Directional drilling construction method for coal roadway strip extraction

Abstract

The directional drilling construction method comprises the following steps that S1, construction preparation is conducted, specifically, the geological structure, coal seam occurrence and gas parameters of a drilling area are found out, a drilling arrangement scheme is determined, and azimuth angle, dip angle and aperture construction parameters are determined; s2, primary drilling construction is conducted, specifically, drilling is conducted to a preset position, hole sealing is conducted, and a screen pipe is installed; s3, secondary main hole forming construction is conducted, drilling is conducted to a target area along a top and bottom plate stable rock stratum, the track is controlled through the measurement-while-drilling technology, and hole forming is prevented from being affected by coal seam softness; s4, branch holes are constructed, primary and secondary branch holes are formed from the main hole to the coal seam, and a final hole penetrates through the target coal seam; s5, drilling anti-reflection treatment is carried out; and S6, gas extraction and effect inspection. According to the method, it is ensured that the drill hole can fully cover the coal roadway tunneling key area, the gas control blind area is effectively eliminated, a foundation is built for follow-up construction, and the continuity and safety of the whole construction process are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of coal mine gas control and underground drilling engineering technology, and in particular to a directional drilling construction method for strip extraction in coal roadways. Background Technology

[0002] In coal mining, gas control in high-gas coal seams is a core aspect of ensuring construction safety. Gas outbursts and explosions pose serious risks to efficient and green coal mining. Directional drilling technology, with its advantages of controllable trajectory, wide coverage, and high extraction efficiency, has become the mainstream technology for coal seam gas extraction. However, existing directional drilling technology for coal seam roof and floor still faces many problems that urgently need to be solved: On the one hand, the geological conditions in the drilling area are complex, the coal seam is unstable, and the gas parameters are highly volatile. Traditional pre-construction preparation work lacks sufficient precision in geological parameter exploration, which can easily lead to unreasonable borehole layout, failure to fully cover dangerous areas in coal roadway excavation, and leave blind spots for gas control. On the other hand, the sealing quality of the first borehole is inconsistent, and the stability of the screen pipe installation is insufficient, which can easily lead to problems such as borehole wall collapse and air leakage, affecting the continuity of subsequent borehole construction. At the same time, during the drilling of the second main borehole, the trajectory control precision is low due to the softness of the coal seam and the development of rock fissures, which can easily deviate from the design path and result in substandard coverage of the target area. In addition, the existing branch boreholes have unreasonable spacing and lack targeted selection of borehole diameter, making it difficult to form a uniform gas diversion network. In addition, the natural permeability of the coal seam is poor, so even if conventional permeability enhancement measures are implemented, the gas extraction efficiency is still low, and the extraction effect is evaluated by a single indicator, which cannot comprehensively and accurately assess the control effect.

[0003] As coal mining depths increase and geological conditions become more complex, problems such as high gas content and high ground stress are compounded, making existing construction methods insufficient to meet the demands of efficient gas control. This results in slow coal roadway excavation, high safety risks, and increased production costs. Therefore, developing a directional drilling method for the roof and floor of coal seams that is adaptable to complex geological conditions, features precise borehole layout, stable borehole formation, reasonable branch coverage, significant permeability enhancement, and controllable extraction effects has become a key technical challenge urgently needing to be addressed in the field of safe coal mining. Summary of the Invention

