Non-coal-exposing coal lane strip gas control method for soft coal seam

Abstract

The application discloses a coal seam strip gas control method for soft coal seam without uncovering coal, adopts liquid rock penetrating and gas coal penetrating to alternately form a hole, and constructs a comb-shaped directional drilling hole in the soft coal seam floor, wherein the main hole of the comb-shaped directional drilling hole is in the floor rock stratum and is parallel to the coal seam, each branch hole on the main hole enters the coal seam from the rock stratum and extends along the coal seam in the direction of the coal seam strip, and a screen pipe is lowered to protect the hole after the hole is formed to carry out gas extraction. The application can realize strip gas extraction control without uncovering coal, reduces the drilling construction amount, realizes rapid, safe and low-cost coal seam strip gas control, reduces the gas early warning or outburst risk, and guarantees the engineering safety.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of coal mine underground tunnel drilling and coal and gas control engineering, and particularly relates to a coal roadway strip gas control method for soft and broken coal seams. BACKGROUND

[0002] With the needs of efficient and safe production of coal mines, gas control problems are increasingly prominent. Directional long boreholes in coal mines have become a widely used and extremely effective gas control method due to their large hole depth and accurate and controllable trajectory. At present, hydraulic screw motor directional drilling is widely used in rock and hard coal seams. However, for the problem that hydraulic directional drilling cannot form a hole in soft and broken coal seams, the developed pneumatic screw drilling directional drilling technology and supporting equipment have gradually entered the stage of engineering application. At present, the conventional method for advanced control of coal roadway driving in soft and broken coal seams is to first excavate a floor roadway, and then a large number of through-seam boreholes are drilled in the floor roadway for coal roadway strip gas pre-drainage and outburst elimination. However, the floor rock roadway is difficult to excavate, has high cost, and the large amount of work and low coal penetration rate of the through-seam boreholes greatly reduce the gas drainage efficiency and the safety of coal mine production. The coal seam directional long borehole coal roadway strip gas control technology based on pneumatic directional drilling technology needs to be drilled in the coal roadway after the coal is exposed. Moreover, when the borehole encounters complex structure, the hole depth often cannot meet the requirements. Therefore, it is necessary to develop a coal roadway strip gas control method based on directional long boreholes without exposing coal. The method is to drill liquid directional drilling and pneumatic directional drilling alternately in the coal seam floor upward along the direction of coal roadway excavation to form a comb-shaped branch hole. The liquid directional drilling is used to form a hole in the floor rock, the pneumatic directional drilling is used to form a hole along the coal seam after entering the coal seam, and the branch holes are overlapped in the coal seam to realize strip gas drainage and control in the complex structure coal roadway without exposing coal and replacing the floor roadway and through-seam boreholes, greatly improving the strip gas control efficiency, reducing the gas control cost, meeting the actual needs of gas control in soft and broken coal seams, and ensuring the safe and efficient production of coal mines.

[0003] At present, the main technical scheme for gas drainage and outburst elimination in the strip area of soft and broken coal seams is to pre-excavate a floor roadway and drill through-seam boreholes upward in the floor roadway for gas pre-drainage, or to expose the coal seam and use directional long boreholes along the coal seam for gas drainage and outburst elimination. The coal roadway to be excavated needs to be in the pressure relief area of the pre-excavated floor roadway. The existing technology has the following defects:

[0004] (1) When the floor rock roadway is pre-excavated, the distance from the coal roadway to be excavated changes greatly due to the large changes in the coal seam undulation, and it is difficult to control the distance to ensure that the coal roadway to be excavated is completely in the pressure relief area of the floor roadway.

[0005] (2) The through-seam boreholes need to be arranged in a fan shape in the full cross-section area of the coal roadway to be excavated, and the number of drilled boreholes is large, the control accuracy of a single borehole is poor, and the overall pre-drainage period is long and the efficiency is low.

[0006] (3) Excavation of the bottom rock tunnel is slow and involves a large amount of work, resulting in high treatment costs and long cycles.

[0007] (4) For coal roadways in broken and soft coal seams that do not meet the conditions for coal exposure, it is not possible to directly construct long directional boreholes along the coal seam.

