Coal seam group fixed-point section control hole sealing pre-extraction method

Abstract

The present application relates to a kind of coal group fixed point control section hole sealing pre-extraction methods, belong to gas prevention and control engineering field, in coal seam group floor gas extraction lane is implemented through layer extraction drilling, according to the layer number that drilling penetrates coal seam in turn, the interlayer distance between each coal seam that penetrates, after realizing the accurate positioning of first mining key coal seam n by mine drilling imaging instrument, fixed point hole sealing device and extraction pipe are arranged between first mining key coal seam n and its adjacent coal seam, realize the fixed point control section hole sealing pre-extraction of first mining key coal seam n, according to the extraction cycle of first mining key coal seam and gas extraction parameter, carry out gas extraction standard evaluation.The present application realizes the enrichment of first mining key coal seam during the layer drilling of coal seam group floor penetrates multiple coal seams in turn, and fast standard is reached.

Description

Technical Field

[0001] This invention belongs to the field of gas control engineering technology and relates to a method for pre-drainage of fixed-point control sections in coal seams. Background Technology

[0002] During the development, construction, and mining deployment of mines with closely spaced outburst-prone coal seams, key issues such as the selection of roadway strata and the first coal seam to be mined are generally faced. In particular, the key links for safe and efficient mining include advanced detection and prevention of accidental coal seam penetration during inter-layer tunneling of closely spaced outburst-prone coal seams, determination of the first coal seam to be mined and the pressure relief effect of mining, and prevention and drainage of coal and gas outbursts in the first coal seam. Based on the experience of mining closely spaced outburst-prone coal seams and efficient gas drainage, a combination of mining protective layers and pre-draining coal seam gas is generally adopted. The "Detailed Rules for the Prevention and Control of Coal and Gas Outbursts" requires that the following principles should be followed when selecting protective layers: (1) Prioritize the selection of coal seams without outburst risk as protective layers. When all coal seams in the mine have outburst risk, the coal seam with the lower degree of outburst risk should be selected as the protective layer; (2) When several coal seams in the coal seam group can be used as protective layers, the coal seam with the best protection effect should be mined first; (3) Prioritize the selection of upper protective layers. When selecting the lower protective layer for mining, the mining conditions of the protected layer shall not be damaged; (4) When mining a coal seam group, if there is a coal seam with a thickness of 0.50m or more without outburst danger within the effective protection vertical distance, it shall be mined first as a protective layer, except in cases where the distance to the outburst coal seam is too close to threaten the safety of the protective layer working face or may damage the mining conditions of the outburst coal seam.

[0003] When selecting a non-outburst-prone coal seam as a protective layer in a coal seam group with close proximity to outbursts, cross-layer drilling is often used in the construction of floor gas drainage roadways to simultaneously extract coal seam gas in order to effectively prevent coal and gas outbursts. Cross-layer drilling in floor gas drainage roadways typically penetrates multiple coal seams for simultaneous extraction. However, during joint gas extraction in a coal seam group, it is difficult to effectively trace and measure the gas extraction from each coal seam and assess whether the extraction meets standards. Furthermore, blowouts and collapses that occur during drilling through each coal seam result in low gas extraction efficiency. During the mining of a coal seam group, the prevention of coal and gas outbursts and the achievement of gas extraction standards in the first coal seam are critical nodes, and the decompression effect of the first coal seam is also the core of coal seam group mining. Because of the joint extraction of multiple coal seams, it is difficult to guarantee the extraction effect of the first coal seam, and there is currently no effective method to identify the gas extraction effect of each coal seam, causing significant challenges to gas extraction and safe mining in coal seam groups.

[0004] Currently, one known method for pre-evaluating the compliance of joint gas extraction in coal seams (CN104612635B) uses software numerical calculations to obtain the theoretical extraction volume, residual gas content, and desorbable gas content of each coal seam, and then pre-evaluates the compliance of gas extraction in each coal seam. Another known method for quantitatively determining the mixed-source ratio of gas in joint gas extraction in coal seams (CN110286003A) employs isotope geochemistry. It measures the content and isotopic values ​​of conventional and rare gas components in the gas at control points of each target coal seam within the control area. This identifies the main controlling gas components characteristic of different target coal seams, and fits contour maps of the main controlling gas component content and its isotope. Interpolation is used to obtain the content and isotopic values ​​of the main controlling gas components in each target coal seam of the joint extraction borehole. Based on the principle of mass conservation of chemical composition, a calculation model is established to quantitatively determine the mixing ratio of gas from each target coal seam in the mixed-source gas.

[0005] In summary, there are currently no effective technical methods for preventing coal and gas outbursts and achieving gas drainage standards in the first coal seam during coal seam gas drainage. The evaluation of the drainage effect of each coal seam is mainly determined by theoretical calculations and isotope identification. However, there are certain differences between theoretical calculations and actual field conditions. The isotope identification method requires a lot of basic work and has a long cycle. The source metering model also needs further optimization. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for pre-drainage of fixed-point control sections in coal seam groups to achieve safe mining and pressure relief protection of the first mining layer in coal seam groups.

