Regional outburst elimination method for ground drilling of well and roadway in strong outburst coal seam

Abstract

The application discloses a method for eliminating outburst in a ground drilling area of a well roadway in a strong outburst coal seam, and comprises the following steps: S1, ground drilling: sequentially drilling a corresponding main hole and branch holes from the ground, all the drilling holes being drilled through the target coal seam to a certain distance of the coal seam floor, and the branch holes being uniformly arranged around the main hole. In the application, in the process of hole reaming, coal body deformation and displacement of the coal seam around the drilling hole occur, and the coal body is filled into a first reserved space. After the multiple main holes and branch holes are sequentially made permeable, the coal seam around all the drilling holes and within a certain distance of the coal seam is expanded and deformed, and pressure is released, so that the permeability coefficient of the coal seam is improved. Through continuous and efficient extraction of the branch hole drilled last, regional outburst elimination is realized. The first reserved space of the main hole and the branch hole is injected with a solid material through the last drilled branch hole, so that the safety of the roadway during coal uncovering is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal mine gas control, more particularly to a method for eliminating outburst in the area of ground drilling for uncovering coal in a well or roadway of a strong outburst coal seam. BACKGROUND

[0002] Uncovering coal in a well or roadway of an outburst coal seam is a link with a relatively high risk of gas in the process of coal production. Before the well or roadway uncovers the coal seam, the amount of gas released from the coal seam is small. Once the coal seam is uncovered, a large amount of initial release gas expansion energy will be released from the coal body, which may induce coal and gas outburst and other gas accidents. In order to ensure the safety of gas during the uncovering of the coal seam, the "Provisions for the Prevention and Control of Coal and Gas Outburst" requires that regional outburst prevention measures be implemented 7 m before the minimum normal distance of the coal seam from the working face of the coal seam uncovering. The commonly used regional outburst prevention measures for uncovering the coal seam in the well or roadway are to take the measure of drilling holes to pre-drain the coal seam gas in the underground; however, with the increase in the depth of coal seam mining, the gas content and pressure are further intensified, and the contradiction between the underground gas control engineering and the replacement of mining is increasingly prominent, especially in the area where the gas pressure reaches 3 MPa or more, it is not allowed to directly construct a drilling hole in the underground.

[0003] The construction of a ground drilling hole for eliminating outburst in the area of uncovering the coal seam is a technical direction for uncovering the coal seam in a well or roadway of a strong outburst coal seam. The ground drilling hole is expanded and coal is removed from the ground, which has a large working space and high safety. After the ground drilling hole is expanded and coal is removed, the pressure relief of the coal body around the drilling hole is more sufficient, and the permeability of the coal seam also increases. After the drilling hole is expanded and coal is removed, a larger hole is formed in the coal body, the pressure relief of the coal body around the drilling hole is more sufficient, and the permeability of the coal seam also increases, the gas effect is improved, and the influence of the expansion of the drilling hole diameter on the gas extraction amount can be calculated according to the following formula:

[0004] Q = 3.14 m λ 0.9 p0 1.85 R 0.2 α 0.1 t -0.1

[0005] It can be seen that when the gas extraction time is long and the stable flow state is entered, the total gas flow Q of the borehole is proportional to the coal seam thickness m, and is proportional to the 1.85 power of the coal seam gas pressure p0, the 0.9 power of the gas permeability coefficient λ, and the 0.2 power of the borehole radius R. In the area of the coal seam, the diameter of the through-hole drilled in the underground construction is generally 113 mm. Assuming that the p0 and α (coal seam gas content coefficient) remain unchanged after the borehole is reamed and coal is removed, and the borehole diameter increases from Φ113 mm to 1500 mm, the theoretical calculation shows that the gas extraction amount after the borehole is reamed and coal is removed is 1.7 times that before the borehole is reamed and coal is removed. During the period of uncovering coal in the underground, the number of through-holes drilled in the construction is more than 50 times the number of ground drilling and branch holes drilled in the construction of the experimental site in the area, and the construction of the same ground main hole and its branch holes affects each other. The gas extraction time of the ground main hole and its branch holes is limited. Therefore, through the construction of ground drilling and branch holes and the reaming and removal of coal, the purpose of expanding the pressure relief range of the borehole and assisting in outburst elimination can be achieved, but the goal of regional outburst elimination cannot be achieved.

