Method for advanced gas control in well site centralized liquid supply and distributed fracturing area

Abstract

The present invention relates to a method for centralized liquid supply on the ground well site and advanced gas control in the distributed fracturing area underground, belonging to the technical field of coal mine gas drainage. The present invention sets up a centralized fracturing well site on the ground, penetrates the ground well through construction to connect with the centralized well site in the coal mining area underground, constructs advanced directional long boreholes along the strike or dip of the coal seam or the roof and floor in specific drill sites on the up and down mountains in the coal mining area underground and performs full-section or sectional sealing of the boreholes, connects the centralized fracturing well site on the ground to the advanced directional long boreholes through the centralized well site in the coal mining area underground by using fracturing pipelines, utilizes the fracturing equipment in the centralized well site on the ground to perform distributed full-section or sectional fracturing on the advanced directional long boreholes, and finally conducts network drainage on the advanced directional long boreholes. The present invention can effectively solve the problem that the fracturing equipment in the coal mine underground is restricted by the size of the working roadway and cannot perform advanced regional coal seam fracturing, and further realizes the efficient drainage of advanced regional coal seam gas in the coal mine underground.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal mine gas drainage, and particularly relates to a method for centralized liquid supply on the ground well site and advanced gas control in the underground distributed fracturing area. Background Art

[0002] According to statistics, more than 50% of the mines in China are high-gas or outburst mines, which are characterized by high coal seam gas content and large gas emission. The large amount of gas emission in the mine will seriously affect the safe production of coal mines. Therefore, the "Interim Provisions on the Standardization of Coal Mine Gas Drainage" clearly states that high-gas or outburst mines must carry out gas drainage. At the same time, the "Coal Mine Safety Regulations" and the "Detailed Rules for the Prevention and Control of Coal and Gas Outbursts" also stipulate that the outburst prevention work in outburst mines must adhere to the principle of prior regional measures. The regional outburst prevention measures for pre-draining coal seam gas mainly include ground well pre-drainage and underground borehole pre-drainage. Among them, ground well pre-drainage has defects such as difficult ground land acquisition and demolition, large drilling difficulty, high construction and maintenance costs, and is only applied in a few mining areas such as the Qinshui Basin and the Ordos Basin. In the regional outburst prevention measures of underground borehole pre-drainage, directional long boreholes have been gradually promoted in recent years. However, in view of the characteristics of soft and low-permeability coal seams in high-gas or outburst mines in China, the single directional long borehole has a small drainage radius and low efficiency, and it is difficult to achieve the standard of coal seam gas drainage in a short time. As an enhanced permeability measure for coal seam gas drainage, hydraulic fracturing has successfully developed underground small-scale fracturing equipment and achieved certain results. However, when using the underground small-scale fracturing equipment to fracture the coal seam or the roof and floor through directional long boreholes, due to the limitation of underground roadway conditions, the fracturing equipment has a small displacement (generally less than 1 m3 / min), difficult sand addition, and difficult movement, and cannot reach the capacity of ground fracturing equipment. Therefore, it is necessary to combine ground fracturing equipment and underground directional long boreholes to achieve the effect of regional advanced gas control.

[0003] In the prior art, a method for fracturing gas holes in coal mines (patent number ZL2010102521787) is disclosed. The method uses surface fracturing equipment to fracture the long boreholes along the coal seam on both sides of the roadway through surface drilling constructed above the roadway. For the advanced gas control in underground areas of coal mines, this method requires arranging multiple surface well sites according to different roadway positions, and this defect limits the application of this method. The prior art also discloses a method for enhancing gas extraction from long boreholes in underground coal mines with ground assistance (patent number CN2018105437516). The method uses surface fracturing equipment to fracture the gas drainage holes of a working face through the conveying holes arranged in the middle roadway area of the gas extraction working face. This method realizes the regional gas control of a working face, but still cannot solve the problem of advanced gas control in underground areas. The prior art also discloses a method for efficiently extracting gas from fractured soft and low-permeability coal seams through combined surface and underground fracturing in a region (patent number CN2020103806585). The method uses surface fracturing equipment to fracture the directional long boreholes covering multiple working faces in a mining area along the roof or floor of the coal seam through the through-tunnel wells connected to the main roadway or working roadway in the mining area. This method is suitable for reforming fractured soft and low-permeability coal seams in underground coal mines, but still cannot completely solve the problem of advanced gas control in the region covering all working faces in a mining area from a technical level.

