Method for measuring effective extraction radius of drill hole in high-energy gas blasting coal seam

Abstract

The invention discloses a method for measuring the effective extraction radius of drill holes in a high-energy gas blasting coal seam, which comprises the following steps: constructing a group of drill holes in the coal seam, the drill holes comprising a blasting hole and a plurality of extraction holes; each extraction hole is sealed, and an extraction pipe is installed at the hole opening; performing high-energy gas blasting on the blast hole; the blast hole is sealed, and an inflatable valve is installed at a hole opening; the blast hole is filled with SF6 gas, then the valve is closed, and the SF6 gas is supplemented regularly; the extraction pipes at the openings of the extraction holes are connected into a mine extraction system for extraction; starting from the gas injection day of the blast hole, collecting gas samples of each extraction hole every day, and detecting whether the gas samples contain SF6 or not; when the SF6 gas is detected in the gas sample of a certain extraction hole, the detection work of the extraction hole is ended, and the time when the extraction hole detects the SF6 gas is the extraction influence time; the extraction compensation time is calculated through a time compensation method; and based on the effective extraction time obtained through calculation, the effective extraction radius of the coal seam drill hole is determined.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal seam gas extraction in underground coal mines, and particularly relates to a method for determining the effective extraction radius of a high-energy gas blasting coal seam drilling hole based on time compensation. Background Art

[0002] Coal mine gas is one of the main causes of coal mine disasters in my country. To ensure safe production in coal mines, coal seam gas extraction is necessary. However, my country's gas storage conditions are characterized by "three lows and one high" (low saturation, low permeability, low reservoir pressure, and high metamorphic degree). The permeability of coal seams in most mining areas is 0.987×10 -7 ~0.987×10 -6 μm 2 (10 -4 ~10 -3 ). This results in the problems of rapid gas attenuation in a single hole, small gas extraction volume, long extraction time, and high extraction cost. In response to this characteristic, domestic and foreign researchers have continuously adopted technical means such as cross-drilling, hydraulic punching, hydraulic fracturing, explosive blasting, and high-energy gas blasting to strengthen coal seam cracks and improve coal seam permeability. In recent years, the newly emerging high-energy gas blasting permeability enhancement technology uses the instantaneous release of high-pressure gas (including air, carbon dioxide, and nitrogen) to form a blasting effect, impacting the coal body around the borehole, and generating a network of cracks of varying sizes that are interconnected, thereby effectively increasing the permeability of the coal seam.

[0003] Since the pressure during high-energy gas blasting is relatively high, usually around 100 to 300 MPa, it has a good blasting effect on the coal body and promotes the development of coal body cracks. If the pressure reduction method is used to determine the effective extraction radius, the cracks will develop after the blasting, causing the pressure value of the pressure measuring borehole to decay rapidly, and the extraction time cannot be determined. When using the current "Direct Determination of Coal Seam Gas Extraction Radius in Coal Mines - Extraction Quantity Method" (GB / T42638-2023) to determine the effective radius of the borehole, there is a disadvantage of needing to analyze the gas extraction volume data of each underground borehole, resulting in a long calculation cycle. The most critical problem is that the large range of cracks leads to low gas extraction concentration or inaccurate extraction measurement, making it impossible to determine the accurate effective extraction radius.

[0004] Therefore, the present invention provides a method for measuring the effective extraction radius of coal seam drilling holes by high-energy gas blasting based on time compensation, so as to solve the problem that the effective extraction radius of coal seam drilling holes cannot be measured efficiently and accurately when using high-energy gas blasting permeability enhancement technology. Summary of the Invention

[0005] In response to the above problems, the purpose of the present invention is to provide a method for measuring the effective extraction radius of coal seam drilling holes by high-energy gas blasting based on time compensation, so as to solve the problem that the existing methods cannot efficiently and accurately measure the effective extraction radius of coal seam drilling holes.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions.