[0008] (5) Conventional hydraulic directional drilling technology cannot be used to construct long directional boreholes in soft and fractured coal seams. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a method for controlling strip gas in coal roadways of fractured and soft coal seams without exposing the coal seam. This method employs alternating drilling techniques of "hydraulic rock penetration and pneumatic coal penetration" to construct comb-shaped directional branch holes in the bottom plate of the fractured and soft coal seam. The holes enter the coal seam from the bottom plate and are constructed along the strip of the coal roadway. Gas extraction is carried out in the screen pipe protection holes in the coal hole section, thereby achieving the goal of strip gas extraction and control without exposing the coal seam.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] A method for controlling strip gas in coal roadways of fragmented and soft coal seams without exposing the coal seam includes the following steps:

[0012] Hole Formation: In the bottom roadway drilling site, hydraulic directional drilling is used to drill upwards through the rock strata. After entering the coal seam, pneumatic directional drilling is used to extend along the coal seam and into the coal seam section. When drilling along the coal seam cannot continue and the length of the drilling along the coal seam does not meet the requirement of the coal seam section length, the drilling is reversed back to the rock strata section, and hydraulic directional drilling is used to continue drilling the main hole of the rock strata section. The above process of hydraulic directional drilling upwards through the rock strata section and pneumatic directional drilling along the coal seam section through the coal seam is repeated to obtain branch holes until the length of the drilling along the coal seam reaches the requirement of the coal seam section length. Finally, the main hole of the rock strata section and multiple branch holes extending upwards into the coal seam section are obtained. The main hole and the multiple branch holes above it form a comb-shaped directional borehole.

[0013] Screening pipe installation: After the construction of each branch hole is completed and before the construction of the next branch hole, a branch hole screen pipe must be installed in the branch hole. The branch hole screen pipe is installed at the bottom of the branch hole by hydraulic screen pipe installation in the drill rod and is suspended at the bottom of the hole to ensure the smooth flow of gas extraction channels in the coal seam section. After the construction of the last branch hole is completed, the main hole screen pipe is installed in the main hole.

[0014] Gas extraction: After the main borehole screen pipe is lowered, the borehole is immediately sealed and connected to the negative pressure extraction pipeline for gas extraction and treatment, so that the gas pressure and gas content in the coal roadway strip area are reduced to a safe range, thereby eliminating the risk of gas disasters during the excavation of coal roadways in outburst-prone coal seams and achieving rapid and safe excavation.

[0015] The present invention also includes the following technical features:

[0016] Specifically, the length of the along-seam borehole is required to be greater than 30-50 m of the length of the coal roadway strip.

[0017] Specifically, the main borehole is located in the floor stratum 3-6 m away from the coal seam.

[0018] Specifically, there is no extraction blind area between the adjacent branch boreholes on the same main borehole, that is, the coal-seam-seeing depth of the next branch borehole minus the terminal depth of the previous branch borehole is less than the extraction range.

[0019] Specifically, the area where the comb-shaped directional boreholes are arranged is 15 m on each side of the coal roadway to be excavated, and the distance between the adjacent two groups of comb-shaped directional boreholes is 5-6 m.

[0020] Specifically, the diameter of the comb-shaped directional borehole is not less than 90 mm, and the drill bit of the rock stratum section is larger than the size of the borehole in the coal seam section.

[0021] Specifically, the vertical distance between the floor roadway drilling field and the coal seam is within 20 m.

[0022] Specifically, the length of the screen pipe section of the branch borehole is greater than the depth of the coal borehole section of the branch borehole by 2-3 m.

[0023] Specifically, the gas extraction of the borehole needs to be monitored throughout the process, the mixed flow, the pure flow, and the total extraction amount are monitored, after extraction, the borehole in the coal roadway strip area is inspected, and the gas extraction effect is inspected.

[0024] Compared with the prior art, the present application has the following technical effects:

[0025] (1) The present application realizes the "roadway replaced by borehole" coal roadway strip gas control of the comb-shaped branch borehole in the floor of the broken soft outburst coal seam along the seam.

[0026] (2) The present application uses the "hydraulic rock penetration, pneumatic coal penetration" alternate borehole technology to construct the comb-shaped directional branch borehole in the floor of the broken soft coal seam, enters the coal seam from the floor, constructs along the coal roadway strip along the seam, and carries out gas extraction in the coal borehole section with the screen pipe hole protection, realizes the directional long borehole coal roadway strip gas control method in the broken soft outburst coal seam without uncovering the coal seam, and guarantees the disaster control safety.

[0027] (3) Compared with the traditional floor roadway + through-layer borehole strip gas control method, the present application saves the floor roadway, reduces the drilling construction amount, realizes the rapid, safe, and low-cost coal roadway strip gas control. Compared with the seam strip gas control method after uncovering the coal seam, the present application reduces the gas early warning or outburst risk, and guarantees the engineering safety. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a cross-sectional schematic view of the floor comb-shaped borehole arrangement in the coal roadway strip area.

