Bridge plug capable of quickly flowback

Abstract

The invention relates to a quick flowback bridge plug which comprises a base, a central pipe and a conical seat, a slip is arranged between the base and the conical seat, the slip is arranged outside the central pipe, one end of the central pipe is connected with the conical seat, the other end of the central pipe is connected with the base, and a plurality of flowback holes are formed in the base. According to the invention, the operation efficiency of the underground flowback fluid of the bridge plug can be improved, and the stability and reliability are high.

Description

Technical Field

[0001] The present application relates to a bridge plug, and in particular to a bridge plug capable of rapid flowback. Background Art

[0002] Downhole plugging tools are used to plug the lower well section during the construction of oil and water well stratified fracturing, stratified acidizing, and stratified oil testing in oil field exploration and development. Common downhole plugging tools include bridge plugs and packers. The following is an example of bridge plugs. At present, the bridge plugs used in oil and gas fields will be backflowed after the construction is completed. The backflow work is an important part of oil and gas production. Whether it goes smoothly or not will directly affect the progress of production. Therefore, adjusting and optimizing the bridge plug structure and improving the efficiency of the backflow fluid are of great significance to oil and gas production.

[0003] In the prior art, the return fluid is only returned through the cavity in the middle of the bridge plug, and the return fluid efficiency is low. In addition, the structure of the central tube connecting the two end components of the existing bridge plug is mainly ordinary thread, which has the advantages of simple processing and assembly, but the disadvantage is that when the thread is subjected to a large load, it may cause the threaded connection structure to fail, that is, the thread assembly will slip. Slipping means structural failure, failure to enter the well, and will also increase time and economic costs. In addition, during the use of the existing bridge plug, the bridge plug slip component expands unevenly when it is sealed, and cannot withstand the high-pressure working environment and often fails.

[0004] For example, a Chinese patent application with application number 202210072257.2 discloses a bridge plug sealing mechanism, in which the disclosed petal-claw type fixed sleeve includes a second locking block, a fixed sleeve ring and a fixed sleeve petal claw, the upper end of the fixed sleeve petal claw is connected to the fixed sleeve ring, and the lower end of the fixed sleeve petal claw is connected to the second locking block. The fixed sleeve petal claw is in the form of opening to one side. The problem brought about by this structural form is that the force is uneven during movement, and the movement trajectory of each petal is offset, thereby causing the sealing to be offset. In addition, the return fluid is only returned through the cavity in the middle of the bridge plug, and the return fluid efficiency is low. Summary of the invention

[0005] The purpose of this application is to provide a bridge plug that can quickly return flow, which can improve the downhole return fluid operation efficiency of the bridge plug and has high stability and reliability. This application also proposes an empirical formula for calculating the expansion force of the bridge plug, which can be used for the size design of the bridge plug and the expansion force verification.

[0006] The present application relates to a bridge plug capable of rapid backflow, comprising a base, a center pipe and a conical seat, wherein a slip is provided between the base and the conical seat, the slip is arranged on the outside of the center pipe, one end of the center pipe is connected to the conical seat, the other end of the center pipe is connected to the base, and a plurality of backflow holes are provided on the base.

[0007] Wherein, a plurality of slip flaps are arranged at intervals on the slip, and a separation groove is arranged between adjacent slip flaps, and the separation groove opens toward the direction of the cone seat. A weakened groove opening toward the base is also arranged on each of the slip flaps.

[0008] Wherein, each of the slip petals is also provided with an inlay hole, in which a slip tooth is inlaid, and the inlay holes are staggeredly arranged on the slip petals.

[0009] Among them, the cone angle of the slip body is 5-8°, and the angle between the axis of the slip tooth and the radial line of the slip is 10-20°; the cone angle of the slip body is 7°, and the angle between the axis of the slip tooth and the radial line of the slip is 18°.

[0010] Wherein, the return hole is arranged obliquely, and the angle between the axis of the return hole and the axis of the base is 45-55°.

[0011] Among them, the center tube and the base are connected by ACME thread or 90° one-way thread; the first expansion ring and the second expansion ring are provided on the outside of the conical seat; one end of the center tube is connected to the conical seat by interference fit; the intersection of the extension lines of the two side edges of the cava petal does not coincide with the center of the cava.

