Coal-bed gas well extraction and drainage arrangement structure

Abstract

The utility model discloses a coal-bed gas well extraction and drainage arrangement structure which comprises a vertical shaft vertically and downwards penetrating through a coal reservoir, and the lower end of the vertical shaft extends into a rock stratum below the coal reservoir; a plurality of layers of radial extraction sections are arranged in the coal reservoir around the vertical shaft in the vertical direction; a casing pipe is arranged in the vertical shaft, a plurality of vertical drainage channels are arranged on the outer circle of the casing pipe, well cementation gravel blocks are filled between any two adjacent vertical drainage channels in the vertical shaft, and an inner port of each layer of radial extraction section is communicated with the interior of the casing pipe. And a plurality of water guide pipes are uniformly arranged at the interface between the bottom of the coal reservoir and the rock layer on the wall of the sleeve along the circumferential direction. The plurality of layers of radial extraction sections are uniformly arranged in the circumferential direction of the vertical shaft, so that the vertical shaft is particularly suitable for a thicker coal reservoir, the extraction range of the vertical shaft in the radial direction is extended, the extraction yield of a single well is improved, a smooth drainage channel is designed, moisture in the coal reservoir is reduced, and the drainage efficiency is improved. Therefore, economy, high efficiency, safety and stability of coal bed gas exploitation are guaranteed.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of coalbed gas development, and particularly relates to a coalbed gas well drainage arrangement structure. BACKGROUND

[0002] Coalbed gas (CBM), commonly known as "gas", is unconventional natural gas with methane (CH4) as the main component, which is adsorbed on the surface of coal matrix particles or is free in coal pores, and is a coal associated mineral resource.

[0003] For a high-gas coal reservoir, gas needs to be extracted before coal mining, which not only improves the safety of coal mining operation, but also concentrates high-purity gas extraction. At present, the straight well (vertical shaft) in the gas extraction of the high-gas coal reservoir is the earliest and most widely used well type in coalbed gas exploitation, which has low cost. Although the straight well can be applied to the gas extraction of the thick coal reservoir, the single well yield is generally low (only the straight well can be used as the center to extract within a small radius), therefore, the straight well is suitable for the medium-high permeability coal seam. Therefore, in order to improve the single well yield and for the thick coal reservoir, the extraction structure of the existing coalbed gas well (straight well) needs to be optimized and improved. SUMMARY

[0004] The utility model aims at providing a coalbed gas well drainage arrangement structure which has large extraction range, good extraction effect, easy drainage and is suitable for thick coal reservoir.

[0005] In order to solve the above technical problems, the utility model adopts the following technical scheme: the coalbed gas well drainage arrangement structure comprises a vertical shaft which vertically penetrates through the coal reservoir, the lower end of the vertical shaft extends into the rock layer below the coal reservoir; a plurality of layers of radial extraction sections are vertically arranged around the vertical shaft in the coal reservoir; a casing is coaxially arranged in the vertical shaft, a plurality of vertical drainage channels are arranged between the casing outer circle and the vertical shaft wall, a well cementation rubble is filled between any two adjacent vertical drainage channels in the vertical shaft, and the inner end of each layer of radial extraction section is in communication with the inside of the casing; a plurality of water guide pipes are uniformly arranged on the casing wall at the interface between the coal reservoir bottom and the rock layer in the circumferential direction, the outer end of the water guide pipe extends into the coal reservoir, and the inner end of the water guide pipe penetrates through the casing and is flush with the inner circle of the casing.

[0006] The plurality of layers of radial extraction sections are uniformly arranged in the vertical shaft height direction, each layer of radial extraction section comprises four extraction holes which are arranged in a circular array around the center line of the vertical shaft, the extraction holes are arranged in an inclined manner with the inner end being higher than the outer end along the center line direction, and the included angle between the center line of the extraction hole and the horizontal plane is 3-10°; when the vertical projection of any two adjacent layers of radial extraction sections is on a plane, the included angle between the two adjacent extraction holes is 45°.

[0007] Each of the extraction holes is provided with an extraction screen pipe, the outer end of the extraction screen pipe is provided with a filter hole plate, a through hole corresponding to each layer of the radial extraction section is formed on the sleeve, and the inner diameter of the extraction screen pipe is smaller than the diameter of the through hole; the inner end of the extraction screen pipe is fixedly connected to the outer circle of the sleeve, each of the extraction screen pipes is communicated with the inside of the sleeve through one of the through holes, and the lowest position of the inner end of the extraction screen pipe is lower than the lowest position of the through hole.

