Coalbed methane horizontal well reformation method based on controllable shock wave

Abstract

The application discloses a coal bed gas horizontal well yield increasing method based on controllable shock waves, which comprises the following steps: S1, selecting a group of upward directional drilling construction sites in a horizontal well service underground roadway of a mine, and the directional drilling target positions are respectively coal seams opposite to a plurality of positions of a horizontal well perforation point away from the horizontal well; S2, drilling a hole at a target point A meters away, judging whether the hole is in a fracturing influence range and a horizontal well drainage influence range; if the hole target point is in the fracturing influence range, controllable shock wave construction is performed; if the hole target point is not in the fracturing influence range, construction is performed on other target points again until a target point in the fracturing influence range is found and the construction is stopped; S3, drilling and judgment are performed on each horizontal well perforation by using S2 until target points in the fracturing influence range are found for all the horizontal well perforations, and controllable shock wave construction is performed. The application has the beneficial effects of improving the yield of a coal bed gas well, further expanding a seepage channel and prolonging the production life of the coal bed gas well.

Description

Technical Field

[0001] The present invention relates to the field of energy mining, and in particular to a method for increasing the production of a coalbed methane horizontal well. Background Art

[0002] Coalbed methane (gas) disasters are a major threat to coal mine safety production in my country. With the continuous deepening of coal mining, coalbed methane (gas) disasters in coal mines have become more serious.

[0003] Due to factors such as formation pressure and the inherent gas pressure of the coal seam, fracturing in soft, low-permeability coalbed methane wells can create unsustainable fractures, resulting in rapid drainage attenuation and low production. While CN107956505A, a method for increasing permeability in underground coal mine drilling using controlled shock wave technology, is currently available, the impact wave technology was implemented without prior investigation, resulting in poor results and still low production.

[0004] The information disclosed in this background section is only intended to enhance understanding of the overall background of the invention and should not be considered as an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: how to solve the current problem of rapid attenuation and low output of coalbed methane.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] A method for increasing the production of a coalbed methane horizontal well based on a controllable shock wave, wherein the horizontal section of the surface well includes N horizontal well perforations, where N is an integer greater than 1, and is characterized by comprising the following steps:

[0008] S1: A group of upward directional drilling construction sites are selected in the underground roadway of the horizontal well service mine. The directional drilling target locations are the coal seams at the distances of A meters, AB meters, A-2B meters, A-3B meters, and A-4B meters from the horizontal well perforation point.

[0009] S2: First, drill a hole at the target point A meters away. During the drilling process, determine whether it has entered the fracturing influence range. After the hole enters the coal seam, determine whether it is within the horizontal well drainage influence range.

[0010] If the drilling target is located within the fracturing influence range, controlled shock wave construction is performed;

[0011] If the drilling target point is not within the fracturing influence range, drill again at the target point AB meter, A-2B meter, A-3B meter, or A-4B meter until the target point within the fracturing influence range is found;

[0012] S3: For each horizontal well perforation, drilling is performed according to step S2, and judgment is made until all horizontal well perforations find the target position within the fracturing influence range, and controllable shock wave construction is performed.

[0013] Preferably, in step S2, the method for drilling a hole at a target point A meters is as follows: start drilling 15-30 meters, install casing and orifice sealing gate valve, and inject cement slurry into the hole to seal it; after the cement solidifies, re-drill the hole to a point 1.5-2.5 meters away from the coal seam bottom plate and end at a point 1.5-2.5 meters away from the coal seam roof plate after the hole penetrates the coal.

[0014] Preferably, during the construction process, the water samples and drill cuttings produced by the drilling are tested and analyzed to determine whether they have entered the fracturing influence range. If there is fracturing fluid in the water sample and fracturing sand in the drill cuttings, then they have entered the fracturing influence range. If there is no fracturing fluid in the water sample and no fracturing sand in the drill cuttings, then they have not entered the fracturing influence range.

