Soft low-permeability coal seam hole protecting and permeability increasing integrated pipeline and using method

Abstract

According to the soft low-permeability coal seam hole protecting and permeability increasing integrated pipeline and the using method, a plurality of drill hole protecting and permeability increasing structures are all located in the deep position of a drill hole, hole sealing treatment is conducted on an extraction pipeline, the passive hole protecting, collapse preventing and supporting effects can be achieved on a gas extraction drill hole, and at the moment, gas extraction work is directly conducted; after the flow of the extracted gas is continuously reduced, the drilling hole is sealed firstly, the interior of the drilling hole is pressurized through free desorption of the gas, then gas is injected into all the annular gas bags through the gas injection pipe, all the annular gas bags are expanded in sequence to extrude the positions with collapsed holes so that the positions can be pressed and expanded, and active hole protection work is achieved; and meanwhile, the annular air bag expands to compress the space in the drill hole, so that the air pressure in the drill hole is increased, then the annular air bag retracts when gas is exhausted, and the cycle is repeated, so that variable-frequency pneumatic shock waves can be formed in the gas extraction drill hole to crack a coal body, and the coal seam gas is displaced to be quickly desorbed into the drill hole after fracturing, so that efficient gas extraction is realized.

Description

Technical Field

[0001] The invention relates to a soft and low-permeability coal seam hole protection and permeability enhancement integrated pipeline and a use method thereof, belonging to the technical field of coal seam gas extraction. Background Art

[0002] At present, some of the mined mines are high-gas mines, and gas control is the prerequisite for ensuring the safe and efficient production of this type of mines. However, there are still soft coal seams in this type of mines, that is, the main coal seams in many mining areas are soft, low-permeability, and high-gas coal seams, which leads to the danger of coal and gas outbursts in these mines. Pre-extraction of coal seam gas by construction drilling is an effective means of gas control, and it is also a measure commonly adopted by the coal mining industry. However, in the process of drilling and extracting gas from soft coal seams, due to its soft characteristics, it is very easy to collapse the hole, thereby blocking the channel for gas outflow and flow. At the same time, the low permeability of the coal seam affects the gas desorption rate. The superposition of multiple factors seriously affects the gas extraction effect. At present, in order to effectively control gas, this type of mine adopts a method of investing more manpower, capital and time to construct a large number of extraction boreholes. In this way, even if some boreholes collapse and are blocked, the remaining boreholes can continue to extract gas. Although this method can temporarily solve the problem, it will consume a lot of manpower, capital and time, and its final output only partially improves the gas extraction effect, resulting in a serious mismatch between input and output.

[0003] Therefore, how to provide a new device and method that can improve the gas extraction effect of each single extraction borehole by protecting and increasing the permeability of each extraction borehole under the premise of constructing fewer extraction boreholes, and ultimately achieve safe and efficient gas extraction at a lower cost, is the research direction required by the present invention. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides an integrated pipeline for hole protection and permeability enhancement in soft and low-permeability coal seams and a method for use. Under the premise of constructing fewer extraction boreholes, the gas extraction effect of each extraction borehole can be improved by protecting the boreholes and increasing the permeability of each extraction borehole, thereby ultimately achieving safe and efficient gas extraction at a lower cost.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: an integrated hole protection and permeability enhancement pipeline for soft and low-permeability coal seams, including multiple hole protection and permeability enhancement structures, extraction pipelines and gas injection pipes; the multiple hole protection and permeability enhancement structures are all located in the gas extraction borehole.

[0006] The hole protection and permeability enhancement structure includes a flower tube and an annular air bag, the annular air bag is sleeved on the outer wall of the flower tube, and the inner wall of the annular air bag is pressed and contacted with the outer wall of the flower tube; multiple flower tubes of the hole protection and permeability enhancement structure are coaxially connected head to tail, and two adjacent annular air bags are connected through a hollow tube, and the flower tube at the head end is placed at the deepest part of the gas extraction borehole.

[0007] One end of the extraction pipeline extends into the gas extraction borehole and is connected to the flower pipe at the tail end for gas extraction.

