A method for eliminating coal area sudden changes

Abstract

The embodiment of the present application discloses a method for eliminating coal regional outbursts, the method comprising: obtaining a first parameter, the first parameter being characterized as the geological conditions of the target area; selecting a coal seam fracturing strategy based on the geological conditions of the coal mine, the fracturing strategies of the present invention comprising a main fracturing strategy and an auxiliary strategy, the present invention adopts a main fracturing strategy to handle the fracturing elimination of the main vein coal seam, and adopts an auxiliary strategy to handle the elimination of outbursts in special coal seam structures (such as faults and dead ends), and there are several auxiliary strategies, each targeting a different special coal seam structure. The combination of the main fracturing strategy and a certain auxiliary strategy selected based on the first parameter is the target fracturing strategy implemented by the present invention; the target fracturing strategy is used to comprehensively and fully fracture the target area and extract gas from the fracturing area.

Description

Technical Field

[0001] The present application relates to coal mine outburst elimination technology, and specifically to a coal mine outburst elimination method. Background Art

[0002] Coal and gas outbursts are a highly dynamic process in which gassy coal and rock mass rapidly move from the coal seam toward the mining site, accompanied by the eruption of large amounts of gas. These events are extremely harmful natural disasters in coal mines and pose a serious threat to safe production. Reducing the risk of coal and gas outbursts while ensuring or improving coal seam gas extraction efficiency has long been a major challenge for coal mines.

[0003] In order to eliminate coal seam gas outbursts, the existing technology generally involves drilling horizontal fracturing wells from the ground to fracture the coal seam, and drilling negative pressure extraction wells from the ground to extract the gas in the coal seam from the fracturing cracks to prevent gas outburst accidents during subsequent coal mining.

[0004] Another method for eliminating coal seam outbursts is a solution introduced by the inventor in another patent application, namely, drilling a long horizontal borehole from underground to fracture the coal seam, and drilling short gas extraction holes from the side mining surfaces of the underground rock tunnel or the main coal tunnel to the fractured crack area, and extracting the gas in the coal seam through the cracks, thereby preventing gas outburst accidents.

[0005] However, the geological structure of coal mines varies. Some coal seams are intact and continuous, while others have faults or significant undulations. Intact coal seams are well-suited for long-hole horizontal drilling and fracturing. However, in areas with faults and significant undulations, horizontal well fracturing is not suitable.

[0006] Furthermore, the aforementioned horizontal long-bore fracturing creates a roughly elliptical fracture zone, while staged horizontal long-bore fracturing creates several elliptical fracture zones. The area to be treated for coal outburst reduction in a coal mine is generally a rectangular block. The corners where the elliptical fracture zone doesn't match the rectangular mining block create unfractured dead corners.

[0007] Horizontal wells typically extend horizontally along the strike of a coal seam. If a coal seam has faults or exhibits significant undulations in its strike, the horizontal well may penetrate the coal seam and enter the rock formation. After fracturing, fracture gaps may form in the faulted or undulating sections of the coal seam. These fracture gaps and fracture blind spots can still lead to gas outburst accidents. Summary of the Invention

[0008] In order to solve the existing technical problems, the embodiment of the present application provides a method for eliminating coal outbursts in a special geological structure area.

[0009] Before introducing the technical solutions of the embodiments of the present application, the following technical terms used in the present application are explained:

[0010] 1) The first geological parameter refers to the coal seam geological data obtained before determining the fracturing plan, which is used to determine whether the coal seam vein is intact, whether there are faults that cannot be covered by the main fracturing strategy, or areas with excessive coal seam undulations; the first geological parameter described in this application also includes the geological data of the coal seam fracture range obtained after fracturing, which is used to analyze whether there are fracturing dead corners and the location of the fracturing dead corners.

[0011] 3) Geological conditions refer to the geological conditions of the area where the coal seam is to be operated. In the case of this application, they mainly refer to the continuity of the coal seam, faults and the length of the faulted coal seam.

[0012] 4) Coal seam fault refers to a section of the main vein of the coal seam where the coal seam is disconnected from the main vein due to geological uplift or subsidence, or is located above or below the main vein. In this application, areas with excessive coal seam fluctuations can also be regarded as faults.

[0013] 5) The first geological condition refers to the geological condition that the coal seam in the area to be operated is continuous and complete, but after horizontal staged fracturing, there may be fracturing dead corners.

[0014] 6) The second geological condition refers to the geological condition that there are a few faults in the coal seam in the area to be operated, and the faults are relatively long.

[0015] 7) The third geological condition refers to the geological condition that there are many faults in the coal seams in the area to be operated and the length of the fault coal seams is relatively short.

[0016] 8) Primary fracturing strategy: This strategy employs staged fracturing via long horizontal boreholes, creating a large fracturing zone. The length of the long horizontal borehole is typically 300-1000 meters. Staged fracturing via long horizontal boreholes can be performed from the surface or underground, as described in another patent application by the applicant. The primary fracturing strategy is primarily applicable to fracturing of primary mineral veins.

[0017] 9) Auxiliary strategies, including auxiliary fracturing strategies and auxiliary grid density short drilling strategies. The auxiliary fracturing strategy involves drilling short fracturing holes from the coal mine rock lanes or coal lanes to the coal seam fault segments or dead corners that the primary fracturing strategy fails to reach. This fracturing strategy involves using short fracturing holes to perform local fracturing on the relevant coal seam fault segments or dead corners. There are two types of short fracturing holes: single-stage horizontal short fracturing holes and downhole drilling short fracturing holes.