[0015] Preferably, after drilling into the coal seam, fixed-point closed sampling is carried out, and the gas content of the coal sample is measured to determine whether it is within the influence range of horizontal well drainage; if the coal sample is compared with the original gas in the coal seam and the gas content in the coal sample is reduced, it means that it has entered the influence range of horizontal well drainage; if the gas in the coal sample has not changed, it means that it has not entered the influence range of horizontal well drainage.

[0016] Preferably, the drilling sequence is to first drill the hole at the target point A meters away, and if it is determined to have entered the fracturing influence range, then perform controlled shock wave construction;

[0017] If the borehole at the target point A meters away does not enter the fracturing influence range, there are two situations:

[0018] Case 1: When it is determined that it is not within the influence range of drainage, the drilling is redesigned and the drilling target position is the coal seam within the range of A-2B meters;

[0019] The second case: when it is determined to be within the range of drainage influence but not within the range of fracturing influence, the drilling is redesigned and the drilling target position is the coal seam within the range of AB meters.

[0020] Preferably, after drilling at the construction target point A-2B meters, if it is determined that it has entered the fracturing influence range, controlled shock wave construction is performed;

[0021] If it does not enter the fracturing influence range, there are two situations:

[0022] When it is determined that the drilling is not within the impact range of drainage, the drilling target is redesigned and the coal seam is located within the range of A-4B meters;

[0023] When it is determined to be within the range of drainage influence but not within the range of fracturing influence, the drilling hole is redesigned, the drilling target position is the coal seam in the range of A-3B meters, and the original construction borehole is sealed and pressure measured.

[0024] Preferably, when the drilling hole at the construction target point AB meter position is judged to have entered the fracturing influence range, controlled shock wave construction is performed;

[0025] If it does not enter the fracturing influence range, there are two situations:

[0026] When it is determined that the drilling is not within the affected range of drainage, the drilling target point is the coal seam within the range of A-3B meters;

[0027] When it is determined that the area is affected by drainage but not by fracturing, the drilling hole is redesigned, the drilling target is located in the coal seam within the range of A-2B meters, and the original construction borehole is sealed and pressure measured;

[0028] Continue drilling at the target points A-3B meters and A-4B meters until the target point is found within the fracturing influence range.

[0029] A preferred method for performing controlled shock wave construction is as follows: After drilling, a controlled shock wave generator is delivered via a drilling rig to the layer where the fracturing sand or fracturing fluid is found. The sealing device is closed, and water is injected into the borehole through a reserved pipe. When the controlled shock wave generator detects that the water pressure has reached a set value, the shock wave operation is initiated.

[0030] Preferably, after the shock wave construction corresponding to the perforation of a horizontal well is completed, the changes in the drainage parameters before and after the shock are examined;

[0031] If the instantaneous gas volume and casing pressure increase, it indicates that the shock wave is effective; the shock wave construction can continue at the next horizontal well perforation point using the shock wave intensity W.

[0032] If the casing pressure decreases, it indicates that the shock wave intensity is too large, and the next horizontal well perforation point can be subjected to shock wave construction with a shock wave intensity of 0.8W;

[0033] If the instantaneous gas volume and casing pressure do not change, the next horizontal well perforation point can be subjected to shock wave construction using a shock wave intensity of 1.2W.

[0034] Adjust the impact intensity in time according to feedback to ensure the impact effect.

[0035] Preferably, before carrying out shock wave construction operations, surface well drainage and production construction personnel should be notified to always pay attention to drainage parameters such as bottom hole flow pressure, casing pressure, instantaneous gas production, etc.; if any abnormality occurs, the underground construction personnel should be notified.

[0036] The advantages of the present invention are:

[0037] The technical solution of this invention allows underground coal mine construction without affecting surface coalbed methane well production. Directional drilling is performed within the fracturing range, and controlled shock wave equipment is used to transform the fissures created by surface well fracturing. The fracturing fluid in the fissures propagates shock waves, altering the pressure distribution in the coal seam and breaking down the barriers between the fissures, thereby increasing coalbed methane production.