[0008] One end of the gas injection pipe extends into the gas extraction borehole and is connected to the annular airbag at the tail end; when gas is injected into the annular airbag and then released through the gas injection pipe, each annular airbag expands and retracts in turn, and by compressing and restoring the volume in the gas extraction borehole, a variable frequency pneumatic shock wave is generated in the gas extraction borehole to increase the permeability of the coal seam.

[0009] Furthermore, the annular airbag completely wraps the outer wall of the flower tube, and a plurality of through holes are provided on the annular airbag (the through holes are not connected to the inside of the annular airbag), and the positions of the through holes correspond to the sieve holes on the flower tube, and the flower tube is connected to the inside of the gas extraction borehole through the sieve holes. The completely wrapped method ensures the effect of the annular airbag expansion, and the arrangement of the through holes enables the gas in the borehole to enter the flower tube through the through holes and the sieve holes on the flower tube when extracting gas, and be extracted out, thereby ensuring the gas extraction efficiency.

[0010] Furthermore, two adjacent flower tubes and one end of the flower tube and the extraction pipeline are connected by threads. This connection method is convenient for assembly and sealing performance.

[0011] Furthermore, the axes of the gas injection pipe and each hollow pipe are parallel to the axis of the flower pipe. This method is convenient for layout and installation.

[0012] Furthermore, the extraction pipeline is composed of a plurality of extraction pipes connected coaxially end to end, which makes it easier to determine the length of the extraction pipeline.

[0013] Furthermore, the extraction tube and the flower tube have the same length, both in the range of 2.0 to 4.0 m; the ventilation holes and the sieve holes have the same diameter, both in the range of 3 to 6 mm.

[0014] Furthermore, the maximum air pressure that the annular airbag can withstand is not less than 2 MPa, thus ensuring the required performance of the annular airbag expansion.

[0015] The working method of the above-mentioned soft low-permeability coal seam hole protection and permeability enhancement integrated pipeline has the following specific steps:

[0016] Step 1: Determine the initial data: construct a gas extraction borehole at the required location in the soft and low-permeability coal seam, obtain the depth of the borehole and the required sealing depth, and then determine the number of flower pipes and extraction pipes; the sealing depth determines the number of extraction pipes.

[0017] Step 2: Install the pipeline: place the hole protection and permeability enhancement structure at the head end into the gas extraction borehole, and connect the flower tubes and annular air bags of each subsequent hole protection and permeability enhancement structure in sequence and send them into the gas extraction borehole until the number of flower tubes reaches the number determined in step one, then connect one end of the extraction pipe with the flower tube at the tail end, and connect each subsequent extraction pipe in sequence and push the entire pipeline to continue to go deeper into the gas extraction borehole until the number of extraction pipes reaches the number determined in step one; extend one end of the gas injection pipe into the gas extraction borehole and connect it with the annular air bag at the tail end. Initially, each annular air bag is in an unexpanded state, and the valve of the gas injection pipe is in a closed state.

[0018] Step 3: Borehole sealing and gas extraction: Seal the holes at the location of each extraction pipe to form a sealing section, and the sealing section has the same total length as each extraction pipe; finally, connect the extraction pipe at the tail end to the underground gas extraction branch pipe to extract gas from the gas extraction borehole.

[0019] Step 4: Gas desorption and pressurization: When the pure gas extraction flow rate is less than 0.001m 3 / min, close the control valve of the underground gas extraction branch pipe in step 3, and seal the gas extraction borehole for 24 to 36 hours to allow the gas in the surrounding coal body to be freely desorbed into the borehole, thereby increasing its internal gas pressure.

[0020] Step 5: Borehole protection and permeability enhancement treatment: Connect the other end of the gas injection pipe to the downhole compressed air system, and open the valve of the gas injection pipe, first inject gas into each annular air bag, and each annular air bag expands in turn to squeeze the position where the collapsed hole exists to expand the hole under pressure, thereby realizing an active hole protection work; at the same time, the expansion of the annular air bag will compress the space inside the borehole, thereby increasing the air pressure in the borehole, and performing a high-pressure impact on the coal body around the borehole. After completion, disconnect the downhole compressed air system to discharge the gas inside the annular air bag from the gas injection pipe. At this time, the annular air bag retracts, and the internal space of the borehole recovers and increases, reducing the air pressure inside the borehole; then connect it to the downhole compressed air system again, and carry out the next annular air bag expansion and borehole internal pressurization impact process. Repeat this for a period of time to form a variable frequency pneumatic shock wave in the borehole to cause fracturing and permeability enhancement of the coal body around the borehole.

