CN113605874B - Method for extracting coal bed gas of broken soft coal bed top and bottom double-layer horizontal well - Google Patents
Method for extracting coal bed gas of broken soft coal bed top and bottom double-layer horizontal well Download PDFInfo
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- 239000003245 coal Substances 0.000 title claims abstract description 147
- 238000000034 method Methods 0.000 title claims abstract description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000010276 construction Methods 0.000 claims abstract description 6
- 238000004519 manufacturing process Methods 0.000 claims description 23
- 238000005553 drilling Methods 0.000 claims description 9
- 238000005488 sandblasting Methods 0.000 claims description 9
- 239000012530 fluid Substances 0.000 claims description 7
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 6
- 239000000654 additive Substances 0.000 claims description 3
- 230000000996 additive effect Effects 0.000 claims description 3
- 230000002579 anti-swelling effect Effects 0.000 claims description 3
- 239000011152 fibreglass Substances 0.000 claims description 3
- 235000011164 potassium chloride Nutrition 0.000 claims description 3
- 239000001103 potassium chloride Substances 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 238000005086 pumping Methods 0.000 claims description 3
- 239000000725 suspension Substances 0.000 claims description 3
- 238000000605 extraction Methods 0.000 abstract description 13
- 239000007789 gas Substances 0.000 description 52
- 230000000694 effects Effects 0.000 description 5
- 239000002817 coal dust Substances 0.000 description 3
- 238000002309 gasification Methods 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- 239000004576 sand Substances 0.000 description 3
- 239000003208 petroleum Substances 0.000 description 2
- 238000003795 desorption Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 239000002918 waste heat Substances 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells
- E21B43/305—Specific pattern of wells, e.g. optimising the spacing of wells comprising at least one inclined or horizontal well
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/006—Production of coal-bed methane
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/04—Directional drilling
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/20—Driving or forcing casings or pipes into boreholes, e.g. sinking; Simultaneously drilling and casing boreholes
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/28—Enlarging drilled holes, e.g. by counterboring
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Abstract
The invention belongs to the technical field of coal bed gas extraction, and particularly relates to a method for extracting coal bed gas of a broken soft coal bed top-bottom double-layer horizontal well, wherein a group of bottom plate U-shaped wells and a top plate L-shaped well are adopted to jointly extract coal bed gas of a target broken soft coal bed, and each bottom plate U-shaped well consists of a bottom plate L-shaped well and a vertical well; during construction, a vertical well is constructed, a bottom plate L-shaped well is constructed, the horizontal section of the bottom plate L-shaped well is positioned below the bottom plate of the target broken soft coal seam, the horizontal section of the bottom plate L-shaped well is drilled in a descending mode and communicated with the vertical well, finally, a top plate L-shaped well is drilled in a well hole of the bottom plate L-shaped well, the horizontal section of the top plate L-shaped well is positioned above the top plate of the target broken soft coal seam, and the horizontal section of the top plate L-shaped well is drilled in the descending mode to a final hole at a preset distance away from the vertical well; arranging operation sections at intervals on the horizontal section of the L-shaped well of the bottom plate, wherein the operation sections comprise a middle fracturing section and front and rear bottom plate perforation sections; a top plate perforation section is arranged on the horizontal section of the top plate L-shaped well; and (4) draining water from the vertical well, and extracting gas from the L-shaped well on the top plate.
Description
Technical Field
The invention belongs to the technical field of coal bed gas extraction, and particularly relates to a method for extracting coal bed gas of a broken soft coal bed top and bottom double-layer horizontal well.
Background
The extraction of the broken soft coal bed gas is a worldwide problem, which always troubles the coal bed gas industry and seriously threatens the safe production of coal. At present, the average gas production rate of vertical wells of broken soft coal seams is less than 500 square/day, the average gas production rate of horizontal wells of coal seams is less than 3000 square/day, and the gas production rate of roof horizontal wells implemented in recent years breaks through 5000 square/day. The broken soft coal seam is soft in coal quality and easy to collapse due to low permeability, the horizontal section of the coal seam gas horizontal well cannot be maintained in the coal seam, gas production fracture channels are blocked, the coal seam gas extraction effect is affected, the coal mine safety has gas risks, and no better method is available for breaking through the difficulty of the broken soft coal seam gas extraction technology.
