Downward borehole water lock solution based on controllable shock waves

Abstract

The application discloses a downhole drilling water locking solution method based on controllable shock waves, which comprises the following steps: S1, taking a coal sample of a target coal seam to conduct a laboratory test, and determining the minimum shock wave intensity W and the shock frequency N required by the coal seam pressure equalization; S2, investigating a downhole pre-drainage borehole constructed in a mine roadway, and finding out a water locking borehole; S3, delimiting a gas outburst elimination range, and determining a water locking borehole in the gas outburst elimination range to be treated by the controllable shock waves; and S4, according to the construction effect of the controllable shock waves in the previous gas outburst elimination range, constructing a next gas outburst elimination range. The application has the beneficial effects that the downhole drilling water locking phenomenon can be eliminated, the gas flow in a soft and low permeability coal seam is enhanced, and a high pressure gas area is eliminated.

Description

Technical Field

[0001] This invention relates to the field of energy development technology, and more particularly to a solution for water-locking in downhole drilling based on controllable shock waves. Background Technology

[0002] As mining progresses, the confining pressure on the coal and rock mass increases significantly. Under high confining pressure, the rock and coal exhibit ductile deformation characteristics, which are quite different from the properties of traditional coal and rock masses.

[0003] According to classical fluid theory, fluid will flow as long as a pressure difference exists between the two ends of an object, and the flow will only stop when the pressure difference between the two ends decreases to zero. However, in underground coal seams, under the influence of confining pressure and gas pressure, gas flow requires a starting pressure to overcome the resistance generated by the flow. In particular, the starting pressure for gas flow is higher in soft, low-permeability coal and rock.

[0004] After pre-draining gas from soft, low-permeability coal seams, the presence of starting pressure can create low-pressure gas zones guided by boreholes and high-pressure gas zones formed by factors such as high stress and borehole trajectory deviations. If the high-pressure gas zones are not properly managed, during coal roadway excavation into these zones, the situation can range from a slight increase in gas levels at the working face to a major coal and gas outburst, or even a gas explosion.

[0005] Existing technologies all involve permeability enhancement treatment of the original coal seam. However, due to factors such as confining pressure and the coal seam's own gas pressure, the resulting fractures are difficult to preserve. In particular, the "water-locking" effect in downward drilling can block the throat of micro-fractures, making it difficult for gas to be depressurized and flow.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The technical problem to be solved by this invention is: how to solve the problem that the fractures generated by factors such as confining pressure and the gas pressure of the coal seam itself are difficult to preserve and the gas is difficult to depressurize and flow.

[0008] The present invention solves the above-mentioned technical problems through the following technical means:

[0009] The solution for water-locking in downward drilling based on controllable shock waves includes the following steps:

[0010] S1: Take coal samples from the target coal seam for laboratory testing to determine the minimum shock wave intensity W and the number of shocks N required for coal seam equalization.

[0011] S2: Investigate the downward pre-extraction boreholes in the underground roadway to find the water-locked boreholes;

[0012] S3: Delineate the area for shock wave suppression, and within the area for shock wave suppression, determine a water-locked borehole for controlled shock wave treatment;

[0013] S4: Based on the controllable shock wave construction effect of the previous shock wave suppression range, construct the next shock wave suppression range.

[0014] This invention obtains the minimum shock wave intensity W and number of impacts N required for the coal seam through laboratory testing. By taking measures (such as pressure-maintaining coring to determine residual gas, measuring gas pressure, and comparing the extraction volume of each borehole in the comparative area), the existing boreholes are examined to identify water-locked boreholes. A gas outburst mitigation zone is delineated near these water-locked boreholes. Controllable shock wave treatment of one of the water-locked boreholes can achieve enhanced extraction within the gas outburst mitigation zone. Finally, the construction parameters are adjusted based on the construction results. This invention can eliminate water-locking phenomena in downward boreholes, enhance gas flow in soft, low-permeability coal seams, and eliminate high-pressure gas zones.