[0021] Step 6: Continuous gas extraction: Close the valve of the gas injection pipe, open the control valve of the underground gas extraction branch pipe to continue gas extraction from the gas extraction borehole, and repeat steps 4 and 5 multiple times until the gas extraction of the coal seam where the gas extraction borehole is located meets the standard.

[0022] Furthermore, the diameter of the flower tube is 0.4 to 0.6 times the diameter of the gas extraction borehole, and the diameter of the annular airbag after inflation is 0.85 to 0.95 times the diameter of the borehole.

[0023] Furthermore, the duration of step 5 is 2 to 4 days.

[0024] Compared with the prior art, the extraction pipeline of the present invention is used as the sealing section of the gas extraction borehole for sealing treatment. Multiple borehole protection and permeability enhancement structures are all located deep in the borehole inside the sealing section. Since the borehole protection and permeability enhancement structure is composed of a flower tube and an annular air bag, after the borehole protection and permeability enhancement structure is placed in the gas extraction borehole, the flower tube is a rigid material and can play a passive hole protection and anti-collapse support effect on the gas extraction borehole; at this time, the gas extraction work is directly realized through the extraction pipe; when the gas flow rate of the extraction continues to decrease, the borehole is first sealed to increase the pressure in the borehole by utilizing the free desorption of gas, and then the gas injection pipe is used to inject gas into each The annular airbags are injected with gas, so that each annular airbag expands in turn to squeeze the position where the collapsed hole exists, so that it is compressed and expanded, and active hole protection is realized; and the expansion of the annular airbags will compress the space inside the borehole, thereby increasing the air pressure in the borehole, and performing a high-pressure impact on the coal body around the borehole, and then the gas inside the annular airbag is discharged, and then the next gas injection expansion and high-pressure impact process is carried out, and this cycle is repeated, which can not only realize active hole protection, but also form a variable frequency pneumatic shock wave in the borehole to fracture the coal body, and after fracture, the coal seam gas is quickly desorbed into the borehole, thereby realizing efficient gas extraction. Through the above, it can be concluded that the present invention realizes the integration of hole protection and coal seam permeability enhancement, and its operation is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the first section of the pipeline according to an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of an intermediate pipeline in an embodiment of the present invention;

[0028] Figure 4 Schematic diagram of the extraction pipeline in an embodiment of the present invention.

[0029] In the figure: 1. first section of pipeline; 2. middle pipeline; 3. gas injection pipe; 4. extraction pipeline; 5. internal thread; 6. external thread; 7. extraction pipe; 1-1. flower tube; 1-2. annular air bag; 1-3. hollow tube; 1-4. sieve hole. DETAILED DESCRIPTION

[0030] The present invention will be further described below.

[0031] like Figure 1 As shown, a soft low-permeability coal seam hole protection and permeability enhancement integrated pipeline includes multiple hole protection and permeability enhancement structures, a gas extraction pipeline 4 and a gas injection pipe 3; the multiple hole protection and permeability enhancement structures are all located in the gas extraction borehole.

[0032] The hole protection and permeability enhancement structure includes a flower tube 1-1 and an annular airbag 1-2, the flower tube 1-1 is made of rigid material, and the annular airbag 1-2 is made of elastic material; the annular airbag 1-2 is sleeved on the outer wall of the flower tube 1-1, and the inner wall of the annular airbag 1-2 is pressed and contacted with the outer wall of the flower tube 1-1; multiple flower tubes 1-1 of the hole protection and permeability enhancement structure are coaxially connected head to tail, and two adjacent annular airbags 1-2 are connected through a hollow tube 1-3, and the flower tube 1-1 at the head end is placed at the deepest part of the gas extraction borehole; the annular airbag 1-2 completely wraps the outer wall of the flower tube 1-1, and a plurality of through holes are opened on the annular airbag 1-2 (the through holes are not connected to the inside of the annular airbag 1-2), and the positions of each through hole correspond to the sieve hole 1-4 on the flower tube 1-1, and the flower tube 1-1 is connected to the inside of the gas extraction borehole through each sieve hole 1-4. The completely wrapped method ensures the expansion effect of the annular airbag 1-2, and the arrangement of the through holes enables the gas in the borehole to enter the flower tube 1-1 through the through holes and the sieve holes 1-4 on the flower tube 1-1 and be extracted when extracting gas, thereby ensuring the gas extraction efficiency.