[0008] A plurality of screen holes are formed on the pipe wall of the extraction screen pipe between the position 0.5-1m away from the sleeve and the filter hole plate, and a plurality of hemispherical support air permeable nets are fixedly welded to the outer circle of the extraction screen pipe, each of the hemispherical support air permeable nets covers one of the screen holes.

[0009] The vertical drainage channel adopts a semicircular pipe welded to the outer circle of the sleeve, all the semicircular pipes are arranged in a circular array along the center line of the sleeve, the upper end of the semicircular pipe is higher than the ground and is provided with an air permeable cover plate, the lower end of the semicircular pipe is communicated with the water guide pipe, a plurality of drainage holes are uniformly formed on the semicircular pipe along the length direction, and a stainless steel filter screen covering the drainage holes is welded to the outer circle of the semicircular pipe.

[0010] By using the above technical scheme, compared with the prior art, the utility model has the following technical effects:

[0011] (1) The utility model opens a vertical shaft, and a plurality of layers of radial extraction sections are uniformly opened from top to bottom in the coal reservoir, each of the radial extraction sections includes extraction holes with an included angle of 90°, so that the vertical shaft can radially radiate a farther extraction range, thereby improving the single well extraction amount, and when the vertical projection of any two adjacent layers of radial extraction sections is on a plane, the included angle between the two adjacent extraction holes is 45°, such a structure can open the extraction holes as few as possible, and can also make the extraction radiation range of each extraction hole as uniform as possible, so that the cylindrical region with the vertical shaft as the center line is more balanced in the fracturing and permeability improvement and the coal bed gas extraction operation, and basically has no dead angle.

[0012] (2) The extraction screen pipe is arranged in the extraction hole, which can not only support the extraction hole to avoid hole collapse, but also uniformly open a plurality of screen holes on the extraction screen pipe, so that the fracturing gas can be injected through the screen holes and into the coal reservoir, and the gas in the coal reservoir can enter the extraction screen pipe through the screen holes and be extracted when the coal bed gas is extracted. The filter hole plate is arranged to improve the permeability of the extraction screen pipe and the coal reservoir, and to block the coal from entering the extraction screen pipe.

[0013] (3) in the lower part of the casing in the circumferential direction evenly set several water pipes, the water in the coal reservoir under the infiltration to the top of the rock layer no longer along the rock layer infiltration, the water in the upper rock layer and coal reservoir can be through the drainage hole into the semicircular pipe, and then down through the water pipe into the water storage part of the casing bottom, at the same time through the filling of the well cementation gravel infiltration, finally all through the water pipe to the casing, at the same time, there will also be coal powder through the water pipe into the casing, the submersible pump set in the casing will mix the water to the ground. Because the water in the coal reservoir and the rock layer above the coal reservoir cannot flow downward through the shaft wall, which will increase the moisture content in the coal reservoir, affecting the production of coal bed methane, so several semicircular pipes are set to not only have the function of quickly guiding water, but also have the function of improving the strength of the casing.

[0014] (4) each drainage screen pipe is set with low outside and high inside, avoiding the water infiltrating into the drainage screen pipe flowing to the inner port of the drainage screen pipe. Because the inner diameter of the drainage screen pipe is smaller than the diameter of the through hole, and the lowest position of the inner port of the drainage screen pipe is lower than the lowest position of the through hole, this structure further avoids the water in the drainage screen pipe entering the through hole on the casing through the inner port of the drainage screen pipe. In order to avoid the coal entering the drainage screen pipe through the screen hole, a plurality of hemispherical support air permeable nets can be fixedly welded outside the circle of the drainage screen pipe, each hemispherical support air permeable net covers a screen hole, which not only can support the coal, but also will not reduce the air permeation area between the screen hole and the coal. The sum of the outer diameter of the drainage screen pipe and the diameter of the hemispherical support air permeable net should be slightly smaller than the inner diameter of the drainage hole, which not only facilitates the installation of the drainage screen pipe into the drainage hole, but also provides a larger pressure relief space for the coal between the outer circle of the inserted drainage screen pipe and the inner circle of the drainage hole according to the principle of borehole pressure relief, thereby improving the safety of the coal bed methane drainage process. The drainage screen pipe is provided with several sections, and adjacent two sections are connected through threads or welded.