[0018] There are two methods of fracturing short boreholes: one is fracturing using a downhole pressure pump, and the other is fracturing using ground fracturing equipment.

[0019] 10) Single-stage fracturing short horizontal borehole: This refers to a short borehole drilled obliquely from a rock or coal laneway, then extending horizontally along the strike of the target coal seam by changing the drill bit angle after entering the coal seam. The extended length of a single-stage fracturing short horizontal borehole can reach 80-200 meters. When fracturing with downhole pressure pumps, the horizontal extension of a single-stage fracturing short horizontal borehole should not exceed 100 meters. When fracturing with surface fracturing equipment, the horizontal extension of a single-stage fracturing short horizontal borehole can reach over 200 meters.

[0020] 11) Downhole Fracturing Short Borehole: This refers to a short borehole drilled from a rock or coal roadway into a coal seam, drilling to approximately halfway through the coal seam thickness to fracture the target coal seam. Downhole fracturing short boreholes can be fractured using either downhole pressure pumps or surface fracturing equipment. The resulting fracturing area will vary depending on the fracturing equipment used.

[0021] 12) Grid-Dense Short Drilling Strategy: This involves drilling a dense grid of short drill holes from a coal mine rock lane or coal lane into unfractured coal seam faults, unfractured sections, or dead ends in horizontal long boreholes. Without fracturing, these densely packed short drill holes form gas extraction channels within the target coal seam, allowing gas to be extracted through these short drill holes. This grid-dense short drill hole strategy can be used directly to extract gas.

[0022] Grid-intensive drilling technology is not a fracturing technique, but rather a technique that uses underground coal mine drills to drill holes from the roadway into the coal seam at regular intervals, such as 4 meters. This drilling technology is equivalent to adding more gas extraction channels, namely gas extraction holes, to the fractures produced by long-hole staged fracturing, short-hole single-stage fracturing, and downhole fracturing. Extracting gas from more gas extraction holes can speed up extraction. The holes drilled by grid-intensive drilling technology are 10-200 meters deep and approximately 50mm in diameter. Negative pressure is used to extract gas from the boreholes to eliminate sudden gas outbursts.

[0023] 13) Fracturing dead corner: In this application, fracturing dead corner refers to the coal seam area that is still not covered by fracturing compared with the planned coal mining area after the coal seam is fractured by the horizontal long drilling hole of the main fracturing strategy.

[0024] 14) Fracturing blank area. In this application, the fracturing blank area refers to the fractured section of the coal seam (including the section with too much undulation of the coal seam) that the horizontal long drill hole of the main fracturing strategy cannot penetrate. After the horizontal well is fracturing, the corresponding section of the coal seam is not fractured.

[0025] 15) The first fracture system refers to the three-dimensional network of fractures generated by the main fracturing strategy for coal seam fracturing.

[0026] 16) Second fracture system: refers to the three-dimensional network of fractures generated by the auxiliary fracturing strategy for coal seam fracturing.

[0027] 17) Gas extraction channel: The gas extraction channel consists of gas extraction boreholes and gas extraction pipelines, which are used to extract gas from fractured coal seams.

[0028] 18) Gas Extraction Short Borehole: This refers to a borehole drilled from the surface into a fractured coal seam, or a short gas extraction borehole drilled from an underground rock or coal roadway into a fractured coal seam. The gas extraction short boreholes used in this application are very similar to single-stage horizontal short boreholes, underground short boreholes, and grid-like short boreholes drilled from underground rock or coal roadways into the target coal seam. Therefore, the short boreholes drilled from underground rock roadways into coal seams in this application can also be used as gas extraction boreholes.

[0029] 19) Gas extraction pipeline: In this application, the gas extraction pipeline refers to the gas pipeline laid underground, which is connected to all gas extraction boreholes and the terminal of the pipeline is connected to the negative pressure extraction equipment.

[0030] The technical solution of the embodiment of the present application is implemented as follows:

[0031] The present invention provides a method for eliminating coal outbursts in a special geological structure region, the method comprising:

[0032] obtaining a first geological parameter, wherein the first geological parameter represents a geological condition of a target area;

[0033] A target fracturing strategy is determined that matches the first geological parameter.

[0034] The target fracturing strategy includes at least one of a main fracturing strategy and several auxiliary strategies.

[0035] The main fracturing strategy is a horizontal long drilling + surface staged fracturing strategy. The main fracturing strategy is used to perform regional fracturing on the coal seam in the target area to obtain the main fracturing area.

[0036] The auxiliary strategies include auxiliary fracturing strategies and grid-intensive short drilling strategies of non-fracturing technology.

[0037] The auxiliary fracturing strategy adopts the method of drilling short holes from the coal mine rock lane or coal lane to the coal seam fault section or coal seam undulating section that has not been passed by the horizontal long drilling hole of the main fracturing strategy, as well as the dead corner that the horizontal long drilling hole of the main fracturing strategy cannot reach, and uses the short drilling holes to locally treat the unfractured coal seam section or the fracturing dead corner.

[0038] The above-mentioned short boreholes include horizontal single-stage fracturing short boreholes and downhole short boreholes; among them, the horizontal single-stage fracturing short boreholes can be fractured by a downhole pump group in a single stage or a surface pump group in a single stage; the downhole short boreholes can be fractured by a downhole pump group or a surface pump group.

