resume normal water discharge and gas production operations.

9. A method for producing gas from coalbed methane horizontal wells in coal mining areas according to claim 8, characterized in that: When the drainage and gas production are completed, the underground orifice is directly connected to the extraction pipeline. During the working face mining, the coal seam pressure relief gas from the working face and the gas from the goaf enter the extraction pipeline through the perforations, achieving dual use of one well.

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