[0004] The purpose of this invention is to provide a directional drilling construction method for strip extraction in coal roadways, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution: The present invention provides a method for directional drilling for strip extraction in coal roadways, comprising the following steps: S1, Construction preparation: Investigate the geological structure, coal seam occurrence and gas parameters of the drilling area, determine the drilling layout plan, and clarify the azimuth, dip angle and borehole diameter construction parameters to ensure coverage of the predetermined range in front of and on both sides of the coal roadway. S2, drilling construction begins, according to... Drill a 193mm diameter borehole to the predetermined position at 50m, seal the borehole using a two-plug, one-injection cementing method, and install... 127mm screen tube, with an effective sealing length of not less than 8m; S3, second main borehole construction, along the stable rock strata of the top and bottom plates. Drilling to the target area with a 98mm diameter hole, the trajectory is controlled by measurement-while-drilling technology to avoid the soft coal seam affecting the hole formation; S4, branch hole construction: Primary and secondary branch holes are drilled from the main hole into the coal seam. The spacing between primary branch holes is 50m, and the hole diameter is... 93mm~ 125mm, the final hole penetrated the target coal seam; S5, borehole permeability enhancement treatment, uses hydraulic fracturing technology to form interconnected fractures in the coal seam through high-pressure water flow to improve permeability; S6. Gas extraction and effectiveness verification: Connect the borehole to the high negative pressure extraction system, monitor the extraction parameters, and verify the effectiveness using residual gas content and pressure indicators.

[0006] According to the directional drilling construction method for strip extraction in coal roadways provided by the present invention, in S1, the borehole covers at least 60m in front of the coal roadway excavation working face and at least 15m outside the outline of both sides of the roadway; the borehole is densely arranged in areas with abnormal geological structures to ensure that there are no blank extraction zones.

[0007] According to the directional drilling construction method for strip extraction in coal roadways provided by the present invention, in S2, before drilling, debris in the drilling area must be cleaned, and the verticality deviation of the drilling shall not exceed 0.5%; the screen pipe shall be made of high-strength wear-resistant material, both ends shall be firmly fixed, the strength grade of the sealing cement shall not be lower than 42.5, and the curing time shall not be less than 72 hours.

[0008] According to the directional drilling construction method for strip extraction in coal roadways provided by the present invention, in S3, the drilling trajectory is monitored in real time during the drilling process, and adjustments are made in a timely manner when the deviation exceeds 0.3m; the main hole must be located in the stable rock strata of the top and bottom plates, and not less than 5m away from the coal seam boundary to avoid the collapse of the hole due to mining.

[0009] According to the directional drilling construction method for strip extraction in coal roadways provided by the present invention, in S4, the branch hole construction adopts directional drilling technology, the angle between the secondary branch hole and the primary branch hole is controlled at 30° to 60°, and the final hole position deviation does not exceed 1m, so as to ensure that the extraction range uniformly covers the target coal seam.

[0010] According to the directional drilling construction method for strip extraction in coal roadways provided by the present invention, in S5, the hydraulic fracturing pressure is controlled at 15-25 MPa, the fracturing time per hole is not less than 4 hours, and the fracturing fluid adopts a formula of water and fracturing aid, with the fracturing aid added at a ratio of 0.5%-1.0% to improve the fracture propagation effect.

[0011] According to the directional drilling construction method for strip extraction in coal roadways provided by the present invention, in S6, the negative pressure of the extraction system is not less than 13 kPa, and a flow meter and a methane concentration sensor are installed in the extraction pipeline to monitor the flow rate and concentration in real time; the pipeline connection is sealed by a flange and a sealing ring.

[0012] According to the directional drilling construction method for strip extraction in coal roadways provided by the present invention, in S6, the effect verification test points are arranged in areas with low borehole density in the pre-extraction range, and each test area has no less than 5 test points.

[0013] The present invention discloses the following technical effects: This invention precisely controls the core geological and construction parameters through a comprehensive construction preparation process, ensuring that the boreholes can fully cover the key areas of coal roadway excavation, effectively eliminating blind spots in gas control, laying a solid foundation for subsequent construction, and ensuring the continuity and safety of the overall construction process.

[0014] This invention relies on scientific graded drilling construction and trajectory control technology to avoid the impact of unfavorable geological conditions such as soft coal seams on the quality of borehole formation. At the same time, it forms an efficient flow guiding network through reasonable branch hole arrangement, thereby improving the coverage and effect of the borehole on the target coal seam.

