A method for determining drilling parameters for a hole drilled with a hole-making drill spaced from a conventional drill

Abstract

The application discloses a kind of drilling parameter determination methods of cave drilling and ordinary drilling interval arrangement, comprising the following steps: 1) hydraulic cave drilling construction;2) ordinary drilling construction;3) effective extraction radius test;4) extraction drilling arrangement;5) gas extraction.Through the determination of the effective extraction radius R1 of hydraulic cave drilling and the effective extraction radius R2 of ordinary drilling, hydraulic cave drilling and ordinary drilling are arranged at intervals, ordinary drilling is located between two hydraulic cave drillings, and the hole spacing D between two hydraulic cave drillings should satisfy 2R1<D<2(R1+R2), and the cave spacing d of hydraulic cave drilling should satisfy R1<d<2R1.Using the drilling arrangement and hole arrangement parameters, the extraction blind area of hydraulic cave drilling can be reduced, the extraction efficiency of ordinary drilling can be increased, and the probability of stringing hole accident can also be reduced, which improves the gas extraction efficiency while reducing the construction cost or not significantly increasing the construction cost.

Description

Technical Field

[0001] This invention relates to the field of gas extraction technology, and in particular to a method for determining borehole parameters when cavitation boreholes and ordinary boreholes are arranged at intervals. Background Technology

[0002] my country possesses abundant coal resources, and coal will remain the dominant energy source in the country for a considerable period. However, a significant proportion of my country's coal mines are high-gas mines, with complex coal seam gas occurrence conditions, typically characterized by high gas pressure and content, and low permeability – a "high-storage, low-permeability" pattern. Gas is not only highly flammable and explosive, but its high pressure and content are also significant factors contributing to coal and gas dynamic disasters, making gas a primary challenge to safe coal mining. Gas extraction from coal seams can reduce gas content and mitigate gas hazard risks, while also ensuring the full utilization of gas resources. However, the presence of low-permeability coal seams renders conventional borehole gas extraction methods ineffective, resulting in small effective extraction radii, low extraction efficiency, and long extraction times. Therefore, permeability enhancement and gas extraction technologies for low-permeability coal seams have always been a research hotspot and a challenging area.

[0003] In recent years, hydraulic drilling for gas drainage has been widely used in domestic coal mines. The damage and stress concentration caused by the high-pressure water jet to the coal seam create a pressure relief zone around the drainage hole, increasing the permeability of the coal seam and thus enhancing gas extraction. However, this technology still has some shortcomings: although hydraulic drainage can significantly increase the effective extraction radius of the coal seam, this increase corresponds to a larger borehole spacing. Compared to ordinary boreholes, the increased spacing in hydraulic drainage creates a larger drainage blind zone (as shown in the attached figure). Figure 1 (As shown). To eliminate the extraction blind zone, it is necessary to shorten the borehole spacing. However, since the high-pressure water jet creates a large decompression zone in the coal seam, shortening the borehole spacing will greatly increase the probability of cross-hole accidents. In addition, compared with ordinary boreholes, the in-seam hydraulic cavity creation process (one borehole with multiple cavities) will generate a large amount of additional engineering work. Shortening the borehole spacing will obviously lead to a multiple increase in the amount of construction work and construction time.

[0004] Therefore, combining the characteristics of conventional boreholes with hydraulic cavity drilling to explore new methods for drilling along the bedding plane can improve gas extraction efficiency while reducing or not significantly increasing construction costs, thus achieving efficient gas extraction from "low-permeability coal seams." This has significant engineering value for eliminating mine gas safety hazards and promoting the efficient exploitation and application of coalbed methane. Summary of the Invention

[0005] This invention addresses the technical challenge of gas extraction from low-permeability coal seams by providing a method for determining borehole parameters for the alternating arrangement of cavity boreholes and ordinary boreholes. This aims to improve gas extraction efficiency, accelerate coal seam mining progress, and enhance the safety of coal mining while reducing or not significantly increasing construction costs.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for determining drilling parameters for alternating cavity-making boreholes and ordinary boreholes, comprising the following steps:

[0007] 1) Hydraulic cavity drilling construction: Using integrated mining drilling and punching equipment, drilling along the bedding plane is carried out from the conveyor belt roadway or return air roadway into the coal mining face. After the drilling is completed, hydraulic cavity construction is carried out by high-pressure water jet at fixed cavity distance d intervals during the drilling process, forming a hydraulic cavity chamber with multiple cavities in one hole, and generating a large number of fracture damage networks around the borehole. Then the hole is sealed and a gas extraction hole is reserved.