[0029] Figure 2 A top plan view showing the arrangement of comb-shaped holes in the floor slab of a coal roadway strip area;

[0030] Figure 3 Schematic diagram of the distribution of branch holes and main holes for gas drainage screens.

[0031] Meaning of the symbols in the attached diagram: 1. Coal seam, 2. Branch hole, 3. Main hole, 4. Bottom drilling site, 5. Coal roadway to be excavated, 6. Untreated area, 7. Branch hole screen pipe, 8. Main hole screen pipe, B1. First branch point, B2. Second branch point, B3. Third branch point; L. Length of the coal section of the branch hole, h. Distance of the main hole from the bottom of the coal seam. Detailed Implementation

[0032] This invention provides a method for controlling strip gas in coal roadways of fractured and soft coal seams by combining hydraulic and pneumatic directional drilling technologies in coal mines. This method utilizes comb-shaped directional branch holes in the floor along the coal seam to achieve this control. When coal seams are not suitable for exposure or are extremely fractured and structurally complex, comb-shaped holes are drilled in the floor drilling site along the strip direction of the coal roadway to pre-drain gas from the strip area, thereby reducing the regional gas pressure and content to a safe range and achieving safe and efficient tunneling. This invention uses a set of comb-shaped directional long boreholes in the coal seam floor within the strip area to achieve strip gas extraction and control in coal roadways without the need for coal seam exposure. Fractured and soft coal seams generally cannot be drilled using hydraulic directional drilling technology for long directional boreholes or the borehole depth is less than 100m; therefore, underground pneumatic directional drilling technology is required to construct long directional boreholes for gas extraction within the coal seam.

[0033] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0034] Example 1:

[0035] like Figures 1 to 3 As shown, this embodiment provides a method for controlling strip gas in coal roadways of broken and soft coal seams without exposing the coal seam. Figure 1 This is a schematic cross-sectional view of the strip along the coal roadway according to the present invention. Figure 2 This is a top-down plan view of a strip area in a coal roadway. Figure 3The schematic diagram is shown in the figure. As shown in the figure, the bottom plate comb-shaped directional hole soft coal seam coal roadway strip gas extraction and control method of the embodiment is to construct the bottom plate comb-shaped directional hole by using the "hydraulic rock penetration, pneumatic coal penetration" alternate hole forming technology, and the gas pre-extraction and control function of the coal roadway to be excavated is realized by the main hole and the branch hole at one time. The branch hole enters the coal roadway for gas extraction and pressure relief, and the coal seam sections of each branch hole in the main hole realize front and rear overlap, that is, the coal depth of the next branch hole is less than or equal to the distance between the terminal hole depth of the last branch hole, which ensures that there is no blind area for gas extraction. The main hole provides a main channel for gas extraction of each branch hole, and after gas extraction is carried out through a sufficient number of main holes and branch holes in the coal roadway strip area, the gas pressure and gas content in the coal roadway strip area are reduced to a safe range, thereby eliminating the gas disaster risk of the coal roadway excavation in the outburst coal seam, and realizing rapid and safe excavation.

[0036] The embodiment upwardly opens a hole in the floor rock stratum drilling field, extends a certain distance into the coal seam to be excavated, and then drills along the coal seam in the direction of the coal roadway. When the coal seam is broken and soft to a certain extent or other structures or broken conditions cannot continue to extend along the coal seam, the branch hole is opened in the rock main hole to continue to drill into the coal seam, and the process is repeated until the designed coal roadway strip length is covered. After the branch hole is completed, before the next branch hole is opened, the branch coal hole section L needs to be protected by a screen pipe to prevent the coal hole from being blocked after the hole collapses, and to ensure the smoothness of the gas channel in the coal hole section.

[0037] According to the deflecting characteristics of directional drilling, the vertical distance between the roadway where the hole is opened and the coal seam to be excavated should be less than or equal to 20 m, and at the same time, it should also be ensured that the construction position is outside the allowable safe distance, and the first coal hole depth should not exceed 100 m, that is, the invalid hole section area should not exceed 100 m.

[0038] As shown in Figure 2 , the hole arrangement range is generally a strip width of 15 m on both sides of the coal roadway to be excavated, and the number of holes is determined according to the drilling extraction radius, which is generally 7 holes with a hole spacing of 5-6 m. Among them, a hole needs to be arranged in the center line of the coal roadway to be excavated. The coverage length of one hole arrangement is generally not less than 300 m to meet the requirements of the relevant regional outburst elimination safety regulations.