[0038] According to whether it is located in the fracturing influence range and the fracturing influence range, the target position of the next drilling is adjusted to avoid blind construction and improve drilling efficiency.

[0039] Adjust the impact intensity in time according to feedback to ensure the impact effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the structure of a method for increasing the production of a coalbed methane horizontal well based on controllable shock waves according to an embodiment of the present invention;

[0041] Figure 2 Schematic diagram of the drilling process according to an embodiment of the present invention;

[0042] Figure 3 1 is a flow chart of a method for increasing the production of a coalbed methane horizontal well based on controllable shock waves according to an embodiment of the present invention;

[0043] Numbers in the figure:

[0044] 1. Horizontal section of surface well; 2. Perforation of horizontal well; 3. Coal seams at different distances from horizontal well; 4. Exploration hole of fracturing impact zone; 5. Controllable shock wave construction hole; 6. Drilling and coring section; 7. 2-meter line of coal seam roof and floor. DETAILED DESCRIPTION

[0045] 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.

[0046] like Figure 1As shown, the horizontal section 1 of the surface well includes nine horizontal perforations 2. These perforations 2 are fractured, using high-pressure water flow to fracture and penetrate the underground rock formation, increasing the permeability and mobility of oil and gas. Fracturing sand is also injected into the horizontal perforations. After fracturing, gas accumulates within the horizontal perforations 2, and coalbed methane is extracted. Verifying and examining where the gas can be extracted into the horizontal section 1 of the surface well requires further investigation. Therefore, this example first examines the fracturing influence range (the area where the fracturing sand and fracturing fluid are located; the presence of fracturing sand or fracturing water indicates the pressure influence range; otherwise, it indicates whether the gas is within the pressure influence range) and the horizontal well production influence range (whether the gas is reduced; a reduction indicates the gas is within the production range; a lack of reduction indicates the gas is not within the production range). The horizontal well production influence range is larger than the fracturing influence range. When within the fracturing influence range, controlled shock wave operation can be performed to increase production.

[0047] Specifically, the method for increasing the production of coalbed methane horizontal wells based on controllable shock waves includes the following steps:

[0048] Step S1: The horizontal service mine tunnel is used as the construction point for upward directional drilling. The directional drilling target points are respectively opposite to the horizontal well perforation point (the horizontal well perforation point is Figure 1 The target points are the coal seams at positions A, AB, A-2B, A-3B, and A-4B meters from the horizontal well. In this embodiment, the directional drilling target points are the coal seams at positions 70 meters, 60 meters, 50 meters, 40 meters, and 30 meters from the horizontal well perforation point (hereinafter referred to as the target position at 70 meters, the target position at 60 meters, the target position at 50 meters, the target position at 40 meters, and the target position at 30 meters).

[0049] The values ​​of A and B may also be selected according to actual conditions such as the thickness of the coal seam, and this embodiment is not limited to the number of target points, that is, it may also be extended to positions of A-5B meters, A-6B meters, and so on.

[0050] A can be 50-200 meters, and B can be 2-20 meters.

[0051] Step S2: First, construction is carried out at a position 70 meters from the target point. The first hole constructed is called the fracturing influence zone investigation hole 4. The purpose is to examine whether it is within the fracturing influence range. However, the fracturing influence zone investigation hole 4 may eventually coincide with the controlled shock wave construction hole 5. If not, re-construction is required. Therefore, the fracturing influence zone investigation hole 4 may not eventually coincide with the controlled shock wave construction hole 5.

