A method for deep drainage of coal bed methane by horizontal well

Abstract

The application discloses a method for deeply pumping coal bed gas in a horizontal well and belongs to the technical field of pumping coal bed gas in a horizontal well. The purpose is to make the pump hanging position in the horizontal well as low as the landing point, the suction inlet of the pump can be deeply in the horizontal well, and the pump can continuously and stably operate. The following technical scheme is adopted: first, according to the actually drilled track data of the horizontal well, the pump hanging position, the position of the second suction inlet and the position of the liquid inlet of the inner tube are determined; second, the horizontal well is cleaned; third, a sand prevention device for the horizontal well is assembled and connected below the pump; fourth, the horizontal well is smoothly lowered; fifth, a tubing well mouth hanger is connected and is seated in the well mouth large four-way joint; sixth, a ground pumping equipment is installed; seventh, pressure test is conducted for 20 minutes; eighth, the well is washed with clean water and the downhole unit is cleaned; ninth, the equipment is started to pump out liquid, and the pump efficiency is more than 80%, which is qualified. The application is used for pumping coal bed gas in a horizontal well.

Description

Technical Field

[0001] The invention discloses a method for deep extraction of coalbed methane through a horizontal well, belonging to the technical field of horizontal well extraction of coalbed methane. Background Art

[0002] The gas volume of a single coalbed methane pre-extraction horizontal well gradually decreases over time. To further release reservoir energy, the pump hanger needs to be lowered further. However, after the pump hanger is lowered, powder and sand spitting out from the wellbore affects the continuous and stable operation of the downhole pump. Furthermore, over time, the horizontal section fluctuates erratically, and sand bridges easily form at the troughs, affecting extraction efficiency. Currently, the lowest pump hanger position in operational horizontal wells is 80-85° inclination, with a flow pressure of 0.1-0.15 MPa from the coal seam, preventing further release of reservoir energy. How to lower the pump hanger while ensuring continuous and stable pump operation, allowing water from deeper depths in the horizontal well to be further discharged and coalbed methane to be released, thereby increasing production, is a major challenge in the industry. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for deep extraction of coalbed methane from horizontal wells, so that the pump hanging position in the horizontal well can be as low as the landing point, the pump suction port can be deep into the horizontal well, and can operate continuously and stably.

[0004] To achieve the above object, the present invention adopts the following technical solution: a method for deep extraction of coalbed methane from a horizontal well, comprising the following steps:

[0005] The first step is to determine the pump hanger position based on the actual horizontal well drilling trajectory data: the horizontal well landing point or within 50 meters above the landing point. The second suction port of the horizontal well sand control device is located 10 to 80 meters beyond the first perforated section near the wellbore along the horizontal drilling direction. The inner tube fluid inlet is located between the first and second suction ports of the horizontal well sand control device.

[0006] The second step is to clean the horizontal well;

[0007] The third step is to assemble the horizontal well sand control device according to the positions of the components determined in the first step, connect the horizontal well sand control device to the bottom of the pump, and connect the relevant pipe string and cable to the top of the pump;

[0008] Step 4: Smoothly lower the device connected in step 3 into the horizontal well at a speed not exceeding 200 m / h.

[0009] Step 5: Connect the tubing wellhead hanger and place it into the wellhead big four-way, tighten and install all the big four-way bolts and jackscrews;

[0010] Step 6: Install the surface extraction equipment, connect the high-pressure water line, and fill the surface facility water tank with water;

[0011] Step 7: Test pressure for 20 minutes;

[0012] Step 8: Use clean water to wash the well. After the circulation is established, wash the well continuously for 30 minutes to clean the downhole unit.

[0013] The ninth step is to start the pumping equipment until liquid is discharged and test the pump efficiency. A pump efficiency of more than 80% is qualified.

[0014] Preferably, in the first step, the vertical depths at the positions of the first suction port and the second suction port are both higher than the vertical depth at the position of the liquid inlet.

[0015] Preferably, in the second step, the process of cleaning the horizontal well is: first pull out all the pipes in the horizontal well, then use a diameter gauge to clear the well to 30-50 meters behind the second suction port position of the horizontal well sand control device, and then bailing sand to the bottom of the artificial well.