[0039] The grid-intensive short drilling method is a non-fracturing technique and can be applied alone or in addition to all the special geological conditions listed in this application.

[0040] All short fracturing boreholes are used for fracturing coal seams and are also used as gas extraction holes; grid-dense short boreholes are only used for gas extraction.

[0041] The coal seam sections that the aforementioned long horizontal boreholes do not or cannot penetrate primarily refer to fault sections and sections with large undulations in the coal seam. The areas that the aforementioned long horizontal borehole fracturing cannot reach primarily refer to blind spots where the elliptical area of the long horizontal borehole fracturing does not match the planned coal mining face.

[0042] This application mainly includes two steps: main fracturing strategy and auxiliary strategy, to fully and comprehensively eliminate gas outbursts in the entire coalfield area.

[0043] In the above scheme, the geological conditions corresponding to the first geological parameter are divided into the following four categories according to whether the coal seam has faults and the degree of disconnection:

[0044] Among them, the coal seams are continuous and unbroken, which means the geological conditions are relatively ideal;

[0045] There are a few faults in the coal seam, indicating good geological conditions;

[0046] There are some faults in the coal seam, which indicates normal geological conditions;

[0047] There are many faults in the coal seams, and the geological conditions are harsh.

[0048] The above is a classification of geological conditions from a geological exploration perspective. For technical implementation purposes, this application categorizes these four geological conditions into three categories: ideal geological conditions (defined as the first geological condition); good and average geological conditions (defined as the second geological condition); and poor geological conditions (defined as the third geological condition). Furthermore, the second and third geological conditions have been expanded to include the length of faults and fracture-free coal seams.

[0049] When the first geological parameter indicates that the geological conditions of the target area are the first geological conditions (i.e., there may be a fracturing dead zone after the primary fracturing strategy is implemented), the target fracturing strategy includes a primary fracturing strategy and a downhole short-hole fracturing auxiliary fracturing strategy; or a primary fracturing strategy and a downhole short-hole surface fracturing auxiliary fracturing strategy. The number of fracturing short holes in the auxiliary fracturing strategy depends on the dead zone area and can be one or more.

[0050] When the first geological parameter indicates that the geological conditions in the target area are the second geological conditions (i.e., after the primary fracturing strategy is implemented, unfractured faults and unfractured sections remain, and the coal seam with faults and unfractured sections is relatively long), the target fracturing strategy includes the primary fracturing strategy and the horizontal short-hole single-stage fracturing strategy. Because the second geological condition contains multiple coal seam faults and / or unfractured sections, the number of single-stage horizontal short-hole fracturing should match the number of coal seam faults. If the coal seam faults are long, the horizontal sections of the single-stage horizontal short-hole fracturing can be extended to the end of the coal seam. If the end of the coal seam exceeds 100 meters, multiple single-stage horizontal short-hole fracturing holes can be arranged, with the distance between each single-stage horizontal short-hole fracturing hole being roughly equal to or less than the range of the single-stage horizontal short-hole fracturing. The fracturing range of a typical downhole pressure pump group is approximately 6 meters wide and 100 meters long. Therefore, when multiple single-stage horizontal short-hole fracturing holes are arranged, the spacing between them should be approximately ≤100 meters.

[0051] In another embodiment of the present application, a single-stage fracturing horizontal short borehole can be connected to a high-power fracturing equipment on the ground through a pipeline. The displacement of the ground fracturing equipment is much larger than that of the downhole pump group. The use of the ground fracturing equipment can increase the length of a single-stage fracturing to more than 100 meters. When fracturing with the ground fracturing equipment, the spacing of the fracturing short boreholes can be increased to the single-stage maximum fracturing range of the ground fracturing equipment.

[0052] When the first geological parameter characterizes the target area's geological conditions as the third geological condition (i.e., the coal seam with the fault and the fracturing gap is a scattered, fragmented coal seam segment (Jiwo Mine Segment)), the target fracturing strategy includes a primary fracturing strategy and a downhole short-bore auxiliary fracturing strategy. Specifically, for the scattered, fragmented coal seam segment (Jiwo Mine Segment), one or a group of downhole short-bore fracturing holes are drilled from the nearest rock or coal roadway toward the target coal seam. These downhole short-bore fracturing holes do not need to extend horizontally within the coal seam; once they penetrate approximately halfway through the coal seam thickness, they can be directly fractured using a downhole fracturing pump assembly. If the coal seam fault is long but shorter than the second geological condition standard, multiple short-bore fracturing holes can be arranged, with the distance between each short-bore hole roughly less than or equal to the short-bore fracturing diameter. The maximum fracturing range of a typical downhole pressure pump assembly is approximately 6-15 meters wide. Therefore, when multiple short-bore fracturing holes are arranged, their spacing should be approximately 6 to 15 meters.

[0053] In another embodiment of the present application, the downhole short fracturing borehole can be connected to the high-power fracturing equipment on the ground through a pipeline. The displacement of the ground fracturing equipment is much larger than the downhole pump group. The use of the ground fracturing equipment can increase the single-stage fracturing length to more than tens of meters. When fracturing with the ground fracturing equipment, the spacing of the downhole short fracturing boreholes can be increased to ≦ the single-stage maximum fracturing range of the ground fracturing equipment.