[0004] Therefore, aiming at the technical problem that the current underground coal mine fracturing equipment is restricted by the roadway size and cannot perform regional advanced coal seam fracturing, a method for regional advanced gas control with centralized liquid supply from surface well sites and distributed fracturing underground is proposed, which realizes the efficient extraction of advanced coal seam gas in underground coal mines and has very important significance for ensuring the safety production of coal mines. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for regional advanced gas control with centralized liquid supply from surface well sites and distributed fracturing underground. To achieve the above purpose, the present invention provides the following technical solutions:

[0006] 1. A method for regional advanced gas control with centralized liquid supply from surface well sites and distributed fracturing underground, the method is specifically as follows: Set up a centralized fracturing well site 1 on the ground, construct a surface well 2 between the centralized fracturing well site 1 on the ground and the centralized well site 3 in the underground coal mine mining area, set up regional advanced directional long boreholes 7 in specific drill sites 6 on the up and down mountain roads in the underground coal mine mining area, seal the whole section or segmented of the regional advanced directional long boreholes 7, connect the centralized fracturing well site 1 on the ground, the centralized well site 3 in the underground coal mine mining area and the regional advanced directional long boreholes 7 in sequence by using fracturing pipelines 4, use the fracturing equipment 5 of the centralized fracturing well site 1 on the ground to perform distributed whole-section or segmented fracturing on the regional advanced directional long boreholes 7, and finally perform network extraction on the regional advanced directional long boreholes.

[0007] Preferably, a set of centralized fracturing well sites 1 on the ground and a centralized well site 3 in the coal mine underground mining area are set in a mining area at the same level within the mine range.

[0008] Preferably, the construction displacement of the fracturing equipment 5 is greater than the liquid absorption capacity of the coal and rock reservoir after fracturing by the regional advanced directional long borehole 7 and not less than 800 L / min, and the fracture initiation pressure of the regional advanced directional long borehole is not less than 30 MPa.

[0009] Preferably, the regional advanced directional long borehole 7 is arranged along the coal seam roof 13 or the coal seam floor 14 in soft coal quality and is fractured in one go, and is arranged along the coal seam and fractured in sections in medium-hard or harder coal quality.

[0010] Preferably, the regional advanced directional long borehole 7 includes any one or several of the regional advanced directional long borehole I 7-1 with an opening set at a specific drill site 6 in the mining area's up and down mountain, the regional advanced directional long borehole II 7-2 at the coal seam roadway 8 that has been driven at the edge of the mining area, and the regional advanced directional long borehole III 7-3 at the roadway 9 at the coal seam roof or floor that has been driven in the middle of the mining area.

[0011] Preferably, the regional advanced directional long borehole I 7-1 is constructed along any direction in the coal seam, the coal seam roof 13 or the coal seam floor 14 to cover a mining face.

[0012] Preferably, the regional advanced directional long borehole II 7-2 is constructed along any direction inclined in the coal seam, the coal seam roof 13 or the coal seam floor 14 to cover multiple mining faces on one side of a mining area.

[0013] Preferably, the regional advanced directional long borehole III 7-3 is constructed along any direction inclined in the coal seam, the coal seam roof 13 or the coal seam floor 14 to cover multiple mining faces on both sides of a mining area.

[0014] Preferably, the centralized well site 3 in the coal mine underground mining area is located at the position of the connecting roadway 11 with the shortest total distance from the opening position of the regional advanced directional long borehole 7 to the mining area's up and down mountain 10.