[0016] Preferably, the method further includes a tenth step, in which, after six months of operation, all equipment and tubing lowered into the horizontal well are pulled out for overhaul. During the overhaul, the silt in the sand control device for the horizontal well is cleaned, and the silt situation in the well is judged based on the amount of silt therein. If the sand accumulation is serious, the sand is bailed out, and then all equipment is lowered into the horizontal well to continue operation, and the next overhaul time is determined.

[0017] Preferably, the pump is a hydraulic tube pump.

[0018] In the above steps, the horizontal well sand control device used includes an outer tube and an inner tube, the front end of the outer tube is open, and the tail end is connected to the outer tube plug, the front end of the inner tube is open, and the tail end is connected to the inner tube plug, the outer tube is sleeved on the outside of the inner tube, and the inner wall of the outer tube and the outer wall of the inner tube are between the diversion channel, the outer tube sieve holes are densely covered on the tube wall at both ends of the outer tube, and the inner tube sieve holes are densely covered on the tube wall in the middle of the inner tube;

[0019] The inner wall of the outer tube is evenly distributed with multiple sections of annular grooves, which serve as sand prevention steps;

[0020] The front end of the inner tube is flush with the front end of the outer tube, and the rear end is located at the outer tube sieve hole at the rear end of the outer tube;

[0021] The outer tube sieve hole at the front end of the outer tube is the first suction port, the outer tube sieve hole at the rear end of the outer tube is the second suction port, and the inner tube sieve hole on the inner tube is the inner tube liquid inlet.

[0022] Preferably, the outer pipe includes a first oil pipe, a second oil pipe and an outer screen pipe. Multiple first oil pipes are arranged in a row from front to back. A second oil pipe is connected between each of two adjacent first oil pipes. The outer diameter of the second oil pipe is adapted to the inner diameter of the first oil pipe. Both ends of the second oil pipe are respectively inserted into the end of the adjacent first oil pipe. The two first oil pipes at both ends are respectively connected to an outer screen pipe. The outer screen pipe is densely covered with outer pipe sieve holes. The outer screen pipe at the tail end is connected to the outer pipe plug. The inner wall of the first oil pipe and the thickness of the two adjacent second oil pipes form a sand control step.

[0023] Preferably, the inner tube includes a third oil tube, a fourth oil tube and an inner screen tube, one end of the third oil tube is a front end, and the other end is connected to one end of the inner screen tube, the other end of the inner screen tube is connected to one end of the fourth oil tube, and the other end of the fourth oil tube is a tail end, which is connected to the inner tube wire plug, and the inner screen tube is densely covered with inner tube sieve holes.

[0024] Preferably, both the outer tube and the inner tube are hoses.

[0025] Preferably, the third oil pipe and the fourth oil pipe are both formed by connecting multiple oil pipes in sequence.

[0026] Compared with the prior art, the present invention has the following beneficial effects.

[0027] 1. The present invention realizes that the pump hanging position is lowered to the landing point. After the suction port penetrates deep into the horizontal section, the pump can still run continuously and stably, so that the coalbed methane in the horizontal well is further released, greatly improving the output.

[0028] 2. In the sand control device for horizontal wells, a diversion channel is formed between the outer tube and the inner tube. The accumulated liquid entering from both ends of the outer tube enters the inner tube through the diversion channel, avoiding the influence of sand bridges in the horizontal section on the extraction effect.

[0029] 3. In the sand control device for horizontal wells, after the accumulated liquid enters the diversion channel from both ends of the outer tube, the accumulated liquid flows slowly in the diversion channel and is not affected by gas disturbance, which is conducive to the sedimentation of silt. At the same time, the sand will be deposited through multiple sections of sand control steps, effectively preventing silt from entering the working pump, optimizing the working environment of the pump, providing technical support for the discharge of mixed sand and accumulated liquid in deeper horizontal sections, and improving production capacity. In general horizontal wells, the pump can run stably and continuously for more than half a year, reducing the frequency of maintenance and replacement of the working pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments.