[0054] Among the geological conditions mentioned above, the geology of the first geological condition is better than that of the second geological condition, and the geology of the second geological condition is better than that of the third geological condition.

[0055] In practice, for several faults, fracturing blank sections and dead-end areas, their respective geological conditions should be determined separately, and the auxiliary strategies that should be adopted for each fault, fracturing blank section and dead-end area with special geological conditions should be determined separately.

[0056] In a certain embodiment of the present application, a main fracturing strategy is used to fracture the target area to obtain a fracturing area, wherein the fracturing area has a first fracture system; an auxiliary fracturing strategy is used to fracture the target area to obtain a second fracture system, and gas is extracted through gas extraction short boreholes of each fracture system.

[0057] In another embodiment of the present application, the fractures of the first fracture system are connected to the fractures of the second fracture system, and the gas in the first fracture system and the second fracture system is extracted through the short gas extraction borehole of the first fracture system.

[0058] In another embodiment of the present application, the fractures of the first fracture system are connected to the fractures of the second fracture system, and gas is extracted through the gas extraction boreholes of the second fracture system, so that gas flows from the first fracture system to the second fracture system.

[0059] In another embodiment of the present application, the fractures of the first fracture system are connected to the fractures of the second fracture system, and gas is extracted simultaneously through the gas extraction boreholes of the first fracture system and the gas extraction boreholes of the second fracture system to accelerate the gas extraction speed.

[0060] The single-stage fracturing short horizontal borehole and downhole fracturing short borehole described in the present application are fracturing boreholes drilled from a downhole rock lane or coal lane to a target coal seam section.

[0061] In another embodiment of the present application, the single-stage fracturing short horizontal drill hole and the downhole fracturing short drill hole are fracturing drill holes drilled from the coal roadway to the target coal seam section.

[0062] The localized fracturing area achieved by single-stage fracturing in short horizontal boreholes and downhole fracturing in short boreholes is smaller than the fracturing area achieved by staged fracturing in the target area using the primary fracturing strategy of long horizontal boreholes. The auxiliary fracturing strategy, using single-stage fracturing in short horizontal boreholes and downhole fracturing in short boreholes, provides only localized fracturing, supplementing the fracturing of areas not reached by the primary fracturing.

[0063] In a preferred embodiment of the present invention, the single-stage fracturing short horizontal borehole and the downhole fracturing short borehole can also be used as gas extraction boreholes at the same time. In this embodiment, the single-stage fracturing short horizontal borehole and the downhole fracturing short borehole orifice are connected to a wellhead device, which has a pressure relief nozzle, a gas-water separator, a gas metering device, and is connected to a gas extraction pipeline, a drainage pipeline, and a negative pressure extraction pipeline; the wellhead has at least four interfaces, interface 1 is connected to an anti-gas and water outburst device, and the other end of the anti-gas and water outburst device is connected to the single-stage fracturing short horizontal borehole or downhole fracturing short borehole orifice; interface 2 is connected to the fracturing pipeline; interface 3 is installed with a pressure gauge for observing the changes in the orifice pressure; interface 4 is connected to the pressure relief nozzle, and the other end of the pressure relief nozzle is connected to the device of the subsequent gas extraction process, such as a gas-water separator, a gas metering device, a gas extraction pipeline, a drainage pipeline, a negative pressure extraction pipeline, etc.

[0064] Before the main fracturing strategy is implemented, close the wellhead valve connected to the extraction process. After the fracturing construction, close the fracturing pipeline valve, open the extraction process valve, observe the wellhead pressure gauge, and perform pressure relief and extraction operations through the pressure relief nozzle.

[0065] An alternative technical solution to the present invention involves drilling a dense grid of short holes in underground tunnels within faulted sections of the coal seam and in areas with blind spots caused by fracturing. Gas can be directly extracted from these holes without fracturing. This technical solution uses these densely-packed short holes as extraction channels within the coal seam. Therefore, to fully mitigate outbursts, the density of these holes should be sufficiently high.

[0066] This invention provides a method for eliminating coal outbursts in a region, addressing the shortcomings of single-horizontal long-bore staged fracturing, which leaves unfractured or under-fractured coal seams, thereby fully eliminating outbursts in the entire target coal seam area. Furthermore, gas is a high-quality energy resource. The more thorough the fracturing of the coal seam, the more gas is extracted, resulting in higher gas output and improved production efficiency.

[0067] The present invention combines the target fracturing strategy with the auxiliary strategy, thereby achieving successful gas extraction and eliminating dead corners in coal fracturing, thereby improving the safety of coal operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0069] Figure 1 A schematic diagram of the implementation process of the coal area sudden relief method provided in the embodiment of the present application;

[0070] Figure 2 Schematic diagram of the long-bore staged fracturing technology provided in the embodiment of this application Figure 1 ;

[0071] Figure 3 Schematic diagram of the long-bore staged fracturing technology provided in the embodiment of this application Figure 2 ;

[0072] Figure 4 A schematic diagram of a downhole short borehole surface fracturing technology provided in an embodiment of the present application;

[0073] Figure 5 A schematic diagram of a downhole horizontal fracturing short drilling technology provided in an embodiment of the present application;

[0074] Figure 6 A schematic diagram of the downhole drilling and downhole fracturing technology provided in an embodiment of the present application;

[0075] Figure 7 A schematic diagram of a grid-intensive drilling technology provided in an embodiment of the present application;

[0076] Figure 8 Schematic diagram of the main fracturing strategy and several different auxiliary strategies fracturing ranges and gas extraction areas provided in the embodiments of the present application. DETAILED DESCRIPTION

[0077] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Unless there is a conflict, the embodiments in the present application and the features in the embodiments can be arbitrarily combined with each other. The steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions. In addition, although a logical order is shown in the flowchart, in some cases, the steps shown or described can be performed in an order different from that here.

