A well type structure and opening method for single well field near-end connection with coalbed methane

Abstract

The present invention discloses a well structure for proximal docking of coalbed methane in a single well field, including an engineering well and a drainage well, wherein the engineering well and the drainage well are opened in the same well field, and the engineering well and the drainage well can be docked and connected. The present invention also discloses a method for opening a well structure for proximal docking of coalbed methane in a single well field. The present invention constructs an engineering well and a drainage well in the same well field, and connects the engineering well and the drainage well, and when a screw pump is lowered from the drainage well to drain water, the two wells produce gas at the same time. Compared with a U-shaped well, the present invention saves one well field and one pilot hole, and the coalbed methane transmission pipeline is simple, which reduces the development cost; compared with an L-shaped horizontal well, the dogleg degree is reduced, and the screw pump is lowered below the elevation of point A, which generally improves the drainage and gas production effect.

Description

Technical Field

[0001] The invention relates to the technical field of current sampling, and in particular to a well type structure and an opening method for a single well field proximal-end connection with coalbed methane. Background Art

[0002] Coalbed methane is an adsorbed gas. The coal reservoir has low permeability and low abundance. In order to improve development efficiency and gas production, horizontal well development is generally adopted. The horizontal well structures currently used are L-type and U-type. The L-type well is a horizontal well. The two ends of the horizontal section are located at the bottom of the structure and the high part of the structure respectively. Water is drained and gas is produced at the wellhead at the same time. The U-type well consists of a vertical well and a horizontal well. The vertical well is drilled first, and then the horizontal well is drilled. The U-type well is fully connected through the docking of the horizontal well and the vertical well. In the actual implementation process, the horizontal well is located at the high part of the target layer structure, and the vertical well is located at the low part of the structure. The vertical well is drained, and the horizontal well and the vertical well produce gas at the same time.

[0003] The advantage of L-type wells is that they require one less vertical well and one less well site to be constructed than U-type wells, resulting in lower investment; but the disadvantage of L-type wells is that the well body has a large dogleg degree, which causes serious eccentric wear of the drainage pump, large torque, difficulty in pump starting, low pump efficiency, short pump service life, and high pump inspection frequency, which seriously affects the drainage effect; the screw pump cannot reach the horizontal section, resulting in high abandonment pressure and low coalbed methane extraction rate.

[0004] The advantage of U-type wells is that the screw pump can go down below the target layer, the drainage pump has a long service life and high drainage efficiency; the disadvantage of U-type wells is that one more vertical well is constructed than L-type wells, and two well sites are required for construction, the coalbed methane transmission pipeline is long, and the extraction efficiency is low; some coal mining areas have undulating ground ridges and gullies, and the two well sites and corresponding roads bring great difficulties to construction preparation, the project investment is large, the construction period is long, and there is serious waste of land.

[0005] The invention patent application with publication number CN112901120A discloses a coalbed methane U-shaped well gas injection circulation negative pressure extraction device and method, which injects a mixture of coalbed methane produced by the coal reservoir and high-temperature water vapor into the coal reservoir, combined with ground negative pressure extraction, and the three aspects work together to improve the gas production efficiency. However, the U-shaped well it uses is still a conventional structure, and the above-mentioned problems still exist. Summary of the invention

[0006] The technical problem to be solved by the present invention is to solve the problems of poor drainage effect of existing L-shaped wells and long coalbed methane transmission pipelines and low extraction efficiency in U-shaped wells.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A well structure for connecting the coalbed methane near the single well field comprises an engineering well and a drainage well. The engineering well and the drainage well are opened in the same well field and can be connected and connected.

[0009] Advantages: The invention constructs engineering wells and drainage wells in the same well site, and connects the engineering wells with the drainage wells. When the screw pump is pumped into the drainage well, the two wells produce gas at the same time. Compared with the U-shaped well, the invention saves one well site and one pilot hole, and the coalbed methane transmission pipeline is simple, which reduces the development cost; compared with the L-shaped horizontal well, the dogleg degree is reduced, and the drainage and gas production effect is generally improved.

[0010] Preferably, the drainage and production well adopts a two-opening wellbore structure, including a deflection section, and the deflection section is connected to the engineering well at the landing point A.

[0011] Preferably, the engineering well is an L-shaped well.

[0012] Preferably, the engineering well adopts a three-opening wellbore structure, and the engineering well includes a horizontal section target layer, and the two ends of the horizontal section target layer are landing point A and landing point B respectively, and the landing point A is the point that connects with the drainage well.