[0031] Figure 1 This is a schematic diagram of the positions of the pump and the horizontal well sand control device after being lowered into the horizontal well.

[0032] Figure 2 It is a structural schematic diagram of the sand control device for horizontal wells in the present invention.

[0033] In the figure: 1 is an outer pipe, 11 is an outer pipe sieve hole, 12 is a first oil pipe, 13 is a second oil pipe, 14 is an outer sieve pipe, 2 is an inner pipe, 21 is an inner pipe sieve hole, 22 is a third oil pipe, 23 is a fourth oil pipe, 24 is an inner sieve pipe, 3 is an outer pipe thread plug, 4 is an inner pipe thread plug, 5 is a diversion channel, 6 is a sand control step, 7 is a pump, 8 is a sand control device for horizontal wells, and 9 is a first perforating section. DETAILED DESCRIPTION

[0034] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] The present invention provides the following examples.

[0036] like Figure 1 As shown, the present invention provides a method for deep extraction of coalbed methane from a horizontal well, comprising the following steps:

[0037] The first step is to determine, based on the actual drilling trajectory data of the horizontal well, the position of the pump 7 at the horizontal well landing point or within 50 meters above the landing point. The second suction port of the horizontal well sand control device 8 is located a distance, such as 10 to 80 meters, beyond the first perforation section 9 near the wellbore in the horizontal drilling direction. The position of the inner tube liquid inlet is located between the first and second suction ports of the horizontal well sand control device 8. The vertical depths of the first and second suction ports are both higher than the vertical depth of the liquid inlet.

[0038] The pump 7 is a rodless pump, specifically a hydraulic tube pump, model YFWGB70-44-3.7.

[0039] The second step is to clean the horizontal well. The cleaning process is as follows: first, pull out all the pipes in the horizontal well, then use a drift gauge to clear the well to 30-50 meters behind the second suction port position of the horizontal well sand control device 8, and then bailing sand to the bottom of the artificial well;

[0040] The third step is to assemble the horizontal well sand control device 8 according to the positions of the components determined in the first step, and connect the horizontal well sand control device 8 to the bottom of the pump 7. The top of the pump 7 is connected to the relevant pipe string and cables, including the pressure gauge holder, electronic pressure gauge, central pipe, etc.;

[0041] Step 4: Smoothly lower the device connected in step 3 into the horizontal well at a speed not exceeding 200 m / h. During the process, the horizontal well sand control device 8 is lowered every 100 m, and clean water is poured into the outer pipe 1 and the inner pipe 2 to ensure that the fixed valve on the pump 7 is in the closed state.

[0042] Step 5: Connect the tubing wellhead hanger and place it into the wellhead big four-way, tighten and install all the big four-way bolts and jackscrews;

[0043] Step 6: Install the surface extraction device, connect the high-pressure water line, and fill the surface facility water tank with water;

[0044] Step 7: Test pressure for 20 minutes;

[0045] Step 8: Use clean water to wash the well. After the circulation is established, wash the well continuously for 30 minutes to clean the downhole unit.

[0046] The ninth step is to start the pumping equipment until the liquid is discharged and test the pump efficiency. The pump efficiency is more than 80%, which is qualified.

[0047] Step 10: After six months of operation, all equipment and tubing lowered into the horizontal well are removed for overhaul. During the overhaul, the silt in the horizontal well sand control device 8 is cleaned, and the downhole silt situation is determined based on the amount of silt in the device. If the accumulated sand occupies more than half of the cross-section of the diversion channel, the sand is bailed out, and then all equipment is lowered into the horizontal well to continue operation, and the next overhaul time is determined.

[0048] like Figure 2 As shown, the horizontal well sand control device 8 includes an outer tube 1 and an inner tube 2. The front end of the outer tube 1 is open, and the tail end is connected to the outer tube plug 3. The front end of the inner tube 2 is open, and the tail end is connected to the inner tube plug 4. The outer tube 1 is sleeved on the outside of the inner tube 2. The inner wall of the outer tube 1 and the outer wall of the inner tube 2 are provided with a diversion channel 5. The outer tube sieve holes 11 are densely distributed on the tube walls at both ends of the outer tube 1, and the inner tube sieve holes 21 are densely distributed on the tube wall in the middle of the inner tube 2.