[0015] The beneficial effects of the present invention are as follows: The present invention discloses a method for centralized liquid supply in a surface well site and advanced gas control in a distributed fracturing area underground in a coal mine, which has the following advantages: (1) In the present invention, a set of centralized fracturing well sites on the surface and a centralized well site in the mining area underground in a mining area at the same level are arranged, which can greatly reduce the construction costs on the surface and underground, drilling costs, and the construction costs of implementing hydraulic fracturing operations; (2) The present invention uses fracturing equipment at the centralized well site on the surface for underground directional long borehole construction, which can greatly increase the construction displacement of the fracturing equipment, ensure the initiation pressure in the borehole, and at the same time reduce the fracturing equipment cost and increase the coal seam gas extraction effect; (3) According to different coal seam toughness coefficients, this method arranges regional advanced directional long boreholes along the coal seam, the roof of the coal seam, or the floor of the coal seam to implement different process fracturing operations, which can greatly increase the length of the directional long boreholes, reduce the difficulty of fracturing construction, and increase the coal seam gas extraction effect; (4) The present invention constructs directional long boreholes covering one or more mining faces in different areas of a mining area and implements distributed fracturing to achieve efficient extraction of regional advanced gas in a mining area, which can greatly improve the fracturing construction efficiency, shorten the fracturing construction time, and reduce the gas extraction cost; (5) The present invention sets the well positions of the centralized well site in the mining area underground at the position of the crossheading connecting the up and down headings of the mining area, which can greatly shorten the length of the high-pressure pipeline during fracturing operations, reduce the fracturing construction cost, and reduce the safety risk of fracturing operations. Therefore, the method of the present invention is an important breakthrough in the field of coal mine gas extraction technology, which can effectively solve the problem that the fracturing equipment underground in a coal mine is restricted by the roadway size and cannot perform regional advanced coal seam fracturing, and further achieve efficient extraction of regional advanced coal seam gas underground in a coal mine, ensuring the balance of coal mining, extraction, and the safe production of the mine.

[0016] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be learned from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail and preferably with reference to the accompanying drawings, where:

[0018] Figure 1 It is a schematic diagram of the coal mine area layout for a method of centralized liquid supply in a surface well site and advanced gas control in a distributed fracturing area underground;

[0019] Figure 2 is Figure 1 The A-A' sectional view of;

[0020] Figure 3 is Figure 1 The B-B' sectional view of;

[0021] Figure 4 is Figure 1 C-C' sectional view;

[0022] Among them, 1 is a centralized fracturing well site, 2 is a surface well, 3 is a centralized well site in the coal mine underground mining area, 4 is a fracturing pipeline, 5 is a fracturing equipment, 6 is a specific drilling site in the up and down mountain of the mining area, 7 is a regional advanced directional long borehole, 7-1 is regional advanced directional long borehole I, 7-2 is regional advanced directional long borehole II, 7-3 is regional advanced directional long borehole III, 8 is a coal seam roadway that has been driven at the edge of the mining area, 9 is a roadway at the roof or floor of the coal seam that has been driven in the middle of the mining area, 10 is the up and down mountain of the mining area, 11 is a connecting roadway, 12 is a coal seam, 13 is the coal seam roof, and 14 is the coal seam floor. Specific implementation mode

[0023] The following uses specific specific examples to illustrate the implementation mode of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0024] Example 1

[0025] A method for centralized liquid supply at the surface well site and distributed fracturing in the underground for regional advanced gas control. The layout schematic diagram of the coal mine area in this method is as Figure 1 shown. The specific method is as follows:

[0026] Select a suitable location on the ground within the mine field to set up a centralized fracturing well site 1. Construct a surface well 2 between the centralized fracturing well site 1 and the centralized well site 3 in the coal mine underground mining area. Set up regional advanced directional long boreholes 7 at specific drill sites 6 in the up and down mountain areas of the mining area in the coal mine (where the specific drill site refers to a position where it is preferably selected to make the directional long borehole easy to construct and the comprehensive distance is the shortest). The regional advanced directional long boreholes 7 include any one or several of the following: regional advanced directional long borehole I 7-1 with an opening set at the specific drill site 6 in the up and down mountain areas of the mining area, regional advanced directional long borehole II 7-2 with an opening set at the excavated coal seam roadway 8 at the edge of the mining area, and regional advanced directional long borehole III 7-3 with an opening set at the roadway 9 at the roof or floor of the excavated coal seam in the middle of the mining area. And perform full-section or segmented sealing of the regional advanced directional long boreholes. Connect the centralized fracturing well site 1 on the ground, the centralized well site 3 in the coal mine underground mining area, and the regional advanced directional long boreholes 7 in sequence using a fracturing pipeline 4. Use the fracturing equipment 5 at the surface fracturing well site 1 to perform distributed full-section or segmented fracturing on the regional advanced directional long boreholes 7. Finally, use the gas drainage pipeline network in the coal mine underground to conduct network drainage on the regional advanced directional long boreholes 7.