[0033] One end of the extraction pipeline 4 extends into the gas extraction borehole and is connected to the flower pipe 1-1 at the tail end for gas extraction; the extraction pipeline 4 is composed of a plurality of extraction pipes 7 connected coaxially end to end. This makes it easy to determine the length of the extraction pipeline 4.

[0034] One end of the gas injection pipe 3 extends into the gas extraction borehole and is connected to the annular airbag 1-2 at the tail end; when gas is injected and released into the annular airbag 1-2 through the gas injection pipe 3, each annular airbag 1-2 expands and retracts in turn, and by compressing and restoring the volume in the gas extraction borehole, a variable frequency pneumatic shock wave is generated in the gas extraction borehole to increase the permeability of the coal seam.

[0035] As an improvement of the present invention, two adjacent flower tubes 1-1 and one end of the flower tube 1-1 and the extraction pipeline 4 are connected by threads (i.e., the two pipeline ports are respectively provided with external threads and internal threads, and the two are connected in cooperation with each other). This connection method is convenient for assembly and sealing performance. The axes of the gas injection pipe 3 and each hollow tube 1-3 are parallel to the axis of the flower tube 1-1. This method is convenient for layout and installation.

[0036] As another improvement of the present invention, Figure 3 and 4 As shown, the extraction tube 7 and the flower tube 1-1 have the same length, both in the range of 2.0 to 4.0 m; the diameters of the vent holes and the sieve holes 1-4 are the same, both in the range of 3 to 6 mm. The maximum air pressure that the annular airbag 1-2 can withstand is not less than 2 MPa. This ensures the performance required for the expansion of the annular airbag 1-2.

[0037] The working method of the above-mentioned soft low-permeability coal seam hole protection and permeability enhancement integrated pipeline has the following specific steps:

[0038] Step 1: Determine the initial data: construct a gas extraction borehole at the required location of the soft and low-permeability coal seam, obtain the depth of the borehole and the required sealing depth, and then determine the number of flower pipes 1-1 and extraction pipes 7; the sealing depth determines the number of extraction pipes 7.

[0039] Step 2: Install the pipeline: Place the hole protection and anti-permeability structure at the head end as the first section of the pipeline 1 into the gas extraction borehole. Figure 2 As shown, each subsequent hole protection and anti-reflection structure is used as an intermediate pipeline 2 as shown in Figure 3 As shown, the flower tubes 1-1 and annular air bags 1-2 of each intermediate pipeline 2 are connected in sequence and sent into the gas extraction borehole until the number of flower tubes 1-1 reaches the number determined in step one, then one end of the extraction tube 7 is connected with the flower tube 1-1 at the tail end, and each subsequent extraction tube 7 is connected in sequence and the pipeline as a whole is pushed to continue to go deeper into the gas extraction borehole until the number of extraction tubes 7 reaches the number determined in step one; one end of the gas injection pipe 3 is extended into the gas extraction borehole and connected with the annular air bags 1-2 at the tail end, initially each annular air bags 1-2 are in an unexpanded state, and the valve of the gas injection pipe 3 is in a closed state; after the pipeline is installed, the hole protection and permeability enhancement structure can play a passive support and hole protection effect in the borehole; the diameter of the flower tube 1-1 is 0.4 to 0.6 times the diameter of the gas extraction borehole, and the diameter of the annular air bag 1-2 after inflation is 0.85 to 0.95 times the diameter of the gas extraction borehole.