[0012] Among them, the assembly process of the bridge plug is: first, the center tube is passed through the cavity of the conical seat and installed on the conical seat, then the first expansion ring and the second expansion ring are installed on the outside of the conical seat, and then the slip is installed on the conical seat, and finally the base is installed under the slip, and the contact surface between the center tube and the conical seat is formed with an interference fit by tightening the spiral between the base and the center tube.

[0013] Expansion force F of bridge plug T Calculate according to the following formula:

[0014] F T =max[F P1 , F P2 ],

[0015]

[0016] In the formula, F P1 is the radial breaking force of the slip connection, F P2 is the tangential fracture force of the slip connection, σ L1 is the tensile strength of the slip material, L K is the slip length, L C is the length of the separation slot, D KW is the maximum outer diameter of the slip, D KNis the maximum inner diameter of the slip, S is the number of slip petals, θ is the angle of each slip petal, γ is the cone angle of the slip body, and R1 is the diameter of the slip petal.

[0017] A bridge plug capable of rapid flowback according to the present application has the following technical advantages:

[0018] (1) The return fluid structure design with a return hole added to the base through structural optimization improves the efficiency of the return fluid, saves the production cycle, and improves economic and time benefits;

[0019] (2) The center tube and the cone seat are designed to be connected with a stepped interference fit, which avoids the defect of thread slippage leading to failure of the bridge plug;

[0020] (3) The slips are optimized and adjusted. By setting staggered slip nails, the slip nails are optimized under different stress conditions at different depths, so that the force on the slip nails increases evenly when the slips expand, thereby achieving uniform petal separation during the expansion of the slips, avoiding abnormal clamping force and pressure leakage caused by uneven expansion at both ends and around, avoiding rework and saving a lot of secondary construction costs;

[0021] (4) The bridge plug design structure of the present application perfectly solves the above-mentioned shortcomings of slow return flow and uneven expansion of slips, improves the qualified rate of bridge plugs entering the well and the return flow efficiency, thereby saving time and construction costs;

[0022] (5) This application proposes an empirical formula for calculating the expansion force of a bridge plug. The expansion force of the bridge plug can be calculated based on the size and performance parameters of the bridge plug, and the size design of the bridge plug can also be guided based on the design value of the expansion force. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a cross-sectional view of the bridge plug capable of rapid flowback of the present application.

[0024] Figure 2 It is a schematic diagram of the structure of the slip of the bridge plug of the present application.

[0025] Figure 3 It is a partial detail diagram of the bridge plug of this application.

[0026] Figure 4 It is a schematic diagram of the base of the bridge plug of the present application.

[0027] Figure 5 It is a schematic diagram of angle A in this application.

[0028] Figure 6 It is a three-dimensional diagram of the base of the bridge plug of the present application.

[0029] Figure 7 It is a schematic diagram of the thread structure on the center tube and base of the bridge plug of the present application.

[0030] Figure 8 It is a cross-sectional view of the slip of the bridge plug of the present application.

[0031] Fig. 9 It is a schematic diagram of a single-card single-tube bridge plug adopting the structure of the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present application more clear, the embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily without conflict.

[0033] It should be noted that all directional indications in this application, such as up, down, left, right, front, back, etc., are only used to explain the relative position relationship, movement, etc. between the components in a certain specific posture as shown in the accompanying drawings. If the specific posture changes, the directional indication will also change accordingly. In addition, the descriptions of "first", "second", etc. in this application are only used for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0034] A fast backflow bridge plug according to the present application includes a base 6, a center pipe 4 and a cone seat 1. A slip 5 is provided between the base 6 and the cone seat 1. The slip 5 is arranged outside the center pipe 4. One end of the center pipe 4 is interference fit with the cone seat 1, and the other end of the center pipe 4 is connected to the base 6 through a thread. A second expansion ring 3 and a first expansion ring 2 are provided outside the cone seat 1. Figure 1 and 3 As shown, the thread between the central tube 4 and the base 6 can be an ACME thread. An alternative solution can be adjusted to a 90° one-way thread, such as Figure 7 The advantage of the one-way thread is that it has one-way anti-slip properties. In this bridge plug, under the premise of ensuring the material strength of the central tube 4 and the base 6, the thread structure used can also achieve the anti-slip effect. Figure 7As shown, the thread is arranged in a right-angled trapezoidal shape, and the angle between the hypotenuse of the thread and the longitudinal direction of the thread is 30 degrees. In order to ensure the tightness of the threaded connection between the center tube 4 and the base 6, the thread shapes on the two match each other. The present application adopts such a 90° one-way thread, and the right-angled sides of the two threaded parts are interlocked with each other, so as to form a joint surface perpendicular to the longitudinal direction, thereby maximizing the joint surface and ensuring the connection strength and tightness of the thread. The bridge plug of the present application can be an all-metal slip or a rubber cartridge slip. The slip-type bridge plug of the present application is preferably an all-metal soluble bridge plug.