[0008] 2) Ordinary drilling construction: Using integrated mining drilling and punching equipment, drilling along the coal face is carried out from the conveyor belt roadway or return air roadway, and then the holes are sealed and gas extraction holes are reserved.

[0009] 3) Effective extraction radius test: Coal seam gas extraction was carried out on hydraulic cavity boreholes and ordinary boreholes, and the gas concentration and gas flow rate changes of the gas extraction boreholes were monitored in real time. The effective extraction radius of hydraulic cavity boreholes and ordinary boreholes was calculated using the borehole gas flow rate method, specifically using the following formula:

[0010] when M ≤2 R hour: (1)

[0011] when M >2 R hour: (2)

[0012] In the formula, M The coal seam thickness is in meters (m). R The effective extraction radius is in meters (m). t The sampling time is d; q (t) represents the average daily gas extraction flow rate from the borehole, in m³. 3 / d; ρ The density of coal, t / m³ 3 ; η The pre-sampling rate is 30%. l W represents the length of coal seam encountered during borehole drilling (m); W represents the original gas content of the coal seam (m). 3 / t;

[0013] 4) Drainage borehole layout: The drainage boreholes are arranged according to the calculated effective drainage radius R1 of the hydraulic cavity-forming boreholes and the effective drainage radius R2 of the ordinary boreholes. The borehole layout method is to arrange the in-seam hydraulic cavity-forming boreholes and ordinary boreholes at intervals, with the ordinary boreholes located in the middle of two hydraulic cavity-forming boreholes. The borehole spacing D between two hydraulic cavity-forming boreholes should satisfy 2R1 < D < 2(R1 + R2), and the cavity-forming spacing d of the hydraulic cavity-forming boreholes should satisfy R1 < d < 2R1, so that there is a certain drainage crossover area in the effective drainage range of the boreholes, reducing the drainage blind area. After the drainage boreholes are arranged, they are sealed and gas drainage holes are reserved;

[0014] 5) Gas drainage: Gas is drained through the reserved gas drainage holes to reduce the gas content in the coal seam.

[0015] Furthermore, in steps 1), 2) and 4), the drilling depths of the hydraulic cavity-forming boreholes and ordinary boreholes depend on the length of the coal mining face. If the length of the coal mining face < 200 m, it is selected to construct in-seam boreholes from either side of the belt entry or the return airway into the coal mining face, and upward boreholes are used, which is conducive to drainage and slag discharge. If the length of the coal mining face > 200 m, it is selected to drill holes from both sides of the belt entry and the return airway towards the coal mining face, and the boreholes on both sides are arranged in a staggered manner to prevent the boreholes from penetrating through.

[0016] Furthermore, in steps 1), 2) and 4), the "two-block-one-injection" pressure sealing method is adopted for the hydraulic cavity-forming boreholes and ordinary boreholes, and the sealing depth is not less than 8 m.

[0017] Furthermore, in steps 1) and 4), the distance between the cavity-forming area of the hydraulic cavity-forming boreholes and the two sides of the roadway should be the effective drainage radius R1 of the hydraulic cavity-forming plus the sealing depth.

[0018] The beneficial effects of this invention are: it combines the characteristics of conventional drilling and hydraulic cavity drilling. Conventional drilling has a small effective extraction radius and low extraction efficiency, but the amount of construction work is significantly less than that of hydraulic cavity drilling. Although hydraulic cavity drilling has high extraction efficiency, it has a large amount of construction work and is prone to producing large extraction blind zones. Reducing the hole spacing of hydraulic cavity drilling can easily lead to cross-holes. By alternating hydraulic cavity boreholes and conventional boreholes, with conventional boreholes positioned between two hydraulic cavity boreholes, the spacing between the hydraulic cavity boreholes is increased, reducing the construction workload of hydraulic cavity drilling and offsetting the increased workload of adding conventional boreholes. Furthermore, conventional boreholes reduce the increase in drainage blind zones caused by the increased spacing of hydraulic cavity boreholes, and the numerous fracture damage networks formed by hydraulic cavity boreholes in the coal seam can, to some extent, increase the drainage efficiency of conventional boreholes due to their pressure-relieving and permeability-enhancing effects. Finally, since the influence range of conventional boreholes is much smaller than that of hydraulic cavity boreholes, placing conventional boreholes between two hydraulic cavity boreholes can also reduce the probability of cross-hole accidents. This alternating arrangement of hydraulic cavity boreholes and conventional boreholes can improve gas drainage efficiency while reducing construction costs or not significantly increasing them, promoting efficient gas drainage in low-permeability coal seams and eliminating mine gas safety hazards. Attached Figure Description