[0039] The adjacent branch holes of each main hole need to overlap in the coal seam to leave no extraction blind area, that is, the difference between the coal depth of the next branch hole and the terminal hole depth of the last branch hole is less than the extraction range, which ensures the coverage of the area without blind area.

[0040] The branch hole coal hole section needs to be protected by a screen pipe, and the screen pipe should be immediately lowered after the terminal hole of the branch hole. The screen pipe section length should be not less than L+2 m, that is, the length of the exposed coal hole section δL≥2 m, which ensures that the opening end of the screen pipe is located in the stable rock hole and is not blocked by coal, and at the same time, it does not affect the construction of the main hole and the next branch hole.

[0041] The main hole of the floor comb hole is generally located at a position of 3-6 m from the coal seam, which can ensure that the drilling hole is located in the stable rock stratum and can guarantee the need of branch construction.

[0042] In the embodiment, the effect of regional gas control before the coal roadway excavation is tested, and after the effect test shows that there is no outburst danger, the coal roadway excavation can be performed.

[0043] The strip gas control method for the soft coal seam of the coal roadway without uncovering coal, specifically comprises the following steps:

[0044] In the first step, hole forming: the rock stratum section hole is drilled upward by using the hydraulic directional drilling in the floor roadway drilling field, and after entering the coal seam, the coal seam section hole is drilled along the coal roadway strip direction by using the pneumatic directional drilling, when the drilling along the coal seam cannot continue and the length of the drilling along the coal seam does not reach the requirement of being greater than the length of the coal roadway strip, the rock stratum section hole is retreated to the suitable branch point and the rock stratum section main hole is drilled forward by using the hydraulic directional drilling, the above-mentioned upward drilling of the rock stratum section hole and the drilling of the coal seam section hole along the coal seam are repeated to obtain the branch holes, until the length of the drilling along the coal seam reaches the requirement of being greater than the length of the coal roadway strip, finally, the rock stratum section main hole and the branch holes extending to the coal seam section are obtained, the trajectory of the main hole is parallel to the coal seam, and the main hole and the branch holes thereon form the comb directional drilling hole; specifically, due to the drilling characteristics of the soft coal seam, the sectional construction is needed in the comb directional drilling construction, that is, the water is used as the medium in the rock stratum section, and the hydraulic screw motor is used for directional drilling to form the hole; after entering the coal seam, the air or nitrogen is used as the medium in the coal seam section, and the pneumatic screw motor is used for directional drilling to form the hole; when the pneumatic drilling is performed, the water construction section needs to be blown by the air to ensure that the hole is dry and the air is used for deslagging.

[0045] Specifically, the length of the drilling along the coal seam needs to reach 30-50 m greater than the length of the coal roadway strip. The main hole is located in the floor rock stratum 3-6 m from the coal seam to ensure sufficient drilling climbing distance, and the main hole is used as the main channel for gas extraction. The branch points of the branch holes on each main hole are determined according to the softness of the coal seam and the structure, and each branch hole extends along the coal seam as much as possible. The adjacent branch holes on the same main hole are seamlessly connected to ensure that there is no blind area, and the coal seam depth reached by the previous branch hole can reach the coal seam depth of the next branch hole. The area of the comb directional drilling hole is 15 m on each side of the coal roadway to be excavated, the hole spacing is determined according to the drilling extraction radius of the target coal seam, the distance between the adjacent two groups of comb directional drilling holes is 5-6 m, the diameter of the comb directional drilling hole is not less than 90 mm, generally 96 mm or 108 mm, and the drill bit size of the rock stratum section is greater than that of the coal seam section to ensure sufficient deslagging channel. The vertical distance between the floor roadway drilling field and the coal seam is within 20 m to minimize the invalid depth of the drilling climbing section.

[0046] Second step, screen pipe: each branch hole construction end and the next branch hole construction, need to be in the branch hole into the branch hole screen pipe, branch hole screen pipe through the drill pipe inside the water screen pipe mode into the branch hole bottom, and suspended in the hole bottom, to ensure the smoothness of the coal seam section drilling gas extraction channel; After the construction of the last branch hole is completed, the main hole also enters the main hole screen pipe; Specifically, the length of the branch hole screen pipe is greater than the depth of the coal hole section in the branch hole by 2-3m, so as to ensure that the outer opening of the branch hole screen pipe is in the rock hole.