[0006] The existing patent document with the patent announcement number CN 112901252 A discloses a ground drilling and coal removal auxiliary outburst elimination method for a deep well high gas pressure coal uncovering area, which comprises the following steps: S1, drilling a multi-bottom directional well process: drilling a coal removal well on the ground in the deep well high gas pressure coal uncovering area, the one is a main well section, and the multi-bottom directional well comprises six branch well sections; S2, gas extraction: connecting the six branch well sections with a ground negative pressure system respectively to extract coal seam gas to the maximum extent; S3, after the gas extraction is completed, first sealing the six branch well sections with cement respectively, and then sealing the main well section with cement; S4, underground verification: arranging seven verification holes around the six branch well sections to measure the maximum gas content;

[0007] Although the method of "one multi-bottom directional well and six branch well sections" is adopted, the drilling construction progress is improved, the extraction effect is improved, the drilling and extraction time is shortened, and the safe, rapid and efficient uncovering of coal in the deep well high gas pressure coal uncovering area is realized, but through the construction of ground drilling and branch holes and the reaming and removal of coal, the purpose of expanding the pressure relief range of the borehole and assisting in outburst elimination can be achieved, and regional outburst elimination cannot be achieved. SUMMARY

[0008] The technical problem to be solved by the present application is how to realize regional outburst elimination for well and roadway coal uncovering in a strong outburst coal seam.

[0009] The present application solves the above technical problems by the following technical means: a ground drilling regional outburst elimination method for well and roadway coal uncovering in a strong outburst coal seam, characterized by comprising the following steps:

[0010] S1, ground drilling: sequentially drilling corresponding main holes and branch holes from the ground, all the drilling holes penetrating the target coal seam to a certain distance of the coal seam bottom, and the branch holes being uniformly arranged around the main holes;

[0011] S2, reaming and coal extraction for permeability enhancement: after the main borehole and its branch boreholes are completed, the target coal seam is first reamed and extracted in multiple stages, and then the target coal seam is subjected to hydraulic fracturing for permeability enhancement, thereby expanding the range of pressure relief and permeability enhancement of the coal seam;

[0012] S3, grouting: before the next branch borehole is constructed, the non-shared passageway of the already constructed main borehole or branch borehole from a certain distance above the roof of the target coal seam to the already constructed main borehole and other already constructed branch boreholes is grouted, and the target coal extraction section and a certain distance above the roof thereof are left empty to form a first storage space;

[0013] S4, extraction: continuous extraction is performed through the last constructed branch borehole, and the extraction is stopped after the ground borehole area is evaluated to be outburst-free;

[0014] S5, borehole grouting: the first storage space of the main borehole and its branch boreholes is grouted using the last constructed branch borehole, and the branch borehole and the shared passageway of the branch borehole and the main borehole are grouted.

[0015] The reaming and coal extraction can achieve partial pressure relief of the coal body, leave space for the coal body, facilitate gas extraction, and assist in outburst elimination. The non-shared passageway of the already constructed main borehole or branch borehole that is affected by the branch borehole is grouted, and a first storage space is formed between the grouting end of the already constructed branch borehole or main borehole and the empty space of the coal extraction. During the reaming and coal extraction for permeability enhancement of the adjacent borehole, the coal body of the coal seam around the borehole deforms and displaces and fills into the first storage space. After the permeability of multiple main boreholes and branch boreholes is enhanced in turn, the boreholes and the coal seam within a certain distance around the boreholes expand and deform, and the pressure is relieved, thereby improving the permeability coefficient of the coal seam. Continuous and efficient extraction is performed through the last constructed branch borehole, and regional outburst elimination is achieved. The first storage space of the main borehole and its branch boreholes is grouted using the last constructed branch borehole, and the safety of the construction during the coal extraction of the roadway is improved.