[0019] Figure 1 This is a comparison diagram of the blind zones of conventional drilling and hydraulic cavity drilling provided by the present invention.

[0020] Figure 2 This is a construction schematic diagram of an alternating arrangement of cavity-making boreholes and ordinary boreholes provided by the present invention;

[0021] Figure 3 This is a partial front view of the borehole arrangement provided by the present invention;

[0022] Figure 4 This is a partial top view of the borehole arrangement provided by the present invention;

[0023] Among them, 1-hydraulic cavity drilling, 2-ordinary drilling, 3-fracture damage network, 4-extraction intersection zone, 5-extraction blind zone, 6-coal mining face, 7-conveyor belt roadway, 8-return air roadway. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of application of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0025] like Figures 2-4As shown, a method for determining drilling parameters for alternating cavity-making boreholes and ordinary boreholes includes the following steps:

[0026] 1) Construction of hydraulic cavity drilling 1: Using integrated mining drilling and punching equipment, boreholes are drilled from the conveyor belt roadway 7 or the return air roadway 8 into the coal face 6. After the borehole construction is completed, the cavity spacing is fixed by high-pressure water jet during the drill withdrawal process. d To perform hydraulic cavity creation construction at intervals, a hydraulic cavity creation chamber with multiple cavities in one borehole is formed, and a large number of fracture damage networks 3 are generated around the borehole. Then the borehole is sealed and a gas extraction hole is reserved.

[0027] 2) Construction of ordinary borehole 2: Using mining drilling and punching integrated equipment, drill along the seam from the conveyor belt roadway 7 or the return air roadway 8 into the coal mining face 6, then seal the borehole and reserve a gas extraction hole;

[0028] 3) Effective extraction radius test: Coal seam gas extraction was carried out on hydraulic cavity borehole 1 and ordinary borehole 2, and the gas concentration and gas flow rate changes of the gas extraction boreholes were monitored in real time. The effective extraction radius of hydraulic cavity borehole 1 and ordinary borehole 2 was calculated by the borehole gas flow rate method, specifically using the following formula:

[0029] when M ≤2 R hour: (1)

[0030] when M >2 R hour: (2)

[0031] In the formula, M The coal seam thickness is in meters (m). R The effective extraction radius is in meters (m). t The sampling time is d; q (t) represents the average daily gas extraction flow rate from the borehole, in m³. 3 / d; ρ The density of coal, t / m³ 3 ; η The pre-sampling rate is 30%. l W represents the length of coal seam encountered during borehole drilling (m); W represents the original gas content of the coal seam (m). 3 / t;

[0032] 4) Drainage borehole layout: Based on the calculated effective drainage radius of hydraulic cavity borehole 1 R 1. Effective extraction radius of ordinary borehole 2 R 2. The extraction boreholes are arranged in a manner that alternates between hydraulic cavity-forming boreholes 1 and ordinary boreholes 2. The ordinary boreholes 2 are located between the two hydraulic cavity-forming boreholes 1, and the spacing between the two hydraulic cavity-forming boreholes 1 is [not specified]. D Should meet 2R 1 <D<2( R 1+ R 2) Spacing of hydraulic cavity-forming borehole 1 d It should also satisfy R 1< d <2 R 1. Make the effective extraction range of the borehole have a certain extraction intersection zone 4, thereby reducing the extraction blind zone 5. After the extraction borehole is arranged, seal the borehole and reserve gas extraction holes.

[0033] 5) Gas drainage: Gas is drained through pre-reserved gas drainage holes to reduce the gas content of the coal seam.