Disclosure of Invention
The invention aims to solve the problems that the broken soft coal seam is soft and easy to collapse due to low permeability, the horizontal section of a coal bed gas horizontal well cannot be maintained in the coal seam, a gas production fracture channel is blocked, the coal bed gas extraction effect is influenced, and the coal mine safety has gas risk.
In order to achieve the purpose, the invention provides a method for extracting coal bed gas of a double-layer horizontal well at the top and bottom of a broken soft coal bed, which adopts a group of bottom plate U-shaped wells and a top plate L-shaped well to jointly extract the coal bed gas of a target broken soft coal bed, wherein the bottom plate U-shaped well is formed by combining a bottom plate L-shaped well and a vertical well; during construction, a vertical well is constructed firstly, then a bottom plate L-shaped well is constructed, the bottom plate L-shaped well drills through a target broken soft coal seam from the ground surface downwards, a horizontal section is located below a bottom plate of the target broken soft coal seam, the horizontal section of the bottom plate L-shaped well drills downwards and communicates with the vertical well, a packer is placed in the bottom plate L-shaped well, finally a top plate L-shaped well is drilled in a well hole of the bottom plate L-shaped well in an inclined mode, the horizontal section of the top plate L-shaped well is located above a top plate of the target broken soft coal seam, and the horizontal section of the top plate L-shaped well drills downwards to a final hole at a preset distance away from the vertical well; arranging operation sections at intervals on the horizontal section of the L-shaped well of the bottom plate, wherein the operation sections comprise a middle fracturing section and front and rear bottom plate perforation sections; a top plate perforation section is arranged on the horizontal section of the top plate L-shaped well, the top plate perforation section and the operation section are staggered in space, and the top plate perforation section is positioned between the two operation sections; and an oil pumping unit or a screw pump is arranged at the wellhead of the vertical well for drainage, the bottom plate L-shaped well does not discharge oil, and the wellhead of the top plate L-shaped well is connected with an oil production pipeline for gathering and transportation.
Furthermore, after the vertical well penetrates through the bottom plate of the target soft coal seam by a preset depth, a borehole cave is formed, and the horizontal section of the L-shaped well of the bottom plate extends to be connected with the borehole cave.
Further, the vertical well adopts a double-open-well structure; firstly, drilling a hole 2m below the ground surface, and then, putting a glass fiber reinforced plastic sleeve; secondly, drilling a target broken soft coal seam, drilling a final hole to a designed depth, and putting a petroleum casing pipe; and (3) cementing the whole vertical well, and reaming and making a cave at a position 2 meters away from the bottom plate of the target broken soft coal seam after cementing, wherein the radius of the cave of the well is more than 0.5m.
Furthermore, when the bottom plate L-shaped in-well fracturing section is constructed, a perforating gun or hydraulic sand blasting is adopted to vertically and directionally perforate towards the direction of a target broken soft coal layer, and then the continuous oil pipe is fractured in sections from far to near; constructing a bottom plate perforation section after fracturing is finished, and vertically and directionally perforating in the direction of the target broken soft coal layer by adopting a perforation gun or hydraulic sand blasting again before and after the fracturing section; and perforating vertically and directionally towards the direction of the target broken soft coal layer in the top plate L-shaped well by adopting a perforating gun or hydraulic sand blasting.
Furthermore, the interval of the operation section on the L-shaped well of the bottom plate is 60m, the lengths of the fracturing section and the bottom plate perforation section are both 10m, and the length of the top plate perforation section is 20m.
Furthermore, the perforation pitch on the fracturing section is 1 meter, the phase angle deviation is less than 5 degrees, and the hole density is 16 holes/meter; the perforation pitch on the perforation section of the bottom plate is 1 meter, the phase angle deviation is less than 5 degrees, and the hole density is 16 holes/meter; the perforation pitch on the perforation section of the top plate is 1 meter, the phase angle deviation is less than 5 degrees, and the hole density is 16 holes/meter.
Furthermore, in the L-shaped underground fracturing process of the bottom plate, active water is formed by mixing clean water and potassium chloride in the fracturing fluid, and a resistance reducing or anti-swelling additive is added into the fracturing fluid according to the coal quality condition.