[0078] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0079] The embodiments of the present application relate to coal outburst elimination technology, specifically to a method for eliminating coal outbursts in a regional area. This method, through the combination of a main fracturing strategy and an auxiliary strategy, can achieve comprehensive and sufficient outburst elimination of the entire fracturing coal seam and its fracturing dead corners, coal seam fault sections, and coal seam undulating sections during the fracturing process of the coal seam, thereby at least ensuring the safety of coal operations and the successful extraction of gas, and further improving the extraction efficiency on the basis of eliminating coal seams with dead corners, coal seam fault sections, and coal seam undulating sections.

[0080] The coal area sudden relief method provided in the embodiment of the present application can be regarded as an operation method for extracting coal gas.

[0081] like Figure 1 As shown, the method includes the following steps:

[0082] S101: Obtain a first geological parameter, where the first geological parameter represents a geological condition of a target area;

[0083] In this step, the target area can be the area to be operated, which usually includes a coal seam. In practical applications, it includes the case where the coal seam is continuous, and also includes the case where the coal seam is discontinuous (the coal seam is disconnected). The geological conditions of the target area refer to whether the underground coal seam in the area to be operated is continuous or disconnected. Among them, the unconnected coal seam can be called a structural coal seam. If it is disconnected, the degree of disconnection is general or severe, etc. The first geological parameter is any reasonable representation of the geological conditions of the area to be operated. For example, if the coal seam in the area to be operated is continuous, the geological conditions are relatively ideal; if there are a few faults in the coal seam in the area to be operated, the geological conditions are good; if there are some faults in the coal seam in the area to be operated, the geological conditions are general; if there are many faults in the coal seam in the area to be operated, the geological conditions are poor. The above is a classification of geological conditions, but the above classification is not limited to all possible situations included in the embodiments of the present application. Any reasonable situation is covered within the scope of the embodiments of the present application. For example, it is no longer considered that a coal seam with poor geological conditions such as many faults is a type of area to be operated. That is, the geological conditions of the area to be operated include ideal, good, general and poor. For technical implementation purposes, this application categorizes the aforementioned four geological conditions into three categories: ideal geological conditions (defined as the first geological condition); good and average geological conditions (defined as the second geological condition); and poor geological conditions (defined as the third geological condition). Furthermore, the second and third geological conditions are supplemented with criteria for determining the length of the coal seam with faults and fracture-free sections.

[0084] The first geological parameter is any reasonable parameter representing geological conditions, such as the presence or absence of faults, the number of faults, and the length of faults. The first geological parameter may be obtained by surveying the operating area using professional exploration tools or by analysis by experienced operators.

[0085] S102: Selecting a primary fracturing strategy and determining at least one auxiliary strategy matching the first geological parameter from at least a plurality of auxiliary strategies; the combination of the primary fracturing strategy and the auxiliary strategy is determined as a target fracturing strategy.

[0086] In this step, a target fracturing strategy corresponding to the first geological parameter is found from among several pre-set combinations of primary and secondary fracturing strategies. Each target fracturing strategy can be considered a fracturing method, such as a pre-set primary fracturing strategy + downhole short-hole downhole fracturing strategy, a primary fracturing strategy + downhole short-hole surface fracturing strategy, a primary fracturing strategy + downhole horizontal short-hole downhole single-stage fracturing strategy, a primary fracturing strategy + downhole horizontal short-hole surface single-stage fracturing strategy, or a primary fracturing strategy + downhole grid-intensive short-hole downhole strategy.

[0087] The pre-set correspondence between the fracturing method and the first geological parameter can be reflected in which fracturing method is required to be used for the operation in the area to be operated under which geological conditions.

[0088] For example, the above-mentioned primary fracturing strategy plus downhole short-bore fracturing strategy, or the primary fracturing strategy plus downhole short-bore surface fracturing strategy, targets the first and third geological conditions, namely, situations where the primary fracturing strategy results in fracturing dead zones or dispersed unfractured faults, and the coal seam is not long. The primary fracturing strategy addresses structurally significant coal seams, while the downhole short-bore downhole fracturing strategy or the downhole short-bore surface fracturing strategy addresses fracturing dead zones and dispersed faults.

[0089] The main fracturing strategy + downhole horizontal short drilling single-stage fracturing strategy and the main fracturing strategy + downhole horizontal short drilling ground single-stage fracturing strategy are aimed at the second geological condition, that is, the main coal seam structure is good, continuous, there are not many faults, and the length of the faults is long. Among them, the main fracturing strategy handles the main coal seam, and the downhole horizontal short drilling single-stage fracturing strategy or the downhole horizontal short drilling ground single-stage fracturing strategy handles the coal seam faults.

[0090] The above-mentioned main fracturing strategy + downhole grid-intensive short drilling strategy can be applied to any of the three geographical conditions mentioned above.