[0049] The inner wall of the outer tube 1 is evenly distributed with multiple annular grooves, which serve as sand prevention steps 6;

[0050] The front end of the inner tube 2 is flush with the front end of the outer tube 1, and the rear end is located at the outer tube sieve hole 11 at the rear end of the outer tube 1;

[0051] The outer tube sieve hole 11 at the front end of the outer tube 1 is the first suction port, the outer tube sieve hole 11 at the rear end of the outer tube 1 is the second suction port, and the inner tube sieve hole 21 on the inner tube 2 is the inner tube liquid inlet.

[0052] The outer pipe 1 includes a first oil pipe 12, a second oil pipe 13 and an outer screen pipe 14. Multiple first oil pipes 12 are arranged in a row from front to back. A second oil pipe 13 is connected between each adjacent first oil pipe 12. The outer diameter of the second oil pipe 13 is adapted to the inner diameter of the first oil pipe 12. Both ends of the second oil pipe 13 are respectively inserted into the end of the adjacent first oil pipe 12. The two first oil pipes 12 at both ends are respectively connected to an outer screen pipe 14. The outer screen pipe 14 is densely covered with outer pipe sieve holes 11. The outer screen pipe 14 at the tail end is connected to the outer pipe plug 3. The inner wall of the first oil pipe 12 and the pipe thickness of the two adjacent second oil pipes 13 form a sand control step 6.

[0053] The inner tube 2 includes a third oil tube 22, a fourth oil tube 23 and an inner screen tube 24. One end of the third oil tube 22 is a front end, and the other end is connected to one end of the inner screen tube 24. The other end of the inner screen tube 24 is connected to one end of the fourth oil tube 23. The other end of the fourth oil tube 23 is a tail end, which is connected to the inner tube plug 4. The inner screen tube 24 is densely covered with inner tube sieve holes 21.

[0054] The outer tube 1 and the inner tube 2 are both hoses.

[0055] The third oil pipe 22 and the fourth oil pipe 23 are both formed by connecting multiple oil pipes in sequence.

[0056] In the present invention, as described in the first step, after the pump hanging position, the positions of the second suction port, and the inner tube liquid inlet are determined, the total length of the outer tube 1 and the length of the third oil tube 22 in the horizontal well sand control device 8 are determined. The specific lengths of the first oil tube 12, the second oil tube 13, the outer screen tube 14, the fourth oil tube 23, and the inner screen tube 24 are then specifically allocated and designed. During the specific design process, the pump hanging position, the second suction port, and the inner tube liquid inlet can also be fine-tuned according to the length of the existing oil tube.

[0057] During the construction process of the present invention, the following requirements and precautions must be met.

[0058] Ground process construction requirements are:

[0059] (1) Carefully remove foreign matter such as iron filings, rust, welding slag, etc. from equipment, valves, and pipelines to prevent large particles from clogging the nozzle.

[0060] (2) Ground pipelines must be tested for tightness to ensure that there is no leakage in the process.

[0061] (3) The wellhead and ground processes should be subjected to necessary anti-corrosion and thermal insulation as required.

[0062] During construction, please pay attention to:

[0063] (1) To ensure a successful operation, the weight indicator must be installed when raising and lowering the pipe string, and the operation must be smooth. It is strictly forbidden to brake or release suddenly, and it is strictly forbidden to drop objects into the well.

[0064] (2) The well washing fluid must be clean, the downhole tools and oil pipes must not fall to the ground and must be kept clean.

[0065] (3) Downhole equipment and tools must be inspected in detail before being lowered into the well to ensure that the model is correct and the oil pipe connections are sealed reliably.

[0066] (4) Carefully check the oil pipes in the outer pipe 1 and the inner pipe 2 to ensure they are intact and free of defects such as damage, cracks, holes, etc.

[0067] (5) All external oil pipes, short-circuits, joints, internal oil pipes and adjustment short-circuits from the pump working cylinder to the wellhead must be passed by oil pipe gauges and rely on their own weight. Those that fail to pass are strictly prohibited from being lowered into the well. External pipe 1 must be passed by a Φ50mm gauge.

