A method for arranging pressure relief gas extraction directional drilling in a coal seam containing dirt band

Abstract

This invention discloses a method for directional borehole layout for gas drainage in coal seams containing interbedded gangue, comprising the following steps: S1, performing main borehole drilling across the strata; S2, using simulation software to establish a model of the actual stratigraphic structure of the coal seam area traversed by the main borehole, including the interbedded gangue coal seam; S3, conducting coal sample tests on the interbedded gangue coal seam to obtain the basic physical parameters of the coal sample and the basic physical parameters of the solid-gas coupling model of each coal-rock stratum, obtaining the effective drainage radius of the borehole in the coal-rock stratum, and supplementing the model with the model of top-exploration branch boreholes; S4, starting from the end of the target stratum reached by the main borehole, performing transverse wave-shaped cross-strata drilling; S5, establishing a model of multiple branch wave-shaped cross-strata boreholes parallel to the transverse wave-shaped cross-strata boreholes in the model, and performing branch wave-shaped cross-strata drilling based on the model. This invention utilizes the gas diversion channel at the interface to promote gas drainage, thereby improving drainage efficiency.

Description

Technical Field

[0001] This invention relates to the field of underground gas extraction technology in coal mines, and in particular to a method for directional drilling layout for gas extraction from coal seams containing intercalated gangue. Background Technology

[0002] With the development of modern coal mining, its scale is expanding daily. The production process involves potentially dangerous sources with enormous energy reserves, leading to various disasters such as gas explosions and coal and gas outbursts. However, gas is also an abundant, clean, and efficient new energy source. Therefore, the safe and effective extraction of gas can not only reduce mine accidents but also provide clean energy for industrial power generation, vehicle fuel, and daily gas consumption, thus achieving significant environmental benefits.

[0003] Currently, there are two main methods for gas extraction from protected coal seams: underground cross-seam drilling and surface drilling. Surface drilling has been applied in protective coal seam mining faces in several mining areas across the country, achieving some success, but its overall effect is not ideal. The main reason is that surface drilling frequently results in well collapses and blockages. Underground cross-seam drilling is more stable, involving drilling holes into the coal seam through roadways excavated from the roof or floor to reduce gas emissions and outburst risks during mining. It also facilitates the assessment of the protective layer's effectiveness, hence its widespread use.

[0004] However, the method of extracting depressurized gas from protected coal seams using cross-layer drilling involves a large amount of drilling work and requires significant human and material resources. According to relevant research, interbedded rock hinders gas flow across layers, severely limiting the efficiency of gas depressurization and extraction from rock-bearing protective layers. Cross-layer drilling can weaken the impact of interbedded rock on gas flow. Furthermore, directional cross-layer drilling can connect with interface flow channels, creating multiple negative pressure zones at the interface that influence a certain range of extraction. This facilitates gas desorption at the interface and its convergence into the borehole through interface flow guidance, thereby improving the gas extraction efficiency from rock-bearing coal seams. Therefore, it is necessary to optimize the borehole layout to save on human and material costs. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems in the related art.

[0006] To achieve the above objectives, this invention proposes a method for directional borehole layout for gas drainage in coal seams containing intercalated gangue, comprising the following steps:

[0007] S1. Using a drilling rig, the main hole is drilled through the coal protective layer at a predetermined angle to penetrate the interbedded coal seam to the target rock layer.

[0008] S2. Using simulation software, a model of the actual stratigraphic structure of the coal seam area through which the main borehole passes, including interbedded coal seams, is established.

[0009] S3. Collect coal samples from the interbedded coal seam and conduct tests on the coal samples to obtain the basic physical parameters of the interbedded coal seam and the basic physical parameters of the solid-gas coupling model of each coal and rock layer. Then, input them into the model in step S2 to obtain the effective extraction radius of the borehole in the coal and rock layer, and supplement the model with the model of transverse wave through-layer borehole for model supplementation and planning.

[0010] S4. According to the simulation plan of transverse wave cross-layer drilling in S3, take the arrival of the main hole at the end of the target rock layer as the starting point and carry out the drilling operation of transverse wave cross-layer drilling.

