Coal seam gas extraction method

Abstract

The invention provides a coal seam gas extraction method which comprises the steps that a ground vertical well is arranged on the ground of a working face, and ground vertical well fracturing is carried out on a target coal seam based on the ground vertical well so as to form a ground vertical well anti-reflection area on the target coal seam; gas extraction is conducted on the ground vertical well anti-reflection area, and when the gas content of the ground vertical well anti-reflection area reaches a preset threshold value, bottom plate roadway anti-reflection is conducted based on a bottom plate roadway; gas extraction is conducted on the layer-crossing drilling permeability-increasing area formed after permeability increasing of the bottom plate roadway is completed, and when the gas content of the layer-crossing drilling permeability-increasing area reaches the preset threshold value, bedding drilling is conducted on the basis of the coal seam roadway to form a bedding drilling extraction area; and gas extraction is conducted on the bedding drilling extraction area, and when the gas content of the bedding drilling extraction area reaches the preset threshold value, coal mining operation is conducted on the working face. According to the invention, gas control in the whole space-time range of the high-watster thick coal seam is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mine gas extraction, and in particular to a coal seam gas extraction method. Background Art

[0002] Coal seams in high-gas mines are characterized by high coal strength, high gas content, and high coal thickness. Due to the high degree of coal metamorphism, the coal micropores are developed and the residual gas is large. If conventional extraction methods without coal seam permeability enhancement are adopted, it will take a long time to achieve gas extraction standards. Moreover, a single permeability enhancement method cannot meet the needs of multi-coal seam high-gas mines to achieve extraction standards within the specified time, which will affect the mine extraction and excavation continuity, and seriously restrict the economic benefits of mine production. Therefore, it is urgent to seek efficient coal seam permeability enhancement and gas extraction technology.

[0003] The existing gas pre-extraction technology takes into account the different time and space stages of gas extraction, and manages gas in the whole life cycle of the mine planning area and preparation area, production area production and extraction, and goaf area post-extraction, and plays a demonstrative role in the all-round and all-time management technology of gas. However, it is poorly applicable to high-gas and thick coal seam mines that have an urgent need to achieve gas extraction standards within the specified time, which in turn affects the mine extraction and mining continuity, and seriously affects the safe production of the mine. Summary of the invention

[0004] The present disclosure aims to at least solve the technical problem in the prior art of poor applicability in high-gas and thick coal seam mines where there is an urgent need to achieve gas extraction standards within a specified time.

[0005] To this end, one object of the present disclosure is to provide a coal seam gas extraction method, the coal seam gas extraction method comprising:

[0006] A surface vertical well is set on the ground of the working face, and a surface vertical well fracturing is performed on the target coal seam based on the surface vertical well to form a surface vertical well permeability enhancement zone in the target coal seam;

[0007] Performing gas extraction on the surface vertical well permeability enhancement zone, and when the gas content in the surface vertical well permeability enhancement zone reaches a preset threshold, performing bottom lane permeability enhancement based on the bottom lane;

[0008] Gas extraction is performed on the through-layer drilling permeability enhancement zone formed by completing the permeability enhancement of the bottom roadway, and when the gas content of the through-layer drilling permeability enhancement zone reaches the preset threshold, drilling along the layer is performed based on the coal seam roadway to form a along-layer drilling extraction zone;

[0009] Gas extraction is performed on the in-layer drilling extraction area, and when the gas content in the in-layer drilling extraction area reaches the preset threshold, coal mining operations are performed on the working face.

[0010] In some embodiments, performing floor lane antireflection based on floor lanes includes:

[0011] Based on the bottom plate tunnel, directional long drilling fracturing is performed to form a directional long drilling permeability enhancement zone;

[0012] Gas extraction is performed on the directional long borehole permeability enhancement zone. When the gas content in the directional long borehole permeability enhancement zone reaches the preset threshold, through-layer drilling and fracturing are performed based on the bottom plate tunnel to form a through-layer drilling and permeability enhancement zone.