[0013] Preferably, the landing point A of the target layer of the horizontal section of the L-shaped well is located at a low part of the coal seam structure, and the landing point B is located at a high part of the coal seam structure.

[0014] Preferably, the target layer of the horizontal section of the engineering well can be located at the roof of the coal seam, in the coal seam or at the bottom of the coal seam.

[0015] The present invention also discloses a method for opening a well structure using the above-mentioned single well field proximal end connection with coalbed methane, comprising the following steps:

[0016] S1. Drilling of drainage wells in a set well site;

[0017] S2. Drilling of engineering wells is carried out in the same well site, and the engineering wells are connected with the drainage wells;

[0018] S3. Place a drainage pump in the drainage well to drain water, and extract gas from the drainage well and the engineering well at the same time.

[0019] Preferably, the drilling construction process of the drainage well in step S1 includes:

[0020] S11, once started, drill to 10m below the bedrock layer, lower the surface casing, and return the cement to the surface;

[0021] S12, Second opening: Drill to a depth of 30m-50m below the landing point A, lower the production casing, and return the cement to 200m above the target layer in the horizontal section; make a hole and expand the hole at the landing point A in the inclined section, and the hole diameter should be greater than 0.5m.

[0022] Preferably, the dogleg angle of the inclination section during the secondary opening process of the drainage and production well does not exceed 1° / 30m, and the azimuth angle remains unchanged.

[0023] Preferably, the drilling construction process of the engineering well in step S2 includes:

[0024] S21, First opening: Drill to 10m below the bedrock layer, lower the surface casing, and return the cement to the surface;

[0025] S22, Second opening: Drill to the target layer in the horizontal section, run the technical casing, and cement the well to 200m above the target layer in the horizontal section;

[0026] S23, third drilling: Directional connection to the landing point A of the production well and then increase the inclination drilling to the designed depth; to facilitate cementing of the main borehole of the horizontal well, fill the cave created by the production well with sand after connection, and the sand filling depth is higher than the top surface of the created cave. After filling with sand, cement plug is driven on it. After the pressure test is qualified, casing is installed in the main borehole of the horizontal well for cementing.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention combines the advantages and disadvantages of L-type horizontal wells and U-type horizontal wells. By constructing engineering wells and drainage wells in the same well site, the drainage wells are connected to the L-type wells at landing point A. When the screw pump is lowered from the drainage well to drain water, the two wells produce gas at the same time. Compared with the U-type well, the present invention saves one well site and one pilot hole, and the coalbed methane transmission pipeline is simple, which reduces the development cost; compared with the L-type horizontal well, the dogleg degree is reduced, and the screw pump is lowered below the elevation of point A, which generally improves the drainage and gas production effect.

[0029] (2) The well structure of the present invention reduces the well site, drilling rigs, roads, underground second pilot hole construction and drainage pipelines, reduces the preparation time for well construction, improves its applicability in mountainous and hilly areas, reduces land occupation, and reduces costs and increases efficiency.

[0030] (3) The drainage well of the present invention has a small dogleg degree, which can reduce the number of pump inspections and increase drainage stability.

[0031] (4) The drainage pump of the present invention is lowered below the coal seam to improve the coal seam gas recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of Embodiment 1 of the present invention;

[0033] In the figure: 1, drainage and production well; 11, inclination section; 2, engineering well; 21, horizontal section target layer; 3, well site; 4, coal seam. DETAILED DESCRIPTION

[0034] In order to facilitate those skilled in the art to understand the technical solution of the present invention, the technical solution of the present invention is further described in conjunction with the accompanying drawings of the specification.

[0035] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] Embodiment 1

[0037] See also Figure 1 This embodiment discloses a well type structure for proximal docking of coalbed methane in a single well field, including an engineering well 2 and a drainage well 1. The engineering well 2 and the drainage well 1 are opened in the same well field 3, and the engineering well 2 and the drainage well 1 can be docked and connected.

[0038] The drainage well 1 adopts a two-opening wellbore structure, including a deflecting section 11, which is connected to the engineering well 2 at the landing point A. Specifically, the first opening of the drainage well 1 is a vertical section pointing vertically downward, and the second opening of the drainage well 1 is an inclined deflecting section 11.

[0039] In some embodiments, the dogleg angle of the deflection section 11 of the drainage well 1 does not exceed 1° / 30m, and the azimuth angle remains unchanged, thereby reducing the number of pump inspections and increasing drainage stability.