[0040] Step 3: Borehole sealing and gas extraction: Seal the holes at the positions of the extraction pipes 7 to form sealing sections, and the sealing sections have the same total length as the extraction pipes 7; finally, connect the extraction pipe 7 at the tail end to the underground gas extraction branch pipe to extract gas from the gas extraction boreholes.

[0041] Step 4: Gas desorption and pressurization: When the pure gas extraction flow rate is less than 0.001m 3 / min, close the control valve of the underground gas extraction branch pipe in step 3, and seal the gas extraction borehole for 24 to 36 hours to allow the gas in the surrounding coal body to be freely desorbed into the borehole, thereby increasing its internal gas pressure.

[0042] Step 5: hole protection and permeability enhancement treatment: connect the other end of the gas injection pipe 3 to the underground compressed air system, open the valve of the gas injection pipe 3, first inject gas into each annular airbag 1-2, and each annular airbag 1-2 expands in turn to squeeze the position where the collapsed hole exists to expand the hole under pressure (that is, the soft collapsed coal mud can be pushed back to the wall of the borehole by expansion and squeezing, so as to extend the extraction cycle of the borehole as much as possible), and realize an active hole protection work; at the same time, the expansion of the annular airbag 1-2 will compress the space inside the borehole, thereby increasing The air pressure in the borehole performs a high-pressure impact on the coal body around the borehole. After completion, the downhole compressed air system is disconnected to discharge the gas inside the annular air bag 1-2 from the gas injection pipe 3. At this time, the annular air bag retracts, and the internal space of the borehole is restored and increased, so that the air pressure inside the borehole is reduced; then it is connected to the downhole compressed air system again to carry out the next expansion of the annular air bag 1-2 and the pressurization impact process inside the borehole. This is repeated to form a variable frequency pneumatic shock wave in the borehole to cause fracturing and permeability enhancement of the coal body around the borehole. After 2 to 4 days, the hole protection and permeability enhancement treatment are completed.

[0043] Step 6: Continuous gas extraction: Close the valve of the gas injection pipe 3, open the control valve of the underground gas extraction branch pipe to continue gas extraction from the gas extraction borehole, and repeat steps 4 and 5 multiple times until the gas extraction of the coal seam where the gas extraction borehole is located meets the standard.

[0044] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A soft and low-permeability coal seam hole protection and permeability enhancement integrated pipeline, characterized in that: It includes multiple hole protection and permeability enhancement structures, extraction pipelines and gas injection pipes; the multiple hole protection and permeability enhancement structures are all located in the gas extraction borehole; The hole protection and permeability enhancement structure comprises a flower tube and an annular air bag, the annular air bag is sleeved on the outer wall of the flower tube, and the inner wall of the annular air bag is pressed and contacted with the outer wall of the flower tube; the flower tubes of the hole protection and permeability enhancement structure are coaxially connected head to tail, and two adjacent annular air bags are connected through a hollow tube, and the flower tube at the head end is placed at the deepest part of the gas extraction borehole; One end of the extraction pipeline extends into the gas extraction borehole and is connected to the flower pipe at the tail end for gas extraction; One end of the gas injection pipe extends into the gas extraction borehole and is connected to the annular airbag at the tail end; when gas is injected into the annular airbag and then released through the gas injection pipe, each annular airbag expands and retracts in turn, and by compressing and restoring the volume in the gas extraction borehole, a variable frequency pneumatic shock wave is generated in the gas extraction borehole to increase the permeability of the coal seam.

2. The integrated pipeline for protecting the borehole and increasing the permeability of soft and low-permeability coal seams according to claim 1 is characterized in that: The annular airbag completely wraps the outer wall of the flower tube, and a plurality of through holes are provided on the annular airbag. The positions of the through holes correspond to the sieve holes on the flower tube respectively, and the flower tube is connected with the inside of the gas extraction borehole through the sieve holes.

3. The integrated pipeline for protecting the borehole and increasing the permeability of soft and low-permeability coal seams according to claim 1 is characterized in that: Two adjacent flower tubes as well as the flower tube and one end of the extraction pipeline are connected through threads.