[0013] In some embodiments, gas extraction is performed on the permeability enhancement zone of the through-layer drilling holes formed by the permeability enhancement of the bottom roadway, and when the gas content of the through-layer drilling holes permeability enhancement zone reaches the preset threshold, drilling along the layer based on the coal seam roadway to form a drilling extraction zone along the layer includes:

[0014] Gas extraction is performed on the permeability enhancement zone of the through-layer drilling holes formed by the permeability enhancement of the bottom roadway, and when the gas content in the permeability enhancement zone of the through-layer drilling holes reaches the preset threshold, the stone gate coal uncovering operation and the excavation of the coal seam roadway are performed;

[0015] Based on the coal seam roadway, in-layer drilling and fracturing are carried out to form an in-layer drilling and extraction area.

[0016] In some embodiments, the gas content of the surface vertical well permeability enhancement zone is determined based on the gas extraction volume of the surface vertical well and the original coal seam gas content;

[0017] The gas content of the directional long borehole permeability enhancement zone is determined based on the gas extraction volume of the directional long borehole and the gas content of the original coal seam;

[0018] The gas content of the permeability enhancement zone of the through-layer drilling hole is determined based on the gas extraction volume of the through-layer drilling hole and the gas content of the original coal seam.

[0019] In some embodiments, the method further includes: monitoring the gas extraction effect based on the gas extraction volume of the ground vertical well, the directional long borehole and the through-layer borehole.

[0020] In some embodiments, there is no overlapping area between any two of the surface vertical well permeability enhancement zone, the directional long borehole permeability enhancement zone, and the through-layer borehole permeability enhancement zone.

[0021] In some embodiments, the vertical ground wells are arranged at intervals along the direction of the coal seam, and the vertical ground wells enter the coal seam from the top plate of the working face and then pass through the bottom plate of the working face.

[0022] In some embodiments, gas extraction is performed on the in-layer drilling extraction area, and when the gas content in the in-layer drilling extraction area reaches the preset threshold, it also includes: after coal mining operations are carried out on the working face, high-level drilling is performed based on the fracture zone formed after mining to form a high-level drilling extraction area, and gas is extracted from the high-level drilling extraction area through the high-level drilling.

[0023] In some embodiments, when coal mining operations are carried out on the working face, the gas outflow from coal falling from the coal wall and the gas concentration in the upper corner are monitored.

[0024] In some embodiments, the method further includes: after performing coal mining operations on the working face, extracting gas from the goaf through a vertical well on the ground.

[0025] The coal seam gas extraction method provided by the embodiment of the present disclosure has the following beneficial effects:

[0026] Gas is extracted from extra-thick coal seams at different times through vertical wells on the ground, directional long boreholes, through-layer boreholes set up during the permeability enhancement process of floor tunnels, along-layer boreholes, and high-position boreholes set up after mining, so as to achieve gas control in the full time and space range of high-gas extra-thick coal seams;

[0027] In the planning area, the surface vertical well fracturing is carried out for overall permeability enhancement, and in the preparation area, directional long-hole fracturing is carried out for large-scale permeability enhancement and through-layer drilling fracturing is carried out for supplementary permeability enhancement, which can achieve three-dimensional full-area permeability enhancement of extra-thick coal seams, thereby improving the gas extraction effect;

[0028] After setting up a surface vertical well to form a surface vertical well permeability enhancement zone, gas extraction is carried out. When the gas content in the surface vertical well permeability enhancement zone is qualified, the bottom plate tunnel permeability enhancement is carried out. After the gas content in the through-layer drilling permeability enhancement zone formed by the bottom plate tunnel permeability enhancement is qualified, the in-layer drilling fracturing is carried out to form the in-layer drilling permeability enhancement zone. When the gas content in the in-layer drilling permeability enhancement zone is qualified, the working face coal mining operation is carried out, which is beneficial to ensure the safety during the mining process. In addition, through real-time monitoring of the gas content in the surface vertical well permeability enhancement zone, the directional long drilling permeability enhancement zone formed by the bottom plate tunnel permeability enhancement and the through-layer drilling permeability enhancement zone, the monitoring effect of the gas content in the gas extraction process is optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 is a flow chart of steps of a coal seam gas extraction method in an embodiment of the present disclosure;

[0031] Figure 2 is a schematic diagram of a coal seam in an embodiment of the present disclosure;

[0032] Figure 3 is a schematic diagram of surface vertical well perforation in an embodiment of the present disclosure;

[0033] Figure 4 It is a schematic diagram of the preset fracturing range and the actual fracturing area of ​​the ground vertical well in the embodiment of the present disclosure;

[0034] Figure 5 It is a schematic diagram of a preset trajectory of directional long-hole fracturing drilling in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0035] Various aspects and features of the present disclosure are described herein with reference to the drawings.