Furthermore, the bottom plate L-shaped well and the top plate L-shaped well adopt a three-opening well body structure; and the first opening is used for placing a surface casing pipe, the second opening is used for placing a technical casing pipe, the third opening is used for placing a production casing pipe, the production casing pipe is fixed at the tail end of the technical casing pipe by adopting a suspension device, and the whole well of the bottom plate L-shaped well and the top plate L-shaped well is cemented.
Furthermore, the horizontal section of the bottom plate L-shaped well is 2m away from the bottom plate of the target soft coal seam, the horizontal section of the top plate L-shaped well is 2m away from the top plate of the target soft coal seam, and the horizontal section of the top plate L-shaped well is drilled to a final hole 10 meters away from the vertical well.
Compared with the prior art, the invention has the advantages that:
the invention provides a method for extracting coal bed gas of a broken soft coal bed top-bottom double-layer horizontal well.
The L-shaped well is arranged in the top floor rock stratum of the coal bed for construction and well cementation, so that the stability of the well body structure is favorably kept, the drilling does not have the risk of collapse of the coal bed, the coal reservoir is not polluted, the fractured coal bed can better communicate with the pores of the coal reservoir, the necessary means for increasing the yield of the coal bed gas at the present stage is provided, and the well cementation can ensure that each fractured section is not communicated with each other, so that the coal bed is effectively reformed. According to the principle that gas moves upwards and water is produced downwards, hydraulic fracturing is carried out by adopting a bottom plate L-shaped well, fracturing fluid is convenient to flow back, then production is carried out through a vertical well, the top plate L-shaped well is not fractured and only perforated, a top plate perforated section, a bottom plate L-shaped well fractured section and a bottom plate perforated section are avoided, fracture generated by bottom plate fracturing is prevented from being damaged by top plate perforation, only gas is discharged and generated in the later period, a gas generation channel is stabilized, coal dust and fracturing sand are prevented from flowing back to block coal seam fracture due to drainage and water production migration, coal dust and fracturing sand generated by a coal seam in the later period drainage and production process easily flow to the bottom of the vertical well due to the fact that horizontal sections are drilled downwards, well repairing can be carried out on the bottom plate L-shaped well in the later period if necessary, coal dust and fracturing sand left by a horizontal section are cleaned, but a vertical well is not generally used, well repairing is convenient only aiming at the well, the coal seam is not easily polluted and the fracture is not easily damaged, and a top plate horizontal well is mainly used for extracting broken soft coal seam gas extraction, and the problem of a coal seam gas extraction of a working face is particularly obvious.
Drawings
FIG. 1 is a schematic view of the present invention.
In the figure: 1-a roof L-well; 2-a bottom plate L-well; 3-a packer; 4-a top plate perforation section; 5-target soft coal seam; 6-fracturing section; 7-a bottom plate perforation section; 8-vertical wells; a9-well cavity.
Detailed Description
In order to more clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings. The drawings are only for the purpose of illustrating the technology of the invention and are not to be construed as representing actual proportions or actual shapes of products, wherein like reference numerals indicate identical or functionally similar elements.
In this context, "parallel", "perpendicular", and the like are not strictly mathematical and/or geometric limitations, but may also include tolerances as would be understood by one skilled in the art and allowed for in the manufacture or use of the product. In addition, "perpendicular" includes not only perpendicular to each other when two objects are directly connected in space but also perpendicular to each other when two objects are not connected in space.
As shown in fig. 1; a broken soft coal seam top and bottom plate double-layer horizontal well coal bed gas extraction method aims at the problems that broken soft coal seam coal quality is soft, low in permeability and prone to collapse, a horizontal section of a coal bed gas horizontal well cannot be maintained in a coal seam, gas production crack channels are blocked, coal bed gas extraction effect is affected, and gas risks exist in coal mine safety. According to the principle of coal bed gas drainage and gas production (desorption, diffusion and seepage), the coal bed gas extraction of the broken soft coal bed top and bottom plate double-layer horizontal well is innovatively provided by combining the technical processes of a double-coal bed gas horizontal well and a coal bed top plate coal bed gas horizontal well. A group of bottom plate U-shaped wells and a top plate L-shaped well 1 are combined to extract coal bed gas of a target broken soft coal bed 5, and each bottom plate U-shaped well is formed by combining a bottom plate L-shaped well 2 and a vertical well 8.
