Gas extraction construction method for outburst coal seam

Abstract

The invention provides an outburst coal seam gas extraction construction method, and relates to the technical field of coal mine underground gas extraction. The outburst coal seam gas extraction construction method comprises the following steps that firstly, large-diameter drilling construction is conducted; 2, an extraction pipe and a hole sealing assembly are fed into the large-diameter drill hole; 3, the extraction pipe is fixed through expansion, and the large-diameter drill hole is drilled; 4, the blowout prevention four-way joint and matched equipment parts are connected; 5, small-diameter drilling construction is carried out; step 6, drilling and sealing; and step 7, supplementing and sealing. According to the outburst coal seam gas extraction construction method, secondary drilling (large-diameter drilling and small-diameter drilling) and secondary hole sealing (fixing of an extraction pipe and the large-diameter drilling and sealing connection of the extraction pipe and the large-diameter drilling) are adopted; and the hole spraying risk in the drilling construction process is reduced, and the sealing quality of the gas extraction drill hole is effectively improved.

Description

Technical Field

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

[0002] Gas disasters are the "number one killer" of coal mine safety production. Pre-drilling and gas extraction along the coal and gas outburst seams is the main engineering means to control gas and resource utilization at the working face. However, due to the high gas pressure and gas content of the outburst coal seams, when no anti-blowout measures are taken, a large amount of gas will be analyzed from the boreholes during the drilling construction, and it is very easy to have dynamic phenomena such as blowouts during the drilling construction. On the one hand, a large amount of gas and coal dust will flow into the tunnel, causing the gas in the tunnel to exceed the limit; on the other hand, it may cause casualties such as blowout injuries, drilling rig tipping injuries, and gas suffocation.

[0003] At present, the pre-extraction drilling construction of the protruding coal seam mainly uses a drill bit of the same specification and size to drill a hole at one time. After the drilling construction reaches the bottom of the hole, the drill rod is withdrawn, and then the consolidation type sealing material such as expansive cement is used to perform "two blockages and one injection" drilling sealing. The construction process of this process is simple, but there is a risk of blowout during the drilling process due to the lack of drilling blowout prevention or the inability of the blowout prevention device to be fixed stably. In addition, for the long drilling construction in soft coal seams, the construction time is long, and the drilling hole loses stability and deformation after the drill is withdrawn. It is difficult to send the extraction pipe and the sealer to the predetermined position in the hole. The sealing depth cannot meet the sealing requirements, resulting in a decrease in the quality of drilling sealing. Summary of the invention

[0004] The present invention provides a method for gas extraction construction in a protruding coal seam, which reduces the risk of blowholes during the drilling construction process and effectively improves the sealing quality of the gas extraction boreholes.

[0005] In order to achieve the above object, the technical solutions adopted by the present invention are as follows:

[0006] A method for extracting gas from a protruding coal seam, the method comprising the following steps:

[0007] Step 1: Install a drill bit with a diameter of a on the drilling rig, start the drilling rig and drill into the coal seam to form a large diameter borehole;

[0008] Step 2: The sealing assembly is arranged on the outer wall of the extraction pipe, and the sealing assembly is sent into the large diameter borehole along with the extraction pipe;

[0009] Step 3, at least part of the sealing assembly is grouted to fix the connection between the extraction pipe and the inner wall of the large diameter borehole;

[0010] Step 4: Install a drill bit with a diameter of b on the drilling rig, where b is smaller than the inner diameter of the extraction pipe, connect the front end of the blowout prevention cross to the outer end of the extraction pipe, connect the rear end of the blowout prevention cross to the drilling rig, connect the upper end of the blowout prevention cross to the extraction negative pressure pipeline, and connect the lower end of the blowout prevention cross to the water drainage and slag removal device;

[0011] Step 5: Start the drilling rig to continue drilling into the coal seam from the inner end face of the large-diameter borehole to form a small-diameter borehole. The negative pressure extraction pipeline provides negative pressure to transport the gas generated during the construction of the small-diameter borehole. The coal and rock cuttings and water generated during the construction of the small-diameter borehole are collected and discharged through the drainage and slag discharge device.