[0052] like Figure 2As shown in the figure, during the drilling process: the drilling is started from 20 meters, the casing and the orifice sealing gate valve are installed, and cement slurry is injected into the hole to seal it; after the cement solidifies, the drilling is restarted, starting from 2 meters from the coal seam floor and ending at 2 meters from the coal seam roof after the hole penetrates the coal;

[0053] During the construction process, the water samples and drill cuttings produced by the drilling are tested and analyzed. The K ion concentration in the water samples is measured (or other indicators are used as an auxiliary) to compare and analyze whether there is fracturing fluid in the water. The water content of the drill cuttings and the presence of fracturing sand are also analyzed (spectral analysis of the composition of suspected samples can be performed) to determine whether they have entered the fracturing influence range.

[0054] At the same time, after the borehole enters the coal seam, fixed-point closed sampling is carried out, and the gas content of the coal sample is measured (compared and analyzed with the original gas content of the coal seam) to determine whether it is within the influence range of horizontal well production; determining whether it has entered the influence range of fracturing and determining whether it is within the influence range of horizontal well production are carried out simultaneously during drilling.

[0055] If the water gushing out becomes larger during the drilling process, stop drilling immediately and close the gate valve to seal the hole if necessary.

[0056] As mentioned above: first construct the drill hole at a position of 70 meters from the target point. If the fracturing fluid or fracturing water determines that it has entered the fracturing influence range, then carry out controlled shock wave construction.

[0057] The controlled shock wave construction method is as follows: After drilling, the controlled shock wave generator is sent into the layer where the fracturing sand or fracturing fluid is found using a drilling rig. The sealing device is closed, and water is injected into the borehole through a reserved pipe. When the controlled shock wave generator detects that the water pressure has reached the set value, the shock wave operation begins.

[0058] If the borehole at 70 meters from the target point does not enter the fracturing influence range, there are two situations:

[0059] The first case: when it is determined that it is not within the influence range of drainage and production, it means that the fracturing of the horizontal well perforation has no effect on the coal seam gas, which means that the current position is still far away from the fracturing range. Then the drilling can be redesigned, and the drilling target position is a coal seam within 50 meters of the farther target position (then enter step S21).

[0060] The second case: when it is determined to be within the drainage influence range but not within the fracturing influence range, the fracturing of the horizontal well perforation does affect the coal seam gas, but the current position is not far from the fracturing range, then the drilling is redesigned and the drilling target is located in the coal seam within 60 meters of the target position;

[0061] Since the borehole at the 70-meter position of the target point is no longer of use, the borehole at the 70-meter position of the target point is sealed and pressure measured.

[0062] Step S21: After drilling at a position 50 meters from the construction target, if it is determined that it has entered the influence range of hydraulic fracturing, controlled shock wave construction is performed; if it has not entered the influence range of hydraulic fracturing, there are two situations: when it is determined that it is not within the influence range of drainage and production, the drilling hole is redesigned, and the drilling target position is the coal seam within a position range of 30 meters (then enter step S24); when it is determined that it is within the influence range of drainage and production, but not within the influence range of hydraulic fracturing, the drilling hole is redesigned, and the drilling target position is the coal seam within a position range of 40 meters (then enter step S23), and the original construction borehole is sealed and pressure measured.

[0063] Step S22: When the borehole at the construction target point 60 meters away is judged to have entered the influence range of hydraulic fracturing, controlled shock wave construction is carried out; if it has not entered the influence range of hydraulic fracturing, there are two situations: when it is judged that it is not within the influence range of drainage and production, the borehole is redesigned, and the target position of the borehole is the coal seam within the 40-meter range; when it is judged to be within the influence range of drainage and production, but not within the influence range of hydraulic fracturing, the borehole is redesigned, and the target position of the borehole is the coal seam within the 50-meter range, and the original construction borehole is sealed and pressure measured.