[0015] Preferably, in step S1, the laboratory test on the ground is a triaxial stress cyclic impact coal rock dynamics test or / and X-CT scan test, in which the intensity of the sample that produces new cracks is W, and the number of impacts that produce through cracks in the sample is N.

[0016] Preferably, in step S1, the minimum shock wave intensity W is 200 to 350 MPa, and the number of impacts N is 5 to 15.

[0017] Preferably, in step S2, the method for identifying water-locked boreholes is as follows: each shift, the gas concentration, negative pressure, and temperature of the boreholes used for gas suppression are checked; when the gas concentration in the borehole decreases by more than 20%, the negative pressure increases, and the temperature decreases, it is determined that the borehole has a water-locking problem.

[0018] Preferably, in step S3, the range for eliminating the protrusion is a radius of 15-30m.

[0019] Preferably, in step S3, the controlled shock wave treatment is performed by sending a controlled shock wave generator into the bottom of the hole. The generator carries N energetic rods with a shock wave intensity of W to perform the first shock wave operation, with N shock waves.

[0020] Preferably, in step S4, if the gas extraction purity Q of the main pipeline at the construction drilling site is higher than 1.5 times the purity before construction after the controllable shock wave construction within the previous gas outburst suppression range, then the construction shock wave parameters remain unchanged within the next gas outburst suppression range.

[0021] Preferably, in step S4, if the pure gas extraction volume Q of the main pipeline of the drilling site is less than 1.5 times the pure volume before construction after the controllable shock wave construction within the previous gas outburst suppression range, then 2N energy rods will be used for controllable shock wave operation construction within the next gas outburst suppression range.

[0022] Preferably, in step S4, if the gas concentration is still above 90% and the difference between the borehole temperature and the surrounding rock temperature is no more than 5 degrees Celsius in the previous gas outburst suppression range, the next gas outburst suppression range shall be operated with a controllable shock wave with an intensity of 1.5W.

[0023] Preferably, in step S4, if the gas concentration in the main pipe of the drilling site is less than 0.8 times the concentration before construction after the controllable shock wave construction in the previous gas suppression range, the next gas suppression range will use an energetic rod with a strength of 0.8W for controllable shock wave operation.

[0024] Based on the construction results of the previous gas outburst suppression area, adjust the construction parameters of the next gas outburst suppression area in a timely manner to ensure the final elimination of the high-pressure gas zone.

[0025] The advantages of this invention are:

[0026] This invention obtains the minimum shock wave intensity W and number of impacts N required for the coal seam through laboratory testing, examines existing boreholes to identify water-locked boreholes, delineates the outburst mitigation zone near these boreholes, and achieves enhanced mining within the mitigation zone by applying controlled shock wave treatment to one of the water-locked boreholes. Finally, the construction parameters are adjusted based on the construction results. This invention utilizes the disturbance characteristics of waves propagating in the formation to different media surfaces to eliminate water-locking phenomena in boreholes (including horizontal, downward, and upward boreholes or downward boreholes in coalbed methane wells), enhances gas flow in soft, low-permeability coal seams, and eliminates high-pressure gas zones.

[0027] Based on the construction results of the previous gas outburst suppression area, adjust the construction parameters of the next gas outburst suppression area in a timely manner to ensure the final elimination of the high-pressure gas zone. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the downward drilling waterlock solution based on controllable shock waves in an embodiment of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of 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 some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1:

[0031] The solution for water-locking in downward drilling based on controllable shock waves includes the following steps:

[0032] S1: Take coal samples from the target coal seam for laboratory testing to determine the minimum shock wave intensity W and the number of shocks N required for coal seam equalization.