During construction, a vertical well 8 is constructed, and a borehole cave 9 is constructed after the vertical well 8 penetrates through the bottom plate of the target soft coal seam 5 by a preset depth. The vertical well 8 adopts a double-well-bore structure; firstly, drilling a hole 2m below the ground surface, and then, putting a glass fiber reinforced plastic sleeve; secondly, drilling a target broken soft coal seam 5, drilling to a final hole with a designed depth, and putting a petroleum casing; and (3) cementing the vertical well 8 in the whole well, and reaming and making a cave at a position 2 meters away from the bottom plate of the target broken soft coal seam 5 after cementing, wherein the radius of a borehole cave 9 is more than 0.5m.
And constructing a bottom plate L-shaped well 2, wherein the bottom plate L-shaped well 2 downwards drills through the target broken soft coal seam 5 from the ground surface, and the horizontal section is positioned below the bottom plate of the target broken soft coal seam 5. Specifically, the horizontal section of the bottom plate L-shaped well 2 is 2m away from the bottom plate of the target soft coal seam 5, and the horizontal section of the bottom plate L-shaped well 2 extends to be connected with the borehole cave 9, so that the bottom plate L-shaped well 2 is communicated with the vertical well 8.
And (3) setting a packer 3 into a certain section of a shaft of the bottom plate L-shaped well 2 according to the deflecting radius curvature requirement of the top plate L-shaped well 1 to perform sidetracking deflecting, wherein the horizontal section of the top plate L-shaped well 1 is positioned above the top plate of the target soft coal seam 5. Specifically, the horizontal section of the top plate L-shaped well 1 is 2m away from the top plate of the target soft coal seam 5, and the horizontal section of the top plate L-shaped well 1 is drilled into a final hole at a preset distance away from the vertical well 8 in a downhill mode. Specifically, the horizontal section of the L-shaped well 1 on the top plate is drilled to a final hole 10 meters away from the vertical well.
Arranging operation sections at intervals on the horizontal section of the L-shaped well 2 of the bottom plate, wherein the operation sections comprise a middle fracturing section 6 and front and rear bottom plate perforation sections 7; a horizontal section of the top plate L-shaped well 1 is provided with a top plate perforation section 4, the top plate perforation section 4 is staggered with the space of the operation sections, and the top plate perforation section 4 is positioned between the two operation sections; and a pumping unit or a screw pump is arranged at the mouth of the vertical well 8 for draining water, the bottom plate L-shaped well 2 does not discharge and produce, and the mouth of the top plate L-shaped well 1 is connected with a gas production pipeline for gathering and transporting.
When the fracturing section in the L-shaped well 2 with the bottom plate is constructed, a perforating gun or hydraulic sand blasting is adopted to vertically and directionally perforate towards the direction of a target broken soft coal layer, the perforation hole distance is 1 meter, the phase angle deviation is less than 5 degrees, and the hole density is 16 holes/meter. And then performing staged fracturing on the continuous oil pipe from far to near, wherein the fracturing fluid adopts active water formed by mixing clean water and potassium chloride, and a resistance-reducing or anti-swelling additive is added into the fracturing fluid according to the coal quality condition. And constructing a bottom plate perforation section 7 after fracturing is finished, vertically and directionally perforating in the direction of the target broken soft coal layer by adopting a perforating gun or hydraulic sand blasting within 10 meters before and after the fracturing section, wherein the perforations are spaced by 1 meter in the middle, the phase angle deviation is less than 5 degrees, and the hole density is 16 holes/meter. Perforating guns or hydraulic sand blasting is adopted in the top plate L-shaped well 1 to vertically orient and perforate towards the direction of a target broken soft coal layer, the perforation pitch is 1 meter, the phase angle deviation is less than 5 degrees, and the hole density is 16 holes/meter. The distance between the operation sections on the bottom plate L-shaped well 2 is 60m, the length of each fracturing section 6 is 10m, and the length of the top plate perforation section 4 is 20m.