[0011] S5. In the model of S3, establish a model for multiple branch wave-penetrating boreholes parallel to the transverse wave-penetrating borehole, and carry out the drilling operation of the branch wave-penetrating boreholes based on the model.

[0012] This invention, by establishing transverse wave-shaped perforated boreholes connected to the main borehole and multiple branch wave-shaped perforated boreholes, can fully penetrate each rock stratum. The gas diversion channels at the joints of each rock stratum are connected to the transverse wave-shaped perforated boreholes and branch wave-shaped perforated boreholes, making full use of the gas diversion channels at the rock stratum interfaces to promote gas extraction, thereby improving the gas extraction efficiency of gangue-bearing coal seams. At the same time, the transverse wave-shaped boreholes and wave-shaped perforated boreholes optimize the traditional borehole layout, forming a three-dimensional extraction network, effectively reducing the amount of drilling work and improving extraction efficiency.

[0013] Optionally, in S1, the main hole extends from the opening of the protective layer borehole toward the coal seam away from the protective layer, and sequentially penetrates the top of the coal seam, the upper coal layer, the interbedded gangue coal layer, and the lower coal layer.

[0014] Furthermore, in S3, the standard sample is machined to a diameter of 50 mm. Height 100mm.

[0015] Furthermore, in S3, the basic mechanical parameters of the raw coal sample and the rock sample were obtained, including the elastic modulus and Poisson's ratio. The permeability of the sample was tested using a triaxial synchronous loading-seepage test device, and the full stress-strain-permeability change curve of the sample was obtained. At the same time, the permeability change curve of the interface structure under the fixed-axis pressure relief confining pressure was obtained.

[0016] Furthermore, the transverse wave-shaped perforation borehole starts from the tail end of the main borehole, and sequentially penetrates the lower coal layer, the interbedded coal layer, and the upper coal layer in the direction of the protective layer. Then, it changes direction and sequentially penetrates the upper coal layer, the interbedded coal layer, and the lower coal layer. This constitutes one cycle of wave-shaped borehole segments. The transverse wave-shaped perforation borehole is continuously equipped with multiple cycles of wave-shaped borehole segments.

[0017] Furthermore, all the branch wave-penetrating boreholes are connected to the main borehole, and the branch wave-penetrating boreholes are arranged parallel to the transverse wave-penetrating boreholes.

[0018] Furthermore, the spacing between the branch wave-penetrating boreholes and the spacing between the branch wave-penetrating boreholes and the transverse wave-penetrating boreholes are both no greater than twice the effective gas extraction radius.

[0019] Furthermore, within a single cycle, the spacing between symmetrical borehole locations of transverse wave-penetrating boreholes should not exceed twice the effective gas extraction radius.

[0020] Furthermore, after completing step S5, a three-dimensional network extraction model is formed, which includes the main borehole, transverse wave-shaped cross-layer boreholes, and multiple branch wave-shaped cross-layer boreholes. A database is established to store the data of this model, and a data matching and calling module is established for subsequent construction to call the model data.

[0021] Furthermore, in S1, the main borehole extends from the opening of the protective layer borehole toward the coal seam away from the protective layer, and sequentially penetrates the top of the coal seam, the upper coal layer, multiple interbedded coal seams, and down to the lower coal layer.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0024] Figure 1 A schematic diagram illustrating the steps of a method for arranging directional boreholes for gas extraction from interbedded coal seams according to the present invention;

[0025] Figure 2 This is a schematic diagram of the longitudinal cross-layer drilling profile of a directional drilling arrangement method for decompression gas extraction in coal seams containing interbedded gangue, according to the present invention.

[0026] Figure 3 This is a schematic diagram of the borehole cross-layer distribution structure according to a directional borehole arrangement method for gas extraction from coal seams containing interbedded gangue, based on the present invention.

[0027] Figure 4This is a top view cross-sectional diagram of a borehole arrangement method for directional drilling for gas extraction in coal seams containing intercalated gangue, according to the present invention. It aims to demonstrate the parallel arrangement structure of branch wave-shaped cross-layer boreholes and transverse wave-shaped cross-layer boreholes.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. Upper coal seam; 2. Interbedded gangue layer; 3. Lower coal seam; 4. Main borehole; 5. Lateral wave-shaped cross-layer borehole; 6. Branch wave-shaped cross-layer borehole. Detailed Implementation

[0030] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0031] This invention provides a method for directional borehole layout for gas drainage in coal seams containing intercalated gangue, as described below. Figures 1 to 4 To elaborate in detail.