[0068] (6) The oil pipes lowered into the well should be measured one by one and recorded. During the process of lowering the pipe string, it is strictly forbidden to lower the pipe rigidly without getting stuck in the middle.

[0069] (7) Each oil pipe joint must be coated with high-pressure sealing grease (applied to the male buckle) or wrapped with polytetraethylene tape, and tightened to the specified torque.

[0070] (8) The inner tube is screwed manually without hydraulic clamps. During the lowering process, the thread must be fully tightened and the lowering speed must be controlled.

[0071] The present invention has been specifically applied to actual horizontal well reconstruction, with very good results, which will be specifically illustrated below with examples.

[0072] The reconstructed well is located in Xuchang City, Henan Province. Part of the actual drilling trajectory data of this horizontal well is shown in Table 1. The positions of the pump hanger, the first suction port, the second suction port, and the inner tube liquid inlet determined according to the actual drilling trajectory data are all marked.

[0073]

[0074] Table 1 Part of the actual drilling trajectory data of horizontal wells

[0075] When cleaning the horizontal well, all the pipes in the horizontal well were first removed, then the well was cleared to 1,100 meters using a bore gauge, and then sand was bailed to the bottom of the artificial well.

[0076] In the horizontal well sand control device 8 used in this horizontal well, the outer screen pipe 14 is a 2.0m long drilled screen pipe with an outer pipe screen hole 11 of 8mm in diameter. The first oil pipe 12 is an 89 oil pipe with a length of 5.5m and an outer diameter of 88.9mm. The second oil pipe 13 is a 73 oil pipe with a length of 0.5m and an outer diameter of 73mm. The third oil pipe 22 is formed by connecting 6 oil pipes with a length of 7m and an outer diameter of 36mm. The fourth oil pipe 23 is also formed by connecting 6 oil pipes with a length of 7m and an outer diameter of 36mm. The inner screen pipe 34 is a 6m long screen pipe with an outer diameter of 36mm. The total length of the horizontal well sand control device 8 is 100 meters, and the total length of the inner pipe 2 is 90 meters.

[0077] In addition, the pump is a YFWGB70-44-3.7 hydraulic tube pump with a stroke of 3.7m, a stroke rate of 0-3 times / min, and a theoretical displacement of 31m 3 / d, maximum outer diameter 101.2mm, length 8500mm, and well depth 948m.

[0078] There are also other accessories such as Ф73mm 939.5m long pressure gauge holder, Ф73mm flat oil pipe hanger, etc.

[0079] The foregoing description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be readily conceived by a person skilled in the art within the technical scope disclosed herein should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for deep extraction of coalbed methane from a horizontal well, characterized in that The following steps are involved: The first step is to determine the pump hanging position as the horizontal well landing point or within 50 meters above the landing point based on the horizontal well actual drilling trajectory data, the position of the second suction port in the horizontal well sand control device (8) is: 10 meters to 80 meters beyond the first perforation section (9) near the wellbore along the horizontal section drilling direction, and the position of the inner pipe liquid inlet is between the first suction port and the second suction port in the horizontal well sand control device (8); The second step is to clean the horizontal well; The third step is to assemble the horizontal well sand control device (8) according to the positions of the components determined in the first step, and connect the horizontal well sand control device (8) to the bottom of the pump (7), and connect the relevant pipe string and cable to the top of the pump (7); Step 4: Smoothly lower the device connected in step 3 into the horizontal well at a speed not exceeding 200 m / h. Step 5: Connect the tubing wellhead hanger and place it into the wellhead big four-way, tighten and install all the big four-way bolts and jackscrews; Step 6: Install the surface extraction equipment, connect the high-pressure water line, and fill the surface facility water tank with water; Step 7: Test pressure for 20 minutes; Step 8: Use clean water to wash the well. After the circulation is established, wash the well continuously for 30 minutes to clean the downhole unit. The ninth step is to start the pumping equipment until the liquid is discharged and test the pump efficiency. The pump efficiency should be above 80% to pass the test. The horizontal well sand control device (8) comprises an outer tube (1) and an inner tube (2), wherein the outer tube (1) has an opening at the front end and is connected to an outer tube plug (3) at the rear end, and the inner tube (2) has an opening at the front end and is connected to an inner tube plug (4) at the rear end, the outer tube (1) is sleeved on the outside of the inner tube (2), a flow guide channel (5) is formed between the inner wall of the outer tube (1) and the outer wall of the inner tube (2), outer tube sieve holes (11) are densely distributed on the tube wall at both ends of the outer tube (1), and inner tube sieve holes (21) are densely distributed on the tube wall in the middle of the inner tube (2); The inner wall of the outer tube (1) is evenly distributed with multiple annular grooves, which serve as sand prevention steps (6); The front end of the inner tube (2) is flush with the front end of the outer tube (1), and the rear end is located at the outer tube sieve hole (11) at the rear end of the outer tube (1); The outer tube sieve hole (11) at the front end of the outer tube (1) is the first suction port, the outer tube sieve hole (11) at the rear end of the outer tube (1) is the second suction port, and the inner tube sieve hole (21) on the inner tube (2) is the inner tube liquid inlet.

