A cable-type full-bore fracturing sliding sleeve system and its construction method

Abstract

This invention discloses a cable-type full-bore fracturing sliding sleeve system and its construction method, relating to the fields of oil and gas well cementing and fracturing operations. The system includes: a sliding sleeve structure comprising a first casing, a second casing, and a third casing connected in sequence, as well as a fourth casing and a fifth casing connected in sequence; a bridge plug structure comprising: an inner tie rod with its bottom end connected to the top end of a central tube; a fixing ring fitted onto the outer wall of the bottom end of the central tube; a sphere supported on the inner wall of the central tube; a push rod fitted onto the outer wall of the central tube; the outer wall of the push rod having a first inclined surface and a first serrated surface below it; a seat ring and a push rod base both fitted onto the outer circumference of the push rod; the inner wall of the seat ring having a second inclined surface; multiple slots arrayed on the top end of the push rod base; a second serrated surface on the inner wall of the push rod base; a stepped groove at the bottom of the push rod base; and a fixing ring located within the stepped groove. This solution achieves precise positioning, reliable sealing, and convenient opening of the sliding sleeve, while simplifying the construction process and reducing operating costs and risks.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well cementing and fracturing operations, and in particular to a cable-type full-bore fracturing sliding sleeve system and its construction method. Background Technology

[0002] In the development of oil and gas wells, especially for low-permeability and unconventional oil and gas reservoirs, staged fracturing technology is a core means to improve single-well production and ultimate recovery rate. As one of the key tools in staged fracturing operations, the structural design, operation method, and wellbore condition after fracturing directly affect the efficiency of fracturing operations, sealing reliability, operating costs, and the smooth progress of subsequent production operations.

[0003] Currently, existing fracturing sliding sleeve technology mainly suffers from the following problems: (1) Complex operation process and low construction efficiency. Some traditional fracturing sliding sleeves use a ball-dropping and pressurizing method to open the sliding sleeve step by step. This method requires dropping balls of different sizes into the wellbore in sequence, and the balls cooperate with the ball seats in the corresponding sliding sleeves to achieve sealing and pressurization opening. However, this method requires extremely high positioning accuracy for the balls, and problems such as ball jamming, ball seat wear, or premature setting are prone to occur during construction, resulting in the sliding sleeve not being able to open normally. In addition, the ball-dropping operation process is cumbersome, and the step-by-step ball dropping takes a long time, which significantly increases the construction time and operational risks. Some other sliding sleeves use a complex mechanical setting method, which requires the use of a special tubing string structure to achieve setting and opening. The tubing string structure is complex, the construction cost is high, and the technical requirements for operators are high, which is not conducive to fast and efficient on-site operations.

[0004] (2) Residual tools after fracturing affect the full borehole diameter. After fracturing operations are completed, most existing fracturing sleeves will have their core functional components (such as ball seats, sealing components, locking mechanisms, etc.) permanently remaining in the wellbore. These residual components will cause local reduction in the inner diameter of the wellbore, forming a "reduced diameter" area, which will seriously affect subsequent well workover, production logging, secondary fracturing and stimulation, and the running and passage of subsequent tools. If drilling and grinding operations are carried out to remove the residual components, it will not only increase the additional operation cycle and cost, but may also damage the casing, increasing the downhole operation risk and overall development cost.

[0005] (3) Insufficient sealing reliability and adaptability. Some existing tools using expandable sealing elements have defects in expansion accuracy and sealing stability. For example, the contact pressure between the expanded sealing element and the inner wall of the sliding sleeve or casing is uneven, which can easily lead to sealing failure during high-pressure fracturing operations, resulting in fluid leakage, inability to effectively pressurize and open the sliding sleeve, and even fracturing operation failure. At the same time, the expansion parameters of these sealing tools are often difficult to accurately adapt to the matching requirements of cementing casing and sliding sleeve of specific sizes, resulting in poor versatility and difficulty in meeting the precise fracturing requirements under different well conditions.