[0016] As a preferred technical solution, it further includes determining the coal extraction control range of the coal extraction roadway and measuring the original gas parameters near the coal extraction roadway, the number of the main borehole and its branch boreholes is determined according to the original gas parameters, and the distance between the coal-seeing points of the main borehole and its branch boreholes is not greater than the effective hydraulic fracturing radius of the coal seam in the region.

[0017] As a preferred technical solution, the horizontal projections of the main borehole and its branch boreholes are uniformly arranged within the coal extraction control range.

[0018] As a preferred technical solution, the volume fraction of the coal body in the coal extraction control range is ensured to be not less than 5‰ by controlling the number of the ground borehole and its branch boreholes and the diameter of the reaming and coal extraction of the coal-seeing section of the ground borehole and its branch boreholes.

[0019] As a preferred technical scheme, the main hole is a three-opening structure, the first opening section and the second opening section are shared channels, the coal-seeing section of the main hole is the third opening section to a certain distance above the coal seam roof, the branch hole is drilled from the bottom of the second opening section of the main hole to a certain distance of the target coal seam floor, the third opening section of the main hole or the branch hole is injected in step S3, the branch hole of the main hole is connected to the side end of the bottom of the second opening section of the main hole, and the main hole is constructed first and then each branch hole is constructed in step S1.

[0020] As a preferred technical scheme, in step S4, the residual gas parameters of the coal body in the coal uncovering control range are measured underground before the ground drilling area is evaluated for outburst elimination.

[0021] As a preferred technical scheme, in step S2, after the hydraulic fracturing and permeability improvement, a plurality of hydraulic fracturing cracks are formed in the main hole and the branch hole, and the cracks are connected to the already constructed main hole and branch hole, and the coal body in the coal seam fills the first reserved space.

[0022] As a preferred technical scheme, in step S2, the hole expansion and coal removal is multiple-stage hole expansion and coal removal.

[0023] As a preferred technical scheme, in step S1, the main hole opening includes the following steps:

[0024] The first opening section: the drill bit is used to drill into the stable bedrock layer for not less than 30m, the oil casing is lowered for wall protection, and the oil well cementing process is used for cementing; the cement is cured for not less than 48 hours, and then the water stop inspection is performed;

[0025] The second opening section: the drill bit is used for directional drilling to the coal floor, the oil casing is lowered, and the oil well cementing process is used for cementing; the cement is cured for 72 hours, and then the water stop inspection is performed;

[0026] The third opening section: the drill bit is used for directional drilling to the target point.

[0027] As a preferred technical scheme, the hole diameter of the first opening section of the main hole is greater than that of the second opening section, and the hole diameter of the second opening section is greater than that of the third opening section.

[0028] The advantages of the present application are:

[0029] In the application, the coal body is partially relieved by the coal extraction through the reaming, so that a space is left in the coal body, which is convenient for the gas extraction and the auxiliary outburst elimination. The non-shared channel of the branch hole which has been constructed or the main hole which has been constructed and other branch holes which have been constructed is injected and solidified, and the bottom end of the injection surface of the branch hole or the main hole and the space left by the coal extraction form a first space. In the process of the coal extraction and the penetration enhancement of the reaming hole, the coal body of the coal seam around the reaming hole is deformed and displaced, and is filled into the first space. After the penetration enhancement of the multiple main holes and branch holes, the coal seam around the reaming hole is deformed and relieved, and the permeability coefficient of the coal seam is improved. The regional outburst elimination is realized by the continuous and efficient extraction through the last branch hole. The first space of the main hole and the branch hole is injected and solidified by the last branch hole, and the safety of the construction during the coal extraction of the roadway is improved. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The main hole and the branch hole of the regional outburst elimination method of the ground drilling hole for the coal extraction of the strong outburst coal seam are provided for the embodiment of the application, and the top view schematic diagram is shown in the figure.

[0031] Figure 2 The ground drilling hole plan view of the regional outburst elimination method of the ground drilling hole for the coal extraction of the strong outburst coal seam is provided for the embodiment of the application.