[0040] In the specific embodiment of this embodiment, the second drilling construction process of the drainage well 1 is as follows: the first drilling is based on the well site 3, drilled to 10m below the bedrock layer, and the surface casing is lowered, and the cementing cement is returned to the ground. In the second drilling, drill to 30m-50m below the landing point A, and the production casing is lowered, and the cementing cement is returned to 200m above the horizontal section target layer 21; the landing point A of the inclined section 11 is used for hole making and expansion, and the cave diameter is greater than 0.5m. Among them, the target docking layer section of the drainage well 1 and the engineering well 2 adopts a slit production casing, such as a fiberglass pipe or a PVC pipe. The drainage well 1 of this embodiment is lowered 30m-50m below the landing point A, so that the drainage pump can be lowered below the coal seam 4, thereby improving the gas recovery rate of the coal seam 4.

[0041] Engineering well 2 is an L-shaped well. Engineering well 2 adopts a three-opening wellbore structure. Engineering well 2 includes a horizontal section target layer 21. The two ends of the horizontal section target layer 21 are landing point A and landing point B respectively. Landing point A is the point that connects with the drainage well 1.

[0042] In the specific implementation of this embodiment, the first opening is based on the same well site 3, drilled to 10m below the bedrock layer, lowered the surface casing, and cemented the cement back to the ground. The second opening is based on the first opening, drilled to the horizontal section target layer 21, lowered the technical casing, and cemented the cement back to 200m above the horizontal section target layer 21. The third opening is to increase the inclination drilling to the designed depth after directional docking to the landing point A of the drainage and production well 1; to facilitate cementing of the main wellbore of the horizontal well, sand is filled in the cave created by the inclined well after connection, and the sand filling depth must be higher than the top surface of the created cave. After filling the sand, cement plugs are driven on it. After the pressure test is qualified, casing is lowered and cemented in the main wellbore of the horizontal well.

[0043] In some embodiments, the horizontal section target layer 21 of the engineering well 2 can be located at the top of the coal seam, in the coal seam, or at the bottom of the coal seam.

[0044] In some embodiments, landing point A is set at a low part of the coal seam structure, and landing point B is set at a high part of the coal seam structure. This setting is conducive to the fluid carrying sand and coal powder in the wellbore from the high landing point B to the low landing point A during the drainage process, and finally deposited in the sand settling pipe below the landing point A. After a certain period of drainage, the sand settling pipe is taken out to the ground for cleaning. Prevent coal powder and the like from accumulating in the wellbore and causing wellbore blockage and blocking the seepage channel. At the same time, landing point A is located at a low position, which can minimize the residual pressure of the formation, increase gas production and coal seam gas control effect.

[0045] This embodiment combines the advantages and disadvantages of L-type horizontal wells and U-type horizontal wells. By constructing the engineering well 2 and the drainage well 1 in the same well site 3, the drainage well 1 is connected to the L-type well at the landing point A. When the screw pump is lowered from the drainage well 1 to drain water, the two wells produce gas at the same time. Compared with the U-type well, the present invention saves one well site 3 and one pilot hole, and the coalbed methane transmission pipeline is simple, which reduces the development cost; compared with the L-type horizontal well, the dogleg degree is reduced, and the screw pump is lowered below the elevation of point A, which generally improves the drainage and gas production effect.

[0046] The well structure of this embodiment reduces the well site 3, drilling rigs, roads, underground second pilot hole construction and production pipelines, reduces the preparation time for well construction, improves its applicability in mountainous and hilly areas, reduces land occupation, reduces costs and increases efficiency.

[0047] Embodiment 2

[0048] This embodiment also discloses a method for opening a well structure for the proximal end of the single well field 3 connected to the coalbed methane as described in the first embodiment, comprising the following steps:

[0049] S1. Drilling construction of the drainage well 1 is carried out in the set well site 3.

[0050] S2. Drilling construction of the engineering well 2 is carried out in the same well site 3, and the engineering well 2 is connected with the drainage well 1.

[0051] S3. Place a drainage pump in the drainage well 1 to drain water, and extract gas in the drainage well 1 and the engineering well 2 at the same time.

[0052] The drilling construction process of the drainage well 1 in step S1 includes:

[0053] S11. Once the well is started, drill to 10m below the bedrock layer, lower the surface casing, and return the cement to the surface.

[0054] S12, Second opening: Drill to a depth of 30m-50m below the landing point A, lower the production casing, and return the cement to 200m above the target layer 21 in the horizontal section; make a hole and expand the hole at the landing point A of the target inclined section 11, with the hole diameter greater than 0.5m.