[0015] (5) when the coal reservoir is fractured by gas injection or water injection, the four drainage screen pipes of the same layer radial drainage section can be simultaneously operated. When the coal reservoir is drained by coal bed methane, the four drainage screen pipes of the same layer radial drainage section can be simultaneously operated. Of course, this requires designing a flow guide device which simultaneously communicates with the four drainage screen pipes and is pressure sealed with the inner circle of the casing, which is not within the research and protection scope of the utility model, and will not be described here.

[0016] In summary, this utility model employs a construction shaft. Within the shaft, the coal reservoir section is evenly divided into several radial extraction sections along the height direction according to its thickness. With the shaft as the center line, each radial extraction section includes four extraction holes with an included angle of 90°. The extraction holes of adjacent layers are arranged alternately. Then, a casing is installed in the shaft and cemented. Extraction screens are installed in the extraction holes. A vertical drainage channel is set on the outer circumference of the casing, and a water guide pipe is installed at the lower part of the casing (between the bottom of the coal reservoir and the top surface of the rock strata). Water from the coal reservoir flows into the casing and is extracted by a high-lift submersible pump.

[0017] This invention is based on a scientific principle. By uniformly setting several layers of radial extraction sections in the circumference of the vertical shaft, it is particularly suitable for thicker coal reservoirs. At the same time, it extends the extraction range of the vertical shaft in the radial direction, increases the extraction output of a single well, and designs a smooth drainage channel to reduce the moisture in the coal reservoir, thereby ensuring the economy, efficiency, safety and stability of coalbed methane extraction. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the elevation sectional structure of this utility model;

[0019] Figure 2 yes Figure 1 Sectional view of AA;

[0020] Figure 3 yes Figure 1 BB section view;

[0021] Figure 4 yes Figure 1 A partial enlarged view of the extraction screen tube;

[0022] Figure 5 This is a schematic diagram of the cross-section of a semi-circular tube installed outside the sleeve. Detailed Implementation

[0023] The embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples.

[0024] like Figures 1-5As shown, the coal bed methane well drainage arrangement structure comprises a vertical shaft, the vertical shaft vertically penetrates the coal reservoir 1 downwards, the lower end of the vertical shaft extends into the rock layer 2 below the coal reservoir 1, a plurality of layers of radial drainage sections are vertically arranged around the vertical shaft in the coal reservoir 1, a casing 3 is coaxially arranged in the vertical shaft, a plurality of vertical drainage channels 5 are arranged between the casing 3 and the shaft wall, solid well crushed stones 7 are filled between any two adjacent vertical drainage channels 5 in the vertical shaft, the inner ports of each layer of radial drainage sections are in communication with the inside of the casing 3, a plurality of water guide pipes 8 are uniformly arranged on the casing 3 at the interface between the coal reservoir 1 and the rock layer in the circumferential direction, the outer end of the water guide pipe 8 extends into the coal reservoir 1, and the inner end of the water guide pipe 8 penetrates through the casing 3 and is flush with the inner circle of the casing 3.

[0025] The plurality of layers of radial drainage sections are uniformly arranged in the vertical shaft height direction, each layer of radial drainage section comprises four drainage holes 6 arranged in a circular array around the center line of the vertical shaft, the drainage hole 6 is arranged in a low-high-low inclined manner along the center line direction, and the included angle between the center line of the drainage hole 6 and the horizontal plane is 3-10°; when the vertical projection of any two adjacent layers of radial drainage sections on a plane, the included angle between the two adjacent drainage holes 6 is 45°.

[0026] Each drainage hole 6 is provided with a drainage screen pipe 4, the outer port of the drainage screen pipe 4 is provided with a filter hole plate, a through hole 9 corresponding to each layer of radial drainage section is formed in the casing 3, and the inner diameter of the drainage screen pipe 4 is smaller than the diameter of the through hole 9; the inner end of the drainage screen pipe 4 is fixedly connected with the outer circle of the casing 3, each drainage screen pipe 4 is in communication with the inside of the casing 3 through one through hole 9, and the lowest position of the inner port of the drainage screen pipe 4 is lower than that of the through hole 9.