[0007] The present invention provides a method for measuring the effective extraction radius of a high-energy gas blasting coal seam drilling hole, the method comprising the following steps:

[0008] Step 1: constructing a set of boreholes in the coal seam, the boreholes including a blasting hole and multiple extraction holes;

[0009] Step 2: Seal each extraction hole and install an extraction pipe at the hole mouth;

[0010] Step 3: performing high-energy gas blasting on the blast hole;

[0011] Step 4: Seal the blasting hole and install an inflatable valve at the hole mouth;

[0012] Step 5: Fill the blasting hole with SF6 gas, then close the valve and replenish SF6 gas regularly;

[0013] Step 6: Connect the extraction pipes at the openings of each extraction hole to the mine extraction system for extraction;

[0014] Step 7: Starting from the day of gas injection in the blasting hole, collect gas samples from each extraction hole every day to test whether the gas samples contain SF6;

[0015] Step 8: When SF6 gas is detected in the gas sample of a certain extraction hole, the detection work of the extraction hole is terminated. The time when SF6 gas is detected in the extraction hole is the extraction impact time, recorded as T1, in days;

[0016] Step 9: Calculate the drainage compensation time T2 using the time compensation method. The time compensation method is as follows: after the drainage hole detects SF6 gas after T1 days of drainage, continue to drain for T2 days until the drainage hole reaches the effective drainage radius. At this time, the effective drainage time T = T1 + T2, and the value of T2 is the difference between the drainage impact time and the effective drainage time of the same diameter drilling hole; it also includes: first, based on the existing data of the same mine, the same coal seam, and the same diameter drainage borehole, fit the power function relationship R = At B, where R is the effective drainage radius in meters, t is the drainage compensation time T2 in days, and A and B are constants. Then, the power function relationship is used to deduce the effective drainage radius R corresponding to different drainage compensation times T2. Finally, the drainage compensation time T2 is corrected to a new borehole drainage compensation time T2' = T2 / k, where k is the multiple of the drainage efficiency improvement caused by high-energy gas blasting permeability enhancement.

[0017] Step 10: Calculate the effective extraction time T=T1+T2', and determine the effective extraction radius R of the coal seam drill hole based on the calculated effective extraction time T.

[0018] Furthermore, in step 1, the borehole has a depth of not less than 50m and a diameter of D; the blasting hole is located in the middle of the drilling group, the extraction holes are located on both sides of the blasting hole, and the distance between the extraction holes and the blasting holes is R n .

[0019] Furthermore, the number of the drilling groups is determined according to the on-site conditions, the number of extraction holes is 5, and the distances between each extraction hole and the blasting hole are R1, R2, R3, R4, and R5 respectively.

[0020] Furthermore, in step 2, the sealing depth is not less than 15m.

[0021] Furthermore, in step 5, the periodic replenishment of SF6 gas is to replenish SF6 gas into the blasting hole once a day.

[0022] Furthermore, in step 9, the power function relationship R=At B The effective extraction radius data corresponding to different extraction times were fitted based on the gas pressure reduction method.

[0023] Furthermore, in step 9, the extraction efficiency improvement factor k caused by the high-energy gas blasting enhancement is determined by comparing the inverse relationship between the extraction scalar quantity of the coal seam after high-energy gas blasting enhancement and that of the coal seam without enhancement. Blasting enhancement causes cracks in the coal seam, resulting in an increase in gas concentration and scalar quantity under the same extraction parameters, shortening the time to reach the effective extraction radius.

[0024] Furthermore, in step 10, the extraction radius corresponding to the extraction effective time T is the effective extraction radius R.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) The technical solution of the present invention is based on the extraction time data, effective extraction radius and extraction effect comparison that have been measured and determined before the mine adopts high-energy gas blasting, and corrects the extraction compensation time.