[0015] This invention combines targeted permeability enhancement treatment with comprehensive extraction effect testing, significantly improving coal seam permeability and gas extraction efficiency. It can accurately assess the treatment quality, effectively reduce the risk of gas disasters, and provide reliable technical support for efficient and safe coal mining. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the drilling arrangement of the top and bottom plates of the present invention; Figure 2 This is a schematic diagram of the borehole layout for testing purposes in this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Reference Figure 1-2 This invention provides a method for directional drilling for strip extraction in coal roadways, comprising the following steps: S1, Construction preparation: Investigate the geological structure, coal seam occurrence and gas parameters of the drilling area, determine the drilling layout plan, and clarify the azimuth, dip angle and borehole diameter construction parameters to ensure coverage of the predetermined range in front of and on both sides of the coal roadway. S2, drilling construction begins, according to... Drill a 193mm diameter borehole to the predetermined position at 50m, seal the borehole using a two-plug, one-injection cementing method, and install... 127mm screen tube, with an effective sealing length of not less than 8m; S3, second main borehole construction, along the stable rock strata of the top and bottom plates. Drilling to the target area with a 98mm diameter hole, the trajectory is controlled by measurement-while-drilling technology to avoid the soft coal seam affecting the hole formation; S4, branch hole construction: Primary and secondary branch holes are drilled from the main hole into the coal seam. The spacing between primary branch holes is 50m, and the hole diameter is... 93mm~ 125mm, the final hole penetrated the target coal seam; S5, borehole permeability enhancement treatment, uses hydraulic fracturing technology to form interconnected fractures in the coal seam through high-pressure water flow to improve permeability; S6. Gas extraction and effectiveness verification: Connect the borehole to the high negative pressure extraction system, monitor the extraction parameters, and verify the effectiveness using residual gas content and pressure indicators.

[0021] Further optimize the plan. In S1, the boreholes should cover at least 60m in front of the coal roadway excavation working face and at least 15m outside the outline of both sides of the roadway. In areas with abnormal geological structures, the boreholes should be densely arranged to ensure that there are no gaps in the extraction.

[0022] During the construction preparation phase, it is necessary to enhance the accuracy of geological exploration, and refine the geological structure and coal seam occurrence information by combining drilling and geophysical exploration methods. Regarding the borehole coverage area, a core coverage standard is defined as at least 60m in front of the coal roadway working face and at least 15m outside the outline of both sides of the roadway, ensuring early control of gas risks in front of and around the tunnel. For areas with abnormal geological structures, the borehole layout needs to be densified based on the exploration results. By increasing borehole density and shortening the spacing between boreholes, weak areas in the conventional drainage layout can be filled. Simultaneously, coverage area simulation verification should be conducted after layout to ensure that no drainage gaps exist.

[0023] Further optimize the plan. In S2, before drilling, debris in the drilling area must be cleaned and the verticality deviation of the drilling should not exceed 0.5%. The screen pipe should be made of high-strength wear-resistant material, and both ends should be firmly fixed. The strength grade of the sealing cement should not be lower than 42.5, and the curing time should not be less than 72 hours.

[0024] Before drilling begins, the drilling area must be thoroughly cleaned to remove loose coal, gravel, and other debris to prevent them from affecting drilling accuracy and subsequent sealing quality. During drilling, verticality is monitored in real time using specialized inclination measurement equipment to ensure a deviation of no more than 0.5% and to guarantee a regular borehole trajectory. The screen pipe is made of high-strength, wear-resistant material, suitable for complex underground geological environments. During installation, a two-end fixing process is used to enhance stability and prevent displacement during later use. Special cement with a strength grade of at least 42.5 is used for sealing to ensure sealing strength. After pouring, a curing process of no less than 72 hours is strictly followed. During the curing period, the borehole must not be disturbed to ensure sealing tightness and prevent air and water leakage.

[0025] Further optimization of the scheme: In S3, the borehole trajectory is monitored in real time during drilling, and adjustments are made promptly when the deviation exceeds 0.3m; the main borehole must be located within the stable rock strata of the top and bottom plates, and at least 5m away from the coal seam boundary to avoid borehole collapse caused by mining activities.

