Coal bed gas horizontal well transformation method based on controllable shock waves

Abstract

The coal bed gas horizontal well yield increasing method based on the controllable shock waves comprises the steps that S1, a set of upward directional drilling construction sites are selected in a horizontal well service mine underground roadway, and the positions of directional drilling target spots are coal beds right opposite to the positions, away from a horizontal well, of horizontal well perforation points; s2, construction drilling is conducted on the position, with the target point being A m, of the target point, and whether the position enters the fracturing influence range or not and is the horizontal well drainage and mining influence range or not is judged; if the drilling target point is located in the fracturing influence range, controllable shock wave construction is conducted; if the drilling target spot is not in the fracturing influence range, construction is carried out on other target spot positions again until the target spot position in the fracturing influence range is found; and S3, for each horizontal well perforation, the step S2 is adopted for construction drilling, judgment is conducted till all the horizontal well perforations find the target spot positions of the fracturing influence range, and controllable shock wave construction is conducted. The method has the beneficial effects that the yield of the coal-bed gas well is increased, a seepage channel is further expanded, and the production life of the coal-bed gas well is prolonged.

Description

Technical Field

[0001] The 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 in my country. With the continuous deepening of mining, coalbed methane (gas) disasters in coal mines have become particularly serious. At the same time, coalbed methane is also an important culprit for the greenhouse effect, and its greenhouse effect is more than 20 times that of the same volume of carbon dioxide. Every additional cubic meter of coalbed methane extracted through drainage means is equivalent to reducing more than 20 cubic meters of carbon dioxide emissions.

[0003] At present, in the case of rich coal, poor oil and little gas, coalbed methane is a companion resource of coal mining. Increasing the development of coalbed methane is conducive to energy security. However, coal seams currently generally have the disadvantages of complex geological structure and poor permeability. Despite decades of continuous efforts, the output of coalbed methane has always been lower than expected. Due to factors such as the confining pressure of the formation and the gas pressure of the coal seam itself, the fissures produced by fracturing in soft and low-permeability coalbed methane wells cannot be sustained, the drainage and production decay quickly, and the output is low. Although there is also CN107956505A-coal mine underground drilling permeability enhancement method based on controllable shock wave technology in the prior art, the shock was carried out without investigation, resulting in poor shock effect and still low output.

[0004] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art known to a person 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 coalbed methane horizontal wells based on controllable shock waves, wherein the horizontal section of the ground well includes N horizontal well perforations, where N is an integer greater than 1, and is characterized in that it includes the following steps:

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

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

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

[0011] If the drilling target point is not within the fracturing influence range, the drilling will be re-constructed 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 using 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 at 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 top 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 influence range of fracturing. If there is fracturing fluid in the water sample and fracturing sand in the drill cuttings, then they have entered the influence range 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 influence range of fracturing.

[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 construct the drilling hole at the target point A meter away, and if it is determined that it has entered the fracturing influence range, then perform controllable shock wave construction;

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

[0018] The first case: when it is determined that it is not within the influence range of drainage, the drilling hole is redesigned and the drilling target position is the coal seam within the range of A-2B meters;

[0019] The second situation: when it is judged to be within the influence range of drainage but not within the influence range of fracturing, the drilling hole 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, controllable 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 point is the coal seam within the range of A-4B meters;

[0023] When it is determined to be within the range of influence of drainage but not within the range of influence of fracturing, 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 enter the fracturing influence range, controllable 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 impact range of drainage, the drilling target point is the coal seam within the range of A-3B meters;

[0027] 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 within the range of A-2B meters, and the original construction borehole is sealed and pressure measured;

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

[0029] Preferably, the controlled shock wave construction is carried out in the following manner: after drilling, the controlled shock wave generating device is sent into the layer where the 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 device detects that the water pressure reaches the set value, the shock operation is carried out.

[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 with the shock wave intensity W at the next horizontal well perforation point;

[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 constructed 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 constructed using shock wave intensity of 1.2W.