[0027] 2) Based on time compensation, this technical solution effectively solves the problem of using the gas pressure reduction method to determine the effective extraction radius. This problem is caused by the rapid decay of the gas leakage pressure value in the pressure-testing borehole due to the development of cracks after blasting, making it impossible to determine the extraction time. It also effectively solves the drawbacks of the extraction volume method, which requires analyzing the gas extraction volume data of each underground borehole, resulting in a long calculation cycle, and the problem of low gas extraction concentration or inaccurate extraction measurement due to the large scope of cracks, which makes it impossible to accurately determine the effective extraction radius.

[0028] Other advantages, objectives, and features of the present invention will be described in detail in the following detailed description, and will be apparent to those skilled in the art upon examination and study of the following, or may be learned from practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the drilling arrangement for field testing of the present invention.

[0030] Figure 2 This is a curve of the extraction radius changing with time T2.

[0031] The markings in the figure include: 1. Coal seam; 2. Coal seam roof; 3. Coal seam floor; 4. Extraction hole; 5. Blasting hole; 6. Distance between extraction hole and blasting hole. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] Combine Figure 1 As shown, the present invention provides a method for measuring the effective extraction radius of a high-energy gas blasting coal seam drilling hole, the method comprising the following steps:

[0034] Step 1: In the coal seam 1 between the coal seam roof 2 and the coal seam floor 3, a group of boreholes with a depth of not less than 50m and a diameter of D are constructed using a drilling rig. The boreholes include a blasting hole 5 and multiple extraction holes 4. The blasting hole 5 (also serving as an injection hole) is located in the middle of the borehole group, and the extraction holes 4 are located on both sides of the blasting hole 5. The distance between the extraction holes 4 and the blasting holes 5 is R. n ; Furthermore, the number of the drilling groups and the number of drill holes are determined according to the on-site conditions. In this embodiment, the number of extraction holes 4 in a drilling group is 5, and the distances between each extraction hole 4 and the blasting hole 5 are R1, R2, R3, R4, and R5, respectively.

[0035] Step 2: Seal each extraction hole 4 to a depth of no less than 15 m, and install an extraction pipe at the hole opening;

[0036] Step 3: performing high-energy gas blasting on the blasting hole 5;

[0037] Step 4: Seal the blasting hole 5 and install an inflatable valve at the hole mouth;

[0038] Step 5: Fill the blasting hole 5 with SF6 gas, then close the valve. In the later stage, replenish SF6 gas into the blasting hole 5 once a day;

[0039] Step 6: Connect the extraction pipes at the four openings of each extraction hole to the mine extraction system for extraction;

[0040] Step 7: Starting from the day of gas injection in blasting hole 5, gas samples are collected from each extraction hole 4 every day, and professional instruments are used to detect whether the gas samples contain SF6;

[0041] Step 8: When SF6 gas is detected in the gas sample of a certain extraction hole 4, the detection work of the extraction hole 4 is ended. The time when the extraction hole 4 detects SF6 gas is the extraction impact time, recorded as T1, in days;

[0042] The results measured by the SF6 gas tracer method are only the extraction influence radius. When SF6 gas is detected in the extraction hole 4, it only indicates that under the corresponding time and space conditions, the drilling extraction has affected this point, and does not mean that the extraction effect at this point has reached the effective value range. Therefore, the following step 9 is performed;

[0043] Step 9: Calculate the drainage compensation time T2 using the time compensation method. The time compensation method is as follows: after the drainage hole 4 detects SF6 gas after T1 days of drainage, continue to drain for T2 days until the drainage hole 4 reaches the effective drainage radius. At this time, the effective drainage time T=T1+T2, and the value of T2 is the difference between the drainage impact time and the effective drainage time of the same diameter drilling hole. The method also includes: First, based on the existing data of the same mine, the same coal seam 1, and the same diameter drainage borehole, fit the power function relationship R=At B , where R is the effective drainage radius in meters, t is the drainage compensation time T2 in days, and A and B are constants. Then, using the power function relationship, the effective drainage radius R corresponding to different drainage compensation times T2 is deduced within a certain appropriate distance range. Finally, the drainage compensation time T2 is corrected to a new drilling drainage compensation time T2', where T2' = T2 / k, where k is the multiple of the drainage efficiency improvement caused by high-energy gas blasting permeability enhancement.