The bottom plate L-shaped well 2 and the top plate L-shaped well 1 adopt a three-opening well body structure; and the first opening is used for placing a surface casing pipe, the second opening is used for placing a technical casing pipe, the third opening is used for placing a production casing pipe, the production casing pipe is fixed at the tail end of the technical casing pipe by adopting a suspension device, and the bottom plate L-shaped well 2 and the top plate L-shaped well 1 are completely fixed.
Chinese utility model patent with patent number 201721821119.0 discloses "a two coal seam U shaped coal layer gas well body structures", and with the prior art that this application is close, this application lies in with this prior art's difference: (1) Aiming at different coal beds, the coal bed breaking method mainly aims at broken soft coal beds, and has the difficulties that the coal bed is soft and broken, the extraction effect of the conventional coal bed gas well is poor, and the well body structure is not easy to store; (2) The coal bed gas well is constructed on the top and bottom plates of the coal bed; (3) This application roof L type well is not communicated with vertical well, only adopts gas not drainage, and bottom plate L type well only carries out the drainage, does not adopt gas.
The invention patent of China with the patent number of 202011077949.3, namely 'method, structure and construction method for the coordinated mining of underground coal gasification and coal bed gas', is the prior art which is similar to the application, and the difference between the application and the prior art is as follows: (1) The method does not relate to underground coal gasification, and only aims at a certain target broken soft coal bed to extract the coal bed gas, so that the problem of gas on a strip-shaped working face is mainly solved, and the ground yield of the coal bed gas is supplemented; (2) In the prior art, the coal seam spacing is required to be 50 meters, the lower layer well carries out underground coal gasification, and the coal seam gas extraction of the upper layer well is influenced by using waste heat; according to the coal bed gas production mechanism, the pressure of a coal reservoir is reduced by draining the vertical well, so that the coal bed gas is produced from the top plate L-shaped well; (3) This application still needs to carry out fracturing transformation coal seam to bottom plate L type well to communicate the coal seam crack, increase the gas production passageway, recycle roof L type well perforation, dredge pit shaft and coal seam crack, the coal bed gas of being convenient for is output.
It should be understood that although the present description has been described in terms of various embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and those skilled in the art will recognize that the embodiments described herein may be combined as suitable to form other embodiments, as will be appreciated by those skilled in the art.
The above-listed detailed description is only a specific description of possible embodiments of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the scope of the present invention.
Claims (9)
1. A method for extracting coal bed gas of a double-layer horizontal well at the top and bottom of a broken soft coal bed is characterized by comprising the following steps of: adopting a group of bottom plate U-shaped wells and a top plate L-shaped well (1) to jointly extract coal bed gas of a target crushed soft coal bed (5), wherein the bottom plate U-shaped well is formed by combining a bottom plate L-shaped well (2) and a vertical well (8); during construction, a vertical well (8) is constructed firstly, then a bottom plate L-shaped well (2) is constructed, the bottom plate L-shaped well (2) penetrates through a target broken soft coal seam (5) from the ground surface downwards, a horizontal section is located below a bottom plate of the target broken soft coal seam (5), the horizontal section of the bottom plate L-shaped well (2) is drilled downwards and communicated with the vertical well (8), a packer (3) is placed into the bottom plate L-shaped well (2), finally, a top plate L-shaped well (1) is drilled in a slant mode in a well hole of the bottom plate L-shaped well (2), the horizontal section of the top plate L-shaped well (1) is located above a top plate of the target broken soft coal seam (5), and a final hole is drilled downwards at a preset distance from the vertical well (8); the horizontal section of the L-shaped well (2) of the bottom plate is provided with operation sections at intervals, and the operation sections comprise a middle fracturing section (6) and front and rear bottom plate perforation sections (7); a horizontal section of the top plate L-shaped well (1) is provided with a top plate perforation section (4), the top plate perforation section (4) is staggered with the space of the operation sections, and the top plate perforation section (4) is positioned between the two operation sections; and an oil pumping unit or a screw pump is arranged at the wellhead of the vertical well (8) for draining, the bottom plate L-shaped well (2) is not drained, and the wellhead of the top plate L-shaped well (1) is connected with a gas production pipeline for gathering and transportation.