[0064] And so on:

[0065] Step S23: If the borehole at the construction target point 40 meters away is determined to be within the influence range of hydraulic fracturing, controlled shock wave construction is performed; if it is not within the influence range of hydraulic fracturing, there are two situations: if it is determined to be outside the influence range of drainage and mining, the borehole is redesigned, and the target position of the borehole is the coal seam within the 20-meter range; if it is determined to be within the influence range of drainage and mining, but not within the influence range of hydraulic fracturing, the borehole is redesigned, and the target position of the borehole is the coal seam within the 30-meter range, and the original construction borehole is sealed and pressure measured;

[0066] Step S24: If the drill hole at a position of 30 meters from the construction target is judged to be within the influence range of fracturing, controlled shock wave construction is performed; if it is judged not to be within the influence range of fracturing, the drill hole is sealed and pressure measured;

[0067] S3: For each horizontal well perforation, drilling is performed according to step S2, and judgment is made until all horizontal well perforations find the target position within the fracturing influence range, and controllable shock wave construction is performed.

[0068] After the shock wave treatment for a horizontal well perforation is completed, examine the changes in production parameters before and after the shock wave treatment. If the instantaneous gas volume and casing pressure increase, it indicates that the shock wave treatment is effective. Continue using shock wave intensity W for the next horizontal well perforation. If the casing pressure decreases, indicating that the shock wave intensity is too high, use shock wave intensity 0.8W for the next horizontal well perforation. If the instantaneous gas volume and casing pressure remain unchanged, use shock wave intensity 1.2W for the next horizontal well perforation.

[0069] Before carrying out shock wave construction operations, the surface well production and drainage construction personnel must be notified to pay close attention to the bottom hole flow pressure, casing pressure, instantaneous gas production and other production parameters; if any abnormality occurs, the underground construction personnel must be notified.

[0070] This embodiment, when constructed underground in a coal mine, does not affect surface coalbed methane well production. Directional drilling is performed within the fracturing area, and controlled shock wave equipment is used to reform the fractures created by fracturing in the surface well. The fracturing fluid in the fractures propagates shock waves, altering the pressure distribution in the coal seam and breaking down the barriers between the fractures, thereby increasing coalbed methane well production.

[0071] 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 method for increasing the production of a coalbed methane horizontal well based on controllable shock waves, wherein the horizontal section of the surface well includes N horizontal well perforations, where N is an integer greater than 1, and is characterized in that: The steps include: S1: A group of upward directional drilling construction sites are selected in the underground roadway of the horizontal well service mine. The directional drilling target locations are the coal seams at the distances of A meters, AB meters, A-2B meters, A-3B meters, and A-4B meters from the horizontal well perforation point. S2: First, drill a hole at the target point A meters away. During the drilling process, determine whether it has entered the fracturing influence range; after the hole enters the coal seam, determine whether it is within the horizontal well drainage influence range; If the drilling target is located within the fracturing influence range, controlled shock wave construction is performed; If the drilling target point is not within the fracturing influence range, drill again at the target point AB meter, A-2B meter, A-3B meter, or A-4B meter until the target point within the fracturing influence range is found; S3: For each horizontal well perforation, drilling is performed according to step S2, and judgment is made until all horizontal well perforations find the target position within the fracturing influence range, and controllable shock wave construction is performed.

2. The method for increasing the production of coalbed methane horizontal wells based on controllable shock waves according to claim 1, characterized in that: In step S2, the method for drilling a hole at a target point A meter is as follows: start drilling 15-30 meters, install casing and orifice sealing gate valve, and inject cement slurry into the hole to seal it; after the cement solidifies, re-drill the hole to 1.5-2.5 meters from the coal seam floor and end at 1.5-2.5 meters from the coal seam roof after the hole penetrates the coal.

3. The method for increasing the production of coalbed methane horizontal wells based on controllable shock waves according to claim 1, characterized in that: During the construction process, the water samples and drill cuttings produced by the drilling are tested and analyzed to determine whether they have entered the range of influence of fracturing. If there is fracturing fluid in the water sample and fracturing sand in the drill cuttings, then they have entered the range of influence of fracturing. If there is no fracturing fluid in the water sample and no fracturing sand in the drill cuttings, then they have not entered the range of influence of fracturing.