[0044] Specifically, the extraction compensation time T2 at this time is the time required for the coal seam 1 to move from the extraction influence radius to the effective extraction radius in its original state when the coal seam 1 is not affected by the high-energy gas blasting permeability enhancement. In actual situations, the extraction time and the extraction quantity are inversely proportional. After the high-energy gas blasting, a large number of cracks are generated in the coal seam 1 within a certain distance. Therefore, during extraction, the gas concentration and gas quantity extracted from the borehole with the same extraction parameters will be greater than those of the unpermeable coal seam 1, and a larger effective extraction radius can be achieved in a shorter time, thereby improving the extraction efficiency and effect by k times. That is, the corresponding extraction compensation time T2 is shortened to 1 / k of the original value. Based on this, the extraction compensation time T2 is corrected to obtain a new drilling extraction compensation time T2', T2'=T2 / k.

[0045] Furthermore, in step 9, the power function relationship R=At B The effective extraction radius data corresponding to different extraction times were fitted based on the gas pressure reduction method.

[0046] Furthermore, in step 9, the extraction efficiency improvement factor k caused by the high-energy gas blasting enhancement is determined by comparing the inverse relationship between the extraction scalar quantity of the coal seam after high-energy gas blasting enhancement and that of the coal seam without enhancement. Blasting enhancement causes cracks in the coal seam, resulting in an increase in gas concentration and scalar quantity under the same extraction parameters, shortening the time to reach the effective extraction radius.

[0047] Step 10: Calculate the effective extraction time T=T1+T2', and determine the effective extraction radius R of the coal seam borehole based on the calculated effective extraction time T; wherein the extraction radius corresponding to the effective extraction time T is the effective extraction radius R.

[0048] Example: This example is to investigate the effective extraction radius of high-energy gas blasting drilling in the 2# coal seam in the 8261 working face of the 42nd District of Yangdong Mine, Hebei Jizhong Energy Fengfeng Group Co., Ltd.

[0049] Step 1: Use a drilling rig to construct a group of 6 boreholes with a depth of 50m and a diameter of Φ94mm in the coal seam 1; the middle is a blasting hole 5 (also serving as a gas injection hole), and the two sides are extraction holes 4; the distances 6 between each extraction hole and the blasting hole are 8m, 9m, 10m, 11m, and 12m respectively.

[0050] Step 2: Seal each extraction hole 4 to a depth of 20m and install an extraction pipe at the hole mouth;

[0051] Step 3: Perform high-energy gas blasting on the blast hole 5;

[0052] Step 4: Seal the blasting hole 5 and install an inflatable valve at the hole mouth;

[0053] Step 5: Fill the blasting hole 5 with SF6 gas, and then close the valve; in the later stage, replenish the blasting hole 5 with SF6 gas once a day;

[0054] Step 6: Connect the extraction pipes at the openings of each extraction hole 4 to the mine extraction system for extraction;

[0055] Step 7: Starting from the day of gas injection in blasting hole 5, gas samples from extraction hole 4 are collected every day, and professional instruments are used to detect whether the gas samples contain SF6;

[0056] Step 8: When each extraction hole 4 detects SF6 gas, the detection work is completed. The time when the extraction hole 4 detects SF6 gas is the extraction impact time, recorded as T1 days; the final data is shown in Table 1.

[0057] Table 1 Measurement of extraction radius of Φ94mm in-beam drilling holes after high-energy gas blasting

[0058]

[0059] The results measured by the SF6 gas tracer method are only the extraction influence radius. When SF6 gas is detected in extraction hole 4, it only indicates that under the corresponding time and space conditions, the drilling extraction has affected this point, and does not mean that the extraction effect at this point has reached the effective value range.