[0032] A method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue includes the following steps:

[0033] S1. Using a drilling rig, the main hole 4 is drilled through the coal protective layer at a predetermined angle into the protective layer. The main hole 4 penetrates the interbedded coal seam to the target rock layer.

[0034] S2. Using simulation software, a model of the actual stratigraphic structure of the coal seam area traversed by the main borehole 4, including interbedded coal seams, is established.

[0035] S3. Collect coal samples from the interbedded coal seam and conduct tests on the coal samples to obtain the basic physical parameters of the interbedded coal seam coal samples and the basic physical parameters of the solid-gas coupling model of each coal and rock layer. Then, input them into the model in step S2 to obtain the effective extraction radius of the borehole in the coal and rock layer. Finally, perform model supplementation and planning for the transverse wave through-layer borehole 5.

[0036] S4. According to the simulation plan of the transverse wave cross-layer borehole 5 in S3, take the arrival of the main hole 4 at the end of the target rock layer as the starting point and carry out the drilling operation of the transverse wave cross-layer borehole 5.

[0037] S5. In the model of S2, establish a model of multiple branch wave-penetrating boreholes 6 parallel to the transverse wave-penetrating borehole 5, and carry out drilling operations of branch wave-penetrating boreholes 6 according to the model.

[0038] This invention, by establishing transverse wave-shaped perforation boreholes 5 connected to the main borehole 4 and multiple branch wave-shaped perforation boreholes 6, can fully penetrate each rock stratum. The gas diversion channels at the joints of each rock stratum are connected to the transverse wave-shaped perforation boreholes 5 and the branch wave-shaped perforation boreholes 6, fully utilizing the gas diversion channels at the rock stratum interfaces to promote gas extraction, thus improving the gas extraction efficiency of gangue-bearing coal seams. Simultaneously, the transverse wave-shaped and wave-shaped perforation boreholes optimize the traditional borehole layout, forming a three-dimensional extraction network, effectively reducing the amount of drilling work and improving extraction efficiency. The three-dimensional extraction network can effectively eliminate or reduce the constraint of interbedded gangue layers 2 on gas extraction efficiency, achieving simultaneous and efficient extraction of gas from the upper and lower layers of coal seams containing gangue. Furthermore, this method can be combined with protective layer mining to fully utilize the pressure relief and permeability enhancement effects of the coal seam after protective layer mining, as well as the permeability enhancement effect of the coal-rock interface, effectively utilizing the gas diversion effect of the interface between the interbedded gangue layer 2 and the coal seam, thereby improving gas extraction efficiency. In some other embodiments, this extraction method is also applicable to gas extraction from two or more layers of interbedded coal seams or closely spaced coal seam groups.

[0039] In S1, the main borehole 4 extends from the protective layer borehole opening toward the coal seam away from the protective layer, and sequentially penetrates the coal seam roof, the upper coal layer 1, the interbedded gangue coal layer, and the lower coal layer 3. This ensures that the main borehole 4 can also penetrate each rock layer, effectively utilizing the gas diversion channels at the rock layer interfaces to enhance extraction efficiency.

[0040] In step S2, COMSOL Multiphysics numerical simulation software is used to establish a grid model of coal seams containing interbedded gangue with actual geological structure. Based on the drilling time, drilling speed, and drilling angle of the drilling rig, data simulation is required to establish the depth, length, and diameter of the main borehole 4, and to establish models of the main borehole 4 and each coal seam. In some embodiments, with the geological structure information of each coal seam obtained in advance, the model can be directly simulated with supplementary data. In other embodiments, the coal seam structure information needs to be further supplemented and improved with the basic physical parameters of each coal seam obtained in step S3 before the model can be further improved.