[0027] A plurality of screen holes 10 are formed on the pipe wall between the filter hole plate and the position 0.5-1m away from the casing of the drainage screen pipe 4, a plurality of hemispherical support air permeable nets 11 are fixedly welded on the outer circle of the drainage screen pipe 4, and each hemispherical support air permeable net 11 covers one screen hole 10.

[0028] The vertical drainage channel 5 adopts a semicircular pipe 12 welded on the outer circle of the casing 3, all the semicircular pipes 12 are arranged in a circular array along the center line of the casing 3, the upper port of the semicircular pipe 12 is higher than the ground and is provided with an air permeable cover plate, the lower port of the semicircular pipe 12 is in communication with the water guide pipe 8, a plurality of drainage holes 13 are uniformly formed on the semicircular pipe 12 along the length direction, and a stainless steel filter screen 14 covering the drainage holes 13 is welded on the outer circle of the semicircular pipe 12.

[0029] The working principle and technical effects of the utility model are as follows:

[0030] (1) the utility model discloses a vertical shaft is set up, and multiple radial extraction sections are evenly set up from top to bottom in coal reservoir 1, and each radial extraction section includes extraction hole 6 with 90 ° included angle, so that the extraction range of the vertical shaft can be radially radiated farther, thereby improving the extraction amount of single well, and the included angle between the two adjacent extraction holes 6 is 45 ° when the vertical projection of any two adjacent radial extraction sections is on a plane, and such structure can set up extraction hole 6 as little as possible, and can make the extraction radiation range of each extraction hole 6 as uniform as possible, and the cylindrical region with the vertical shaft as the center line is more balanced in fracturing and coalbed methane extraction operation, and there is basically no dead angle.

[0031] (2) extraction screen pipe 4 is arranged in extraction hole 6, which can not only support extraction hole 6 to avoid hole collapse, but also evenly set up a plurality of screen holes 10 on extraction screen pipe 4, inject fracturing gas and coal reservoir 1 through screen hole 10, and the gas in coal reservoir 1 can enter extraction screen pipe 4 through screen hole 10 and be extracted when extracting coalbed methane. The setting of the filter hole plate improves the permeability of extraction screen pipe 4 and coal reservoir 1, and blocks the coal from entering extraction screen pipe 4.

[0032] (3) a plurality of water guide pipes 8 are evenly arranged in the lower part of the casing 3 in the circumferential direction, and the water in the coal reservoir 1 seeps to the top of the rock layer 2 and no longer seeps along the rock layer 2, and the water in the upper rock layer 2 and the coal reservoir 1 can flow into the semicircular pipe 12 through the drainage hole 13, then flow into the water storage part at the bottom of the casing 3 through the water guide pipe 8, and finally all flow into the casing 3 through the water guide pipe 8, and coal powder will also flow into the casing 3 through the water guide pipe 8, and the submersible pump arranged in the casing 3 will extract the coal powder mixed water to the ground. Since the water in the coal reservoir 1 and the rock layer 2 above the coal reservoir 1 cannot flow downward through the vertical shaft wall, the water content in the coal reservoir 1 will increase, which will affect the yield of coalbed methane, so the plurality of semicircular pipes 12 not only have the function of quickly guiding water, but also have the function of improving the strength of the casing 3.

[0033] (4) Each drainage screen pipe 4 is arranged with an outer low and inner high inclination to avoid water seepage into the drainage screen pipe 4 from flowing to the inner port of the drainage screen pipe 4. Since the inner diameter of the drainage screen pipe 4 is smaller than the diameter of the through hole 9 and the lowest position of the inner port of the drainage screen pipe 4 is lower than the lowest position of the through hole 9, this structure further avoids water in the drainage screen pipe 4 from entering the through hole 9 on the casing 3 through the inner port of the drainage screen pipe 4. In order to avoid coal entering the drainage screen pipe 4 through the screen hole 10, a plurality of hemispherical support gas permeable nets 11 can be fixedly welded outside the drainage screen pipe 4. Each hemispherical support gas permeable net 11 covers one screen hole 10, which not only supports the coal, but also does not reduce the gas permeation area between the screen hole 10 and the coal. The sum of the outer diameter of the drainage screen pipe 4 and the diameter of the hemispherical support gas permeable net 11 should be slightly smaller than the inner diameter of the drainage hole 6, which not only facilitates the installation of the drainage screen pipe 4 into the drainage hole 6, but also provides a larger pressure relief space for the coal according to the principle of borehole pressure relief, thereby improving the safety of the coalbed methane drainage process. The drainage screen pipe 4 is provided with a plurality of sections, and adjacent two sections are connected by threads or welded.