[0012] Step 6: After the small-diameter drilling construction is completed, remove the blowout prevention four-way valve, connect the extraction negative pressure pipeline to the outer end of the extraction pipe, and continue to transport the gas generated in the small-diameter borehole through the extraction negative pressure pipeline; at least partially perform grouting on the sealing component to seal the connection between the extraction pipe and the inner wall of the large-diameter borehole.

[0013] Furthermore, step 7 is also included:

[0014] The gas concentration in the negative pressure extraction pipeline is monitored. When the gas concentration is lower than the set value, the sealing component at least partially performs grouting to seal the connection between the extraction pipe and the inner wall of the large diameter borehole.

[0015] Furthermore, in step 6, after the construction of multiple adjacent small-diameter boreholes is completed, the sealing components corresponding to each borehole are at least partially grouted to seal the connection between the extraction pipe and the inner wall of the large-diameter borehole.

[0016] Furthermore, the sealing assembly includes a sealing inner bag, a sealing outer bag, a bag grouting pipe and a sealing section grouting pipe;

[0017] In step 2, the inner sealing bag is located at the inner end of the extraction tube and is arranged around the extraction tube, the outer sealing bag is located at the outer end of the extraction tube and is arranged around the extraction tube, and one end of the bag grouting pipe is connected to the inner sealing bag and the outer sealing bag; the space between the inner sealing bag, the outer sealing bag, the extraction tube and the large-diameter borehole is defined as the borehole sealing section, and one end of the sealing section grouting pipe is connected to the borehole sealing section;

[0018] In step 3, a set amount of expansion material slurry is injected into the inner and outer sealing bags through the other end of the bag grouting pipe, and the inner and outer sealing bags expand to abut against the inner wall of the large-diameter borehole;

[0019] In step 6, a set amount of drilling sealing material slurry with a set pressure is injected into the drilling sealing section through the other end of the sealing section grouting pipe.

[0020] Furthermore, the expansion material is expansion cement or polyurethane.

[0021] Furthermore, the drilling hole sealing material is a mucus or gel drilling hole sealing material.

[0022] Further, the pressure of the expansion material injected into the sealing inner bag and the sealing outer bag is 1.5-2.5 MPa;

[0023] The pressure of the drilling sealing material injected into the drilling sealing section is 0.5-1.5MPa.

[0024] Furthermore, the distance between the inner sealing bag and the outer sealing bag is 12-20m.

[0025] Furthermore, the blowout prevention cross is connected to the outer end of the extraction pipe, the drilling rig, the extraction negative pressure pipeline and the water and slag discharge device via a flange.

[0026] Furthermore, the depth of the large diameter borehole is 15-30 m, and the depth of the small diameter borehole is 100-200 m.

[0027] The beneficial technical effects of the present invention are:

[0028] The method for extracting gas from a protruding coal seam of the present invention adopts secondary drilling (large diameter drilling + small diameter drilling) + secondary sealing (fixing the extraction pipe and the large diameter drilling + sealing and connecting the extraction pipe and the large diameter drilling); the expansion material in the sealing bag expands and abuts against the inner wall of the large diameter drilling hole, so that a strong fastening force is maintained between the extraction pipe and the drilling hole, and the extraction pipe and the sealing bag can achieve stable support for the large diameter drilling hole. During the construction of the small diameter drilling hole, the extraction pipe and the rear equipment components are stably fixed to the drilling hole, and the instability and deformation of the large diameter drilling hole are avoided. At the same time, the gas generated during the construction of the small diameter drilling hole is transported out by the extraction pipe and the extraction negative pressure pipeline; even if a drilling hole blowout occurs, the extraction pipe and the rear equipment components can be fixed by relying on the fastening force between the extraction pipe and the drilling hole. The equipment parts and the borehole remain stable and fixed, reducing the risk of blowout during drilling construction, avoiding the outflow of large amounts of gas and coal dust into the tunnel, resulting in excessive gas in the tunnel, and avoiding casualties such as blowout injuries, drilling rig tipping injuries, and gas suffocation. After a long period of construction of a small-diameter borehole is completed, a strong fastening force is maintained between the extraction pipe and the borehole, and there is basically no relative displacement between the two, ensuring close contact at the connection of the extraction pipe. The extraction pipe and the sealing bag can achieve continuous and stable support for the large-diameter borehole. After the drill is withdrawn, the large-diameter borehole is almost free of instability and deformation, reducing the degree of expansion of large cracks near the large-diameter borehole during subsequent extraction, and then injecting drilling sealing material into the drilling sealing section to achieve sealing between the extraction pipe and the borehole, effectively improving the sealing quality of the borehole. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a process for extracting gas from a prominent coal seam according to an embodiment of the present invention;