[0007] A method for pre-drainage of a coal seam group with fixed-point control section sealing involves drilling through the coal seam group's bottom gas drainage roadway. Based on the number of coal seams penetrated by the borehole and the interlayer distance between each penetrated coal seam, the key coal seam n to be mined is accurately located using a mine borehole imaging instrument. Then, a fixed-point sealing device and drainage pipe are arranged between the key coal seam n and its adjacent coal seams to achieve fixed-point control section sealing and pre-drainage of the key coal seam n. Based on the drainage cycle and gas drainage parameters of the key coal seam n, a gas drainage compliance assessment is conducted.

[0008] Optionally, the specific steps include:

[0009] S1 carried out cross-seam drainage drilling in the gas drainage roadway at the bottom of the coal seam group, successively penetrating multiple coal seams and recording the drilling parameters;

[0010] S2 determines the coal-bearing length and coal borehole section length of the first key coal seam n based on the borehole parameters and the mine borehole imaging instrument;

[0011] S3 determines the sealing depth based on the coal penetration length of the first key coal seam n, and installs extraction pipes and sealing devices inside the hole to seal the first key coal seam n.

[0012] After the S4 borehole is sealed, the gas drainage parameters of the first key coal seam n are pre-drained at the fixed control section of the borehole. The gas drainage parameters of the first key coal seam n are observed and recorded. Based on the drainage cycle and gas drainage parameters of the first key coal seam n, the gas drainage compliance assessment is carried out.

[0013] Optionally, the drilling parameters include the borehole inclination angle, azimuth angle, borehole diameter, number of coal seams penetrated, and inter-layer distance between coal seams penetrated.

[0014] Optionally, a sealing device may be installed between the first key coal seam n and the (n-1)th penetrating coal seam for grouting and sealing.

[0015] Optionally, based on the extraction cycle of the first key coal seam n, operating parameters including extraction concentration, extraction negative pressure, and extraction flow rate are recorded to conduct a gas extraction compliance assessment.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. The pre-drainage method for fixed-point control section sealing of coal seam groups proposed in this invention can solve the problems of poor sealing air tightness, low drainage effect, and inability to effectively achieve traceability measurement and standard evaluation of gas drainage effect caused by the sequential penetration of bottom gas drainage boreholes through multiple coal seams due to blowouts and borehole collapses.

[0018] 2. The coal seam group fixed-point control section sealing and pre-drainage method proposed in this invention achieves the concentration and consumption reduction of the first coal seam and the rapid extraction to meet the standards by sealing and pre-draining the first key layer during the coal seam group extraction, thereby alleviating the mining succession in the mine; and achieves the prevention and control of coal and gas outbursts in the protected seam through the early mining effect of the first key layer.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0021] Figure 1 This is a schematic diagram of a method for pre-drainage of a coal seam group with fixed-point control section sealing.

[0022] Figure labels: first key coal seam n1, fixed-point sealing device 2, n-1 penetrating coal seam 3, grouting pipe 4, n-2 penetrating coal seam 5, borehole extraction pipe 6, n-3 penetrating coal seam 7, return grout pipe 8, n-4 penetrating coal seam 9, borehole opening 10. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0024] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0025] like Figure 1 As shown, a method for pre-drainage by sealing boreholes in a coal seam group is used for the concentration-reduction and rapid attainment of gas standards in the first mining of the key coal seam n1 during the gas drainage of a coal seam group. Figure 1 The diagram shows the key coal seam n1 being mined first, the fixed-point sealing device 2, the (n-1)th penetrating coal seam 3, the grouting pipe 4, the (n-2)th penetrating coal seam 5, the borehole extraction pipe 6, the (n-3)th penetrating coal seam 7, the return slurry pipe 8, the (n-4)th penetrating coal seam 9, and the borehole opening 10. Based on the number of coal seams penetrated sequentially by the borehole and the interlayer distance between each penetrated coal seam, after accurately locating the key coal seam n1 being mined first using a mine borehole imaging instrument, the fixed-point sealing device 2, the grouting pipe 4, the borehole extraction pipe 6, and the return slurry pipe 8 are arranged between the key coal seam n1 and its adjacent coal seams to achieve fixed-point control section sealing and pre-extraction of the key coal seam n1 being mined first. Specifically, the process includes the following steps: In the coal seam group floor gas drainage roadway, the cross-seam drainage boreholes sequentially penetrate multiple coal seams, and the borehole parameters are recorded; based on the borehole parameters and the mine borehole imaging instrument, the coal-bearing length and borehole section length of the first key coal seam are determined, achieving precise positioning of the first key coal seam; the sealing depth is determined based on the coal-bearing length of the first key coal seam, and a drainage pipe and sealing device are installed inside the borehole to seal the first key coal seam; after sealing, the gas drainage parameters of the first key coal seam are observed and recorded; based on the drainage cycle and gas drainage parameters of the first key coal seam, a gas drainage compliance assessment is conducted.