[0041] In step S3, the standard specimen is machined to a diameter of 50 mm for testing. The height is 100mm. After the standard sample is processed, it is sent for testing. The test obtains the basic mechanical parameters of the raw coal sample and the rock sample, including the elastic modulus and Poisson's ratio. The permeability of the sample is tested using a triaxial synchronous loading-seepage test device, and the full stress-strain-permeability change curve of the sample is obtained. At the same time, the permeability change curve of the interface structure under fixed-axis pressure relief confining pressure is obtained. The above basic physical parameters can be used to improve the model in step S2, thereby obtaining the coal seam solid-gas coupling model of the drilling site. Then, based on this model, the model of transverse wave cross-layer borehole 5 is supplemented and planned, including the planning of the wavelength, amplitude and starting position of transverse wave cross-layer borehole 5. The transverse wave-shaped perforation borehole 5 starts from the tail end of the main borehole 4, and sequentially penetrates the lower coal layer 3, the interbedded coal layer, and the upper coal layer 1 in the direction of the protective layer. Then, it changes direction and sequentially penetrates the upper coal layer 1, the interbedded coal layer, and the lower coal layer 3. This constitutes one cycle of wave-shaped borehole segment. The transverse wave-shaped perforation borehole 5 is continuously set with multiple cycles of wave-shaped borehole segments. Furthermore, when performing simulation modeling and actual drilling operations of the transverse wave-shaped perforation borehole 5, the transverse wave-shaped perforation borehole 5 does not penetrate the protective layer.

[0042] After supplementing and improving the model in S2 based on the data obtained in S3, the effective extraction radius of the coal seam and the radius of influence of the interface on gas flow are simulated. Based on the extraction radius obtained from the simulation, the wavelength of the transverse wave-shaped cross-layer borehole 5 is determined. Within a single cycle, the spacing between the symmetrical boreholes of the transverse wave-shaped cross-layer borehole 5 should not exceed twice the effective gas extraction radius. After completing the planning of the transverse wave-shaped cross-layer borehole 5 in step S3, the drilling operation of the transverse wave-shaped cross-layer borehole 5 can begin at the tail end of the main borehole 4 according to step S4.

[0043] In the coal seam, the arrangement and simulation of transverse wave cross-layer boreholes 5 are carried out because after the coal seam is depressurized, the permeability at the interface increases significantly, forming a connected structure with the extraction boreholes. The negative pressure of extraction at the boreholes and interfaces promotes gas seepage and discharge. Therefore, compared with arranging in-seam extraction boreholes, arranging cross-layer boreholes to extract gas from coal seams containing interbedded gangue can increase the efficiency of coal seam gas extraction.

[0044] In step S5, a connecting auxiliary hole is first drilled vertically along the same horizontal plane at the tail end of the main hole 4. Following the planning simulation of the transverse cross-layer borehole in step S3, branch wave cross-layer boreholes 6 are planned on the connecting auxiliary hole. Furthermore, based on the effective gas extraction radius and the influence radius of the interface on gas flow obtained from the simulation in step S3, the spacing between adjacent branch wave cross-layer boreholes 6, or the spacing between branch wave cross-layer boreholes 6 and transverse wave cross-layer boreholes 5, should, without exceeding twice the effective gas extraction radius, maximize the spacing between adjacent boreholes. This minimizes the overlap between extraction areas of adjacent boreholes, enabling gas extraction covering the maximum coal seam area using fewer branch wave cross-layer boreholes 6. This improves drilling efficiency and significantly increases extraction efficiency compared to traditional multi-hole drilling saturation extraction in the protective layer, while reducing the workload of the drilling project.

[0045] Furthermore, in other embodiments, based on the effective gas extraction radius and the influence radius of the interface on gas flow obtained from the simulation in step S3, different wavelengths, amplitudes, and starting positions can be selected for the branch wave-penetrating boreholes 6. After the drilling operation of the transverse wave-penetrating borehole 5 is completed, the extraction radius of the transverse wave-penetrating borehole 5 has been determined. However, within a single cycle, the two extraction radii covering the symmetrical part of the transverse wave-penetrating borehole 5 will form a concave area. At this time, the branch wave-penetrating boreholes 6 adjacent to the transverse wave-penetrating borehole 5 can be arranged to pass through this area, so that the adjacent boreholes can cover each other's concave areas, thereby further improving the extraction efficiency. At this time, it is necessary to redetermine the starting position, wavelength, and amplitude of each adjacent branch wave-penetrating borehole 6.