[0030] Figure 2 This is a construction layout diagram of coal seam gas extraction in an embodiment of the present invention;

[0031] Figure 3 This is a local structural layout diagram of the coal seam gas extraction construction in an embodiment of the present invention;

[0032] Figure 4 This is a schematic structural diagram of a blowout prevention cross according to an embodiment of the present invention;

[0033] In the figure,

[0034] 11. Tunnel, 12. Coal seam, 2. Drilling rig, 31. Large diameter borehole, 32. Small diameter borehole, 4. Extraction pipe, 51. Inner bag for sealing the hole, 52. Outer bag for sealing the hole, 53. Grouting pipe of bag, 54. Grouting pipe of sealing section, 55. Drilling hole sealing section, 6. Blowout prevention cross, 61. Flange, 7. Extraction negative pressure pipeline, 8. Drainage and slag removal device. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Certain embodiments of the present invention will be described more comprehensively with reference to the accompanying drawings, in which some but not all embodiments will be shown. In fact, the various embodiments of the present invention can be implemented in many different forms and should not be construed as being limited to the embodiments described herein; rather, these embodiments are provided so that the present invention meets applicable legal requirements.

[0036] In the description of the present invention, it should be noted that the terms "inside", "outside", "upper", "lower", "front", "back" and the like indicate directions or positional relationships based on directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0037] This embodiment is combined with the actual situation of a coal mine. Figures 1 to 4 As shown, a method for gas extraction from a protruding coal seam is provided, comprising the following steps.

[0038] Step 1, arrange the drilling rig 2 in the tunnel 11, the tunnel 11 is a track chute or return air chute matching the working face, install a large-diameter drill bit with a diameter of a on the drilling rig 2, start the drilling rig 2 to drill into the coal seam 12 according to the designed drilling angle to form a large-diameter borehole 31, the hole depth of the large-diameter borehole 31 is 15-30m, and after the construction of the large-diameter borehole 31 is completed, withdraw the drill rod.

[0039] Step 2: The sealing assembly is arranged on the outer wall of the extraction pipe 4 , and the sealing assembly is sent into the large-diameter borehole 31 along with the extraction pipe 4 .

[0040] The hole sealing assembly includes an inner hole sealing bag 51, an outer hole sealing bag 52, a bag grouting pipe 53 and a sealing section grouting pipe 54. The inner hole sealing bag 51 is located at the inner end of the extraction pipe 4 and is arranged around the extraction pipe 4, the outer hole sealing bag 52 is located at the outer end of the extraction pipe 4 and is arranged around the extraction pipe 4, the spacing between the inner hole sealing bag 51 and the outer hole sealing bag 52 is 12-20m, one end of the bag grouting pipe 53 is connected to the inner hole sealing bag 51 and the outer hole sealing bag 52; the space between the inner hole sealing bag 51, the outer hole sealing bag 52, the extraction pipe 4 and the large diameter borehole 31 is defined as the borehole sealing section 55, and one end of the sealing section grouting pipe 54 is connected to the borehole sealing section 55.

[0041] Step 3: The sealing assembly at least partially performs grouting to fix the connection between the extraction pipe 4 and the inner wall of the large-diameter borehole 31 .