[0033] In the ground-based laboratory tests, triaxial stress cyclic impact coal rock dynamics experiments and X-CT scans were used to measure relevant basic parameters. Finally, samples were loaded into a controlled shock wave coal seam permeability enhancement simulation experimental system. The system analyzed the experimental parameter thresholds to obtain the intensity W at which new cracks appear in the sample and the number of impacts N at which through-cracks appear. Due to the different coal qualities, the impact intensity is generally between 200 and 350 MPa (±5 MPa), and the number of impacts is generally between 5 and 15.

[0034] S2: Investigate the downward pre-extraction boreholes in the underground roadway to find the water-locked boreholes;

[0035] It should be noted that the downward pre-drainage boreholes used in underground roadways are existing boreholes. This step requires finding the water-lock boreholes within the existing boreholes.

[0036] The method for identifying water-locked boreholes is as follows: Each shift, monitor the gas concentration, negative pressure, and temperature of the gas-blocking boreholes in the drilling site. If the gas concentration drops by more than 20%, the negative pressure increases, and the temperature decreases, it is determined that the borehole has a water-lock problem. Each shift can be 8 hours. A gas concentration drop of more than 20%, an increase in negative pressure, and a decrease in temperature generally occur simultaneously.

[0037] Before examining the gas concentration, borehole negative pressure, and temperature in the outburst suppression borehole, the borehole opening needs to be sealed. In this embodiment, the borehole sealing device is a bag-type sealing device. Gas concentration and temperature detection ports are installed on the outer end of the sealing device.

[0038] S3: Delineate the area for shock wave suppression, and within the area for shock wave suppression, determine a water-locked borehole for controlled shock wave treatment;

[0039] The anti-surge range is a radius of 15-30m. In this embodiment, a diameter of 30m is selected, but it can be selected as needed. The determined water lock borehole is preferably located at the center of the anti-surge range.

[0040] Delineating the gas outburst suppression area refers to identifying a 30m diameter area after locating the water-lock borehole. Controlled shock wave treatment of any one water-lock borehole within this area will eliminate the high-pressure zone of coal seam gas within that area. Drilling a borehole in the center of the delineated area is preferred as it can disturb adjacent boreholes.

[0041] The method for controlling shock wave treatment is as follows: A controllable shock wave generator is sent to the bottom of the hole. The generator carries N energetic rods with a shock wave intensity of W to perform the first shock wave operation, and the number of shocks is N.

[0042] S4: Based on the controllable shock wave construction effect of the previous shock wave suppression range, construct the next shock wave suppression range.

[0043] If, within the previous gas outburst suppression range, the pure gas extraction volume Q of the main pipeline at the drilling site is higher than 1.5 times the pure volume before the operation after the controlled shock wave operation, it indicates that the intensity and frequency of the controlled shock wave are effective and can increase the gas extraction volume. In this case, the parameters of the shock wave operation in the next gas outburst suppression range will remain unchanged.

[0044] If, within the previous gas outburst suppression range, the pure gas extraction volume Q of the main pipeline at the drilling site is less than 1.5 times the pure volume before the operation, it indicates that the intensity and frequency of the controlled shock wave have limited effectiveness and the impact intensity needs to be increased. In the next gas outburst suppression range, 2N energy rods will be used for controlled shock wave operation.

[0045] If, within the previous outburst suppression range, there are still boreholes with a gas concentration of over 90% and a borehole temperature close to the surrounding rock temperature, it indicates that the intensity and frequency of the controllable shock wave have limited effectiveness, and the shock intensity needs to be increased. In the next outburst suppression range, a controllable shock wave with an intensity of 1.5W will be used.

[0046] If, after controlled shock wave operation within the previous outburst suppression range, the gas concentration in the main pipeline of the drilling site is less than 0.8 times the concentration before operation, it indicates that the intensity and frequency of the controlled shock wave may have shattered the borehole, causing debris to block the borehole. Therefore, it is necessary to reduce the intensity of the shock wave. In the next outburst suppression range, controlled shock wave operation will be carried out using an energy rod with an intensity of 0.8W.