[0036] It should be understood that various modifications may be made to the embodiments of the present application. Therefore, the above description should not be considered as limiting, but only as an example of an embodiment. Other modifications within the scope and spirit of the present disclosure will occur to those skilled in the art.

[0037] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the general description of the present disclosure given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure.

[0038] These and other characteristics of the present disclosure will become apparent from the following description of a preferred form of embodiment given as a non-limiting example, with reference to the attached drawings.

[0039] It should also be understood that, although the present disclosure has been described with reference to some specific examples, those skilled in the art will be able to realize many other equivalent forms of the present disclosure that have the features described in the claims and are therefore within the scope of protection defined thereby.

[0040] The above and other aspects, features and advantages of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

[0041] Specific embodiments of the present disclosure are described hereinafter with reference to the accompanying drawings; however, it should be understood that the embodiments claimed are merely examples of the present disclosure, which may be implemented in a variety of ways. Well-known and / or repeated functions and structures are not described in detail to avoid obscuring the present disclosure with unnecessary or redundant details. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but merely serve as a basis and representative basis for the claims to teach those skilled in the art to use the present disclosure in a variety of ways with substantially any suitable detailed structure.

[0042] The first embodiment of the present disclosure provides a coal seam gas extraction method, such as Figure 1 and Figure 2 As shown, the coal seam gas extraction method includes:

[0043] S1: A surface vertical well is set on the ground of the working face, and a surface vertical well fracturing is performed on the target coal seam based on the surface vertical well to form a surface vertical well permeability enhancement zone in the target coal seam.

[0044] Specifically, at the mine planning stage, the drilling location of the ground vertical well is selected for the extra-thick coal seam based on the requirement that the preset ground vertical well fracturing range should cover more than 80% of the coal seam area. In addition, in order to prevent the expansion of the ground vertical well fracturing cracks from being restricted when selecting the ground vertical well drilling location, the selection of the ground vertical well location needs to consider the distance from the ground water exploration, fire exploration drilling holes and ground geophysical exploration drilling holes. For situations where the above-mentioned ground geophysical exploration, water exploration and fire exploration drilling holes cannot be avoided and are within the ground vertical well fracturing range, these ground boreholes should be sealed.

[0045] The rock layers on the upper and lower sides of the coal seam are called the roof and floor respectively. When constructing a vertical well on the ground, the vertical well enters the coal seam from the roof of the working face and then passes through the floor of the working face. This is conducive to ensuring that the vertical well fracturing is carried out within the full thickness of the target coal seam and the fracturing effect of the vertical well on the ground is guaranteed.

[0046] The vertical surface wells here are arranged at intervals along the direction of the coal seam. By setting up multiple vertical surface wells in the target coal seam, it is helpful to ensure the largest possible fracturing range of the vertical surface wells.

[0047] Specifically, Figure 3 As shown in the figure, the target coal seam is perforated in the whole section. In order to ensure the fracturing effect of the extra-thick coal seam, the number of clusters is divided according to the coal thickness, and each perforation cluster is 1m long and the cluster spacing is 1m.

[0048] After the construction of the ground vertical well is completed, the ground vertical well fracturing is carried out. Fracturing refers to the use of hydraulic force to create cracks in the coal seam during the coal mining process, thereby improving the permeability of the coal seam and improving the mineability and efficiency of the coal seam. Specifically, fracturing is to inject high-pressure liquid into the coal seam to create cracks in the coal seam. These cracks can increase the permeability of the coal seam, making it easier for gas and other gases to be released from the coal seam, thereby reducing the gas pressure in the coal seam and improving the safety of coal mining. In addition, ground microseismic monitoring equipment is set up during the ground vertical well fracturing to monitor the ground microseismic conditions during the ground vertical well fracturing. The preset fracturing range of the ground vertical well and the actual fracturing area are as follows: Figure 4 shown.