[0047] Third step, gas extraction: after the main hole screen pipe is lowered, the hole is sealed and the negative pressure extraction pipeline is connected for gas extraction treatment at the hole, so as to reduce the gas pressure and gas content in the coal roadway strip area to a safe range, thereby eliminating the gas disaster risk during the excavation of the coal roadway in the outburst coal seam, and realizing rapid and safe excavation; The drilling gas extraction needs to be monitored throughout the process, including mixed flow, pure flow, extraction total amount, etc., after a certain period of extraction, the drilling in the coal roadway strip area is inspected, and the gas extraction effect is tested.

[0048] The preferred embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the specific details in the above embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0049] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0050] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the technical concept of the present application, and it should also be considered as disclosed by the present application.​

Claims

1. A method for controlling strip gas in coal roadways of fragmented and soft coal seams without exposing the coal seam, characterized in that, Includes the following steps: Hole Formation: In the bottom roadway drilling site, hydraulic directional drilling is used to drill upwards through the rock strata. After entering the coal seam, pneumatic directional drilling is used to extend along the coal seam and into the coal seam section. When drilling along the coal seam cannot continue and the length of the drilling along the coal seam does not meet the requirement of the coal seam section length, the drilling in the rock strata is reversed and hydraulic directional drilling is used to continue drilling the main hole in the rock strata. The above process of hydraulic directional drilling upwards through the rock strata and pneumatic directional drilling along the coal seam is repeated until the length of the drilling along the coal seam meets the requirement of the coal seam section length. Finally, the main hole in the rock strata and multiple branch holes extending upwards into the coal seam are obtained. The main hole and the multiple branch holes above it form a comb-shaped directional borehole. Screening pipe installation: After the construction of each branch hole is completed and before the construction of the next branch hole, the branch hole screen pipe must be installed in the completed branch hole. The branch hole screen pipe is installed at the bottom of the branch hole by hydraulic screen pipe installation in the drill rod and is suspended at the bottom of the hole to ensure the smooth flow of gas extraction channel in the coal seam section. After the construction of the last branch hole is completed, the main hole screen pipe is installed in the main hole. Gas extraction: After the main borehole screen pipe is lowered, the borehole is immediately sealed and connected to the negative pressure extraction pipeline for gas extraction and treatment, so that the gas pressure and gas content in the coal roadway strip area are reduced to a safe range, thereby eliminating the risk of gas disasters during the excavation of coal roadways in outburst-prone coal seams and achieving rapid and safe excavation.

2. The method for controlling strip gas in coal roadways of soft, broken coal seams without coal exposure as described in claim 1, characterized in that, The length of the borehole along the coal seam is required to be 30 to 50 meters longer than the length of the coal roadway strip.

3. The method for controlling strip gas in coal roadways of soft, broken coal seams without coal exposure as described in claim 1, characterized in that, The main borehole is located in the bottom rock strata 3 to 6 meters away from the coal seam.

4. The method for controlling strip gas in coal roadways of soft, broken coal seams without coal exposure as described in claim 1, characterized in that, There is no extraction blind zone between adjacent branch holes on the same main hole, that is, the difference between the coal-bearing depth of the next branch hole and the final hole depth of the previous branch hole is less than the extraction range.

5. The method for controlling strip gas in coal roadways of soft, broken coal seams without coal exposure as described in claim 1, characterized in that, The area where the comb-shaped directional boreholes are arranged is 15m on each side of the coal roadway to be excavated, and the distance between two adjacent sets of comb-shaped directional boreholes is 5 to 6m.

6. The method for controlling strip gas in coal roadways of soft, broken coal seams without coal exposure as described in claim 1, characterized in that, The diameter of the comb-shaped directional borehole shall not be less than 90 mm, and the borehole size in the rock strata section shall be larger than that in the coal seam section.

7. The method for controlling strip gas in coal roadways of soft, broken coal seams without coal exposure as described in claim 1, characterized in that, The vertical distance between the bottom roadway drilling site and the coal seam is within 20m.

8. The method for controlling strip gas in coal roadways of soft, broken coal seams without coal exposure as described in claim 1, characterized in that, The length of the branch hole screen section is 2 to 3 meters greater than the depth of the coal section of the branch hole.

9. The method for controlling strip gas in coal roadways of soft, broken coal seams without coal exposure as described in claim 1, characterized in that, Borehole gas extraction requires full-process monitoring, including monitoring the mixed flow rate, pure flow rate, and total extraction volume. After extraction, inspection boreholes should be drilled in the coal roadway strip area, and the gas extraction effect should be verified.

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