A method for combined extraction of goaf and mining area gas

Abstract

The application aims to provide a goaf and mining area gas combined extraction method, and belongs to the technical field of gas extraction. In the working face or the inclination direction of the stoping working face, a bare hole horizontal hole is constructed in the roof of the proposed mining fractured zone. A bare hole packer is seated in the extraction pipe string to seal before the inclined point of the horizontal section, so that the extraction pipe string can extract and control the goaf gas. The extraction pipe string and the annulus between the bare hole wall can extract the mining area gas. When the goaf advances to the next working face, the bare hole packer of the extraction pipe string is unsealed in advance, and the pipe string is lifted. The inclined drilling tool is lowered and landed on the side 50m close to the air return roadway in the new goaf to be formed. The extraction pipe string with the bare hole packer is lowered in the hole again, and the above steps are repeated to realize the rolling combined extraction of the mining area and goaf gas.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas extraction, and particularly relates to a combined extraction method for goaf and mining area gas. BACKGROUND

[0002] Many gas accidents are caused by the over-limit gas concentration in the fully mechanized working face, and the gas concentration in the working face is mainly derived from the gas emission in the mining area and the goaf, so effective extraction of the gas in the mining area and the goaf can solve the problem of over-limit gas concentration in the working face. The gas control in the mining area mainly adopts ground vertical well, L-shaped well, high-position hole and interception borehole extraction, and has achieved certain results.

[0003] The goaf gas extraction control is divided into three modes of underground, ground and well-ground combined extraction. The commonly used underground goaf gas extraction technology mainly includes goaf buried pipe, high-position borehole and high-extraction roadway, etc. The ground goaf gas extraction includes ground directional well and ground vertical well extraction. The well-ground combined extraction is connected with the extraction pipe in the well and the extraction pipe arranged in the main return air roadway of the goaf, so as to realize the extraction of the gas in the goaf. Overall, the gas extraction modes of the mining area and the goaf mainly include ground drilling and underground drilling, which are seriously affected by the underground space, time and mining replacement, so that the underground gas extraction effect is not ideal. The ground drilling is not limited by the underground space and production arrangement, and has high extraction efficiency, but the gas seepage in the mining fracture field and the rock stability have great influence on the ground gas extraction, so it is necessary to innovate the process and method, and use the ground drilling to efficiently extract the gas in the mining area and the goaf. SUMMARY

[0004] The application aims to provide a combined extraction method for goaf and mining area gas, realize the underground gas control in the mining area and the goaf, and ensure the underground safety production.

[0005] The application adopts the following technical scheme:

[0006] A kind of goaf and mining area gas combined extraction method, in several planning working face or inclination direction of stoping working face, in the roof of stoping working face, bare hole horizontal hole is constructed in fracture zone of mining, horizontal hole terminal is landed in the side 50m of air return roadway in the goaf to be formed with 3 ° / 100m downward inclination, Φ114mm extraction pipe column is lowered in horizontal hole, bare hole packer is sealed before the downward inclination of horizontal section, realize the extraction of goaf gas by Φ114mm extraction pipe column, extraction mining area gas between extraction pipe column and annulus of bare hole wall, considering ground construction progress and the range and time of ground influence by underground stoping, when goaf advances to next working face, bare hole packer of Φ114mm extraction pipe column is unsealed in advance, and pipe column is pulled out, and deviation drilling tool is lowered, and is landed in the side 50m of air return roadway in the goaf to be formed with 3 ° / 100m downward inclination, and Φ114mm extraction pipe column is lowered in hole with bare hole packer, and the above steps are repeated, to realize the rolling combined extraction of mining area and goaf gas.

[0007] Specifically include the following steps:

[0008] First, well location selection

[0009] In the inclination direction of multiple planning working face or stoping working face, bare hole horizontal hole is constructed in fracture zone of mining in the roof of stoping working face, and a three-opening horizontal main hole is arranged, and the drilling target point is located at the side 50m of air return roadway in the goaf to be formed, and the coal seam is exposed downward;

[0010] Second, completion pipe column structure

[0011] After the completion of three-opening horizontal main hole, extraction pipe column with bare hole packer is lowered in horizontal hole and sealed before the downward inclination of horizontal section of three-opening horizontal main hole, the packer is sealed by pressing, and unsealed by lifting, the extraction pipe column realizes the extraction of goaf gas, and the extraction pipe column and the annulus of bare hole wall extract mining area gas;