[0049] The ground vertical well permeability enhancement zone here refers to the ground vertical well permeability enhancement zone delineated by inverting the actual direction of the main cracks of the ground vertical well fracturing through ground microseismic monitoring data.

[0050] S2: gas extraction is carried out in the surface vertical well permeability enhancement area. When the gas content in the surface vertical well permeability enhancement area reaches the preset threshold, the floor roadway permeability enhancement is carried out based on the floor roadway;

[0051] Specifically, after the ground vertical well fracturing is completed, the ground vertical well is connected to the ground gas extraction system to carry out ground coal seam gas extraction. The gas extraction will be carried out for about 5-10 years, and the daily gas extraction data will be recorded. At the same time, the actual expansion direction of the main cracks of the ground vertical well fracturing is inferred through the ground microseismic monitoring data, and the actual permeability enhancement area of ​​the coal seam after the ground vertical well fracturing is delineated.

[0052] The preset threshold here refers to the safe value of gas content, such as 8m3 / t. The gas content of the surface vertical well permeability enhancement zone here is determined based on the gas extraction volume of the surface vertical well and the gas content of the original coal seam.

[0053] The bottom slab tunnel based on the bottom slab tunnel specifically includes:

[0054] S201: Directional long-hole fracturing is performed based on the bottom plate tunnel to form a directional long-hole permeability enhancement zone.

[0055] Specifically, when the gas content of the coal seam in the ground vertical well permeability enhancement area drops below 8m3 / t, the preparation area stage is entered to complete the excavation of the bottom plate tunnel and arrange directional long boreholes at the same time. The preset trajectory of the directional long borehole should avoid the actual permeability enhancement area of ​​the ground vertical well and the ground geophysical exploration boreholes, water exploration boreholes and fire exploration boreholes. Under the premise of preventing the directional long borehole fracturing from penetrating the above-mentioned boreholes and ground vertical well fracturing cracks, supplementary permeability enhancement measures can be taken in areas that are not covered by the actual fracturing range of the ground vertical well. The drilling trajectory of the directional long borehole is as follows: Figure 5 shown.

[0056] Furthermore, since the directional long boreholes are distributed over a long distance, up to 500-600 meters or even 700 meters, staged fracturing is adopted for the directional long boreholes. The directional long borehole permeability enhancement zone refers to the directional long borehole permeability enhancement range delineated by inferring the actual direction of the main fracture of the directional long borehole fracturing through ground microseismic monitoring data during the fracturing process.

[0057] By monitoring the actual fracturing range of ground vertical wells and directional long boreholes, the layout location of the through-layer drill holes can be determined based on the monitoring results, effectively eliminating the fracturing blank zone in the extremely thick coal seams.

[0058] S202: gas extraction is performed on the directional long borehole permeability enhancement zone. When the gas content in the directional long borehole permeability enhancement zone reaches a preset threshold, through-layer drilling and fracturing are performed based on the bottom plate tunnel to form a through-layer drilling permeability enhancement zone.

[0059] Specifically, after the directional long borehole fracturing is completed, the directional long borehole is connected to the gas extraction system, coal seam gas is extracted through the directional long borehole, and daily gas extraction data is recorded. The gas content of the directional long borehole permeability enhancement zone is determined based on the gas extraction volume of the directional long borehole and the original coal seam gas content.

[0060] Furthermore, when the gas content of the coal seam within the directional long borehole extraction range drops below the preset threshold of 8m3 / t, outside the entire permeability enhancement area of ​​the ground vertical well fracturing and all directional long borehole fracturing, a step-by-step drilling site is arranged on both sides of the floor tunnel to construct a through-layer drilling hole for through-layer drilling fracturing. The through-layer drilling hole penetrates about 20-30 meters along the coal seam. After the through-layer drilling fracturing is completed, the through-layer drilling hole is connected to the gas extraction system for gas extraction, and the daily gas extraction data is recorded. The gas content of the through-layer drilling permeability enhancement area is determined based on the gas extraction volume of the through-layer drilling hole and the original coal seam gas content.