[0032] Figure 3 The cross-sectional structure schematic diagram of the main hole and the branch hole of the regional outburst elimination method of the ground drilling hole for the coal extraction of the strong outburst coal seam is provided for the embodiment of the application.

[0033] Figure 4 The three-opening structure schematic diagram of the main hole of the regional outburst elimination method of the ground drilling hole for the coal extraction of the strong outburst coal seam is provided for the embodiment of the application.

[0034] Figure 5 The filling schematic diagram of the main hole of the regional outburst elimination method of the ground drilling hole for the coal extraction of the strong outburst coal seam is provided for the embodiment of the application.

[0035] The figure reference: 1, coal seam; 2, coal extraction roadway; 31, coal-seeing point; 32, coal-stopping point; 4, coal extraction control range; 5, original gas parameter test point; 6, main hole; 61, first main hole; 611, first branch hole; 62, second main hole; 621, second branch hole; 7, residual gas parameter test point. DETAILED DESCRIPTION

[0036] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0037] Referring to Figure 1 , Figure 3 , the regional outburst elimination method of the ground drilling of the strong outburst coal seam well roadway coal uncovering, comprising:

[0038] S0, design the coal uncovering roadway 2 to determine the coal uncovering control range 4, and measure the original gas parameters near the coal uncovering roadway 2, design the main hole 6 and its branch holes, ensure that the distance between the coal-seeing points of the main hole 6 and its branch holes is not greater than the effective radius of the hydraulic fracturing of the coal seam in the region and the horizontal projection of the ground regional outburst elimination drilling 6 and its branch holes is uniformly arranged in the coal uncovering control range 4;

[0039] S1, ground drilling: including sequentially drilling the corresponding main hole 6 and its branch holes from the ground, the main hole is a three-opening structure, one opening section and two opening sections are shared channels, the three opening section is from the coal-seeing section of the main hole to a certain distance above the coal seam roof, all the holes are drilled through the target coal seam to a certain distance of the coal seam floor, and the branch holes are uniformly arranged around the main hole; considering the number of the ground drilling and its branch holes, the coal-seeing section reaming and coal removal diameter of the ground drilling and its branch holes, it is ensured that the coal volume fraction in the coal uncovering control range is not less than 5‰;

[0040] S2, reaming and coal removal for permeability improvement: after the main hole and its branch holes are terminated, first, the target coal seam is reamed and coal removed in multiple stages, and then the target coal seam is subjected to hydraulic fracturing for permeability improvement (the main hole 6 and its branch holes are sequentially subjected to hydraulic fracturing for permeability improvement), thereby expanding the coal seam pressure relief and permeability improvement range;

[0041] S3, three-opening section grouting: the main hole and its branch holes are reamed and coal removed, the branch holes are connected at the bottom of the two opening section of the main hole, when drilling the unconstructed branch hole, the non-shared channels of the already constructed branch hole or the already constructed main hole and other already constructed branch holes which are affected by the branch hole are grouted, that is, the three opening section of the main hole or the branch hole which has an influence on the next branch hole is grouted, wherein the coal removal section of the already constructed branch hole or the main hole and a certain distance above the roof thereof are left empty; and the bottom end of the grouting surface of the already constructed branch hole or the main hole and the empty space of the coal removal are formed into a first reserved space; during construction, the main hole is constructed first, and then the branch holes are constructed.

[0042] S4, extraction: continuous extraction is performed through the last constructed branch hole, and stopped after the ground drilling regional outburst elimination evaluation is qualified;

[0043] S5, after the last constructed branch hole continuously extracts to the ground drilling area and the outburst elimination evaluation is qualified, the last constructed branch hole is used to inject the coal seam of the already constructed branch hole and the coal seam of the non-common channel of the already constructed branch hole and the main hole, and then the branch hole and the common channel of the branch hole and the main hole are injected.