[0034] (5) When the coal reservoir 1 is subjected to gas injection fracturing or water injection fracturing, the four drainage screen pipes 4 of the same layer radial drainage section can be simultaneously subjected to. When the coal reservoir 1 is subjected to coalbed methane drainage, the four drainage screen pipes 4 of the same layer radial drainage section can be simultaneously subjected to. Of course, this requires designing a flow guide device that simultaneously communicates with the four drainage screen pipes 4 and is pressure sealed with the inner circle of the casing 3, which is not within the scope of the research and protection of the present application, and will not be described here.

[0035] The above embodiments illustrate the basic principles and characteristics of the present application, but the above only illustrates the preferred embodiments of the present application, and is not limited by the described embodiments. Those skilled in the art can make many formal deformations and improvements under the inspiration of the present patent without departing from the scope of the present application and the protection scope of the claims. These are all within the protection scope of the present application. Therefore, the present application patent and the protection scope should be subject to the appended claims.

Claims

1. A coalbed methane well extraction and drainage layout structure, characterized in that: This includes a vertical shaft that penetrates the coal reservoir vertically downwards, with its lower end extending into the rock strata below the coal reservoir; several radial extraction sections are arranged vertically around the shaft within the coal reservoir; a casing is installed coaxially within the shaft, with several vertical drainage channels between the casing's outer circumference and the shaft wall; cementing gravel is filled between any two adjacent vertical drainage channels within the shaft; the inner end of each radial extraction section is connected to the inside of the casing; several water guide pipes are evenly arranged circumferentially along the casing wall at the interface between the bottom of the coal reservoir and the rock strata, with the outer end of the water guide pipe extending into the coal reservoir and the inner end of the water guide pipe passing through the casing and flush with the inner circumference of the casing.

2. The coalbed methane well extraction and drainage layout structure according to claim 1, characterized in that: Several radial extraction sections are evenly arranged along the vertical shaft. Each radial extraction section includes four extraction holes arranged in a circular array around the center line of the shaft. The extraction holes are inclined inward and outward along the center line. The angle between the center line of the extraction hole and the horizontal plane is 3-10°. When the vertical projections of any two adjacent radial extraction sections are on the same plane, the angle between the two adjacent extraction holes is 45°.

3. The coalbed methane well extraction and drainage layout structure according to claim 2, characterized in that: Each extraction hole is equipped with an extraction screen tube, and the outer end of the extraction screen tube is equipped with a filter plate. The casing has through holes that correspond to each radial extraction section. The inner diameter of the extraction screen tube is smaller than the diameter of the through hole. The inner end of the extraction screen tube is fixedly connected to the outer circle of the casing. Each extraction screen tube is connected to the inside of the casing through one of the aforementioned through holes. The lowest position of the inner end of the extraction screen tube is lower than the lowest position of the through hole.

4. The coalbed methane well extraction and drainage layout structure according to claim 2, characterized in that: The extraction screen pipe has several screen holes on the pipe wall between the casing and the filter plate at a distance of 0.5-1m. Several hemispherical support and ventilation nets are fixedly welded to the outer circle of the extraction screen pipe, and each hemispherical support and ventilation net covers one screen hole.

5. The coalbed methane well extraction and drainage arrangement structure according to any one of claims 1-4, characterized in that: The vertical drainage channel uses a semi-circular pipe welded to the outer circumference of the casing. All the semi-circular pipes are arranged in a circumferential array along the center line of the casing. The upper end of the semi-circular pipe is higher than the ground and is equipped with a vent cover. The lower end of the semi-circular pipe is connected to the water guide pipe. Several drainage holes are evenly opened on the semi-circular pipe along its length. A stainless steel filter screen is welded to the outer circumference of the semi-circular pipe to cover the drainage holes.

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