[0006] In summary, there is an urgent need to develop a fracturing sleeve and supporting construction method that is simple in structure, easy to operate, reliable in sealing, and can achieve full-bore wellbore fracturing after fracturing, in order to overcome the above-mentioned defects of existing technologies and improve the overall efficiency and economic benefits of segmented fracturing operations in oil and gas wells. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a cable-type full-bore fracturing sliding sleeve system and construction method, which achieves precise positioning, reliable sealing, and convenient opening of the sliding sleeve, while simplifying the construction process and reducing operating costs and risks.

[0008] In order to achieve the objective of this invention, the following solution is proposed: A cable-type full-bore fracturing sliding sleeve system includes a sliding sleeve structure and a bridge plug structure.

[0009] The sliding sleeve structure includes a first sleeve, a second sleeve, and a third sleeve connected in sequence, as well as a fourth sleeve and a fifth sleeve connected in sequence. The outer wall of the second sleeve has multiple fracturing holes in an array. The outer wall of the fourth sleeve is in close contact with the inner wall of the second sleeve, and the two are connected by multiple shear pins. The outer wall of the fifth sleeve is in close contact with the inner wall of the third sleeve. The inner wall of the fourth sleeve is provided with a support ring. The bridge plug structure includes a central tube, a retaining ring, a push rod base, a seat ring, an inner tie rod, and a push rod. The bottom end of the inner tie rod is coaxially connected to the top end of the central tube by assembly or pin. The retaining ring is fitted onto the outer wall of the bottom end of the central tube. The inner wall of the central tube carries a sphere. The push rod is fitted onto the outer wall of the central tube. The outer diameter of the top end of the central tube is larger than the inner diameter of the bottom end of the push rod. The outer wall of the push rod has a first inclined surface and a first serrated surface below it. The seat ring and the push rod base are both fitted onto the outer circumference of the push rod, with the seat ring located on top of the push rod base. The inner wall is provided with a second inclined surface that fits against the first inclined surface. The top of the push rod base has multiple slots arranged in an array. The inner wall of the push rod base is provided with a second serrated surface that meshes with the first serrated surface. The central tube and the fixing ring are both inserted into the push rod base. The bottom of the push rod base is provided with a stepped groove. The fixing ring is located in the stepped groove. When the cable is connected to the top of the inner pull rod, the bridge plug structure is lowered to the preset position in the sliding sleeve structure, and the push rod is subjected to a downward force, it is used to move the push rod into the push rod base, thereby causing the seat ring to expand and lock the inner wall of the fourth sleeve.

[0010] Furthermore, the inner tie rod is equipped with a pin, which is located above the ball.

[0011] Furthermore, the bottom of the seat ring is integrally formed with a collar, and the top of the push rod base is located inside the collar.

[0012] Furthermore, the bridge plug structure also includes a locking ring, which is located between the push rod and the push rod base. The serrations on the inner wall of the locking ring engage with the first inclined surface, and the serrations on the outer wall of the locking ring engage with the second inclined surface.

[0013] A construction method employing the aforementioned cable-type full-bore fracturing sliding sleeve system includes the following steps: The bridge plug structure is lowered into a preset position within the sliding sleeve structure using a cable; A downward force is applied to the push rod, causing it to move into the push rod base. The first inclined surface presses against the seat ring, which in turn causes the seat ring to expand and lock into the inner wall of the fourth sleeve. Use the cable to lift the inner pull rod, causing it to detach from the central tube; A downward force is applied to the central tube and the sphere, causing multiple shear pins to break. The remaining bridge plug structure, the fourth sleeve, and the fifth sleeve move downward as a whole, thereby opening the fracturing hole.

[0014] The beneficial effects of this invention are as follows: 1. Convenient and efficient operation: The tool is lowered using a cable, which accurately positions the target sliding sleeve. The expandable tool can be expanded and the setting tool can be released by igniting the cable. There is no need for complicated mechanical operation or ball throwing process, which greatly simplifies the construction steps and improves the construction efficiency. 2. Reliable sealing: The expandable tool expands from 98mm to 112mm, forming an interference fit with the 108mm inner diameter sliding sleeve support ring, resulting in excellent sealing performance. This effectively prevents fluid leakage during pressurization, ensuring smooth opening of the sliding sleeve and stable fracturing operations. Referring to the sealing principle of self-expanding seals, the sealing reliability and stability are further improved. 3. Full-bore with no residue: After fracturing, the sliding sleeve dissolves on its own, leaving no solid residue. This ensures that the wellbore remains in a full-bore state, solving the problem of residual parts affecting subsequent operations after fracturing of existing sliding sleeves. This reduces operational risks and subsequent maintenance costs. Its dissolvable characteristics are based on the design concept of dissolvable sleeves, achieving residue-free operation. 4. Strong adaptability: The expansion parameters of the expandable tool are precisely matched with the size of the sliding sleeve, ensuring the stability and reliability of the construction process. It can be widely used in the staged fracturing operations of various oil and gas wells. 5. Controllable cost: The simplified construction tools and processes reduce tool recycling and subsequent cleaning operations. At the same time, the design of the dissolvable sliding sleeve reduces the cost of handling residual parts, resulting in a significant reduction in overall construction costs. Attached Figure Description

[0015] Figure 1 The external structural diagram of the sliding sleeve structure is shown; Figure 2 A cross-sectional view of the sliding sleeve structure is shown; Figure 3 An external structural diagram of one type of bridge plug structure is shown; Figure 4 A cross-sectional view of one type of bridge plug structure is shown; Figure 5 for Figure 4 Enlarged view of a portion of point A in the middle; Figure 6 A diagram of one type of push rod structure is shown; Figure 7 A diagram of one type of push rod base structure is shown; Figure 8 An external structural diagram of another bridge plug structure is shown; Figure 9 Another cross-sectional view of the bridge plug structure is shown; Figure 10 for Figure 9 Enlarged view of a section at point B in the middle; Figure 11 Another external structure diagram of the push rod base is shown; Figure 12 Another internal structure diagram of the push rod base is shown; Figure 13 Another push rod structure diagram is shown; Figure 14 A diagram of the locking ring structure is shown; Figure 15 A schematic diagram is shown below the bridge plug structure and inside the sliding sleeve structure. Detailed Implementation

[0016] Example 1 like Figure 15 As shown, this embodiment provides a cable-type full-bore fracturing sliding sleeve system. The system mainly includes two parts: a sliding sleeve structure 1 and a bridge plug structure 2. The two work together to achieve reliable setting, sealing, opening, and fracturing operations of the fracturing sliding sleeve.

[0017] like Figure 1 , Figure 2 As shown, the sliding sleeve structure 1 mainly consists of a first casing 11, a second casing 12, and a third casing 13 connected in sequence, as well as a fourth casing 14 and a fifth casing 15 connected in sequence. The first casing 11, second casing 12, and third casing 13 form the outer casing string, used to connect with the cementing casing and serving as the base for the fracturing channel. Multiple fracturing holes 121 are arranged in a circumferential array on the outer wall of the second casing 12, used to form a channel for fracturing fluid to enter the formation after the sliding sleeve is opened. The fourth casing 14 and the fifth casing 15 are interconnected to form a movable inner sliding sleeve assembly. The outer wall of the fourth casing 14 is tightly attached to the inner wall of the second casing 12, and the outer wall of the fifth casing 15 is tightly attached to the inner wall of the third casing 13. When the sliding sleeve is not open, the fourth casing 14 seals the fracturing holes 121, providing sealing and isolation.

[0018] like Figure 1 , Figure 2As shown, the fourth sleeve 14 and the second sleeve 12 are connected and fixed by multiple shear pins 16. The shear pins 16 break when subjected to a predetermined shear force, thereby realizing the movement of the inner sliding sleeve assembly and opening the fracturing hole 121. A support ring 141 is provided on the inner wall of the fourth sleeve 14. The support ring 141 is used to provide axial positioning and a sitting support surface for the seat ring 24 in the bridge plug structure 2, ensuring that the bridge plug structure 2 can be reliably anchored inside the sliding sleeve structure 1.

[0019] like Figure 3 , Figure 4 As shown, the bridge plug structure 2 is a special tool used for connecting to cables, being inserted into the sliding sleeve structure 1, and setting and opening the sliding sleeve. The bridge plug structure 2 includes a central tube 21, a retaining ring 22, a push rod base 23, a seat ring 24, an inner pull rod 25, and a push rod 26.

[0020] like Figure 3 , Figure 4 As shown, the central tube 21 is a hollow tubular structure, which carries a ball 211 inside. The ball 211 can block the internal channel of the central tube 21 to transmit hydraulic pressure during subsequent pressurization. The bottom end of the inner pull rod 25 is coaxially connected to the top end of the central tube 21 by assembly or pin connection. The top end of the inner pull rod 25 is connected to the cable through a connector, realizing the cable carrying and controlling the entire bridge plug structure 2. A pin 251 is also provided on the inner pull rod 25. The pin 251 is located above the ball 211 and plays a limiting and anti-dislodgement role to prevent the ball 211 from shifting unexpectedly.

[0021] It should be noted here that the bottom end of the inner tie rod 25 is coaxially connected to the top end of the central tube 21 by means of a pin connection. The pin refers to another set of shear pins 16.

[0022] A retaining ring 22 is fitted onto the outer wall of the bottom end of the central tube 21 to limit the axial position of the central tube 21 within the push rod base 23. A push rod 26 is fitted onto the outer wall of the central tube 21, with the outer diameter of the top end of the central tube 21 larger than the inner diameter of the bottom end of the push rod 26, ensuring that the central tube 21 will not dislodge when moving downwards relative to the push rod 26. Figures 4-6 As shown, the outer wall of the push rod 26 has a first inclined surface 261 and a first serrated surface 262 arranged sequentially from top to bottom. Note that the outer diameter of the first inclined surface 261 gradually decreases from top to bottom. The seat ring 24 and the push rod base 23 are both fitted onto the outer circumference of the push rod 26, with the seat ring 24 located at the top of the push rod base 23. The inner wall of the seat ring 24 has a second inclined surface 241 that fits against the first inclined surface 261. When the push rod 26 moves downward, the first inclined surface 261 slides along the second inclined surface 241, compressing the seat ring 24 and causing it to expand radially outward. Figure 4 , Figure 5 , Figure 7As shown, the inner wall of the push rod base 23 is provided with a second serrated surface 231 that meshes with the first serrated surface 262. After the two mesh, the push rod 26 can be locked in one direction relative to the push rod base 23, preventing the push rod 26 from retracting. Figure 7 As shown, the top of the push rod base 23 is also arrayed with multiple slots 232 to provide a certain elastic deformation capacity, which is beneficial for assembly and expansion. The bottom of the push rod base 23 is provided with a stepped groove, in which the retaining ring 22 is accommodated, defining the relative position of the central tube 21 and the push rod base 23.

[0023] To further enhance locking reliability, such as Figures 9-14 As shown, the bridge plug structure 2 may also include a locking ring 27. The locking ring 27 is located between the push rod 26 and the push rod base 23. The serrations on the inner wall of the locking ring 27 engage with the first inclined surface 261, and the serrations on the outer wall of the locking ring 27 engage with the second inclined surface 241, forming a bidirectional locking mechanism to ensure that the seat ring 24 is stable and securely anchored after expansion.

[0024] like Figure 8 , Figure 9 As shown, the bottom of the seat ring 24 can also be integrally formed with a collar 242, and the top of the push rod base 23 is located inside the collar 242, which is more conducive to the uniform expansion and load bearing of the seat ring 24.

[0025] In this embodiment, core components such as the fourth casing 14 and the fifth casing 15 in the sliding sleeve structure 1 can be made of soluble materials, such as soluble magnesium-aluminum alloy. The surface can be further coated with a coating layer to control the dissolution rate using hydrogen reduction technology. This design allows for self-dissolution triggered by environmental factors such as formation fluids and temperature after fracturing operations. After dissolution, the wellbore returns to its full-bore state without any solid residue, avoiding impact on subsequent well workover and production operations. The thickness and composition of the coating layer can be adjusted according to the duration of the fracturing operation to ensure that the sliding sleeve only begins to dissolve after fracturing is completed.

[0026] Example 2 This embodiment provides a method for fracturing operations using the above-described cable-type full-bore fracturing sliding sleeve system, specifically including the following steps: Step 1: Tool Insertion and Positioning After the preliminary preparations are completed, the top end of the inner tie rod 25 of the bridge plug structure 2 is connected to the cable via a connector. The entire bridge plug structure 2 is then lowered into the wellhead using the cable. Using a depth positioning device, the bridge plug structure 2 is precisely positioned within the pre-set location in the downhole sleeve structure 1 (as shown in the image). Figure 15 As shown in the figure, that is, the position of the seat ring 24 corresponding to the support ring 141 on the inner wall of the fourth sleeve 14.

[0027] Step 2: Expansion Sealing and Anchoring After the bridge plug structure 2 is in place, a downward force is applied to the push rod 26 via a cable or a gravity / ignition device connected to the cable. Under the action of the force, the push rod 26 moves inward into the push rod base 23, and the first inclined surface 261 on its outer wall slides along the second inclined surface 241 on the inner wall of the seat ring 24, generating a radial component force, thereby squeezing the seat ring 24 and causing it to expand radially. The expanded seat ring 24's outer wall tightly adheres to and locks the inner wall of the fourth sleeve 14, especially engaging with the support ring 141, forming a firm anchoring and seal. At the same time, the first serrated surface 262 engages with the second serrated surface 231, and the locking ring 27 engages with the first inclined surface 261 and the second inclined surface 241, locking the push rod 26 in one direction to ensure a long-lasting and stable seated state.

[0028] Step 3: Release the cable from the inner pull rod After confirming that the bridge plug structure 2 is reliably anchored within the sliding sleeve structure 1, the inner pull rod 25 is lifted via cable. Since the inner pull rod 25 and the central tube 21 are detachably connected, such as by a pin connection, when the lifting force exceeds the connection strength, the inner pull rod 25 detaches from the central tube 21. Subsequently, the inner pull rod 25 and the cable can be retrieved to the ground via cable, leaving only the central tube 21, ball 211, push rod 26, seat ring 24, fixing ring 22, and push rod base 23 in the well.

[0029] Step 4: Opening the sliding sleeve and fracturing At this point, the ball 211 inside the central tube 21 has blocked the internal passage of the central tube 21. Continuous pressure is applied to the wellbore by the surface fracturing equipment, and the hydraulic pressure is transmitted to the central tube 21 through the ball 211, thereby applying a downward thrust to the entire assembly of the fixed ring 22, push rod base 23, push rod 26, and mounting ring 24. Since the mounting ring 24 is anchored to the inner wall of the fourth casing 14, the thrust ultimately acts on the inner sliding sleeve assembly of the fourth casing 14 and the fifth casing 15. When the thrust exceeds the predetermined shear strength of the shear pins 16, multiple shear pins 16 break simultaneously, and the fourth casing 14 and the fifth casing 15, along with the portion of the bridge plug structure 2 anchored thereon, move downward relative to the second casing 12. The fracturing hole 121, originally blocked by the fourth casing 14, is completely opened, forming a fracturing fluid channel. Afterward, conventional fracturing processes can be performed to carry out staged fracturing operations towards the target oil and gas layer through the fracturing hole 121.

[0030] Step 5: Post-fracturing operations After the fracturing operation is completed, pressurization is stopped. Components made of soluble materials in the sliding sleeve structure 1, such as the fourth casing 14 and the fifth casing 15, begin to dissolve on their own under the influence of downhole temperature and fluid conditions, ultimately achieving a full-bore wellbore with no solid tool residue, facilitating subsequent well workover and production operations.

[0031] It should be noted that the specific dimensions of each component in the above embodiments can be adjusted to adapt to parameters such as the inner diameter of the sleeve in actual application. For example, the inner diameter of the fourth sleeve 14 can be 114.3 mm, the inner diameter of the support ring 141 can be 108 mm, and the initial outer diameter of the seat ring 24 can be 98 mm, which can reach 112 mm after expansion, in order to achieve a reliable interference fit and seal with the inner wall of the sliding sleeve. The "cable ignition" driven expansion and sealing method in this invention can also be replaced by conventional drive forms such as hydraulic drive and mechanical drive according to the actual working conditions. Its core lies in using the precise positioning of the cable and the separable inner pull rod to achieve tool release and retrieval, combined with the expandable anchoring structure and the dissolvable sliding sleeve, to achieve the purpose of simplified construction and no residue throughout the entire diameter.

[0032] The above embodiments are only used to illustrate the technical ideas and features of the present invention, and are not intended to be unique or to limit the present invention. Those skilled in the art should understand that various changes or equivalent substitutions made to the present invention without departing from its scope are all within the scope of protection of the present invention.

Claims

1. A cable-type full-bore fracturing sliding sleeve system, characterized in that, include: The sliding sleeve structure (1) includes a first sleeve (11), a second sleeve (12) and a third sleeve (13) connected in sequence, as well as a fourth sleeve (14) and a fifth sleeve (15) connected in sequence. The outer wall of the second sleeve (12) has multiple fracturing holes (121). The outer wall of the fourth sleeve (14) is close to the inner wall of the second sleeve (12), and the two are connected by multiple shear pins (16). The outer wall of the fifth sleeve (15) is close to the inner wall of the third sleeve (13). The inner wall of the fourth sleeve (14) is provided with a support ring (141). The bridge plug structure (2) includes a central tube (21), a fixing ring (22), a push rod base (23), a seat ring (24), an inner tie rod (25), and a push rod (26). The bottom end of the inner tie rod (25) is coaxially connected to the top end of the central tube (21) by assembly or pin. The fixing ring (22) is sleeved on the outer wall of the bottom end of the central tube (21). The inner wall of the central tube (21) carries a ball (211). The push rod (26) is sleeved on the outer wall of the central tube (21). The outer diameter of the top end of the central tube (21) is larger than the inner diameter of the bottom end of the push rod (26). The outer wall of the push rod (26) is provided with a first inclined surface (261) and a first serrated surface (262) below it. The seat ring (24) and the push rod base (23) are both sleeved on the outer periphery of the push rod (26), and the seat ring (24) is located on the push rod base (25). 3) At the top, the inner wall of the seat ring (24) is provided with a second inclined surface (241) that fits against the first inclined surface (261). The top of the push rod base (23) is arrayed with multiple slots (232). The inner wall of the push rod base (23) is provided with a second sawtooth surface (231) that meshes with the first sawtooth surface (262). The central tube (21) and the fixing ring (22) are both inserted into the push rod base (23). The bottom of the push rod base (23) is provided with a stepped groove. The fixing ring (22) is located in the stepped groove. When the top of the inner pull rod (25) is connected to the cable, the bridge plug structure (2) is lowered to the preset position in the sliding sleeve structure (1), and the push rod (26) is subjected to a downward force, it is used to move the push rod (26) into the push rod base (23), thereby causing the seat ring (24) to expand and lock the inner wall of the fourth sleeve (14).

2. The cable-type full-bore fracturing sliding sleeve system according to claim 1, characterized in that, The inner tie rod (25) is provided with a pin (251), which is located above the ball (211).

3. The cable-type full-bore fracturing sliding sleeve system according to claim 1, characterized in that, The bottom of the seat ring (24) is integrally formed with a collar (242), and the top of the push rod base (23) is located inside the collar (242).

4. The cable-type full-bore fracturing sliding sleeve system according to claim 1, characterized in that, The bridge plug structure (2) also includes a locking ring (27), which is located between the push rod (26) and the push rod base (23). The serrations on the inner wall of the locking ring (27) mesh with the first inclined surface (261), and the serrations on the outer wall of the locking ring (27) mesh with the second inclined surface (241).

5. A construction method, characterized in that, The method using the cable-type full-bore fracturing sleeve system according to any one of claims 1-4 includes the following steps: The bridge plug structure (2) is lowered into the preset position inside the sliding sleeve structure (1) using a cable; A downward force is applied to the push rod (26), causing the push rod (26) to move into the push rod base (23). The first inclined surface (261) squeezes the seat ring (24), thereby causing the seat ring (24) to expand and lock into the inner wall of the fourth sleeve (14). Use the cable to lift the inner pull rod (25) so that the inner pull rod (25) is separated from the central tube (21); A downward force is applied to the central tube (21) and the ball (211), causing multiple shear pins (16) to break, and the remaining bridge plug structure (2), fourth sleeve (14) and fifth sleeve (15) to move downward as a whole, thereby opening the fracturing hole (121).

Images