[0044] Referring to Figure 2 , the coal uncovering roadway 2 is all the cavities drilled in the coal seam or rock stratum by the shaft and roadway for mining work, the shaft and roadway uncovering coal is the whole operation of the shaft and roadway arranged in the rock stratum crossing the coal seam vertically or obliquely, the shaft and roadway arranged in the rock stratum passes through the coal seam 1 from the floor (top) rock pillar to the roof (floor) rock pillar, the roadway with the shaft and roadway uncovering coal is the coal uncovering roadway, including the shaft uncovering coal roadway, the inclined shaft uncovering coal roadway, and the cross-cut uncovering coal roadway, referring to Figure 3 , in the embodiment, the coal uncovering roadway 2 (inclined shaft) is obliquely crossing the coal seam 1 at 15°, the coal uncovering roadway 2 passes through the coal seam 1 from the coal uncovering point 31 (floor rock pillar) at the right end of the coal uncovering roadway 2 to the coal uncovering point 32 (roof rock pillar) toward the left end of the coal uncovering roadway 2;

[0045] After the coal uncovering roadway 2 is determined, the original gas parameter test point 5 is arranged near the coal uncovering roadway, and the original gas pressure, gas content and other gas parameters of the coal seam are measured; the measured gas pressure of the test area is 3.3 MPa, the gas content is 9.8 m 3 / t, after the ground area outburst elimination drilling is constructed, the actual coal uncovering control range 4 is determined, the total gas reserves in the coal uncovering control range 4 is calculated according to the original gas content and gas pressure of the coal seam, the gas extraction rate, residual gas pressure, residual gas content and other indexes in the coal uncovering control range are dynamically calculated according to the gas extraction amount of the ground drilling, and the indexes of the coal uncovering outburst elimination evaluation are compared with the qualified requirements, the indexes of the coal uncovering outburst elimination evaluation of the test site are that the gas extraction rate η is greater than or equal to 45%, the measured residual gas pressure P is less than 0.74 MPa and the residual gas content W is less than 8 m 3 / t (W is less than 6 m 3 / t in the tectonic belt).

[0046] The coal uncovering control range 4 is determined, in order to ensure the safety of the construction during the coal uncovering of the roadway, it is necessary to determine the coal uncovering control range in the coal uncovering section and the surrounding area of the coal uncovering roadway; measures are taken in the coal uncovering control range to ensure the gas safety during the construction of the coal uncovering roadway;

[0047] The "Detailed Rules for the Prevention and Control of Coal and Gas Outbursts" stipulates the following requirements for the control range of coal seam exposure: "The drilling for coal seam gas prevention measures in the coal seam exposure area of ​​the pre-drainage shaft and roadway through-layer drilling should be carried out at least 7m before the coal seam exposure face is at the minimum normal distance from the coal seam, and the coal seam within the following range should be controlled by the through-layer drilling: 12m outside the roadway outline at the coal seam exposure point of the stone gate, vertical shaft, and inclined shaft (6m at the bottom or lower side of steeply inclined coal seams). At the same time, the minimum distance from the outer edge of the control range to the roadway outline (including the outline of the roadway of the expected coal seam exposure section ahead) should not be less than 5m. When the regional outburst prevention measures are difficult to complete in one construction, they can be implemented in sections, but each section should be able to ensure that the coal seam within at least 20m from the coal seam exposure face to the roadway ahead meets the above requirements."

[0048] In this embodiment, the test coal seam exposure roadway 2 adopts surface borehole area gas outburst prevention, and the coal seam exposure control range 4 is determined by referring to the "borehole for coal seam gas outburst prevention measures in the coal seam gas area of ​​the pre-drainage shaft roadway". Figure 1 The control range for coal seam exposure 4 is thus determined: control extends to 15m outside the roadway outline at the coal seam exposure point in the inclined shaft, while also ensuring that the minimum distance from the outer edge of the control range to the roadway outline (including the outline of the expected coal seam exposure section roadway) is not less than 5m.

[0049] In this embodiment, the main borehole 6 is a surface area outburst suppression borehole, that is, a borehole drilled from the surface to the coal seam exposure control area 4, to relieve pressure, increase permeability, and extract coal seam 1, reduce coal seam gas in the coal seam exposure control area, and eliminate the risk of coal seam outburst in the coal seam exposure control area.