[0026] Throughout the second main borehole drilling process, a real-time measurement-while-drilling system was used to monitor the trajectory. If the deviation exceeded 0.3m, corrective measures were immediately taken, such as adjusting drilling parameters and activating directional tools, to ensure the main borehole trajectory met design requirements. Before the main borehole was laid out, a specific assessment of the stability of the roof and floor strata was conducted to clarify the criteria for determining the lithology and thickness of stable strata. This ensured that the main borehole remained within stable strata throughout its length and was at least 5m from the coal seam boundary. This distance was set based on the assessment results of the mining impact range and effectively avoided borehole wall collapse caused by later mining stress, ensuring long-term stable passage of the main borehole.

[0027] Further optimizing the scheme, in S4, directional drilling technology is used for branch hole construction, the angle between the secondary branch hole and the primary branch hole is controlled between 30° and 60°, and the final hole position deviation does not exceed 1m, ensuring that the extraction range uniformly covers the target coal seam.

[0028] The entire branch hole construction process utilizes directional drilling technology, equipped with precision guide drill bits to ensure controllable drilling direction. The angle between the secondary and primary branch holes is controlled between 30° and 60°. This angle range is determined based on the coal seam thickness and the requirement for uniform extraction, enabling efficient superposition of extraction areas. Trajectory monitoring is conducted simultaneously during drilling, and the drilling angle is adjusted based on real-time data to ensure that the final hole position deviation does not exceed 1m. After construction, the distribution density and coverage of the branch holes are verified to ensure uniform coverage of the target coal seam and improve overall extraction efficiency.

[0029] Further optimization of the scheme: In S5, the hydraulic fracturing pressure is controlled at 15-25 MPa, the single-hole fracturing time is not less than 4 hours, and the fracturing fluid adopts a formula of water plus fracturing aid, with the fracturing aid added at a ratio of 0.5%-1.0% to improve the fracture propagation effect.

[0030] Before hydraulic fracturing, the fracturing pressure must be accurately calculated based on parameters such as coal seam permeability and rock strength, and controlled within the range of 15–25 MPa to avoid excessive pressure leading to excessive rock damage or insufficient pressure preventing the formation of effective fractures. The fracturing time per borehole should be no less than 4 hours to ensure sufficient fracture expansion and the formation of a connected network. An environmentally friendly formula of water and fracturing aid should be used for the fracturing fluid. Water is readily available and does not pollute the downhole environment. The fracturing aid ratio is controlled between 0.5% and 1.0%, a ratio determined based on laboratory tests and field measurements, which can significantly improve fracture expansion. During fracturing, the pressure change curve should be monitored in real time, and the fracture development should be judged based on the curve characteristics, with timely adjustments to the construction parameters.

[0031] Further optimization of the scheme: In S6, the negative pressure of the extraction system is not less than 13 kPa, and the extraction pipeline is equipped with a flow meter and a methane concentration sensor to monitor the flow rate and concentration in real time; the pipeline connection uses flanges and sealing rings to achieve sealing.

[0032] The negative pressure setting of the extraction system is no less than 13 kPa. This negative pressure value is determined comprehensively based on the extraction distance, pipeline resistance, and gas concentration to ensure efficient gas extraction. During the installation of the extraction pipeline, flow meters and methane concentration sensors are installed at key nodes to ensure real-time monitoring of extraction flow rate and gas concentration data, providing a basis for adjusting extraction parameters. The pipeline connection adopts a double sealing process using flanges and sealing rings. The sealing rings are made of gas-resistant and wear-resistant materials. During installation, ensure that the flanges fit tightly and the bolts are tightened evenly. After installation, conduct an airtightness test to prevent air leakage from affecting the extraction effect.

[0033] In further optimization of the scheme, in S6, the effect verification test points are arranged in areas with low borehole density in the pre-drilling range, with no less than 5 test points in each verification area.