[0091] It is understood that the above correspondence is only a preferred specific example and does not limit the present application. For example, when the first geological parameter represents that the geological conditions of the target area are the first geological conditions, the target fracturing strategy can be a main fracturing strategy and a horizontal short borehole single-stage fracturing strategy, or a main fracturing strategy + a horizontal short borehole single-stage fracturing strategy + a downhole short borehole downhole or surface fracturing strategy.

[0092] S103: The primary fracturing strategy is used to fracture at least the primary target area, and the auxiliary strategy is used to fracture at least the dead corners, gaps, and faults left after the fracturing, and gas is extracted from the fracturing areas, thereby fully eliminating the primary target area and the special geological area.

[0093] In the present invention, the main fracturing strategy obtains a first fracture system after fracturing the main target area; correspondingly, the auxiliary strategy obtains a second fracture system after fracturing the special target area, thereby extracting gas respectively with the respective matching gas extraction short boreholes.

[0094] In an optional solution, the fractures of the first fracture system are connected to the fractures of the second fracture system, and the gas in the first fracture system and the second fracture system is extracted through a short gas extraction borehole of the first fracture system.

[0095] In another embodiment of the present application, the fractures of the first fracture system are connected to the fractures of the second fracture system, and gas is extracted through the gas extraction boreholes of the second fracture system, so that gas flows from the first fracture system to the second fracture system.

[0096] In another embodiment of the present application, the fractures of the first fracture system are connected to the fractures of the second fracture system, and gas is extracted simultaneously through the gas extraction boreholes of the first fracture system and the gas extraction boreholes of the second fracture system to accelerate the gas extraction speed.

[0097] In one embodiment of the present application, the auxiliary strategy may be a grid-intensive drilling technique. Grid-intensive drilling technology involves using an underground coal mine drill to drill holes from the roadway into the coal seam at intervals of, for example, 4 meters, increasing the number of gas drainage holes. Negative pressure is then used to extract gas from these increased gas drainage holes to eliminate gas outbursts.

[0098] Below, in conjunction with the accompanying drawings, the technical solution of fracturing coal seams by combining a long-hole staged fracturing strategy, a short-hole single-stage fracturing strategy, and a downhole downhole fracturing strategy, and combining grid-intensive drilling technology to eliminate dead corners is further explained.

[0099] 1) Horizontal long-hole staged fracturing strategy (horizontal long-hole staged fracturing method / technology)

[0100] Directional drilling rigs are used to drill 300-1000m long holes in coal mines. High-pressure manifolds are laid from the tunnel entrance to the long borehole mouth for connection. Alternatively, a ground well is drilled to the surface well in the area where gas treatment is to be carried out. Large-scale ground fracturing equipment is passed through the surface well and connected to the underground high-pressure manifold to perform staged fracturing of the long borehole. Water-sand fracturing or other fracturing fluids suitable for the geological characteristics of the coal seams in the area to be fractured are used, with a displacement of 6-8m / min. 3 , cracks are formed quickly, and quartz sand plays a role in supporting the cracks, achieving a large-area sudden relief effect.

[0101] Directional drilling rigs are used to drill wells in coal mines at a depth of 300-1000 meters. After drilling, multi-stage ball-dropping sleeves and open-hole packer segments are lowered, and high-pressure pipelines are connected to the ground. Large-scale ground fracturing equipment ( Figure 2 Fracturing equipment) to connect high pressure pipeline ( Figure 2 The fracturing pipeline in the well) is used to perform segmented fracturing on the underground coal seam borehole. Among them, the multi-stage open hole packer is used to mechanically isolate the open hole horizontal well section, and the multi-stage ball sliding sleeve (such as Figure 3 Four ball-dropping sleeves are distributed throughout the system. The multi-stage fracturing string is lowered into place at once. Before fracturing, the tubing is positively pressurized (the differential pressure sleeves are opened by applying pressure into the tubing to provide access for each segment). This allows the packer to be set, or the packer to be set by immersion. Ball-dropping pressure is applied, and the ball-dropping sleeves are opened to achieve stage-by-stage fracturing. Fracturing fluid is introduced into the formation through a sandblaster, rapidly forming fractures. Quartz sand supports the formed fractures, allowing coal and gas to be extracted from the fractures. Figure 2 The gas extraction holes in the coal seam can be regarded as cracks fracturing by long-hole staged fracturing technology, from which gas in the coal seam can be extracted.

[0102] This technology requires 1-10 ground fracturing trucks, 1 manifold truck, 1 instrument truck, 1 sand mixer truck, and several water storage tanks. The fracturing operation displacement is 6-8m / min. 3 Liquid causes cracks to form quickly in the stratum, and quartz sand is used to support the formed cracks, so as to achieve rapid analysis of the coal seam and extraction of gas from the cracks.

[0103] The aforementioned long-bore staged fracturing method / technology can be applied to areas where coal seams are not disconnected and gas control is to be carried out.

[0104] 2) Horizontal short borehole single-stage fracturing strategy (horizontal short borehole single-stage fracturing method / technology)

[0105] Use directional drilling rig to drill 80-200 meters (m) short borehole in the well, and put steel casing (such as Figure 5 The steel casing in the well is connected to the ground fracturing equipment (such as Figure 4Single-stage fracturing is performed using fracturing equipment (using a fracturing device in the pipeline), controlling the fracturing scale to eliminate outbursts in areas not affected by long-borehole fracturing. Specifically, the casing is inserted obliquely through the rock stratum into the coal seam from the roadway, specifically the drill hole at the drilling site. Cement is used to secure the gap between the casing and the tubing. Fracturing fluid from the surface fracturing equipment is then used to create fractures in the open hole.