[0050] See Figure 4 , Figure 5 The drilling of the main hole 6 and its branch holes, wherein the main hole 6 is a three-section structure, comprising a first section, a second section and a third section connected in sequence, and the final hole is 1m below the bottom plate of coal seam 1. The top of coal seam 1 is the coal roof plate and the bottom of coal seam 1 is the coal floor plate.

[0051] The first section includes a length of 342m from the base surface to 30m below the bedrock surface, with a borehole diameter of Φ311mm. A J55 oil casing with a borehole diameter of Φ244.5×8.94mm is installed. The bottom of the first section is located 30m below the bedrock surface. Oil cementing technology is used to cement the well and isolate the loose formation.

[0052] The second section includes directional drilling with a borehole diameter of Φ216mm from the end of the first section to the coal floor. The length from the reference surface to the coal floor is 781m. N80 oil casing with a borehole diameter of Φ177.8×8.05mm is installed throughout the entire section, and oil cementing is carried out.

[0053] Three sections, with a borehole diameter of Φ152mm, bare holes, two main holes 6 three sections and 11 branch holes were directionally drilled to the target point (1m from the bottom plate of coal seam 1), and the coal seam 1 was enlarged for coal extraction.

[0054] In this embodiment, two main holes 6 are taken as examples, which are a first main hole 61 and a second main hole 62, and are numbered as PM1 hole and PM2 hole respectively. Six first branch holes 611 are arranged around the outside of the first main hole 61, and are numbered as PM1-1 hole, PM1-2 hole, PM1-3 hole, PM1-4 hole, PM1-5 hole and PM1-6 hole respectively. The centers of the PM1-1 hole, PM1-2 hole, PM1-3 hole, PM1-4 hole, PM1-5 hole and PM1-6 hole are 20 m away from the center of the PM1 hole. Five second branch holes 621 are arranged around the outside of the second main hole 62, and are numbered as PM2-1 hole, PM2-2 hole, PM2-3 hole, PM2-4 hole and PM2-5 hole respectively. The centers of the PM2-1 hole, PM2-2 hole, PM2-3 hole, PM2-4 hole, PM2-5 hole and PM1-4 hole are 20 m away from the center of the PM2 hole.

[0055] After the PM1 hole and the PM2 hole are constructed in place, the three sections of the PM1 hole are respectively provided with the PM1 main hole, the PM1-1 hole, the PM1-2 hole, the PM1-3 hole, the PM1-4 hole, the PM1-5 hole and the PM1-6 hole. The three sections of the PM2 hole are respectively provided with the PM2 main hole, the PM2-1 hole, the PM2-2 hole, the PM2-3 hole, the PM2-4 hole and the PM2-5 hole.

[0056] The construction of the TM1 hole (main hole) includes the following steps:

[0057] (1) The first section: a drill bit with a hole diameter of Φ311 mm is used to drill into the stable bedrock layer for not less than 30 m, and then a Φ244.5×8.94 mm J55 oil casing is lowered to protect the wall, and the oil well cementing process is used for cementing. The cement is allowed to stand for not less than 48 hours before the water stop inspection is performed.

[0058] (2) The second section: a drill bit with a hole diameter of Φ216 mm is used for directional drilling to the coal floor, and then a Φ177.8×8.05 mm N80 oil casing is lowered, and the oil well cementing process is used for cementing. The cement is allowed to stand for 72 hours before the water stop inspection is performed.

[0059] (3) The third section: this section of the hole is a bare hole, and a drill bit with a hole diameter of Φ152 mm is used for directional drilling to the target point (1 m from the coal seam 1 floor).