[0026] In this embodiment, drilling parameters include, but are not limited to, drilling inclination angle, azimuth angle, borehole diameter, and the number of coal seams penetrated. When the number of coal seams penetrated sequentially by the borehole is n (n≥2), they are defined as: the first key coal seam to be mined n, the (n-1)th penetrating coal seam, ..., the first penetrating coal seam, with the first penetrating coal seam during drilling construction being the first penetrating coal seam. In the borehole section located between the first key coal seam n and the (n-1)th penetrating coal seam, a fixed-point sealing device 2, a grouting pipe 4, a borehole extraction pipe 6, and a return slurry pipe 8 are arranged. The length of the fixed-point sealing device 2 is determined according to the length of the borehole section between the first key coal seam n and the (n-1)th penetrating coal seam; the grouting pipe 4, the borehole extraction pipe 6, and the return slurry pipe 8 are determined according to the distance and length of each penetrating coal seam.

[0027] The following details the specific steps of the pre-drainage method for fixed-point control sections of coal seams:

[0028] Step 1: Conduct cross-seam drainage boreholes in the gas drainage roadway at the bottom of the coal seam group, sequentially penetrating multiple coal seams, and record the drilling parameters; the drilling parameters include: borehole inclination angle, azimuth angle, borehole diameter, number of coal seams penetrated, and inter-seam distance between the penetrated coal seams.

[0029] Step 2: Based on the drilling parameters and the mining borehole imaging instrument, determine the coal-bearing length and the length of the coal section of the first key coal seam to be mined, so as to achieve accurate positioning of the first key coal seam; when the number of coal seams penetrated by the borehole in sequence is n (n≥2), they are defined as: the first key coal seam to be mined n, the (n-1)th penetrating coal seam, ..., the 1st penetrating coal seam, and the first coal seam penetrated during the drilling construction is the 1st penetrating coal seam.

[0030] Step 3: Determine the sealing depth based on the coal penetration length of the first key coal seam, install extraction pipes and sealing devices in the borehole, and seal the first key coal seam; between the first key coal seam n and the (n-1)th penetrating coal seam, set up a sealing device for grouting and sealing.

[0031] Step 4: After sealing the borehole, observe and record the gas drainage parameters of the first key coal seam; based on the drainage cycle and gas drainage parameters of the first key coal seam, conduct a gas drainage compliance assessment.

[0032] This invention addresses the challenges of gas drainage in coal seam groups. When drilling through multiple coal seams results in issues such as blowouts and collapses that negatively impact gas drainage, it integrates with mine transition planning. By using cross-layer, fixed-point control, and pre-drainage sealing, the invention achieves concentrated and efficient drainage of the first coal seam, ensuring rapid drainage to meet standards. This alleviates the difficulties associated with mine transition and solves problems related to gas drainage drilling in coal seam groups, including blowouts, collapses, poor sealing airtightness, low drainage efficiency, and the inability to effectively trace, measure, and assess the effectiveness of gas drainage.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for pre-drainage of a coal seam group by sealing a controlled section, characterized in that: In the gas drainage roadway of the coal seam group, cross-layer drainage boreholes are drilled. Based on the number of coal seams penetrated by the boreholes and the interlayer distance between each penetrated coal seam, the key coal seam n is accurately located by the mine borehole imaging instrument. Then, a fixed-point sealing device and drainage pipe are arranged between the key coal seam n and its adjacent coal seams to achieve fixed-point control section sealing and pre-drainage of the key coal seam n. Based on the drainage cycle and gas drainage parameters of the key coal seam n, a gas drainage compliance assessment is carried out. Specifically, the following steps are included: S1 carried out cross-seam drainage drilling in the gas drainage roadway at the bottom of the coal seam group, successively penetrating multiple coal seams and recording the drilling parameters; S2 determines the coal-bearing length and coal borehole section length of the first key coal seam n based on the borehole parameters and the mine borehole imaging instrument; S3 determines the sealing depth based on the coal penetration length of the first key coal seam n, and installs extraction pipes and sealing devices inside the hole to seal the first key coal seam n. After the S4 well is sealed, the gas drainage parameters of the first key coal seam n are pre-drained at the fixed control section of the well. The gas drainage parameters of the first key coal seam n are observed and recorded. Based on the drainage cycle and gas drainage parameters of the first key coal seam n, the gas drainage compliance assessment is carried out. Among them, a sealing device is arranged between the first key coal seam n and the (n-1)th penetrating coal seam for grouting and sealing; Drilling parameters include borehole inclination angle, azimuth angle, borehole diameter, number of coal seams penetrated, and inter-layer distance between coal seams penetrated.

2. The method for pre-draining coal seam groups with fixed-point control sections according to claim 1, characterized in that: Based on the extraction cycle of the first key coal seam n, record the operating parameters including extraction concentration, extraction negative pressure and extraction flow rate to conduct a gas extraction compliance assessment.

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