[0055] The dogleg angle of the inclined section 11 during the secondary opening process of the production well 1 does not exceed 1° / 30m, and the azimuth angle remains unchanged.

[0056] The drilling construction process of the engineering well 2 in step S2 includes:

[0057] S21, First opening: Drill to 10m below the bedrock layer, lower the surface casing, and return the cement to the ground.

[0058] S22, second opening: Drill to the target layer 21 in the horizontal section, lower the technical casing, and return the cement to 200m above the target layer 21 in the horizontal section.

[0059] S23, third opening: Directional connection to landing point A of drainage and production well 1 is followed by increasing inclination drilling to the designed depth; to facilitate cementing of the main borehole of the horizontal well, sand is filled in the cave created by drainage and production well 1 after connection, and the sand filling depth is higher than the top surface of the created cave. After sand filling, cement plugs are driven on top. After the pressure test is qualified, casing is installed in the main borehole of the horizontal well for cementing.

[0060] After the L-type well was staged fracturing, cement plugs were drilled through the drainage well 1 and the L-type well in turn, and the wells were dredged to remove the sand filling in the wells, so as to achieve reconnection with the vertical well.

[0061] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0062] The embodiments described above only represent implementation methods of the invention. The protection scope of the present invention is not limited to the embodiments described above. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A well type structure for connecting the proximal end of a single well field to coalbed methane, characterized by: The invention comprises an engineering well (2) and a drainage well (1), wherein the engineering well (2) and the drainage well (1) are opened in the same well field (3), and the engineering well (2) and the drainage well (1) can be butted and connected; the drainage well (1) adopts a two-opening wellbore structure, including a deflection section (11), and the deflection section (11) is connected with the engineering well (2) at a landing point A; the engineering well (2) is an L-shaped well, and the engineering well (2) adopts a three-opening wellbore structure, and the engineering well (2) includes a horizontal section target layer (21), and the two ends of the horizontal section target layer (21) are landing points A and landing points B respectively, and the landing point A is the point for butting with the drainage well (1), and the landing point A of the horizontal section target layer (21) of the L-shaped well is located at a low part of the coal seam structure, and the landing point B is located at a high part of the coal seam structure.

2. The well structure for the single well field proximal connection with coalbed methane according to claim 1 is characterized by: The target layer (21) of the horizontal section of the engineering well (2) can be located at the top of the coal seam, in the coal seam or at the bottom of the coal seam.

3. A method for opening a well structure for coalbed methane with a single well field proximal connection according to claim 1 or 2, characterized in that: The steps include: S1, drilling a drainage well (1) in a set well site (3); S2, drilling a project well (2) in the same well site (3), and connecting the project well (2) with the drainage well (1); S3. A drainage pump is placed in the drainage well (1) to drain water, and gas is extracted simultaneously in the drainage well (1) and the engineering well (2).

4. The method for opening a well structure for a single well field near-end connection with coalbed methane according to claim 3, characterized in that: The drilling construction process of the drainage well (1) in step S1 includes: S11, once started, drill to 10m below the bedrock layer, lower the surface casing, and return the cement to the surface; S12, second opening: Drill to a depth of 30m-50m below the landing point A, lower the production casing, and return the cement to 200m above the target layer (21) in the horizontal section; make a hole and expand the hole at the landing point A in the inclined section (11), and the hole diameter is greater than 0.5m.

5. The method for opening a well structure for a single well field near-end connection with coalbed methane according to claim 4, characterized in that: The dogleg angle of the inclination section (11) during the secondary opening process of the production and drainage well (1) does not exceed 1° / 30m, and the azimuth angle remains unchanged.

6. The method for opening a well structure for a single well field near-end connection with coalbed methane according to claim 3, characterized in that: The drilling construction process of the engineering well (2) in step S2 includes: S21, First opening: Drill to 10m below the bedrock layer, lower the surface casing, and return the cement to the surface; S22, second opening: Drill to the target layer (21) in the horizontal section, run the technical casing, and cement the well to 200m above the target layer (21) in the horizontal section; S23, third drilling: Directional connection to the landing point A of the production well (1) is followed by increasing the inclination drilling to the designed depth; to facilitate cementing of the main borehole of the horizontal well, sand is filled in the cave created by the production well (1) after connection, and the sand filling depth is higher than the top surface of the created cave. After sand filling, cement plugs are driven on the cave. After the pressure test is qualified, casing is installed in the main borehole of the horizontal well for cementing.

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