[0012] Third, borehole trajectory control

[0013] The inclination section of three-opening horizontal main hole is landed in the side 50m of air return roadway in the goaf to be formed with 3 ° / 100m downward inclination, the inclination change rate is controlled to make the drilling trajectory smooth, which is beneficial to drainage after the formation of mining fracture, and avoids water accumulation in the later production process, low-density micro-solid drilling fluid is used in construction, the solid content and specific gravity of drilling fluid are controlled, and mud pollution is reduced;

[0014] Fourth, gas drainage pump station arrangement

[0015] After the well completion, a temporary drainage pump station is newly built near the corresponding ground, at least two sets of water ring vacuum pumps are used, one set is used for extracting the gas in the annulus mining area, and the other set is used for extracting the gas in the goaf; the mixed amount of the extracted gas at the well mouth is controlled by adjusting the air inlet pipe valve, and the corresponding power supply and water supply system in the extraction pump station is matched;

[0016] Fifth step, treatment after working face advancing

[0017] When the goaf advances to the next working face, the extraction pipe column and the open hole packer are unsealed in advance, and the pipe column is pulled out, the build-up tool is lowered, and landed in the new goaf to be formed at 50m away from the return airway side at 3° / 100m, and the extraction pipe column with the open hole packer is lowered again in the hole;

[0018] Sixth step, repeating the third step to the fifth step to realize the rolling combined extraction of the mining area and the goaf gas.

[0019] Further, the number of the working faces or the stoping working faces in the first step is five.

[0020] Further, the structure of the three-opening horizontal main hole in the first step comprises a first opening, a second opening and a third opening, wherein the first opening is drilled below the stable bedrock by a drill bit, the first opening is provided with a casing for sealing and solidifying, the second opening is directionally drilled to a landing point by a drill bit, the second opening is provided with a casing for sealing and solidifying, and the third opening is drilled along the inclination direction of the stoping working face by a drill bit, and the tail end is landed at 50m away from the return airway side of the goaf to be formed at 3° / 100m, and the coal seam is exposed downward, and the goaf to be formed.

[0021] Further, the drill bit diameter of the first opening is Φ444.5mm, and the casing is J55-Φ377.7mm casing.

[0022] Further, the drill bit diameter of the second opening is Φ311.15mm, and the casing is Φ244.5mm*8.05mm casing.

[0023] Further, the drill bit diameter of the third opening is Φ215.9mm.

[0024] Further, the extraction pipe column in the horizontal hole is N80-Φ114mm.

[0025] The beneficial effects of the present application are as follows:

[0026] Compared with the original mining well gas extraction treatment scheme, the present method has the advantages of good effect, high safety factor and repeated use, and can achieve the working target of integration and high efficiency, and realizes the efficient extraction of the mining area and the goaf gas by using the ground drilling. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a drilling well structure diagram of the present application;

[0028] Figure 2 is a drilling well structure diagram of the present application;

[0029] 1 - wellhead; 2 - build-up section; 3 - horizontal section; 4 - drop section; 5 - first opening; 6 - second opening; 7 - third opening; 8 - open hole packer of extraction string. DETAILED DESCRIPTION

[0030] The present application is further described in conjunction with the accompanying drawings.

[0031] In the direction of inclination of multiple planned working faces or mining working faces, a bare hole horizontal hole is constructed in the roof of the mining working face in the mining fissure zone, the terminal of the horizontal hole lands in the 50m of the side close to the air return roadway in the goaf to be formed with a 3° / 100m downward inclination, a Φ114mm extraction string is lowered in the horizontal hole and a bare hole packer is seated before the downward inclination build-up point of the horizontal section, the Φ114mm extraction string realizes the extraction and treatment of the goaf gas, the extraction of the mining area gas is realized between the Φ114mm extraction string and the annulus of the bare hole wall. Considering the ground construction progress, the range and time of the influence of underground mining on the ground and other factors, when the goaf advances to the next working face, the bare hole packer of the Φ114mm extraction string is unseated in advance, the string is pulled out, build-up drilling tools are lowered, the new goaf to be formed is landed in the 50m of the side close to the air return roadway with a 3° / 100m downward inclination, a Φ114mm extraction string is lowered in the hole with a bare hole packer, the above steps are repeated, and the rolling combined extraction of the mining area and the goaf gas is realized.