[0034] Test points are preferentially placed in areas with low borehole density within the pre-drainage range, as these areas are weak points in the drainage process, and the test results from these areas can more comprehensively reflect the overall drainage effect. Each test area should have no fewer than 5 test points, evenly distributed to ensure coverage of the entire test area. The testing equipment should be calibrated before testing, and the testing process should strictly follow the coal mine gas drainage effect inspection specifications, accurately collecting core indicator data such as residual gas content and gas pressure. Through comprehensive analysis of data from multiple test points, the accuracy of the drainage effect can be precisely assessed.

[0035] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0036] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for directional drilling in coal roadway strip extraction, characterized in that, Includes the following steps: S1, Construction preparation: Investigate the geological structure, coal seam occurrence and gas parameters of the drilling area, determine the drilling layout plan, and clarify the azimuth, dip angle and borehole diameter construction parameters to ensure coverage of the predetermined range in front of and on both sides of the coal roadway. S2, drilling construction begins, according to... Drill a 193mm diameter borehole to the predetermined position at 50m, seal the borehole using a two-plug, one-injection cementing method, and install... 127mm screen tube, with an effective sealing length of not less than 8m; S3, second main borehole construction, along the stable rock strata of the top and bottom plates. Drilling to the target area with a 98mm diameter hole, the trajectory is controlled by measurement-while-drilling technology to avoid the soft coal seam affecting the hole formation; S4, branch hole construction: Primary and secondary branch holes are drilled from the main hole into the coal seam. The spacing between primary branch holes is 50m, and the hole diameter is... 93mm~ 125mm, final hole penetrates the target coal seam; S5, borehole permeability enhancement treatment, uses hydraulic fracturing technology to form interconnected fractures in the coal seam through high-pressure water flow to improve permeability; S6. Gas extraction and effectiveness verification: Connect the borehole to the high negative pressure extraction system, monitor the extraction parameters, and verify the effectiveness using residual gas content and pressure indicators.

2. The directional drilling construction method for strip extraction in coal roadways according to claim 1, characterized in that, In S1, boreholes should cover at least 60m in front of the coal roadway excavation working face and at least 15m outside the outline of both sides of the roadway; in areas with abnormal geological structures, the boreholes should be densely arranged to ensure that there are no gaps in the extraction.

3. The directional drilling construction method for strip extraction in coal roadways according to claim 1, characterized in that, In S2, before drilling, debris in the drilling area must be cleaned, and the verticality deviation of the drilling should not exceed 0.5%. The screen pipe should be made of high-strength wear-resistant material, and both ends should be firmly fixed. The strength grade of the sealing cement should not be lower than 42.5, and the curing time should not be less than 72 hours.

4. The directional drilling construction method for strip extraction in coal roadways according to claim 1, characterized in that, In S3, the borehole trajectory is monitored in real time during drilling, and adjustments are made promptly when the deviation exceeds 0.3m; the main borehole must be located within the stable rock strata of the top and bottom plates, and at least 5m away from the coal seam boundary to avoid borehole collapse caused by mining activities.

5. The directional drilling construction method for strip extraction in coal roadways according to claim 1, characterized in that, In S4, directional drilling technology is used for branch hole construction. The angle between the secondary branch hole and the primary branch hole is controlled between 30° and 60°, and the final hole position deviation does not exceed 1m, ensuring that the extraction range uniformly covers the target coal seam.

6. The directional drilling construction method for strip extraction in coal roadways according to claim 1, characterized in that, In S5, the hydraulic fracturing pressure is controlled at 15-25 MPa, the fracturing time per hole is not less than 4 hours, and the fracturing fluid uses a water-plus-fracturing-aid formula with the fracturing-aid additive ratio of 0.5%-1.0% to improve the fracture propagation effect.

7. A method for directional drilling for strip extraction in coal roadways according to claim 1, characterized in that, In S6, the negative pressure of the extraction system is not less than 13 kPa. The extraction pipeline is equipped with a flow meter and a methane concentration sensor to monitor the flow rate and concentration in real time. The pipeline connection is sealed by using flanges and sealing rings.

8. A method for directional drilling for strip extraction in coal roadways according to claim 1, characterized in that, In S6, the test points for effect verification are arranged in areas with low borehole density in the pre-drilling range, with no less than 5 test points in each test area.

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