[0042] Specifically, a set amount of expansion material slurry with a pressure of 1.5-2.5MPa is injected into the inner sealing bag 51 and the outer sealing bag 52 through the other end of the bag grouting pipe 53, and the inner sealing bag 51 and the outer sealing bag 52 expand to abut against the inner wall of the large diameter borehole 31. The expansion material is expansion cement or polyurethane. The expansion material in the inner sealing bag 51 and the outer sealing bag 52 expands and abuts against the inner wall of the large diameter borehole 31, so that a strong fastening force is maintained between the extraction tube 4 and the large diameter borehole 31, and the extraction tube 4 and the sealing bag provide stable support for the large diameter borehole 31.

[0043] Step 4: Install a small-diameter drill bit with a diameter of b on the drilling rig 2, where b is smaller than the inner diameter of the extraction pipe 4. The drill rod and the small-diameter drill bit pass through the extraction pipe 4, connect the front end of the blowout prevention spool 6 to the outer end of the extraction pipe 4, connect the rear end of the blowout prevention spool 6 to the drilling rig 2, connect the upper end of the blowout prevention spool 6 to the extraction negative pressure pipeline 7 through an extraction hose, and connect the lower end of the blowout prevention spool 6 to the drainage and slag discharge device 8 through a drainage and slag discharge hose. The front end, rear end, upper end, and lower end of the blowout prevention spool 6 are interconnected, and the blowout prevention spool 6 is connected to the outer end of the extraction pipe 4, the drilling rig 2, the extraction negative pressure pipeline 7, and the drainage and slag discharge device 8 through a flange 61.

[0044] Step 5, start the drilling machine 2 to continue drilling into the coal seam 12 from the inner end face of the large diameter borehole 31 according to the designed drilling angle to form a small diameter borehole 32, and the hole depth of the small diameter borehole 32 is 100-200m. The extraction negative pressure pipeline 7 provides extraction negative pressure to transport the gas generated during the construction of the small diameter borehole 32, and the coal and rock cuttings and water generated during the construction of the small diameter borehole 32 are collected and discharged through the drainage and slag discharge device 8.

[0045] Step 6: After the construction of the small-diameter borehole 32 is completed, remove the blowout prevention four-way valve 6, connect the extraction negative pressure pipeline 7 to the outer end of the extraction pipe 4, and continue to transport the gas generated in the small-diameter borehole 32 through the extraction negative pressure pipeline 7; at least partially perform grouting on the sealing component to seal the connection between the extraction pipe 4 and the inner wall of the large-diameter borehole 31.

[0046] Specifically, a set amount of drilling sealing material slurry with a pressure of 0.5-1.5 MPa is injected into the drilling sealing section 55 through the other end of the sealing section grouting pipe 54, and the drilling sealing material penetrates and fills the drilling sealing section 55 and the drilling sealing section cracks 551 around the drilling sealing section 55 to achieve the sealing of the borehole. The drilling sealing material is a mucus or gel drilling sealing material, which has better permeability and adhesion, so as to further improve the drilling sealing quality.

[0047] After the construction of multiple adjacent small-diameter boreholes 32 is completed, the sealing assembly corresponding to each borehole is at least partially grouted to seal the connection between the extraction pipe 4 and the inner wall of the large-diameter borehole 31. Specifically, a set amount of borehole sealing material slurry with a pressure of 0.5-1.5MPa is injected into the borehole sealing section 55 through the other end of the sealing section grouting pipe 54. In this way, disturbances in the construction of small-diameter boreholes 32 adjacent to the target small-diameter borehole 32 are avoided. At this time, the borehole sealing material slurry in the large-diameter borehole 31 corresponding to the target small-diameter borehole 32 has not completely penetrated and filled into the borehole sealing section 55 and the borehole sealing section fissure 551, reducing the quality of the sealing connection between the target small-diameter borehole 32 and the extraction pipe 4. In addition, after the construction of multiple adjacent small-diameter boreholes 32 is completed, the sealing assembly corresponding to each borehole is at least partially grouted, and multiple boreholes are sealed at one time to improve the grouting sealing efficiency.