2. The method for extracting the coal bed gas of the broken soft coal seam top and bottom double-layer horizontal well according to claim 1, is characterized in that: and the vertical well (8) penetrates through the bottom plate of the target soft coal seam (5) to a preset depth to form a borehole cave (9), and the horizontal section of the bottom plate L-shaped well (2) extends to be connected with the borehole cave (9).
3. The method for extracting the coal bed gas of the broken soft coal seam top and bottom double-layer horizontal well according to claim 2 is characterized in that: the vertical well (8) adopts a two-well structure; firstly, drilling 2m below the ground surface, and then, inserting a glass fiber reinforced plastic sleeve; secondly, drilling through a target crushed soft coal seam (5) to a final hole with a designed depth, and putting an oil casing; and (3) cementing the vertical well (8) in the whole well, and reaming and making a cave at a position 2 meters away from the bottom plate of the target crushed soft coal seam (5) after cementing, wherein the radius of the borehole cave (9) is more than 0.5m.
4. The method for extracting the coal bed gas of the broken soft coal seam top and bottom double-layer horizontal well according to claim 1, is characterized in that: when the fracturing section (6) in the L-shaped well (2) with the bottom plate is constructed, a perforating gun or hydraulic sand blasting is adopted to vertically and directionally perforate towards the direction of a target broken soft coal layer, and then the staged fracturing of the continuous oil pipe is carried out from far to near; constructing a bottom plate perforating section (7) after fracturing is finished, and vertically and directionally perforating in the direction of the target broken soft coal bed by adopting a perforating gun or hydraulic sand blasting before and after the fracturing section (6); and perforating vertically and directionally towards the direction of the target broken soft coal layer by adopting a perforating gun or hydraulic sand blasting in the top plate L-shaped well (1).
5. The method for extracting coal bed gas of the broken soft coal bed top and bottom double-layer horizontal well according to claim 4 is characterized by comprising the following steps: the interval of the operation sections on the bottom plate L-shaped well (2) is 60m, the lengths of the fracturing section (6) and the bottom plate perforation section (7) are both 10m, and the length of the top plate perforation section (4) is 20m.
6. The method for extracting coal bed gas of the broken soft coal bed top and bottom double-layer horizontal well according to claim 5 is characterized by comprising the following steps: the perforation pitch on the fracturing section (6) is 1 meter, the phase angle deviation is less than 5 degrees, and the hole density is 16 holes/meter; the perforation pitch on the bottom plate perforation section (7) is 1 meter, the phase angle deviation is less than 5 degrees, and the hole density is 16 holes/meter; the perforation pitch on the top plate perforation section (4) is 1 meter, the phase angle deviation is less than 5 degrees, and the perforation density is 16 holes/meter.
7. The method for extracting the coal bed gas of the broken soft coal seam top and bottom double-layer horizontal well according to claim 6, is characterized in that: in the fracturing process in the L-shaped well (2) of the bottom plate, active water formed by mixing clean water and potassium chloride is adopted as the fracturing fluid, and a resistance-reducing or anti-swelling additive is added into the fracturing fluid according to the coal quality condition.
8. The method for extracting the coal bed gas of the broken soft coal seam top and bottom double-layer horizontal well according to claim 1, is characterized in that: the bottom plate L-shaped well (2) and the top plate L-shaped well (1) adopt a three-opening well body structure; and the first opening is used for placing a surface casing pipe, the second opening is used for placing a technical casing pipe, the third opening is used for placing a production casing pipe, the production casing pipe is fixed at the tail end of the technical casing pipe by adopting a suspension device, and the whole well of the bottom plate L-shaped well (2) and the top plate L-shaped well (1) is well-fixed.
9. The method for extracting the coal bed gas of the broken soft coal seam top and bottom double-layer horizontal well according to claim 8, is characterized in that: the horizontal section of the bottom plate L-shaped well (2) is 2m away from the bottom plate of the target soft coal seam (5), the horizontal section of the top plate L-shaped well (1) is 2m away from the top plate of the target soft coal seam (5), and the horizontal section of the top plate L-shaped well (1) is drilled to a final hole 10m away from the vertical well (8).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110915049.XA CN113605874B (en) | 2021-08-10 | 2021-08-10 | Method for extracting coal bed gas of broken soft coal bed top and bottom double-layer horizontal well |
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