[0106] In actual projects, 1-10 ground fracturing trucks, 1 manifold truck, 1 instrument truck, 1 sand mixer truck, and several water storage tanks are required; the fracturing operation displacement is 6-8m / min. 3 Liquid causes cracks to form quickly in the stratum, and quartz sand is used to support the formed cracks, so as to achieve rapid analysis of the coal seam and extraction of gas from the cracks.

[0107] Unlike long-borehole staged fracturing, short-borehole single-stage fracturing reduces the fracturing area and impact range, but can be used to control the fracturing range, for example, in areas where long-borehole staged fracturing cannot eliminate the burst. In other words, short-borehole single-stage fracturing can be used in areas where long-borehole staged fracturing has not eliminated the burst.

[0108] 3) Downhole short drilling and fracturing strategy (downhole drilling and fracturing method / technology)

[0109] Combine Figure 6 As shown in the figure, downhole drilling and downhole fracturing is to drill a hole from the tunnel to the coal seam. The drilling depth is about 100m and the hole diameter is about 108mm. A seamless steel pipe with a diameter of 10mm is inserted and connected with a downhole fracturing pump to fractur the cracks in the coal seam. In actual engineering, the construction pressure is about 10MPa (megapascals) and the displacement is about 0.5-1m 3 / min, using pure water fracturing without sand propping the fractures. This fracturing method offers good controllability of fracture depth and is suitable for applications where long, multi-stage fracturing in corners or single-stage fracturing in short holes (surface fracturing) is impractical. Drilling can be performed using a downhole drill rig, and fracturing can be performed using downhole fracturing equipment.

[0110] 4) Grid-intensive drilling technology

[0111] Combine Figure 7 As shown, grid-intensive drilling technology is not a fracturing technology. It is a technology that uses underground coal mine drills to drill holes from the roadway to the coal seam at regular intervals, such as 4 meters. This drilling technology is equivalent to adding more cracks, namely gas extraction holes, to the cracks produced by long-hole staged fracturing technology, short-hole single-stage fracturing strategy, and underground drilling and fracturing methods. Extracting gas from more gas extraction holes can speed up the extraction process. In actual projects, the depth of the holes drilled by grid-intensive drilling technology is 10-200 meters, and the hole diameter is about 50mm. PE pipes are inserted and negative pressure is used to extract gas from the drill holes to achieve the purpose of eliminating sudden gas outbursts.

[0112] It can be understood that the dead corner areas that have not been fractured by the long-hole staged fracturing technology and the short-hole single-stage fracturing technology can be re-used with the grid-dense drilling technology and downhole drilling and downhole fracturing technology to carry out coal seam permeability improvement transformation in the dead corners of coal mine coal burst elimination, and finally achieve the coal mine coal burst elimination effect in the working face area.

[0113] Because the fracturing equipment of long-hole staged fracturing technology and short-hole single-stage fracturing is on the ground, these two technologies can also be referred to as long-hole ground fracturing technology and short-hole ground fracturing technology respectively. Figure 8 As shown, the area fractured using long-hole and short-hole surface fracturing techniques is larger than the area fractured using downhole drilling and downhole fracturing techniques. If long-hole and short-hole surface fracturing techniques are considered a form of coarse fracturing, then downhole drilling and downhole fracturing techniques can be considered a form of fine fracturing. Fine fracturing is used to fill the dead corners left by coarse fracturing and fracturing these dead corners to eliminate sudden coal outbursts. In addition, using grid-intensive drilling technology, holes can be drilled from the roadway to the coal seam at intervals, which can increase the number of cracks in the fracturing area, which is equivalent to increasing the number of gas extraction holes. Using the increased number of gas extraction holes to extract gas can shorten extraction time and increase extraction efficiency. The combination of four technologies—two coarse fracturing techniques, one fine fracturing technique, and grid-intensive drilling techniques—can greatly achieve the technical goal of eliminating sudden coal outbursts and ensure operational safety.

[0114] In the embodiment of the present application, the long borehole in the coal mine is 300-1000 meters long, and the ground fracturing equipment such as the fracturing truck is connected to the fracturing pipeline and water and sand are used for staged fracturing. In the area where the long borehole ground fracturing has not eliminated the sudden change, a short borehole of about 80-200 meters underground is used for fracturing. The ground fracturing truck is connected to the fracturing pipeline and water and sand are used to control the scale of single-stage fracturing for fracturing. For the long borehole ground fracturing and the short borehole ground fracturing, there are still dead corners where the sudden change has not been eliminated. The grid-dense drilling and downhole drilling downhole fracturing technology are used to fractur e the dead corners to eliminate the sudden change. The ground fracturing equipment is connected to the downhole borehole, and water and sand are used. The displacement reaches 6-8 cubic meters per minute, which can quickly form cracks. Quartz sand is used to support the cracks so that the cracks will not close and affect the extraction and sudden change. In actual engineering, the diameter of the long borehole in the coal mine is 153mm, and the length is 300-1000 meters. The open hole is drilled and the open hole packer is lowered. The diameter of the short borehole in the coal mine is 153mm, the length is 80-200 meters, 101.6mm casing is installed, and the drilling is completed by cementing.