[0060] Step 9: Calculate the extraction compensation time T2 using the time compensation method;

[0061] Furthermore, in step 9, the time compensation method is: after the extraction hole 4 detects SF6 gas after T1 days of extraction, it continues to extract for T2 days so that the extraction hole 4 reaches the effective extraction radius. At this time, the effective extraction time T=T1+T2; the value of T2 is the difference between the extraction impact time and the effective extraction time of the same diameter drilling hole.

[0062] Furthermore, in step 9, first, the effective extraction radius corresponding to different extraction times is determined using the gas pressure reduction method in the same mine, the same coal seam 1, and the same diameter extraction borehole. The values ​​are shown in Table 2.

[0063] Table 2 Measurement of the extraction radius of Φ94mm in-beam drilling holes without high-energy gas blasting

[0064]

[0065] According to existing research, under certain occurrence conditions, through the correlation analysis of gas flow, it is believed that the effective extraction radius of the borehole and the extraction time conform to the power function relationship. Therefore, the power exponential linear fitting of the extraction compensation time T2 and the effective extraction radius R in Table 2 is performed, and the results are shown in Table 2. Figure 2 .

[0066] According to the fitting, the following formula is obtained:

[0067] R=1.1971t 0.4805 (1)

[0068] In formula (1): R is the effective extraction radius, in meters; t is the extraction compensation time T2, in days;

[0069] Secondly, using the above formula, the effective extraction radius R corresponding to different extraction compensation times T2 can be deduced within a certain appropriate distance range. The calculation results based on formula (1) are shown in Table 3 below.

[0070] Table 3 Numerical table of Φ94mm borehole drainage compensation time and estimated drainage radius

[0071]

[0072] Finally, the extraction compensation time T2 is corrected. Since the extraction compensation time T2 at this point is the time required for coal seam 1 to move from the extraction influence radius to the effective extraction radius in its original state, when coal seam 1 is not affected by the high-energy gas blasting permeability enhancement. In reality, the extraction time and the pure extraction quantity are inversely proportional. After high-energy gas blasting, a large number of cracks are generated in coal seam 1 within a certain distance. Therefore, during extraction, the gas concentration and pure gas quantity extracted from the borehole with the same extraction parameters will be greater than that of the unpermeable coal seam 1, and a larger effective extraction radius can be achieved in a shorter time, thereby increasing the extraction efficiency and effect by k times. That is, the corresponding extraction compensation time T2 is shortened to 1 / k of the original value. Based on this, the extraction compensation time T2 is corrected to obtain the new drilling extraction compensation time T2′, T2′=T2 / k.

[0073] According to statistics, the average daily gas extraction volume of a single borehole at the -620m horizontal water tank tunnel in Yangdong Mine after CO2 blasting is 0.09m 3 / min, while the 8261 material transport tunnel did not adopt blasting to increase permeability. The average daily gas extraction volume at the drilling site was 0.03m 3 / min, the two working faces are not far apart and belong to the same geological unit. The occurrence of coal seam 1 is not much different. Based on the current data comparison, it can be considered that 2 # After CO2 blasting, the pure gas extraction rate in coal seams increases by 3.0 times. Therefore, the corresponding extraction time should be shortened to one-third of the original time. Based on this conclusion, the data in Table 3 were revised to obtain the new compensation time T2′ for extraction from a Φ94mm CO2 blasting borehole, as shown in Table 4.

[0074] Table 4 Numerical table of the corrected drainage compensation time and estimated drainage radius for Φ94mm blasting drilling

[0075]

[0076] Step 10: Calculate the effective extraction radius R of the borehole. The extraction radius corresponding to the effective extraction time T is the effective extraction radius R. The results are shown in Table 5.

[0077] Table 5: Determination of effective extraction radius of Φ94mm in-beam borehole after high-energy gas blasting

[0078]

[0079] It can be understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents to achieve the same technical effects; as long as the use requirements are met, they are within the scope of protection of the present invention.