[0047] Based on the construction results of the previous gas outburst suppression area, adjust the construction parameters of the next gas outburst suppression area in a timely manner to ensure the final elimination of the high-pressure gas zone.

[0048] This embodiment obtains the minimum shock wave intensity W and number of impacts N required for the coal seam through laboratory testing, examines existing boreholes to identify water-locked boreholes, delineates the outburst suppression range near these boreholes, and achieves enhanced mining within the suppression range by applying controlled shock waves to one of the water-locked boreholes. Finally, the construction parameters are adjusted based on the construction results. This invention utilizes the disturbance characteristics of waves propagating in the formation to different medium surfaces to eliminate water-locking phenomena in downward boreholes, enhance gas flow in soft, low-permeability coal seams, and eliminate high-pressure gas zones.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. Controllable Shockwave based solution for downhole water lock, characterized in that, The method comprises the following steps: S1: taking a coal sample from a target coal seam for laboratory testing to determine the minimum shock wave intensity W and the number of impacts N required for coal seam equalization; S2: investigating downward pre-drainage boreholes constructed in underground roadways to identify water-locked boreholes; S3: delineating a range for eliminating outbursts, and determining a water-locked borehole within the range for controllable shock wave treatment, the controllable shock wave treatment being performed in the following manner: sending a controllable shock wave generating device to the bottom of the borehole, and performing a first shock wave operation with the device carrying N energy-containing rods with a shock wave intensity of W, the number of impacts being N; S4: based on the controllable shock wave construction effect in the previous outburst elimination range, constructing the next outburst elimination range: If, after the controllable shock wave construction in the previous outburst elimination range, the pure volume Q of gas extraction in the dry pipe of the construction drill field is higher than 1.5 times the pure volume before the construction, the shock wave parameters remain unchanged in the next outburst elimination range; If, after the controllable shock wave construction in the previous outburst elimination range, the pure volume Q of gas extraction in the dry pipe of the construction drill field is lower than 1.5 times the pure volume before the construction, 2N energy-containing rods are used for controllable shock wave operation construction in the next outburst elimination range; If, in the previous outburst elimination range, there are still conditions of a gas concentration of 90% or above and a difference of no more than 5 degrees Celsius between the temperature of the borehole and the temperature of the surrounding rock, a controllable shock wave operation with an intensity of 1.5W is used in the next outburst elimination range; If, after the controllable shock wave construction in the previous outburst elimination range, the gas concentration in the dry pipe of the construction drill field is lower than 0.8 times the concentration before the construction, an energy-containing rod with an intensity of 0.8W is used for controllable shock wave operation in the next outburst elimination range.

2. The controllable shockwave-based downhole water lock solution of claim 1, wherein, In step S1, the laboratory testing on the ground is a triaxial stress cyclic impact coal rock dynamics experiment or / and an X-CT scanning test, a controllable shock wave coal seam permeability enhancement simulation experiment system, system analysis of experimental parameter thresholds, the intensity of the sample appearing new cracks being W, and the number of impacts N of the sample appearing through cracks.

3. The controllable shockwave-based downhole water lock solution of claim 1, wherein, In step S1, the minimum shock wave intensity W is 200 to 350 MPa, and the number of impacts N is 5 to 15 times.

4. The controllable shockwave-based downhole water lock solution of claim 1, wherein, In step S2, the method for identifying water-locked boreholes is as follows: investigating the gas concentration, borehole negative pressure, and temperature of the outburst elimination boreholes in the drill field every shift, and determining the residual gas content by pressure-maintained coring when the borehole gas concentration decreases by more than 20%, the negative pressure increases, and the temperature decreases, which indicates that the borehole has a water locking problem.

5. The controllable shockwave-based downhole water lock solution of claim 1, wherein, In step S3, the outburst elimination range is a range with a radius of 15-30 m.

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