[0061] The directional long drilling and through-layer drilling here are based on drilling holes into the coal seam area and rock area through the bottom plate tunnel.

[0062] The vertical well drilling here conducts preliminary permeability enhancement on the ground of the working face, large-scale permeability enhancement is achieved through directional long drilling, and supplementary permeability enhancement is achieved through through-layer drilling. Through the step-by-step fracturing of vertical well drilling, directional long drilling and through-layer drilling, the target coal seam is fracturing and permeability enhancement is achieved, thereby ensuring the gas extraction effect.

[0063] After setting up a surface vertical well to form a surface vertical well permeability enhancement zone, gas extraction is carried out. When the gas content in the surface vertical well permeability enhancement zone is qualified, the bottom plate tunnel permeability enhancement is carried out. After the gas content in the through-layer drilling permeability enhancement zone formed by the bottom plate tunnel permeability enhancement is qualified, the in-layer drilling fracturing is carried out to form the in-layer drilling permeability enhancement zone. When the gas content in the in-layer drilling permeability enhancement zone is qualified, the working face coal mining operation is carried out, which is beneficial to ensure the safety during the mining process. In addition, through real-time monitoring of the gas content in the surface vertical well permeability enhancement zone, the directional long drilling permeability enhancement zone formed by the bottom plate tunnel permeability enhancement and the through-layer drilling permeability enhancement zone, the monitoring effect of the gas content in the gas extraction process is optimized.

[0064] When gas extraction is carried out here, gas extraction work through ground vertical wells, directional long boreholes and through-layer boreholes should be carried out continuously before coal mining to avoid gas outbursts, gas exceeding the limit and gas accumulation.

[0065] During the gas extraction process, the gas extraction effect is monitored based on the gas extraction volume of ground vertical wells, directional long boreholes and through-layer boreholes. By accumulating the daily gas extraction volume of ground vertical wells, directional long boreholes and through-layer boreholes, combined with the original gas content and coal reserves of each working face, the gas content of each working face after a period of extraction is calculated, thereby monitoring the gas extraction effect.

[0066] Specifically, when the number of vertical wells is e, the vertical well extraction is t x The total amount of gas extracted from the vertical well during the extraction period at the working face is It can be calculated by the following formula:

[0067]

[0068] in, is the gas extraction volume of the ith vertical well on day d1, a n,i is the coverage factor of the ith vertical well on the nth working surface, ranging from 0 to 1. is the gas extraction volume of the ith vertical well at the nth working face on the d1th day, is the extraction time of the i-th vertical well from the start of extraction to the observation time t x The gas extraction volume at the nth working face per day, It is the total amount of gas extracted from all surface vertical wells during the extraction period at the working face.

[0069] When the number of directional long boreholes is f and the extraction time is t y Similarly, the total amount of gas extracted during the directional long borehole extraction period at the working face is It can be calculated by the following formula:

[0070]

[0071] in, is the gas extraction volume of the jth directional long borehole on day d2, a n,j is the coverage factor of the jth directional long drill hole on the nth working surface, ranging from 0 to 1, is the gas extraction volume of the jth directional long borehole at the nth working face on the d2th day, is the extraction time t of the jth directional long borehole from the start of extraction to the investigation time y The amount of gas extracted at the nth working face per day. It is the total amount of gas extracted by all directional long boreholes during the extraction period at the working face.

[0072] Since the penetration drilling has a small range and a single drilling hole is only used for extraction at a certain working face, the coverage factor of the penetration drilling hole is not considered. n , the extraction time is t z When the total amount of gas extracted during the drilling process covering the working face is It can be calculated by the following formula:

[0073]

[0074] in, is the gas extraction volume of the kth through-layer borehole covering the nth working face on day d3, To cover the kth through-layer borehole of the nth working face from the start of extraction to the investigation time extraction t z Gas extraction per day, It is the total amount of gas extracted during the extraction period of all the through-layer drilling holes covering the nth working face.