[0027] The number of the centralized fracturing well site 1 on the ground and the centralized well site 3 in the coal mine underground mining area is arranged by level and by mining area according to the mine scope. One set of the centralized fracturing well site (1) on the ground and the centralized well site (3) in the coal mine underground mining area is arranged in one mining area at the same level, realizing regional advanced gas control in one mining area at the same level, which can greatly reduce the construction costs on the ground and underground, the drilling cost, and the cost of implementing hydraulic fracturing construction.

[0028] Set the construction displacement of the fracturing equipment 5 in the centralized fracturing well site 1 on the ground to be greater than the liquid absorption capacity of the coal-rock reservoir after fracturing of the regional advanced directional long borehole 7, so that the construction displacement can meet the fracturing requirements of the regional advanced directional long borehole 7 at the farthest distance. At the same time, considering the current capabilities of domestic fracturing equipment 5, it is generally required to be not less than 800 L / min. The wellhead pressure of the fracturing equipment 5 at the centralized fracturing well site 1 on the ground is calculated according to the frictional resistance along the way from the centralized fracturing well site 1 on the ground through the centralized well site 3 in the coal mine underground mining area to the regional advanced directional long borehole 7. In addition to considering the frictional resistance along the way, the calculation parameters should also subtract the influence of the liquid gravity generated by the fracturing pipeline 4 passing through the surface well 2. Therefore, considering the current requirements for the capabilities of domestic fracturing equipment 5, ensure that the initial fracturing pressure in the borehole of the regional advanced directional long borehole at the farthest distance is not less than 30 MPa.

[0029] The regional advanced directional long boreholes 7 are arranged according to the occurrence conditions of the coal seam, as follows: When the coal seam is relatively soft, the regional advanced directional long boreholes 7 are arranged along the roof 13 or the floor 14 of the coal seam, and one-time fracturing is carried out on them, which can ensure the construction depth of the directional long boreholes, reduce the construction difficulty, and at the same time form through fractures with the coal seam 12 after fracturing along the roof 13 or the floor 14 of the coal seam, ultimately effectively improving the gas drainage effect of the coal seam; When the coal seam is relatively hard, the regional advanced directional long boreholes are arranged in the middle of the coal seam 12 and segmented fracturing is carried out. After fracturing along the coal seam 12, through fractures are formed in segments in the coal seam 12, directly reducing the drilling construction cost and improving the gas drainage effect of the coal seam.

[0030] The opening of the regional advanced directional long borehole I 7-1 is arranged in the specific drill site 6 of the haulage roadway in the mining area. It is constructed along the coal seam 12 to cover a mining face and distributed fracturing is carried out. After the alternate fracturing of the regional advanced directional long borehole I 7-1 is completed, all the regional advanced directional long boreholes are connected for gas drainage, reducing the fracturing construction cost and realizing the efficient gas drainage in the strike direction of a mining face (the schematic diagram is as Figure 2 shown, which is Figure 1 the A-A' sectional view in

[0031] The opening of the regional advanced directional long borehole II 7-2 is arranged in the driven coal seam roadway 8 at the edge of the mining area. It is constructed along the dip of the roof 13 of the coal seam 12 to cover multiple mining faces on one side of a mining area and distributed fracturing is carried out. After the alternate fracturing of the regional advanced directional long borehole II 7-2 is completed, all the regional advanced directional boreholes are connected for gas drainage, reducing the fracturing construction cost and realizing the efficient gas drainage in the dip direction of multiple mining faces on one side of a mining area (the schematic diagram is as Figure 3 shown, which is Figure 1 the B-B' sectional view in

[0032] The opening of the regional advanced directional long borehole III 7-3 is arranged in the roadway 9 at the roof or floor of the driven coal seam in the middle of the mining area. It is constructed along the dip of the coal seam 12 to cover multiple mining faces on both sides of a mining area and distributed fracturing is carried out. After the alternate fracturing of the regional advanced directional long borehole III 7-3 is completed, all the regional advanced directional boreholes are connected for gas drainage, reducing the fracturing construction cost and realizing the efficient gas drainage in the dip direction of multiple mining faces on both sides of a mining area (the schematic diagram is as Figure 4 shown, which is Figure 1 the C-C' sectional view in

[0033] The well location of the centralized well site 3 in the coal mine underground mining area is determined according to the layout of the regional advanced directional long borehole 7, and is set at the position of the connecting roadway 11 between the upper and lower mine roadways 10 with the shortest total distance from the opening position of the regional advanced directional long borehole 7, effectively shortening the fracturing pipeline distance between the centralized well site 3 in the coal mine underground mining area and the regional advanced directional long borehole 7, reducing the pipeline laying cost, reducing the pipeline pressure loss of the fracturing equipment 5 in the centralized fracturing well site on the ground, ensuring the fracturing effect of the regional advanced directional long borehole, and effectively improving the regional advanced coal seam gas control effect of multiple coal mining faces in one mining area.