[0032] One three-opening horizontal main hole is arranged, the first opening is drilled to below the stable bedrock, the lower layer casing is fixed and solidified, the second opening is directionally drilled to the landing point, the technical casing is fixed and solidified, the third opening is drilled along the direction of inclination of the mining working face, the terminal lands in the 50m of the side close to the air return roadway of the goaf to be formed with a 3° / 100m downward inclination, and the coal seam is exposed downward (the goaf to be formed).

[0033] After the completion of the main borehole, a Φ114mm extraction string is lowered in the horizontal hole with a bare hole packer seated before the downward inclination build-up point of the horizontal section, the packer is seated by pressing, and the unseating is realized by lifting. The string realizes the extraction and treatment of the goaf gas by the Φ114mm extraction string, and the extraction of the mining area gas is realized between the Φ114m extraction string and the annulus of the bare hole wall.

[0034] After the completion of the well, a temporary extraction and drainage pump station needs to be newly built near the corresponding ground, at least two sets of water ring vacuum pumps are used, one set is used for extracting the annulus mining area gas, and the other set is used for extracting the goaf gas; the mixed amount of the extracted and discharged gas at the wellhead is controlled by adjusting the air inlet pipe gas distribution valve. The corresponding supporting power supply, water supply and other systems are provided in the extraction pump station.

[0035] When the goaf advances to the next working face, the Φ114m extraction pipe column bare hole packer is unsealed in advance, and the pipe column is pulled out, the build-up tool is lowered, and landed in the new goaf to be formed at 50m from the return air lane side with 3° / 100m downward inclination, and the Φ114m extraction pipe column with bare hole packer is lowered again in the hole.

[0036] The above steps are repeated to realize the rolling combined extraction of the mining area and the goaf gas.

[0037] The specific implementation method is as follows:

[0038] 1) Layout position selection

[0039] In the inclination direction of multiple planned working faces or stoping working faces (one to five), a bare hole horizontal hole is constructed in the roof of the stoping working face fissure zone. Considering the ground construction progress and the range and time of the influence of underground mining on the ground, the extraction range is from the goaf to multiple parallel working faces in the mining area. A three-opening horizontal main hole is arranged, the drilling target point is located at 50m from the return air lane side of the goaf to be formed, and the coal seam is exposed downward.

[0040] 2) Main borehole drilling well structure

[0041] The drilling structure is described as follows, see Figure 1 .

[0042] A three-opening horizontal main hole is arranged, a Φ444.5mm drill bit is drilled to below the stable bedrock, a J55-Φ377.7mm casing is lowered for cementing, the cementing is waited for 24 hours, and the cementing quality is tested by pressure test according to the regulation, and the fourth system topsoil layer is isolated.

[0043] A Φ311.15mm drill bit is directionally drilled to the landing point, a N80 type Φ244.5mm×8.05mm casing is lowered for cementing, the cementing is waited for 48 hours, and the cementing quality is tested by pressure test according to the regulation.

[0044] A Φ215.9mm drill bit is drilled along the inclination direction of the stoping working face, and the end is landed at 50m from the return air lane side of the goaf to be formed with 3° / 100m downward inclination, and the coal seam (the goaf to be formed) is exposed downward.

[0045] 3) Completion pipe column structure

[0046] After the main borehole is completed, a N80-Φ114mm extraction pipe column with bare hole packer is lowered in the horizontal hole and seated in front of the downward inclination build-up point of the horizontal section, the packer is seated by pressing, and the unseating is realized by lifting. The casing column realizes the extraction and treatment of the goaf gas by the Φ114mm extraction pipe column, and the mining area gas is extracted between the Φ114m extraction pipe column and the annulus of the bare hole wall.

[0047] 4) Well trajectory control

[0048] Three opening drop-off section to 3 ° / 100 m downlink landing in the soon-to-be formed goaf return airway one side 50 m, to strictly control the inclination change rate to make the drilling trajectory smooth, make it after the formation of mining fissure drainage, avoid water accumulation in the production process. In the construction of low density micro solid phase drilling fluid, control the solid content and specific gravity of drilling fluid, reduce mud pollution.

[0049] 5) Gas drainage pump station layout

[0050] After completion, a new temporary drainage pump station needs to be built near the corresponding ground, using at least two sets of water ring vacuum pumps, one set for pumping annulus mining area gas, the other set for pumping goaf gas; by adjusting the air inlet pipe gas distribution valve to control the mixed amount of gas extracted from the drilling wellhead. The corresponding supporting power supply, water supply and other systems in the drainage pump station.