[0035] In terms of structure, considering the fracture between the petals of the slip 5, the structure between the partitions of the slip 5 was weakened by "U" shape and slits. Figure 2 As shown, a plurality of slip flaps are arranged at intervals on the circumference of the slip 5, and a separation groove 12 is arranged between adjacent slip flaps, and the separation groove 12 opens upward, that is, toward the direction of the cone seat. A weakening groove 11 opening downward is also arranged on each slip flap to facilitate the expansion of the slip. The slip structure of the present application can not only expand evenly and has good stability, but also has better anti-fracture ability. Figure 8 As shown, the intersection of the extension lines of the two sides of each slip flap is not at the center of the slip, but on a circle around the center of the slip. The diameter of the slip flap is R1, which represents the distance from the outer edge of the slip flap to the center of the slip flap. Each slip flap is also provided with an inlay hole 7 for inlaying slip teeth. Preferably, the inlay holes 7 are staggered on each slip flap to make the inlay of the slip teeth more uniform.

[0036] In this application, the thread at the end that matches the base 6 adopts ACME thread or 90° one-way thread, which has better anti-slip and anti-slip effect than the conventional 60-degree thread, and the actual sealing effect is not affected. In this application, the thread structure between the center tube and the cone seat is changed to a stepped undercut fitting connection, which avoids the risk of thread failure and improves the stability of the bridge plug operation. At the same time, the thread assembly is adjusted to the plug-in assembly, which makes the processing and assembly simpler and faster.

[0037] The bridge plug assembly process of this application is as follows: Figure 1As shown, firstly, the center pipe 4 is passed downward through the cavity of the cone seat 1 and abutted against the step surface of the cone seat 1, then the first expansion ring 2 and the second expansion ring 3 are installed on the outside of the cone seat 1, and then the slip 5 is installed on the cone seat 1, and finally the base 6 is installed under the slip 5. By tightening the spiral between the base 6 and the center pipe 4, the contact surface between the center pipe 4 and the cone seat 1 forms an interference fit, and the connection is more stable. In the process of pushing the slip 5 toward the cone seat, the interference-fit center pipe 4 and the cone seat 1 are opened again, and the slip 5 has a guiding function, which can prevent the cone seat 1 from having a gap and causing a plugging failure. After the sealing is completed, the structural design with a return hole can improve the return efficiency and the stability of entering the well, while reducing the construction cost.

[0038] The bridge plug of the present application preferably adopts a soluble bridge plug, which is a temporary isolation bridge plug made of water-soluble materials. During operation, the soluble bridge plug setting joint is connected to the setting tool, and the soluble bridge plug is sent to the designed setting position by a cable or a continuous oil pipe. After the position is determined, the plug delivery tool is ignited or liquid is pumped into the ground. The cone seat 1 is pushed by the gas pressure generated by the gunpowder column or the hydraulic pressure generated by the pumped liquid. The setting rod and the components mounted on the setting rod produce relative movement, and the base 6 pushes the first expansion ring 2 and the second expansion ring 3 to approach the end of the cone seat 1. At the same time, the above components will produce radial deformation. When the base moves to a certain extent, the rubber ring on the base contacts the casing and is tightly attached to the inner wall of the casing under the support of the first expansion ring 2, playing a sealing role. At the same time, after the radial deformation of the slip 5 contacts the inner diameter of the casing, the slip teeth on the slip 5 are embedded in the casing wall, playing the role of anchoring the bridge plug. When the thrust reaches a certain level, the setting rod shears off the hand-release thread on the base, and the setting rod is taken out together with the setting tool. Pump soluble balls of corresponding sizes to plug the central tube 4 of the bridge plug, and perform fracturing construction on the upper layer. After the fracturing is completed, the fluid in the lower layer can flow through the single flow channel, so as to carry out normal blowout or production. During the blowout and production process, the soluble bridge plug dissolves in the wellbore fluid and disappears after a certain period of time.