[0034] In summary, the present invention discloses a method for centralized liquid supply on the ground well site and underground distributed fracturing regional advanced gas control, which can effectively solve the problem that the fracturing equipment in the coal mine underground is restricted by the roadway size and cannot perform regional advanced coal seam fracturing. At the same time, it reduces the construction costs on the ground and underground, drilling costs, and the implementation costs of hydraulic fracturing construction, improves the construction displacement of the fracturing equipment, ensures the fracture initiation pressure in the borehole, reduces the cost of the fracturing equipment, increases the length of the directional long borehole, reduces the difficulty of fracturing construction, improves the fracturing construction efficiency, shortens the fracturing construction time, reduces the gas drainage cost, shortens the length of the high-pressure pipeline during the fracturing operation, reduces the fracturing construction cost, and reduces the safety risk of the fracturing operation, ultimately realizing the efficient extraction of regional advanced coal seam gas in the coal mine underground.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for advanced gas control in a well site centralized liquid supply and distributed fracturing area, characterized in that The method is specifically as follows: Set up a centralized fracturing well site (1) on the ground. Construct a surface well (2) between the centralized fracturing well site (1) on the ground and the centralized well site (3) in the coal mine underground mining area. Set up a regional advanced directional long borehole (7) in the up and down hill drilling sites (6) of the mining area in the coal mine underground. Seal the whole section or in sections of the regional advanced directional long borehole (7). Use a fracturing pipeline (4) to connect the centralized fracturing well site (1) on the ground, the centralized well site (3) in the coal mine underground mining area, and the regional advanced directional long borehole (7) in sequence. Use the fracturing equipment (5) at the centralized fracturing well site (1) on the ground to implement distributed whole-section or sectional fracturing on the regional advanced directional long borehole (7). Finally, conduct network drainage on the regional advanced directional long borehole; Set up a group of centralized fracturing well sites (1) on the ground and centralized well sites (3) in the coal mine underground mining area in the same horizontal mining area within the mine scope; The regional advanced directional long borehole (7) includes any one or several of the regional advanced directional long borehole I (7-1) with an opening at the up and down hill drilling site (6) of the mining area, the regional advanced directional long borehole II (7-2) at the coal seam roadway (8) that has been driven at the edge of the mining area, and the regional advanced directional long borehole III (7-3) at the roadway (9) at the roof or floor of the coal seam that has been driven in the middle of the mining area; The centralized well site (3) in the coal mine underground mining area is located at the position of the connecting roadway (11) of the up and down hill (10) with the shortest total distance from the opening position of the regional advanced directional long borehole (7); 2. The method according to claim 1, wherein The construction displacement of the fracturing equipment (5) is greater than the liquid absorption capacity of the coal and rock reservoir after fracturing of the regional advanced directional long borehole (7) and not less than 800 L / min, and the fracture initiation pressure of the regional advanced directional long borehole is not less than 30 MPa; 3. The method according to claim 1, wherein The regional advanced directional long borehole (7) is arranged along the coal seam roof (13) or coal seam floor (14) in soft coal quality and implemented with one-time fracturing, and arranged along the coal seam in medium-hard or harder coal quality and implemented with sectional fracturing; 4. The method according to claim 1, characterized in that The regional advanced directional long borehole I (7-1) is constructed along any one of the coal seam, coal seam roof (13), or coal seam floor (14) to cover one coal mining face; 5. The method according to claim 1, characterized in that The regional advanced directional long borehole II (7-2) is constructed along any one of the coal seam, coal seam roof (13), or coal seam floor (14) in the dip direction to cover multiple coal mining faces on one side of a mining area; 6. The method according to claim 1, characterized in that The regional advanced directional long borehole III (7-3) is constructed along any one of the coal seam, coal seam roof (13), or coal seam floor (14) in the dip direction to cover multiple coal mining faces on both sides of a mining area;

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