[0075] It can be obtained that the nth working face is produced in the vertical well on the ground x Days, directional long hole extraction t y Days, through-layer drilling extraction z At 12:00 am, the gas content of the working face is:

[0076]

[0077] Among them, V 0,n is the initial gas content of the coal seam at the nth working face, W n is the coal reserve of the nth working face, t x ,t y ,t z They are the number of days of extraction from the start of extraction to the investigation time t for the surface vertical well, directional long borehole, and through-layer borehole.

[0078] The gas extraction effect can be monitored by calculating the daily gas extraction volume to observe whether the gas extraction standard conditions are met.

[0079] S3: Gas extraction is carried out in the permeability enhancement zone of the through-layer drilling holes formed by the completion of the permeability enhancement of the bottom plate roadway. When the gas content in the permeability enhancement zone of the through-layer drilling holes reaches the preset threshold, in-layer drilling is carried out based on the coal seam roadway to form an in-layer drilling extraction zone.

[0080] Specifically include:

[0081] S301: gas extraction is performed on the permeability enhancement zone of the through-layer drilling holes formed by the permeability enhancement of the bottom roadway. When the gas content in the permeability enhancement zone of the through-layer drilling holes reaches a preset threshold, the stone gate coal uncovering operation and the excavation of the coal seam roadway are performed;

[0082] That is, when the gas content of coal seams in the extraction range of vertical wells, directional long boreholes and through-layer boreholes drops below 8m3 / t, the stone gate coal uncovering operation and the construction of coal seam tunnels are carried out.

[0083] S302: Drill holes along the coal seam tunnel to form a drilling and extraction area along the coal seam.

[0084] After the coal seam tunnel excavation is completed, drilling construction along the seam is carried out to extract the coal seam in the entire area.

[0085] The layer drilling here refers to the drilling hole that starts from the coal seam roadway and is drilled into the coal seam, wherein the layer drilling hole is arranged horizontally along the coal seam. The layer drilling hole further expands the permeability enhancement area of ​​the coal seam.

[0086] S4: Gas extraction is carried out in the in-layer drilling extraction area. When the gas content in the in-layer drilling extraction area reaches the preset threshold, coal mining operations are carried out on the working face.

[0087] The seam drilling is a borehole that is opened along the coal seam starting from the coal seam tunnel and is only set in the coal seam. The coal seam gas content is tested by drilling and coring. When the coal seam gas content in the seam drilling extraction area drops below 8m3 / t, the production area is entered. While the coal mining operation is in progress, the coal wall coal falling gas outflow and the gas concentration in the upper corner are monitored to determine whether to increase or decrease the recovery rate.

[0088] S5: After coal mining operations are carried out on the working face, high-level drilling is carried out based on the fracture zone formed after mining to form a high-level drilling extraction area, and gas is extracted from the high-level drilling extraction area through high-level drilling.

[0089] Specifically, the area formed after coal mining operations are carried out on the working face is called a goaf. The overlying rock strata on the working face in the goaf are prone to partial collapse along the hydraulic support, and there is a part of coal falling in the goaf, which is the main source of gas outburst.

[0090] The broken part of the roof forms a fracture zone above the goaf, which easily causes gas exceeding the limit in the return air tunnel. Find a location in the return air tunnel to set a high-position drill hole, that is, drill the high-position drill hole 30-40m above the coal seam.

[0091] In addition, after coal mining operations are carried out on the working face, gas is extracted from the goaf through vertical wells on the ground to ensure the effectiveness of gas extraction.

[0092] In the description of the present disclosure, it needs to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present disclosure.

[0093] In the description of the present disclosure, "first feature" or "second feature" may include one or more of the features.

[0094] In the description of the present disclosure, “plurality” means two or more.

[0095] In the description of the present disclosure, a first feature being “on” or “under” a second feature may include that the first and second features are directly in contact with each other, or may include that the first and second features are not in direct contact with each other but are in contact with each other via another feature therebetween.

[0096] In the description of the present disclosure, “above”, “over” and “on top” a first feature of a second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature.