[0039] In conventional bridge plugs, the taper angle of the slip 5 is generally set to 10-20°. The taper angle described in the present application is reflected in the cross-sectional view as the angle between the side extension line of the slip and the longitudinal center axis of the bridge plug. The bridge plug of the present application, according to the design idea of ​​matching its various components and meeting the requirements of improving the efficiency of the return fluid, after optimized design, the taper angle of the slip 5 body is 5-8°, and the best is 7°; and if Figure 5 As shown in FIG. 1 , the angle between the axis of the slip tooth and the radial line of the slip 5 is preferably 10-20°, and the optimal angle value A is 18°. Table 1 records the test results under various angle combinations, that is, the distance the bridge plug retreats in the casing. According to the test data in Table 1, when the taper angle of the slip 5 body is 7° and the angle A is 18°, the best setting effect is achieved, and the bridge plug can be self-locked.

[0040] Table 1 Test data of the distance the bridge plug retreats in the casing at various angle combinations

[0041] Slip cone angle (degrees) Angle A(degrees) Backward distance (mm) 5 10 15 5 18 10 5 26 7 7 10 3 7 18 0 7 26 5 8 10 7 8 18 4 8 26 10 10 10 16 10 18 14 10 26 21

[0042] When designing the bridge plug of this application, the expansion force of the slip is an important design parameter. It can be used to determine the size of the external load that prevents the bridge plug from being set prematurely, which is convenient for protecting the bridge plug during use. It can be used to calculate the release force required for the slip to be fully opened. This is because the release force is guaranteed by the threads of the base, but the release force needs to be designed to meet the requirements and the expansion force requirements. It is also an important reference parameter for the design of the cone angle of the cone seat, because the release force is converted into expansion force through the cone pressure of the cone seat. Figure 2 and 8 The single slip form shown in the figure, the expansion force F of the bridge plug of this application T It can be calculated according to the following empirical formula:

[0043] F T =max[F P1 , F P2 ],

[0044]

[0045] In the formula, F P1 is the radial breaking force of the slip connection, F P2 is the tangential fracture force of the slip connection, σ L1 is the tensile strength of the slip material, L K is the slip length, L C is the length of the partition groove, D KW is the maximum outer diameter of the slip, D KN is the maximum inner diameter of the slip, S is the number of slip petals, θ is the angle of each slip petal, γ is the cone angle of the slip body, and R1 is the diameter of the slip petal.

[0046] Conversely, the expansion force design value F of the bridge plug is known T and the tensile strength of the slip material σ L1 , the designed slip size can be verified to meet the design requirements. The following table is the example data for guiding bridge plug design.

[0047] Table 2 Example of bridge plug design

[0048]

[0049]

[0050] like Figure 4The cross-sectional view of the base 6 shows that the conventional bridge plug discharges the backflow fluid mainly through the middle cavity 9, and the speed is mainly determined by the size of the middle cavity 9. However, the design of the middle cavity of the bridge plug is affected by factors such as the bridge plug structure and strength. Therefore, it is not feasible to infinitely increase the middle cavity. In order to overcome this defect, the bridge plug of the present application optimizes and adjusts the structure of the base 6, such as Figure 4 As shown, the present application is provided with a plurality of return holes 8 arranged obliquely on the base 6. In theory, the more the number of return holes and the larger the aperture, the more beneficial it is to improve the return efficiency, but in fact it will reduce the structural strength of the base. Therefore, it is necessary to strike a balance between the base strength and the return efficiency to avoid affecting the normal operation of the bridge plug. When the return fluid flows out through the return hole 8, the angle of the return hole 8 also affects the outflow of the return fluid. The present application has been verified by experiments. For a base with a commonly used outer diameter of 110 mm, the optimized scheme for the return structure to ensure the best operating conditions of the bridge plug is: the number of return holes 8 is 10, the aperture is 12.5 mm, and the inclination angle of the return hole 8, that is, the angle between its axis and the axis of the base 6 is 45-55°, preferably 50°, which can achieve the best return effect. The specific experimental data are shown in Tables 3 and 4.

[0051] Table 3 Test results of flowback holes with different numbers and diameters

[0052] Number of return holes Diameter of return hole (mm) