Coal bed methane well re-fracturing device and method

Abstract

The application discloses a coal bed gas well repeated fracturing device and method, which comprises a main pipeline, a plurality of sliding sleeves are slidably arranged in the main pipeline, a circle of support blocks is arranged below each sliding sleeve, a plurality of connecting ribs penetrating through the side walls of the sliding sleeves are arranged between the main pipelines above and below the sliding sleeves, a lower water outlet hole is arranged at the lower end of the main pipeline, and a circle of side water outlet holes are arranged in the side walls above the sliding sleeves. Compared with the prior art, the application realizes effective support of the well wall, accurate regulation of the flow, step-by-step injection of the fracturing liquid, and improvement of the system reliability and service life, so that the fracturing operation is more efficient and safe, and can better adapt to different geological conditions.

Description

Technical Field

[0001] This invention relates to the field of coal gas extraction technology, specifically to a coalbed methane well repeated fracturing device and method. Background Technology

[0002] Coalbed methane (CBM) is an important natural gas resource. To improve the productivity and extend the lifespan of CBM wells, repeated fracturing technology has gained increasing attention. However, existing technologies have several shortcomings: When performing multiple fracturing operations, existing fracturing devices cannot effectively control the direction and size of fractures, resulting in fracturing effects that are difficult to achieve the desired results. These deficiencies hinder the improvement of CBM recovery and productivity. During repeated fracturing, insufficient support measures for the wellbore in existing technologies can easily lead to wellbore instability and even collapse. This affects the long-term stable operation of CBM wells and increases maintenance costs. Existing technologies also have problems with fluid injection and control. The inability to precisely adjust the flow rate and injection direction of the fracturing fluid results in uneven distribution of the fracturing fluid, affecting comprehensive coverage of the coal seam. Some equipment is susceptible to wear and corrosion during fracturing operations, reducing equipment lifespan and increasing maintenance costs and operational risks.

[0003] Therefore, it is necessary to provide a coalbed methane well repeated fracturing device and method to solve the problems mentioned in the background art. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution: a coalbed methane well repeated fracturing device, including a main pipeline, in which multiple sliding sleeves are slidably provided, and a ring of support blocks is distributed below each sliding sleeve. The main pipeline above and below the sliding sleeves is fixed by multiple connecting ribs penetrating the side walls of the sliding sleeves, and a lower water outlet is provided at the lower end of the main pipeline.

[0005] Furthermore, as a preferred embodiment, a ring of side water outlet holes is formed on the side wall above the sliding sleeve.

[0006] Furthermore, as a preferred embodiment, the lower part of the sliding sleeve is a downwardly tapering frustum-shaped inclined surface, and the side of the support block near the sliding sleeve is a wedge block that can fit into the inclined surface.

[0007] Furthermore, as a preferred embodiment, the inclined surface has multiple slots, and each support block is slidably embedded into the corresponding slot, with the bottom of the support block slidably connected to the main pipe.

[0008] Furthermore, preferably, the inclined surface is fitted with a polytetrafluoroethylene gasket.

[0009] Furthermore, preferably, the lower part of the sliding sleeve is connected to the main pipe via a spring, the spring providing an elastic force that causes the sliding sleeve to slide upward.

[0010] Furthermore, preferably, the inner diameter of the upper part of the sliding sleeve is larger than the inner diameter of the main pipe.

[0011] Furthermore, as a preferred embodiment, the springs corresponding to the multiple sliding sleeves distributed in the main pipe have progressively increasing elastic force from top to bottom.

[0012] Furthermore, as a preferred embodiment, the lower water outlet is fixedly supported by an upwardly contracting conical water-stop cone at its axial position. The maximum outer diameter of the water-stop cone is smaller than the inner diameter of the lower water outlet, and the maximum outer diameter of the water-stop cone is larger than the inner diameter of the bottom of the sliding sleeve.

[0013] Repeated fracturing methods for coalbed methane wells include:

[0014] S1. After determining the well location on-site, arrange the well locations to ensure the wellhead position is reasonable. Conduct precise measurements to confirm parameters such as the well's coordinates and depth, and then use the drilling rig to carry out drilling operations;

[0015] S2. Vertically install the main pipeline in the coalbed methane well, ensuring that the lower end of the main pipeline is properly positioned at the bottom of the well, and inject fracturing fluid into the main pipeline;

[0016] S3. By using a layer-by-layer fracturing design, the fracturing fluid pressure is gradually increased, so that multiple sliding sleeves from top to bottom sequentially spray fracturing fluid onto the sidewall of the coalbed methane well. Before each sliding sleeve sprays fracturing fluid, the corresponding support block is in close contact with the sidewall of the coalbed methane well, which improves the support force on the well wall and prevents the pressure of the fracturing fluid from causing the main pipeline to deviate.

[0017] S4. At the bottom of the sliding sleeve at the lowest point of the main pipeline, the bottom of the sliding sleeve is gradually blocked by an upward-contracting conical water-stop cone to control the water output of the lower outlet hole. This allows for precise adjustment of the flow rate of fracturing fluid flowing to the bottom of the well. When the water-stop cone completely closes the lower outlet hole, all the fracturing fluid will be ejected through the side outlet hole of each sliding sleeve. This causes the fracturing pressure on the sidewall of the coalbed methane well to gradually increase from top to bottom, which helps maintain the stability of the fracturing operation, forms more targeted and effective fractures, improves the fracturing effect, and increases the permeability and production capacity of coalbed methane.

[0018] S5. Stop injecting fracturing fluid. After the fracturing fluid has diffused and exposed the fracture, resume fracturing operations to further expand the fracture.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] In this invention, a layer-by-layer design allows multiple sliding sleeves to sequentially spray fracturing fluid onto the sidewall of the coalbed methane well from top to bottom, achieving multi-level fracturing of the coal seam. This helps optimize fracturing effects, reduce overall bottomhole pressure, minimize excessive local fracturing of the coalbed methane, and limit fluid intrusion into unfractured layers, thereby improving the productivity and permeability of the coalbed methane well.

[0021] In this invention, the device, through the sliding sleeve and support block, can abut against the sidewall of the coalbed methane well during fracturing, effectively increasing the support force on the well wall. This helps prevent well wall collapse or instability, improves well wall stability, and ensures that the well wall can withstand the pressure from the fracturing fluid during fracturing operations without adverse reactions.

[0022] In this invention, the design of the water-stop cone gradually blocks the bottom of the sliding sleeve, controlling the water flow from the lower outlet hole. This allows for precise adjustment of the fracturing fluid flow rate towards the bottom of the well, resulting in a more concentrated spray of the fracturing fluid onto the sidewall of the coalbed methane well, forming more targeted and effective fractures, thereby improving the fracturing effect. Attached Figure Description

[0023] Figure 1 A schematic diagram of a repeated fracturing device for a coalbed methane well.

[0024] Figure 2 A schematic diagram of the cross-section of the main pipe when the sliding sleeve slides upwards;

[0025] Figure 3 This is a structural schematic diagram of the main pipeline cross-section when the sliding sleeve slides down.

[0026] Figure 4 This is a schematic diagram of the sliding sleeve.

[0027] Figure 5 This is a schematic diagram of a fracturing operation.

[0028] 1. Main pipe; 2. Sliding sleeve; 21. Side outlet; 22. Inclined surface; 23. Gasket; 24. Slot; 3. Support block; 4. Connecting rib; 5. Bottom outlet; 6. Spring; 7. Water-stop cone. Detailed Implementation

[0029] Please see Figure 1 In this embodiment of the invention, the coalbed methane well repeated fracturing device includes a main pipeline 1, in which a plurality of sliding sleeves 2 are slidably provided, and a ring of support blocks 3 is distributed below each sliding sleeve 2. The main pipeline 1 above and below the sliding sleeve 2 is fixed by a plurality of connecting ribs 4 penetrating the side wall of the sliding sleeve 2. A lower water outlet hole 5 is provided at the lower end of the main pipeline 1.

[0030] Please see Figure 2 and Figure 3In this embodiment, a ring of side water outlet holes 21 is formed on the side wall above the sliding sleeve 2. When the sliding sleeve 2 slides upward, the side water outlet holes 21 are embedded in the main pipe 1. When the sliding sleeve 2 slides downward, the side water outlet holes 21 are exposed outside the main pipe 1. Fracturing fluid can be sprayed out from the side of the corresponding sliding sleeve 2 to fracture the side wall of the coalbed methane well.

[0031] Please see Figure 4 In this embodiment, the lower part of the sliding sleeve 2 is a downwardly contracting frustum-shaped inclined surface 22, and the side of the support block 3 near the sliding sleeve 2 is a wedge that can fit against the inclined surface 22. That is, when the sliding sleeve 2 slides downward, it can push the support block 3 outward, so that the support block 3 can abut against the sidewall of the coalbed methane well. This can increase the support force on the well wall during fracturing, help prevent well wall collapse or instability, improve the stability of the well wall, more effectively transfer the energy and force of the fracturing fluid to the well wall, guide the fracturing fluid to the target area, reduce waste and improve operational efficiency, and improve the fracturing effect.

[0032] In this embodiment, the inclined surface 22 has multiple slots 24, and each support block 3 is slidably embedded into the corresponding slot 24. The bottom of the support block 3 is slidably connected to the main pipe 1. This allows the support block 3 to remain in contact with the sliding sleeve 2, ensuring that the support block 3 can leave the well wall when the sliding sleeve 2 slides upward, facilitating the movement and retrieval of the device.

[0033] In this embodiment, a polytetrafluoroethylene (PTFE) gasket 23 is attached to the surface of the inclined surface 22. This reduces the friction between the sliding sleeve 2 and the support block 3, helps to reduce sliding resistance, ensures smoother movement of the support block 3 during sliding, and improves the reliability and lifespan of the system.

[0034] Please see Figure 2 and Figure 3 In this embodiment, the lower part of the sliding sleeve 2 is connected to the main pipe 1 via a spring 6, which provides the elastic force for the sliding sleeve 2 to slide upward. This ensures that the sliding sleeve 2 remains in an upward position under normal operating conditions, preventing the support block 3 from accidentally contacting the well wall.

[0035] In this embodiment, the inner diameter of the upper part of the sliding sleeve 2 is larger than the inner diameter of the main pipe 1. When the fluid passes through the position of the sliding sleeve 2, due to the larger inner diameter of the sliding sleeve 2, the fluid will generate a certain dynamic pressure at this location. Due to the difference in dynamic pressure between the upper and lower parts, the dynamic pressure above the sliding sleeve 2 is larger, while the dynamic pressure below is smaller. This results in a net downward thrust, pushing the sliding sleeve 2 downward. In this way, the flow of fluid indirectly transmits the tension that enables the support block 3 to resist the sidewall of the coalbed methane well by pushing the sliding sleeve 2. Furthermore, when the sliding sleeve 2 moves downward and the side outlet hole 21 is exposed outside the main pipe 1, fracturing fluid can be sprayed from the corresponding side of the sliding sleeve 2 to fracture the sidewall of the coalbed methane well.

[0036] In this embodiment, the springs 6 corresponding to the multiple sliding sleeves 2 distributed in the main pipeline 1 have progressively increasing elastic force from top to bottom. That is, as the fluid pressure inside the main pipeline 1 gradually increases, the multiple sliding sleeves 2 from top to bottom sequentially spray fracturing fluid onto the sidewall of the coalbed methane well, so that the coalbed methane well is subjected to sequential fracturing pressure from top to bottom. This design can realize layer-by-layer fracturing of the coalbed methane well, which can effectively reduce the overall pressure at the bottom of the well and reduce local over-fracturing of the coalbed methane. This can better limit the intrusion of liquid into unfractured layers and reduce the possibility of coalbed methane well collapse.

[0037] In this embodiment, a tapered, upward-contracting water-stop cone 7 is fixedly mounted at the axial position of the lower water outlet 5. The maximum outer diameter of the water-stop cone 7 is smaller than the inner diameter of the lower water outlet 5, and the maximum outer diameter of the water-stop cone 7 is larger than the inner diameter of the bottom of the sliding sleeve 2. That is, when the sliding sleeve 2 at the lowest end of the main pipeline 1 slides downward, the water-stop cone 7 gradually blocks the bottom of the sliding sleeve 2, causing the water flow from the lower water outlet 5 to decrease until it is completely closed. At this time, all the fracturing fluid in the main pipeline 1 is sprayed out to the side water outlet 21 of each sliding sleeve 2. This helps to control and regulate the flow rate of fracturing fluid to the bottom of the well, allowing the fracturing fluid to be sprayed more concentratedly onto the sidewall of the coalbed methane well, forming more targeted and effective fractures, improving the fracturing effect, and increasing the permeability and production capacity of coalbed methane.

[0038] Please see Figure 5 Repeated fracturing methods for coalbed methane wells, including

[0039] S1. After determining the well location on-site, arrange the well locations to ensure the wellhead position is reasonable. Conduct precise measurements to confirm parameters such as the well's coordinates and depth, and then use the drilling rig to carry out drilling operations;

[0040] S2. Vertically install the main pipeline 1 in the coalbed methane well, ensuring that the lower end of the main pipeline 1 is properly positioned at the bottom of the well, and inject fracturing fluid into the main pipeline 1.

[0041] S3. By using a layer-by-layer fracturing design, the fracturing fluid pressure is gradually increased, so that multiple sliding sleeves 2 from top to bottom sequentially spray fracturing fluid onto the sidewall of the coalbed methane well. Before each sliding sleeve 2 sprays fracturing fluid, the corresponding support block 3 is in close contact with the sidewall of the coalbed methane well, which improves the support force on the well wall and prevents the pressure of the fracturing fluid from causing the main pipeline 1 to deviate.

[0042] S4. Below the sliding sleeve 2 at the lowest end of the main pipeline 1, the bottom of the sliding sleeve 2 is gradually blocked by the upward contracting conical water-stop cone 7, controlling the water output of the lower water outlet 5, and realizing precise adjustment of the fracturing fluid flow to the bottom of the well. When the water-stop cone 7 completely closes the lower water outlet 5, the fracturing fluid will be sprayed out through the side water outlet 21 of each sliding sleeve 2, so that the fracturing pressure on the sidewall of the coalbed methane well gradually increases from top to bottom, which helps to maintain the stability of the fracturing operation, form more targeted and effective fractures, improve the fracturing effect, and increase the permeability and production capacity of coalbed methane.

[0043] S5. Stop injecting fracturing fluid. After the fracturing fluid has diffused and exposed the fracture, resume fracturing operations to further expand the fracture.

[0044] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A coalbed methane well repeated fracturing device, comprising a main pipeline (1), characterized in that, The main pipe (1) is slidably provided with multiple sliding sleeves (2), and a ring of support blocks (3) is distributed below each sliding sleeve (2). The main pipe (1) above and below the sliding sleeve (2) is fixed by multiple connecting ribs (4) that penetrate the side wall of the sliding sleeve (2). The lower end of the main pipe (1) is provided with a lower water outlet hole (5). A ring of side water outlet holes (21) is opened on the side wall above the sliding sleeve (2). A tapered water-stop cone (7) that shrinks upward is fixedly mounted on the axial position of the lower water outlet hole (5). The maximum outer diameter of the water-stop cone (7) is smaller than the inner diameter of the lower water outlet hole (5), and the maximum outer diameter of the water-stop cone (7) is larger than the inner diameter of the bottom of the sliding sleeve (2). The lower part of the sliding sleeve (2) is a downwardly tapering frustum-shaped inclined surface (22), and the side of the support block (3) near the sliding sleeve (2) is a wedge block that can fit with the inclined surface (22); The method for repeated fracturing of coalbed methane wells using the above-mentioned device includes the following steps: S1. After determining the well location on site, arrange the well location to ensure that the wellhead position is reasonable, conduct accurate measurements to confirm the well coordinates and well depth and other parameters, and use the drilling rig to carry out drilling operations. S2. The main pipeline (1) is vertically installed in the coalbed methane well, ensuring that the lower end of the main pipeline (1) is properly positioned at the bottom of the well, and fracturing fluid is injected into the main pipeline (1). S3. By using the layer-by-layer fracturing design, the fracturing fluid pressure is gradually increased, so that multiple sliding sleeves (2) from top to bottom spray fracturing fluid onto the sidewall of the coalbed methane well in sequence. Before each sliding sleeve (2) sprays fracturing fluid, the corresponding support block (3) is in close contact with the sidewall of the coalbed methane well, which improves the support force on the well wall and avoids the pressure of the fracturing fluid causing the main pipeline (1) to deviate. S4. At the bottom of the sliding sleeve (2) at the bottom of the main pipeline (1), the bottom of the sliding sleeve (2) is gradually blocked by the upward contraction of the conical water-stop cone (7), and the water output of the lower water outlet (5) is controlled to achieve precise adjustment of the flow rate of the fracturing fluid flowing to the bottom of the well. When the water-stop cone (7) completely closes the lower water outlet (5), the fracturing fluid will be sprayed out through the side water outlet (21) of each sliding sleeve (2), so that the fracturing pressure of the coalbed methane well sidewall gradually increases from top to bottom, which helps to maintain the stability of the fracturing operation, form more targeted and effective fractures, improve the fracturing effect, and increase the permeability and production capacity of coalbed methane. S5. Stop injecting fracturing fluid. After the fracturing fluid has diffused and exposed the fracture, resume fracturing operations to further expand the fracture.

2. The coalbed methane well repeated fracturing device according to claim 1, characterized in that, Multiple slots (24) are provided in the inclined surface (22), and each support block (3) is slidably embedded in the corresponding slot (24). The bottom of the support block (3) is slidably connected to the main pipe (1).

3. The coalbed methane well repeated fracturing device according to claim 1, characterized in that, The inclined surface (22) is fitted with a polytetrafluoroethylene gasket (23).

4. The coalbed methane well repeated fracturing device according to claim 1, characterized in that, The lower part of the sliding sleeve (2) is connected to the main pipe (1) by a spring (6), which provides an elastic force to make the sliding sleeve (2) slide upward.

5. The coalbed methane well repeated fracturing device according to claim 1, characterized in that, The inner diameter of the upper part of the sliding sleeve (2) is larger than the inner diameter of the main pipe (1).

6. The coal bed gas well re-fracturing apparatus of claim 1, wherein, The springs (6) corresponding to the multiple sliding sleeves (2) distributed in the main pipe (1) have increasing elastic force from top to bottom.

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