Claims

1. A method for determining the effective extraction radius of a high-energy gas blasting coal seam borehole, characterized by: The measuring method comprises the following steps: Step 1: constructing a set of boreholes in the coal seam, the boreholes including a blasting hole and multiple extraction holes; Step 2: Seal each extraction hole and install an extraction pipe at the hole mouth; Step 3: performing high-energy gas blasting on the blast hole; Step 4: Seal the blasting hole and install an inflatable valve at the hole mouth; Step 5: Fill the blasting hole with SF6 gas, then close the valve and replenish SF6 gas regularly; Step 6: Connect the extraction pipes at the openings of each extraction hole to the mine extraction system for extraction; Step 7: Starting from the day of gas injection in the blasting hole, collect gas samples from each extraction hole every day to test whether the gas samples contain SF6; Step 8: When SF6 gas is detected in the gas sample of a certain extraction hole, the detection work of the extraction hole is terminated. The time when SF6 gas is detected in the extraction hole is the extraction impact time, recorded as T1, in days; Step 9: Calculate the drainage compensation time T2 using the time compensation method. The time compensation method is as follows: after the drainage hole detects SF6 gas after T1 days of drainage, continue to drain for T2 days until the drainage hole reaches the effective drainage radius. At this time, the effective drainage time T = T1 + T2, and the value of T2 is the difference between the drainage impact time and the effective drainage time of the same diameter drilling hole; it also includes: first, based on the existing data of the same mine, the same coal seam, and the same diameter drainage borehole, fit the power function relationship R = At B , where R is the effective drainage radius in meters, t is the drainage compensation time T2 in days, and A and B are constants. Then, the power function relationship is used to derive the effective drainage radius R corresponding to different drainage compensation times T2. Finally, the drainage compensation time T2 is corrected to a new borehole drainage compensation time T2', where T2' = T2 / k, where k is the multiple of drainage efficiency improvement due to high-energy gas blasting permeability enhancement. Step 10: Calculate the effective extraction time T=T1+T2', and determine the effective extraction radius R of the coal seam drill hole based on the calculated effective extraction time T.

2. The method for measuring the effective extraction radius of a high-energy gas blasting coal seam drilling hole according to claim 1, characterized in that: In step 1, the borehole depth is not less than 50m and the diameter is D; the blasting hole is located in the middle of the drilling group, the extraction holes are located on both sides of the blasting hole, and the distance between the extraction hole and the blasting hole is R n .

3. The method for measuring the effective extraction radius of a high-energy gas blasting coal seam drilling hole according to claim 2, characterized in that: The number of the drilling groups is determined according to the on-site conditions. The number of extraction holes is 5, and the distances between each extraction hole and the blasting hole are R1, R2, R3, R4, and R5 respectively.

4. The method for measuring the effective extraction radius of a high-energy gas blasting coal seam drilling hole according to claim 1, characterized in that: In step 2, the sealing depth is not less than 15m.

5. The method for measuring the effective extraction radius of a high-energy gas blasting coal seam drilling hole according to claim 1, characterized in that: In step 5, the periodic replenishment of SF6 gas is to replenish SF6 gas into the blasting hole once a day.

6. The method for measuring the effective extraction radius of a high-energy gas blasting coal seam drilling hole according to claim 1, characterized in that: In step 9, the power function relationship R=At B The effective extraction radius data corresponding to different extraction times were fitted based on the gas pressure reduction method.

7. The method for measuring the effective extraction radius of a high-energy gas blasting coal seam drilling hole according to claim 1, characterized in that: In step 9, the extraction efficiency improvement factor k caused by the high-energy gas blasting enhancement is determined by comparing the inverse relationship between the extraction scalar quantity of the coal seam after high-energy gas blasting enhancement and that of the coal seam without enhancement. Blasting enhancement causes cracks in the coal seam, resulting in an increase in gas concentration and scalar quantity under the same extraction parameters, shortening the time to reach the effective extraction radius.

8. The method for measuring the effective extraction radius of a high-energy gas blasting coal seam drilling hole according to claim 1, characterized in that: In step 10, the extraction radius corresponding to the extraction effective time T is the effective extraction radius R.

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