4. The integrated pipeline for protecting the borehole and increasing the permeability of soft and low-permeability coal seams according to claim 1 is characterized in that: The axes of the gas injection pipe and each hollow pipe are parallel to the axis of the flower pipe.

5. The integrated pipeline for protecting the borehole and increasing the permeability of soft and low-permeability coal seams according to claim 1 is characterized in that: The extraction pipeline is composed of a plurality of extraction pipes connected coaxially end to end.

6. The integrated pipeline for protecting the borehole and increasing the permeability of soft and low-permeability coal seams according to claim 5 is characterized in that: The extraction tube and the flower tube have the same length, both in the range of 2.0 to 4.0 m; the ventilation holes and the sieve holes have the same diameter, both in the range of 3 to 6 mm.

7. The integrated pipeline for protecting the borehole and increasing the permeability of soft and low-permeability coal seams according to claim 1 is characterized in that: The maximum air pressure that the annular airbag can withstand is not less than 2MPa.

8. A method for using the integrated pipeline for protecting the borehole and increasing the permeability of soft and low-permeability coal seams according to any one of claims 1 to 7, characterized in that: The specific steps are: Step 1: Determine the initial data: construct a gas extraction borehole at the required location of the soft and low-permeability coal seam, obtain the depth of the borehole and the required sealing depth, and then determine the number of flower pipes and extraction pipes; Step 2: Install the pipeline: place the hole protection and permeability enhancement structure at the head end into the gas extraction borehole, and connect the flower tubes and annular air bags of each subsequent hole protection and permeability enhancement structure in sequence and send them into the gas extraction borehole until the number of flower tubes reaches the number determined in step 1, then connect one end of the extraction pipe with the flower tube at the tail end, and connect each subsequent extraction pipe in sequence and push the entire pipeline to continue to go deeper into the gas extraction borehole until the number of extraction pipes reaches the number determined in step 1; extend one end of the gas injection pipe into the gas extraction borehole and connect it with the annular air bag at the tail end. Initially, each annular air bag is in an unexpanded state, and the valve of the gas injection pipe is in a closed state; Step 3: Borehole sealing and gas extraction: Seal the holes at the locations of the extraction pipes to form a sealing section, which has the same total length as the extraction pipes; finally, connect the extraction pipe at the tail end to the underground gas extraction branch pipe to extract gas from the gas extraction borehole; Step 4: Gas desorption and pressurization: When the pure gas extraction flow rate is less than 0.001m 3 / min, close the control valve of the underground gas extraction branch pipe in step 3, and seal the gas extraction borehole for 24 to 36 hours to allow the gas in the surrounding coal body to be freely desorbed into the borehole, thereby increasing its internal gas pressure; Step 5: hole protection and permeability enhancement treatment: connect the other end of the gas injection pipe to the underground compressed air system, open the valve of the gas injection pipe, first inject gas into each annular air bag, and each annular air bag expands in turn to squeeze the position where the collapsed hole exists to expand the hole under pressure, thereby realizing an active hole protection work; at the same time, the expansion of the annular air bag will compress the space inside the borehole, thereby increasing the air pressure in the borehole, and performing a high-pressure impact on the coal body around the borehole. After completion, disconnect the underground compressed air system to discharge the gas inside the annular air bag from the gas injection pipe; then connect it to the underground compressed air system again, and carry out the next annular air bag expansion and borehole internal pressurization impact process. Repeat this for a period of time to form a variable frequency pneumatic shock wave in the borehole to cause fracture and permeability enhancement of the coal body around the borehole; Step 6: Continuous gas extraction: Close the valve of the gas injection pipe, open the control valve of the underground gas extraction branch pipe to continue gas extraction from the gas extraction borehole, and repeat steps 4 and 5 multiple times until the gas extraction of the coal seam where the gas extraction borehole is located meets the standard.

9. The method of use according to claim 8, characterized in that: The diameter of the flower tube is 0.4 to 0.6 times the diameter of the gas extraction borehole, and the diameter of the annular airbag after inflation is 0.85 to 0.95 times the diameter of the borehole.

10. The method of use according to claim 8, characterized in that: The repetition time in step 5 is 2 to 4 days.

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