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

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

[0036] The advantages of the present invention are:

[0037] The technical solution of the present invention does not affect the drainage work of the ground coalbed methane wells during construction in the coal mine. Directional drilling is carried out to the fracturing influence range, and the cracks generated by the fracturing of the ground wells are transformed by using controllable shock wave equipment, and the shock waves propagated by the fracturing fluid in the cracks change the pressure distribution of the coal seam, break the barriers between the cracks, and increase the production of the coalbed methane wells.

[0038] According to whether it is located within the influence range of fracturing and the influence range of fracturing, 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 the feedback to ensure the impact effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural schematic diagram 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 It is a construction schematic diagram of the drilling process of an embodiment of the present invention;

[0042] Figure 3 It is a schematic 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 ground well; 2. Perforation of horizontal well; 3. Coal seams at different distances from horizontal well; 4. Investigation 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] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] like Figure 1As shown, the horizontal section 1 of the ground well includes nine horizontal well perforations 2, and the horizontal well perforations 2 are fractured. Through the action of high-pressure water flow, the underground rock formation is fractured and penetrated to increase the permeability and fluidity of oil and gas; and fracturing sand is injected into the horizontal well perforations. After the fracturing is completed, the gas gathers in the horizontal well perforations 2, and the coalbed methane is drained. It is necessary to verify and investigate where the gas can be pumped into the horizontal section 1 of the ground well. Therefore, this embodiment is first to investigate the fracturing influence range (the range where the fracturing sand and fracturing fluid are located, the presence of fracturing sand or fracturing water indicates that it is within the pressure influence range, otherwise it indicates whether it is within the pressure influence range) and the horizontal well drainage influence range (whether the gas is reduced, the reduction indicates that it is within the drainage range, and the non-reduction indicates that it is not within the drainage range). The horizontal well drainage influence range is greater than the fracturing influence range. When it is located in the fracturing influence range, controllable shock wave construction can be carried out to achieve increased 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 black dot in the middle) is located at a coal seam at a distance of A meters, AB meters, A-2B meters, A-3B meters, and A-4B meters from the horizontal well; in this embodiment, the target positions of directional drilling are respectively located at coal seams at a distance of 70 meters, 60 meters, 50 meters, 40 meters, and 30 meters from the horizontal well perforation point directly opposite the horizontal well (hereinafter referred to as the target position of 70 meters, the target position of 60 meters, the target position of 50 meters, the target position of 40 meters, and the target position of 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 investigate whether it is within the fracturing influence range. However, the fracturing influence zone investigation hole 4 may eventually be consistent with the controllable shock wave construction hole 5. If not, re-construction is required. Therefore, the fracturing influence zone investigation hole 4 may not eventually be the controllable shock wave construction hole 5.

[0052] like Figure 2As shown in the figure, during the drilling process: the drilling starts at 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 to start at 2 meters from the coal seam floor and end at 2 meters from the coal seam roof after the drilling 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 sample is measured (or other indicators are used to assist) to compare and analyze whether there is fracturing fluid in the water; and the water content of the drill cuttings and the presence of fracturing sand (spectral analysis of suspected samples can be performed) are analyzed to determine whether it has 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 construction process, stop the drilling immediately and close the gate valve to seal the hole if necessary.

[0056] As mentioned above: first construct the borehole at 70 meters from the target point. If it is determined by the fracturing fluid or fracturing water that it has entered the fracturing influence range, then carry out controllable shock wave construction.

[0057] The method of carrying out controlled shock wave construction is: after drilling, the controlled shock wave generating device is sent into the layer where the 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 device detects that the water pressure reaches the set value, the shock operation is carried out.

[0058] If the borehole at the 70-meter position of the target point does not enter the fracturing influence range, there are two situations:

[0059] The first case: when it is judged 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 judged to be within the influence range of drainage, but not within the influence range of fracturing, it means that the fracturing of horizontal well perforation does have an impact on coal seam gas, but the current position is not far from the fracturing range, then the drilling is redesigned, and the drilling target position is a coal seam within 60 meters of the target position that is closer;

[0061] Since the borehole at 70 meters from the target point is no longer of use value, the borehole at 70 meters from the target point is sealed and pressure measured.