[0051] 6) Treatment after working face advancing

[0052] When the goaf advances to the next working face, the Φ114m drainage pipe column and the open hole packer are unsealed in advance, and the pipe column is pulled out, the build angle drilling tool is lowered, and the landing is landed in the new goaf to be formed near the return airway one side 50 m, and the Φ114m drainage pipe column with open hole packer is lowered again in the hole.

[0053] Repeat steps 2) - 5), realize the rolling combined drainage of mining area and goaf gas.

Claims

1. A method for combined gas extraction from goaf and mining-affected areas, characterized in that: Includes the following steps: The first step is to select the location of the well. In the dip direction of multiple planned working faces or longwall faces, open horizontal holes are drilled in the fracture zone of the roof of the longwall face to be mined, and a three-section horizontal main hole is arranged. The drilling target point is located 50m away from the return airway that will form the goaf, and the coal seam is exposed downwards. Step 2: Completion string structure After the three-section horizontal main borehole is completed, a drainage string with an open hole packer is lowered into the horizontal borehole and sealed before the downward inclination point of the horizontal section of the three-section horizontal main borehole. The packer is sealed by pressure and unsealed by lifting. The drainage string is used to extract and control the gas in the goaf. The drainage string extracts gas in the mining area between the drainage string and the annulus of the open hole wall. The third step is wellbore trajectory control. The downward slope section of the three-section horizontal main borehole lands 50m on the side of the return airway where the goaf will be formed with a downward slope of 3° / 100m. The borehole inclination change rate is controlled to make the borehole trajectory smooth, so that drainage is facilitated after the formation of mining fractures and water accumulation is avoided in the later production process. Low density micro solid phase drilling fluid is used in construction to control the solid phase content and specific gravity of the drilling fluid and reduce mud pollution. Step 4: Layout of the gas drainage pumping station After well completion, a temporary extraction pumping station is built near the corresponding ground surface, using at least two sets of water ring vacuum pumps, one set for extracting gas from the annular mining area and the other set for extracting gas from the goaf area; the amount of gas mixed at the wellhead is controlled by adjusting the gas distribution valve on the gas inlet pipeline, and the extraction pumping station is equipped with corresponding power supply and water supply systems. Step 5: Post-workface advancement processing When the goaf advances to the next working face, the extraction string and open hole packer are unsealed in advance, the string is pulled out, and the directional drilling tool is lowered. It is then lowered at a 3° / 100m downward tilt to land 50m on the side of the new goaf near the return airway. The extraction string with the open hole packer is then lowered back into the hole. Step 6: Repeat steps 3 to 5 to achieve combined rolling gas extraction from the mining area and the goaf.

2. The method for combined gas extraction from goaf and mining-affected areas according to claim 1, characterized in that: The number of working faces or longwall faces mentioned in the first step is five.

3. The method for combined gas extraction from goaf and mining-affected areas according to claim 1, characterized in that: The structure of the three-section horizontal main borehole mentioned in the first step includes section one, section two, and section three. Section one is drilled to below the stable bedrock by the drill bit. Section one is equipped with a casing for sealing and solidification. Section two is drilled to the landing point by the drill bit in a directional manner. Section two is also equipped with a casing for sealing and solidification. Section three is drilled along the dip direction of the mining face by the drill bit in a stable inclination. The end lands at a 3° / 100m downward dip at 50m on one side of the return airway from which the goaf will be formed, and exposes the coal seam downward, which will form the goaf.

4. The method for combined gas extraction from goaf and mining-affected areas according to claim 3, characterized in that: The diameter of the drill bit is Φ444.5mm, and the casing is J55-Φ377.7mm.

5. The method for combined gas extraction from goaf and mining-affected areas according to claim 3, characterized in that: The second drilling bit has a diameter of Φ311.15mm, and the casing has a diameter of Φ244.5mm × 8.05mm.

6. The method for combined gas extraction from goaf and mining-affected areas according to claim 3, characterized in that: The diameter of the three-section drill bit is Φ215.9mm.

7. The method for combined gas extraction from goaf and mining-affected areas according to claim 1, characterized in that: The extraction tubing in the horizontal borehole is N80-Φ114mm.

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