2. The method for deep extraction of coalbed methane from a horizontal well according to claim 1, characterized in that: In the first step, the vertical depths at the positions of the first suction port and the second suction port are both higher than the vertical depth at the position of the liquid inlet.

3. The method for deep extraction of coalbed methane from a horizontal well according to claim 1, characterized in that: In the second step, the process of cleaning the horizontal well is as follows: first, all the pipes in the horizontal well are pulled out, then the well is cleared with a diameter gauge to 30-50 meters behind the second suction port of the horizontal well sand control device (8), and then the sand is bailed to the bottom of the artificial well.

4. The method for deep extraction of coalbed methane from a horizontal well according to claim 1, characterized in that: The tenth step is also included. After half a year of operation, all equipment and pipes lowered into the horizontal well are taken out for maintenance. During the maintenance, the silt in the horizontal well sand control device (8) is cleaned, and the silt situation in the well is judged based on the amount of silt in the device. If the sand accumulation is serious, the sand is bailed out, and then all equipment is lowered into the horizontal well to continue operation, and the next maintenance time is determined.

5. The method for deep extraction of coalbed methane from a horizontal well according to claim 1, characterized in that: The pump (7) is a hydraulic tube pump.

6. The method for deep extraction of coalbed methane from a horizontal well according to claim 1, characterized in that: The outer pipe (1) comprises a first oil pipe (12), a second oil pipe (13) and an outer screen pipe (14). A plurality of first oil pipes (12) are arranged in a row from front to back. A second oil pipe (13) is connected between two adjacent first oil pipes (12). The outer diameter of the second oil pipe (13) is adapted to the inner diameter of the first oil pipe (12). Both ends of the second oil pipe (13) are respectively fitted into the ends of the adjacent first oil pipes (12). The two first oil pipes (12) at both ends are respectively connected to an outer screen pipe (14). The outer screen pipe (14) is densely covered with outer pipe sieve holes (11). The outer screen pipe (14) at the tail end is connected to the outer pipe plug (3). The inner wall of the first oil pipe (12) and the thickness of the two adjacent second oil pipes (13) form a sand control step (6).

7. The method for deep extraction of coalbed methane from a horizontal well according to claim 1 or 6, characterized in that: The inner tube (2) comprises a third oil tube (22), a fourth oil tube (23) and an inner screen tube (24), one end of the third oil tube (22) being a front end and the other end being connected to one end of the inner screen tube (24), the other end of the inner screen tube (24) being connected to one end of the fourth oil tube (23), the other end of the fourth oil tube (23) being a tail end and being connected to the inner tube plug (4), and the inner screen tube (24) being densely covered with inner tube sieve holes (21).

8. The method for deep extraction of coalbed methane from a horizontal well according to claim 1 or 6, characterized in that: The outer tube (1) and the inner tube (2) are both hoses.

9. The method for deep extraction of coalbed methane from a horizontal well according to claim 7, characterized in that: The third oil pipe (22) and the fourth oil pipe (23) are both formed by connecting multiple oil pipes in sequence.

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