4. The method for increasing the production of coalbed methane horizontal wells based on controllable shock waves according to claim 1, characterized in that: After drilling into the coal seam, fixed-point closed sampling is carried out, and the gas content of the coal sample is measured to determine whether it is within the range of influence of horizontal well drainage. If the gas content in the coal sample is reduced when compared with the original gas in the coal seam, it means that it has entered the range of influence of horizontal well drainage. If the gas content in the coal sample does not change, it means that it has not entered the range of influence of horizontal well drainage.

5. The method for increasing the production of coalbed methane horizontal wells based on controllable shock waves according to claim 1, characterized in that: The drilling sequence is to drill the hole at the target point A meters first. If it is determined to have entered the fracturing influence range, the controlled shock wave construction is carried out; If the borehole at the target point A meters away does not enter the fracturing influence range, there are two situations: Case 1: When it is determined that it is not within the influence range of drainage, the drilling is redesigned and the drilling target position is the coal seam within the range of A-2B meters; The second case: when it is determined to be within the range of drainage influence but not within the range of fracturing influence, the drilling is redesigned and the drilling target position is the coal seam within the range of AB meters.

6. The method for increasing the production of coalbed methane horizontal wells based on controllable shock waves according to claim 5, characterized in that: After drilling at the construction target point A-2B meters, if it is determined to have entered the fracturing influence range, controlled shock wave construction will be carried out; If it does not enter the fracturing influence range, there are two situations: When it is determined that the drilling is not within the impact range of drainage, the drilling target is redesigned and the coal seam is located within the range of A-4B meters; When it is determined to be within the range of drainage influence but not within the range of fracturing influence, the drilling hole is redesigned, the drilling target position is the coal seam in the range of A-3B meters, and the original construction borehole is sealed and pressure measured.

7. The method for increasing the production of coalbed methane horizontal wells based on controllable shock waves according to claim 5, characterized in that: When the drilling hole at the construction target point AB meter position is judged to have entered the fracturing influence range, controlled shock wave construction is carried out; If it does not enter the fracturing influence range, there are two situations: When it is determined that the drilling is not within the affected range of drainage, the drilling target point is the coal seam within the range of A-3B meters; When it is determined that the area is affected by drainage but not by fracturing, the drilling hole is redesigned, the drilling target is located in the coal seam within the range of A-2B meters, and the original construction borehole is sealed and pressure measured; Continue drilling at the target points A-3B meters and A-4B meters until the target point is found within the fracturing influence range.

8. The method for increasing the production of a coalbed methane horizontal well based on controllable shock waves according to claim 6 or 7, characterized in that: The method of carrying out controlled shock wave construction is: after drilling construction, the controlled shock wave generating equipment is sent into the layer where fracturing sand or fracturing fluid is found through the drilling rig; the sealing device is closed, and water is injected into the borehole through the reserved pipe. When the controlled shock wave generating equipment detects that the water pressure has reached the set value, the impact operation is carried out.

9. The method for increasing the production of a coalbed methane horizontal well based on controllable shock waves according to claim 6 or 7, characterized in that: After the shock wave construction corresponding to a horizontal well perforation is completed, the changes in drainage parameters before and after the shock are examined; If the instantaneous gas volume and casing pressure increase, it indicates that the shock wave is effective; the shock wave construction can continue at the next horizontal well perforation point using the shock wave intensity W. If the casing pressure decreases, it indicates that the shock wave intensity is too large, and the next horizontal well perforation point can be subjected to shock wave construction with a shock wave intensity of 0.8W; If the instantaneous gas volume and casing pressure do not change, the next horizontal well perforation point can be subjected to shock wave construction using a shock wave intensity of 1.2W.

10. The method for increasing the production of coalbed methane horizontal wells based on controllable shock waves according to claim 9, characterized in that: Before carrying out shock wave construction operations, the surface well drainage and production construction personnel must be notified to pay close attention to the bottom hole flow pressure, casing pressure, and instantaneous gas production drainage parameters; if any abnormality occurs, the underground construction personnel must be notified.

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