[0048] It should be noted that after the construction of the large-diameter borehole 31 is completed, the borehole sealing material slurry is not injected into the borehole sealing section 55 first, but the borehole sealing material slurry is injected into the borehole sealing section 55 after the construction of the small-diameter borehole 32 is completed. The reason is that during the construction of the small-diameter borehole 32, vibration causes cracks in the surrounding rock, and the drilling pressure relief of the small-diameter borehole 32 causes cracks in the surrounding rock. In addition, the construction time of the small-diameter borehole 32 is relatively long, and the surrounding rock rheology over time causes the borehole diameter to shrink and produce cracks. At this time, the borehole sealing material slurry in the large-diameter borehole 31 has not yet completely penetrated and filled the borehole sealing section 55 and the borehole sealing section crack 551, which will reduce the sealing connection quality between the large-diameter borehole 31 and the extraction pipe 4.

[0049] Step 7, monitor the gas concentration in the negative pressure extraction pipeline 7. When the gas concentration is lower than the set value, it indicates that the quality of the borehole seal has been reduced. The sealing assembly at least partially performs grouting to supplement the seal connection between the extraction pipe 4 and the inner wall of the large diameter borehole 31, and infiltrate and fill the newly formed borehole sealing section crack 551. Specifically, a set amount of borehole sealing material slurry with a pressure of 0.5-1.5MPa is injected into the borehole sealing section 55 through the other end of the sealing section grouting pipe 54.

[0050] So far, the present embodiment has been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the construction method for gas extraction from a protruding coal seam of the present invention. The method for extracting gas from a protruding coal seam of the present invention adopts secondary drilling (large diameter borehole 31 + small diameter borehole 32) + secondary sealing (fixing the extraction pipe 4 and the large diameter borehole 31 + sealing and connecting the extraction pipe 4 and the large diameter borehole 31); the expansion material in the sealing bag expands and abuts against the inner wall of the large diameter borehole 31, so that a strong fastening force is maintained between the extraction pipe 4 and the borehole, and the extraction pipe 4 and the sealing bag achieve stable support for the large diameter borehole 31. During the construction of the small diameter borehole 32, the extraction pipe 4 and the rear equipment components are stably fixed to the borehole, and the large diameter borehole 31 is prevented from becoming unstable and deforming. At the same time, the extraction pipe 4 and the extraction negative pressure pipeline 7 transport the gas generated during the construction of the small diameter borehole 32. Even if a borehole blowout occurs, the fastening force between the extraction pipe 4 and the borehole can be relied on to The extraction pipe 4 and the rear equipment components remain stable and fixed to the borehole, reducing the risk of blowout during drilling construction, avoiding a large amount of gas and coal dust gushing into the tunnel, causing excessive gas in the tunnel, and avoiding casualties such as blowout injuries, drilling rig tipping injuries, and gas suffocation. After the small-diameter borehole 32 is completed after a long period of construction, the extraction pipe 4 and the borehole maintain a strong fastening force, and there is basically no relative displacement between the two, ensuring close contact at the connection of the extraction pipe, and the extraction pipe 4 and the sealing bag achieve continuous and stable support for the large-diameter borehole 31. After the drill is withdrawn, the large-diameter borehole 31 hardly undergoes instability and deformation, reducing the degree of expansion of large cracks near the large-diameter borehole 31 during subsequent extraction, and then injecting drilling sealing material into the drilling sealing section 55 to achieve sealing between the extraction pipe 4 and the borehole, effectively improving the sealing quality of the borehole.