[0097] In the description of the present disclosure, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0098] Although embodiments of the present disclosure have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the present disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. A coal seam gas extraction method, characterized in that: include: A surface vertical well is set on the ground of the working face, and a surface vertical well fracturing is performed on the target coal seam based on the surface vertical well to form a surface vertical well permeability enhancement zone in the target coal seam; Performing gas extraction on the surface vertical well permeability enhancement zone, and when the gas content in the surface vertical well permeability enhancement zone reaches a preset threshold, performing bottom lane permeability enhancement based on the bottom lane; Gas extraction is performed on the permeability enhancement zone of the through-layer drilling holes formed by the permeability enhancement of the bottom roadway. When the gas content in the through-layer drilling holes permeability enhancement zone reaches the preset threshold, drilling along the layer is performed based on the coal seam roadway to form a drilling extraction zone along the layer; Gas extraction is performed on the in-layer drilling extraction area, and when the gas content in the in-layer drilling extraction area reaches the preset threshold, coal mining operations are performed on the working face.

2. The coal seam gas extraction method according to claim 1, characterized in that: The bottom plate lane anti-reflection based on the bottom plate lane comprises: Based on the bottom plate tunnel, directional long drilling fracturing is performed to form a directional long drilling permeability enhancement zone; Gas extraction is performed on the directional long borehole permeability enhancement zone. When the gas content in the directional long borehole permeability enhancement zone reaches the preset threshold, through-layer drilling and fracturing are performed based on the bottom plate tunnel to form a through-layer drilling and permeability enhancement zone.

3. The coal seam gas extraction method according to claim 1, characterized in that: Gas extraction is performed on the permeability enhancement zone of the through-layer drilling formed by the permeability enhancement of the bottom roadway. When the gas content of the through-layer drilling permeability enhancement zone reaches the preset threshold, the formation of the permeability enhancement zone by drilling along the layer based on the coal seam roadway includes: Gas extraction is performed on the permeability enhancement zone of the through-layer drilling holes formed by the permeability enhancement of the bottom roadway, and when the gas content in the permeability enhancement zone of the through-layer drilling holes reaches the preset threshold, the stone gate coal uncovering operation and the excavation of the coal seam roadway are performed; Based on the coal seam roadway, in-layer drilling and fracturing are carried out to form an in-layer drilling and extraction area.

4. The coal seam gas extraction method according to claim 2, characterized in that: The gas content of the surface vertical well permeability enhancement zone is determined based on the gas extraction volume of the surface vertical well and the gas content of the original coal seam; The gas content of the directional long borehole permeability enhancement zone is determined based on the gas extraction volume of the directional long borehole and the gas content of the original coal seam; The gas content of the permeability enhancement zone of the through-layer drilling hole is determined based on the gas extraction volume of the through-layer drilling hole and the gas content of the original coal seam.

5. The coal seam gas extraction method according to claim 4, characterized in that: The method further includes: monitoring the gas extraction effect based on the gas extraction volume of the ground vertical well, the directional long borehole and the through-layer borehole.

6. The coal seam gas extraction method according to claim 2, characterized in that: There is no overlapping area between any two of the surface vertical well permeability enhancement zone, the directional long borehole permeability enhancement zone and the through-layer borehole permeability enhancement zone.

7. The coal seam gas extraction method according to claim 1, characterized in that: The vertical ground wells are arranged at intervals along the direction of the coal seam. The vertical ground wells enter the coal seam from the top plate of the working face and then pass through the bottom plate of the working face.

8. The coal seam gas extraction method according to claim 1, characterized in that: Gas is extracted from the in-layer drilling extraction area. When the gas content in the in-layer drilling extraction area reaches the preset threshold, the method further includes: after coal mining operations are carried out on the working face, high-level drilling is performed based on the fracture zone formed after mining to form a high-level drilling extraction area, and gas is extracted from the high-level drilling extraction area through the high-level drilling.

9. The coal seam gas extraction method according to claim 1, characterized in that: When coal mining operations are carried out on the working face, the gas outburst volume of coal falling from the coal wall and the gas concentration in the upper corner are monitored.

10. The coal seam gas extraction method according to claim 1, characterized in that: The method also includes: after the coal mining operation is carried out on the working face, gas extraction is carried out on the goaf through a ground vertical well.

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