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

[0064] And so on:

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

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

[0067] S3: For each horizontal well perforation, drilling is performed using 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 construction corresponding to a horizontal well perforation is completed, the changes in the 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 at the next horizontal well perforation point continues to use the shock wave intensity W. If the casing pressure decreases, it indicates that the shock wave intensity is too large, and the shock wave construction at the next horizontal well perforation point can use the shock wave intensity of 0.8W. If the instantaneous gas volume and casing pressure do not change, the shock wave construction at the next horizontal well perforation point can use the shock wave intensity of 1.2W.

[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 and drainage parameters; if any abnormality occurs, the underground construction personnel must be notified.

[0070] This embodiment does not affect the drainage work of the ground coalbed methane wells during construction in the coal mine. Directional drilling is carried out to the fracturing influence range, and the cracks produced by the fracturing of the ground wells are transformed by using controllable shock wave equipment, and the shock waves propagated by the fracturing fluid in the cracks change the pressure distribution of the coal seam, break the barriers between the cracks, and increase the production of the coalbed methane wells.

[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 the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. 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 embodiments of the present invention.

Claims

1. A method for increasing the production of coalbed methane horizontal wells 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 tunnel of the horizontal well service mine. The directional drilling target points are respectively facing the coal seams at the positions of A meters, AB meters, A-2B meters, A-3B meters, and A-4B meters away from the horizontal well perforation point; S2: First, a construction drilling is performed at the target point A meters away. During the construction process, it is determined whether it has entered the influence range of fracturing; after the drilling hole enters the coal seam, it is determined whether it is within the influence range of horizontal well drainage; If the drilling target point is located within the fracturing influence range, controlled shock wave construction is carried out; If the drilling target point is not within the fracturing influence range, the drilling will be re-constructed 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 using 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 the 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 bottom plate and end at 1.5-2.5 meters from the coal seam roof plate 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 impact range of fracturing. If there is fracturing fluid in the water sample and fracturing sand in the drill cuttings, then they have entered the impact range 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 impact range 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 influence range 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 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.

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 target hole at the A-meter position first. If it is judged to have entered the fracturing influence range, the controlled shock wave construction is carried out; If the borehole at the target point A meter does not enter the fracturing influence range, there are two situations: The first case: when it is determined that it is not within the influence range of drainage, the drilling hole is redesigned and the drilling target position is the coal seam within the range of A-2B meters; The second situation: when it is judged to be within the influence range of drainage but not within the influence range of fracturing, the drilling hole 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 judged to have entered the fracturing influence range, controllable 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 impact range of drainage, the drilling target point is the coal seam within the range of A-4B meters; When it is determined to be within the range of influence of drainage but not within the range of influence of fracturing, 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 enter the fracturing influence range, controllable 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 impact range of drainage, the drilling target point is the coal seam within the range of A-3B 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 within the range of A-2B meters, and the original construction borehole is sealed and pressure measured; Continue drilling holes at the target points A-3B meters and A-4B meters until the target point within the fracturing influence range is found.

8. The method for increasing the production of coalbed methane horizontal wells 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, the controlled shock wave generating device is sent into the layer where the 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 device detects that the water pressure reaches the set value, the shock operation is carried out.

9. The method for increasing the production of coalbed methane horizontal wells based on controllable shock waves according to claim 6 or 7, characterized in that: When the shock wave construction corresponding to a horizontal well perforation is completed, the changes in drainage parameters before and after the shock are investigated; If the instantaneous gas volume and casing pressure increase, it indicates that the shock wave is effective; the shock wave construction can continue with the shock wave intensity W at the next horizontal well perforation point; If the casing pressure decreases, it indicates that the shock wave intensity is too large, and the next horizontal well perforation point can be constructed 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 constructed using 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 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 and drainage parameters; if any abnormality occurs, the underground construction personnel must be notified.

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