[0115] The advantages of the embodiments of the present application are:

[0116] 1. The combination of downhole long borehole surface fracturing, downhole short borehole surface fracturing, grid-intensive drilling and downhole drilling and downhole fracturing can quickly form a large-area pressure reduction zone, increase coal seam permeability, and significantly improve gas extraction efficiency.

[0117] 2. This combined technology not only eliminates dead corners in the fracturing coal seam during fracturing, effectively eliminating regional outbursts at the coal mine working face, thereby ensuring the safety of coal operations, but also improves gas extraction efficiency, achieving the goals of rapid, safe, and cost-effective extraction.

[0118] It can be understood that the numerical descriptions involved in the above scheme, such as 300-1000 meters, 10-200 meters, 50 mm, etc. are only specific examples. Any other reasonable numerical values are within the scope of the embodiments of this application and are not listed one by one.

[0119] In the several embodiments provided in this application, it should be understood that the disclosed methods can be implemented in other ways. The embodiments described above are merely illustrative.

[0120] The methods disclosed in the several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments.

[0121] The features disclosed in the several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments or device embodiments.

[0122] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for eliminating coal mine outbursts in a coal area, characterized in that: include: obtaining a first geological parameter, wherein the first geological parameter represents a geological condition of a target area; selecting a target fracturing strategy for the coal seam based on the first geological parameter, wherein the target fracturing strategy includes a primary fracturing strategy and one or more auxiliary strategies that match the first geological parameter; The main fracturing strategy is used to fracture the main body of the coal seam in the target area; the auxiliary strategy is used to fracture the special geological structure of the coal seam in the target area, or to directly drill extraction holes in the fracturing area to extract gas and eliminate gas outbursts; The first geological parameters are original geological parameters obtained before the fracturing strategy is determined and geological parameters of the main fractured area and the unfractured dead corner area of the target area coal seam obtained after the main fracturing strategy is implemented; The special geological structure of the coal seam is the coal seam fault section that is not reached by the main fracturing strategy, the fracturing blank section and the dead angle area that is not fractured after the main fracturing strategy is implemented; The main fracturing strategy includes: horizontal long-hole staged fracturing; The auxiliary strategies include: auxiliary fracturing strategies and grid-densified short drilling strategies, wherein the auxiliary fracturing strategies further include: horizontal short drilling single-stage fracturing strategies and downhole short drilling fracturing strategies; the downhole short drilling fracturing strategies include downhole short drilling downhole fracturing strategies; for dead corner areas that are not fractured after the implementation of the horizontal long drilling staged fracturing and horizontal short drilling single-stage fracturing strategies, the grid-densified short drilling strategies and downhole short drilling downhole fracturing strategies are used to perform permeability enhancement transformation.

2. The method according to claim 1, characterized in that The horizontal short borehole single-stage fracturing strategy includes a horizontal short borehole downhole single-stage fracturing strategy and a horizontal short borehole surface single-stage fracturing strategy.

3. The method according to claim 1, wherein The downhole short-bore fracturing strategy also includes a downhole short-bore surface fracturing strategy.

4. The method according to any one of claims 1 to 3, characterized in that When the first geological parameter indicates that the geological conditions of the target area are the first geological conditions, the target fracturing strategies include a horizontal long-bore staged fracturing strategy and a downhole short-bore fracturing strategy; the first geological condition refers to a geological condition in which the coal seam in the area to be operated is continuous and complete, but after horizontal staged fracturing, there may be fracturing dead corners; When the first geological parameter indicates that the geological condition of the target area is the second geological condition, the target fracturing strategy includes a horizontal long-bore multi-stage fracturing strategy and a horizontal short-bore single-stage fracturing strategy; The second geological condition refers to the geological condition that there are a few faults in the coal seam in the area to be operated, and the faults are relatively long; When the first geological parameter characterizes that the geological conditions of the target area are the third geological conditions, the target fracturing strategy includes a horizontal long-bore segmented fracturing strategy and an downhole short-bore fracturing strategy; the third geological condition refers to the geological condition that there are many faults in the coal seams in the area to be operated and the length of the fault coal seams is relatively short.

5. The method according to claim 1, wherein The main fracturing strategy forms a first fracture system after fracturing, and the auxiliary strategy forms a second fracture system after fracturing; gas is extracted through the gas extraction boreholes of the first fracture system and the gas extraction boreholes of the second fracture system respectively.

6. The method according to claim 5, characterized in that The fractures of the first fracture system are connected to the fractures of the second fracture system, and gas is extracted simultaneously through the gas extraction boreholes of the first fracture system and the gas extraction boreholes of the second fracture system to accelerate the gas extraction speed.

7. The method according to claim 5, characterized in that The fractures of the first fracture system are connected to the fractures of the second fracture system, and the gas in the first fracture system and the second fracture system is extracted through the gas extraction short borehole of the first fracture system.

8. The method according to claim 5, characterized in that The cracks of the first crack system are connected with the cracks of the second crack system, and gas in both the first crack system area and the second crack system area is extracted through the short gas extraction borehole of the second crack system, so that gas can flow from the first crack system to the second crack system.

9. The method according to claim 1, characterized in that The short boreholes for single-stage fracturing of horizontal short boreholes and the short boreholes for downhole short borehole fracturing drilled by the auxiliary strategy can be used as gas extraction boreholes at the same time.

10. The method according to claim 1 or 6, characterized in that The grid-densified short drilling strategy can be applied to unfractured or fractured coal seams alone or in addition to increase the extraction channels of the target coal seams.

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