[0046] In step S5, the model is further simulated and supplemented by adding multiple branch wave-shaped through-layer boreholes 6 to the model supplemented in step S3, forming a three-dimensional network extraction model that includes the main borehole 4, the transverse wave-shaped through-layer borehole 5, and multiple branch wave-shaped through-layer boreholes 6. After completing step S5, a database is established to save the model data, and a data matching and calling module is established for subsequent construction to call the model data.

[0047] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0048] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0049] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue, characterized in that, Includes the following steps: S1. Using a drilling rig, the main hole is drilled through the coal protective layer at a predetermined angle to penetrate the interbedded coal seam to the target rock layer. S2. Using simulation software, a model of the actual stratigraphic structure of the coal seam area through which the main borehole passes, including interbedded coal seams, is established. S3. Collect coal samples from the interbedded coal seam and conduct tests on the coal samples to obtain the basic physical parameters of the interbedded coal seam and the basic physical parameters of the solid-gas coupling model of each coal and rock layer. Then, input them into the model in step S2 to obtain the effective extraction radius of the borehole in the coal and rock layer, and supplement the model with the model of transverse wave through-layer borehole for model supplementation and planning. S4. According to the simulation plan of transverse wave cross-layer drilling in S3, take the arrival of the main hole at the end of the target rock layer as the starting point and carry out the drilling operation of transverse wave cross-layer drilling. S5. In the model of S3, establish a model for multiple branch wave-penetrating boreholes parallel to the transverse wave-penetrating borehole, and carry out the drilling operation of the branch wave-penetrating boreholes based on the model.

2. The method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue as described in claim 1, characterized in that, In S1, the main hole extends from the opening of the protective layer borehole toward the coal seam away from the protective layer, and sequentially penetrates the top of the coal seam, the upper coal layer, the interbedded gangue coal layer, and the lower coal layer.

3. The method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue as described in claim 1, characterized in that, In S3, the standard sample is machined to a diameter of 50 mm. Height 100mm.

4. The method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue as described in claim 1, characterized in that, In S3, the basic mechanical parameters of raw coal and rock samples, including elastic modulus and Poisson's ratio, were obtained. The permeability of the samples was tested using a triaxial synchronous loading-seepage test device, and the full stress-strain-permeability change curve of the samples was obtained. At the same time, the permeability change curve of the interface structure under fixed-axis pressure relief confining pressure was obtained.

5. The method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue as described in claim 1, characterized in that, The transverse wave-shaped perforation borehole starts from the tail end of the main borehole, and sequentially penetrates the lower coal layer, the interbedded coal layer, and the upper coal layer in the direction of the protective layer. Then, it changes direction and sequentially penetrates the upper coal layer, the interbedded coal layer, and the lower coal layer. This constitutes one cycle of wave-shaped perforation section. The transverse wave-shaped perforation borehole is continuously equipped with multiple cycles of wave-shaped perforation sections.

6. The method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue as described in claim 5, characterized in that, The branch wave-penetrating boreholes are all connected to the main borehole, and the branch wave-penetrating boreholes are arranged in parallel with the transverse wave-penetrating boreholes.

7. A method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue, as described in any one of claims 1-6, characterized in that... The spacing between the branch wave-penetrating boreholes and the spacing between the branch wave-penetrating boreholes and the transverse wave-penetrating boreholes shall not exceed twice the effective gas extraction radius.

8. The method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue as described in claim 5, characterized in that, Within a single cycle, the spacing between symmetrical boreholes in transverse wave-penetrating boreholes should not exceed twice the effective gas extraction radius.

9. The method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue as described in claim 1, characterized in that, After completing step S5, a three-dimensional network extraction model is formed, which includes the main borehole, transverse wave-shaped cross-layer boreholes, and multiple branch wave-shaped cross-layer boreholes. A database is established to store the data of this model, and a data matching and calling module is established for subsequent construction to call the model data.

10. The method for arranging directional boreholes for gas drainage in coal seams containing intercalated gangue as described in claim 1, characterized in that, In S1, the main hole extends from the opening of the protective layer borehole toward the coal seam away from the protective layer, and sequentially penetrates the top of the coal seam, the upper coal layer, multiple interbedded coal seams, and down to the lower coal layer.

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