[0051] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for extracting gas from a protruding coal seam, characterized in that: The method comprises the following steps: Step 1: Install a drill bit with a diameter of a on the drilling rig, start the drilling rig and drill into the coal seam to form a large diameter borehole; Step 2: The sealing assembly is arranged on the outer wall of the extraction pipe, and the sealing assembly is sent into the large diameter borehole along with the extraction pipe; Step 3, at least part of the sealing assembly is grouted to fix the extraction pipe and the inner wall of the large diameter borehole; Step 4: Install a drill bit with a diameter of b on the drilling rig, where b is smaller than the inner diameter of the extraction pipe, connect the front end of the blowout prevention cross to the outer end of the extraction pipe, connect the rear end of the blowout prevention cross to the drilling rig, connect the upper end of the blowout prevention cross to the extraction negative pressure pipeline, and connect the lower end of the blowout prevention cross to the water drainage and slag removal device; Step 5: Start the drilling rig to continue drilling into the coal seam from the inner end face of the large-diameter borehole to form a small-diameter borehole. The negative pressure extraction pipeline provides negative pressure to transport the gas generated during the construction of the small-diameter borehole. The coal and rock cuttings and water generated during the construction of the small-diameter borehole are collected and discharged through the drainage and slag discharge device. Step 6: After the small-diameter drilling construction is completed, remove the blowout prevention four-way valve, connect the extraction negative pressure pipeline to the outer end of the extraction pipe, and continue to transport the gas generated in the small-diameter borehole through the extraction negative pressure pipeline; at least partially perform grouting on the sealing component to seal the connection between the extraction pipe and the inner wall of the large-diameter borehole.

2. A method for extracting gas from a protruding coal seam according to claim 1, characterized in that: Also includes step 7: The gas concentration in the negative pressure extraction pipeline is monitored. When the gas concentration is lower than the set value, the sealing component at least partially performs grouting to seal the connection between the extraction pipe and the inner wall of the large diameter borehole.

3. A method for extracting gas from a protruding coal seam according to claim 1, characterized in that: In step 6, after the construction of multiple adjacent small-diameter boreholes is completed, the sealing components corresponding to each borehole are at least partially grouted to seal the connection between the extraction pipe and the inner wall of the large-diameter borehole.

4. A method for extracting gas from a protruding coal seam according to claim 1, characterized in that: The sealing assembly comprises an inner sealing bag, an outer sealing bag, a bag grouting pipe and a sealing section grouting pipe; In step 2, the inner sealing bag is located at the inner end of the extraction tube and is arranged around the extraction tube, the outer sealing bag is located at the outer end of the extraction tube and is arranged around the extraction tube, and one end of the bag grouting pipe is connected to the inner sealing bag and the outer sealing bag; the space between the inner sealing bag, the outer sealing bag, the extraction tube and the large-diameter borehole is defined as the borehole sealing section, and one end of the sealing section grouting pipe is connected to the borehole sealing section; In step 3, a set amount of expansion material slurry is injected into the inner and outer sealing bags through the other end of the bag grouting pipe, and the inner and outer sealing bags expand to abut against the inner wall of the large-diameter borehole; In step 6, a set pressure and a set amount of drilling sealing material slurry are injected into the drilling sealing section through the other end of the sealing section grouting pipe.

5. A method for extracting gas from a protruding coal seam according to claim 4, characterized in that: The expansion material is expansion cement or polyurethane.

6. A method for extracting gas from a protruding coal seam according to claim 4, characterized in that: The drilling hole sealing material is a mucus or gel drilling hole sealing material.

7. A method for extracting gas from a protruding coal seam according to claim 4, characterized in that: The pressure of injecting the expansion material into the sealing inner bag and the sealing outer bag is 1.5-2.5MPa; The pressure of the drilling sealing material injected into the drilling sealing section is 0.5-1.5MPa.

8. A method for extracting gas from a protruding coal seam according to claim 4, characterized in that: The distance between the inner sealing bag and the outer sealing bag is 12-20m.

9. A method for extracting gas from a protruding coal seam according to claim 1, characterized in that: The blowout prevention cross is connected to the outer end of the extraction pipe, the drilling rig, the extraction negative pressure pipeline and the water and slag discharge device via a flange.

10. A method for extracting gas from a protruding coal seam according to claim 1, characterized in that: The hole depth of large diameter drilling is 15-30m, and the hole depth of small diameter drilling is 100-200m.

Images