[0034] In steps 1), 2), and 4), the drilling depth of hydraulic cavity drilling 1 and ordinary drilling 2 depends on the length of the coal face 6. If the length of the coal face 6 is less than 200m, drilling along the layer is carried out from either side of the conveyor belt roadway 7 or the return air roadway 8 into the coal face 6, using upward drilling to facilitate drainage and slag removal. If the length of the coal face 6 is greater than 200m, drilling is carried out from both sides of the conveyor belt roadway 7 and the return air roadway 8 into the coal face 6, with the drilling holes on both sides staggered to prevent the drilling from being continuous.

[0035] In steps 1), 2), and 4), the hydraulic cavity drilling 1 and the ordinary drilling 2 adopt the "two plugs and one injection" pressurized sealing method, and the sealing depth is not less than 8m.

[0036] In steps 1) and 4), the distance between the cavity-creating area of ​​hydraulic cavity-creating borehole 1 and the two sides of the roadway should be based on the sealing depth plus the effective extraction radius of the hydraulic cavity-creating borehole. R 1.

Claims

1. A method for determining a drilling parameter for a pilot hole arranged at an interval from a common hole, characterized by, Comprise the following steps: 1) Hydraulic cavitation drilling (1) construction: using mine drilling and flushing integrated equipment to construct bedding drilling from the belt gateway (7) or return air gateway (8) to the coal mining face (6), after the bedding drilling construction is completed, the drilling process is retreated through high pressure water jet to form a fixed cavitation interval d To carry out hydraulic cavitation construction at intervals, form a hydraulic cavitation chamber with multiple cavities in one hole, and generate a large number of fracture damage networks (3) around the drilling, then seal the hole and leave a gas extraction hole; 2) General drilling (2) construction: using mine drilling and flushing integrated equipment from the belt entry (7) or return air entry (8) to the coal mining face (6) to construct the bedding hole, then sealing the hole and reserving the gas extraction hole; 3) Effective extraction radius test: coal seam gas extraction is carried out on the water-creating cavity drilling (1) and the general drilling (2), and the gas concentration and gas flow change of the gas extraction hole are monitored in real time, the effective extraction radius of the water-creating cavity drilling (1) and the general drilling (2) is calculated by the drilling gas flow method, and the following formula is used for calculation: When M ≤ 2 R When: (1) When M >2 R Time: (2) In the formula, M is the thickness of the coal seam, m; R is the effective extraction radius, m; t is the extraction time, d; q (t) is the average daily gas extraction flow rate of the borehole, m 3 / d; ρ is the density of the coal, t / m 3 ; η is the pre-extraction rate, taken as 30%; l is the coal seam length, m; W is the original gas content of the coal seam, m 3 / t; 4) Layout of extraction boreholes: the effective extraction radius of the hydraulic cavity-creating borehole (1) and the effective extraction radius of the ordinary borehole (2) calculated R 1 R 2 D 2 R 1<D<2 R 1+ R 2 d 1 R 1 d <2 R 1 , the effective extraction range of the borehole has a certain extraction overlap area (4), thereby reducing the extraction blind area (5). After the layout of the extraction boreholes, the boreholes are sealed and the gas extraction holes are reserved. 5) Gas extraction: gas extraction is carried out through the reserved gas extraction hole to reduce the coal seam gas content.

2. The method of claim 1, wherein, In step 1), step 2) and step 4), the drilling depth of the water-creating cavity drilling (1) and the general drilling (2) depends on the length of the coal mining face (6), if the length of the coal mining face (6) is <200m, the bedding hole is constructed from the belt entry (7) or the return air entry (8) to the coal mining face (6), and the upward drilling is adopted, which is beneficial to water and slag drainage; if the length of the coal mining face (6) is >200m, the drilling hole is punched from both sides of the belt entry (7) and the return air entry (8) to the coal mining face (6), and the two sides of the drilling hole are arranged staggeredly to prevent the drilling hole from penetrating.

3. The method of claim 1, wherein the method is characterized by: In step 1), step 2) and step 4), the water-creating cavity drilling (1) and the general drilling (2) both adopt the "two sealing and one injection" pressure sealing hole sealing method, and the sealing depth is not less than 8m.

4. The method of claim 1, wherein, In step 1) and step 4), the distance between the cavity forming area of the hydraulic cavity forming drilling (1) and the two sides of the roadway should be the sealing depth plus the effective extraction radius of the hydraulic cavity forming R 1.

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