[0060] The construction of the TM1-1 hole (branch hole of the first main hole 61) includes the following steps:

[0061] First, the three open sections of TM1 hole are partially grouted, i.e. the coal seam excavation section is left empty, so that the bottom of the grouted section and the ungrouted area of the three open sections and the area left empty after the coal seam excavation form a first storage space; then, according to the design of TM1-1 hole, drilling is started from the bottom of the second open section of TM1 hole, directional drilling is carried out to the target point (1m below the coal seam 1) and the coal seam is expanded and excavated according to the requirements; after the expansion and excavation, the TM1-1 hole is grouted by using a petroleum well cementing pump truck (F800 mud pump truck) to fracture the coal seam, the water injection pressure is not less than the coal seam cracking pressure (the coal seam cracking pressure in this area is 26MPa), due to the auxiliary free surface effect of TM1-1 hole, the cracks generated by the hydraulic fracturing hole have the effect of guiding and accelerating the expansion, and the cracks are induced to develop from TM1-1 hole to the holes in the surrounding direction (i.e. the dotted circle area in the figure), so as to achieve the purpose of uniform fracturing, improve the gas extraction effect, and prevent gas outburst; in the process of hydraulic fracturing of TM1-1 hole, the coal body in coal seam 1 is displaced to the first empty area, and fills the ungrouted area of the three open sections of TM1 hole, the theoretical value of the coal body swelling deformation rate of this area can reach 5‰, so the permeability coefficient of coal seam 1 will be significantly improved. After hydraulic fracturing, multiple hydraulic fracturing cracks are formed, which realize the communication with the TM1 main hole excavation section through the cracks, and the gas in the empty area of coal seam 1 can be extracted through TM1-1 hole, so that the coal body gas within the effective radius of TM1 hole and TM1-1 hole can be efficiently extracted; after the branch hole is hydraulically fractured, the hole is combined and extracted for 1 day. Finally, the area above 5m of the coal seam roof of TM1-1 hole to the three open sections is grouted with cement slurry, and TM1-2, TM1-3, TM1-4 and TM1-5 are sequentially constructed in the same way.

[0062] Construction of TM1-6 hole

[0063] First, the three open sections of TM1-5 hole are partially grouted, i.e. the coal seam excavation section is left empty, so that the bottom of the grouted section and the ungrouted area of the three open sections and the area left empty after the coal seam excavation form a first storage space; then, according to the design of TM1-6 hole, drilling is started from the TM1 side, directional drilling is carried out to the target point (1m below the coal seam 1) and the coal seam is expanded and excavated according to the requirements; after the excavation, the TM1-1 branch hole is grouted by using a petroleum well cementing pump truck (F800 mud pump truck) to fracture the coal seam, and the TM1-6 hole is connected with the TM1 main hole and the TM1-2, TM1-3, TM1-4 and TM1-5 branch holes, the water injection pressure is not less than the coal seam cracking pressure; after the TM1-6 branch hole is hydraulically fractured, the hole is combined and continuously extracted.

[0064] TM2 ground hole is constructed in the same way, and TM2 hole, TM2-1 hole, TM2-2 hole, TM2-3 hole, TM2-4 hole and TM2-5 hole are sequentially constructed.

[0065] Finally, the TM1-6 hole and TM2-5 hole are continuously pumped to measure the amount of gas, until the ground drilling area of the coal uncovering roadway is qualified for eliminating the outburst, and then the pumping is stopped, otherwise the pumping is continued to control the gas in the area of the coal uncovering.

[0066] The multi-stage and multi-time reaming and coal extraction is to form larger holes in the coal body, the pressure relief of the coal body around the drilling hole is more sufficient, the gas permeability of the coal seam is also increased, and the gas extraction effect is improved; the reaming and coal extraction in the above is all four-stage reaming and coal extraction, and is performed multiple times, since the hole diameter of the third section of the main hole 6 is Φ152mm, after the open hole completion of the coal seam section, the four-stage reaming and coal extraction of Φ350mm, Φ500mm, Φ1200mm and Φ1500mm is performed, that is, four drill bits with different diameters are used to perform reaming in turn, and the diameter of the drilling hole in the target coal seam is expanded to not less than 1.5m (it is expected to be expanded to 1.6-1.8m), the thickness of the coal seam in the coal uncovering area is 7m, and the coal extraction amount of the 13 drilling holes is not less than 160.7m 3 3 Therefore, the coal extraction amount of the coal volume fraction in the coal uncovering control area is not less than 5‰, since the gas permeability of the coal seam in the test area is low, the local pressure relief and auxiliary outburst elimination purposes can be achieved after the reaming and coal extraction.

[0067] Sealing of the ground drilling hole: after the residual gas parameter test point 7 in the coal uncovering roadway 2 is qualified for eliminating the outburst, the gas extraction inspection is performed, and then the ground drilling hole stops pumping, the cement high-pressure grouting is used to seal the ground drilling hole, the grouting methods of the TM1 hole and the branch holes thereof and the TM2 hole and the branch holes thereof are the same, and the TM1 hole and the branch holes thereof are taken as examples for specific description:

[0068] The first space of the TM1 hole and the TM1-1, TM1-2, TM1-3, TM1-4, TM1-5 and TM1-6 is filled with the TM1-6 hole, so as to improve the safety of the construction during the coal uncovering of the roadway; finally, the TM1-6 hole and the second section and the first section of the TM1 hole are filled with the cement slurry.

[0069] The above examples are only used to illustrate the technical solutions of the present application, but not to limit the same; although the present application is described in detail with reference to the foregoing examples, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by the equivalent ones; and the modification or replacement does not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solutions of the embodiments of the present application.​

Claims

1. A method for eliminating outburst in the area of surface drilling for uncovering coal seams in strong outburst coal seams, characterized in that, The method comprises the following steps: designing a coal uncovering roadway to determine a coal uncovering control range, and measuring original gas parameters near the coal uncovering roadway; the number of main holes and branch holes is determined according to the original gas parameters, and the distance between the main hole and the branch hole is not greater than the effective radius of hydraulic fracturing of the coal seam in the region. S1, ground drilling: including sequentially drilling the main hole and the branch hole from the ground, all the holes penetrating the target coal seam to a certain distance of the coal seam floor, the main hole being a three-opening structure, the first opening section and the second opening section being a shared channel, the coal uncovering section of the main hole to a certain distance above the coal seam roof being a third opening section, the branch hole being drilled from the bottom of the second opening section of the main hole to a certain distance of the target coal seam floor, the main hole being drilled first, and then the branch hole being drilled; S2, hole enlarging and coal removing for permeability improvement: after the main hole and the branch hole are drilled, the target coal seam is first subjected to multi-stage hole enlarging and coal removing, and then is subjected to hydraulic fracturing for permeability improvement, so as to enlarge the range of pressure relief and permeability improvement of the coal seam; after the hydraulic fracturing for permeability improvement, a plurality of hydraulic fracturing cracks are formed in the main hole and the branch hole, and the cracks are connected with the main hole and the branch hole that have been drilled; S3, third opening section injection: before drilling the next branch hole, the main hole or the branch hole that has been drilled is injected from a certain distance above the target coal seam roof to the non-shared channel of the main hole and other branch holes that have been drilled, the coal removing section of the target coal seam and a certain distance above the roof are left empty, and a first reserved space is formed; S4, extraction: continuous extraction is performed through the last drilled branch hole, and the extraction is stopped after the ground drilling area is evaluated to be out of danger; S5, hole injection: the first reserved space of the main hole and the branch hole is injected through the last drilled branch hole, and then the branch hole and the shared channel of the branch hole and the main hole are injected.

2. The outburst area elimination method for coal seam uncovering by surface drilling in a coal seam with high outburst in a mine roadway according to claim 1, characterized in that, The horizontal projections of the main hole and the branch hole are uniformly arranged in the coal uncovering control range.

3. The method according to claim 1, wherein, The number of the ground drilling and the branch hole, and the hole diameter of the coal uncovering section of the ground drilling and the branch hole are controlled, so that the coal removing amount of the coal volume fraction in the coal uncovering control range is not less than 5 ‰.

4. The outburst area elimination method for coal seam uncovering by surface drilling in a coal seam with high outburst in a mine roadway according to claim 1, characterized in that, In the step S4, the residual gas parameters of the coal in the coal uncovering control range are measured underground before the evaluation of the ground drilling area.

5. The method according to claim 1, wherein, The hole enlarging and coal removing in the step S2 is multi-time and multi-stage hole enlarging and coal removing.

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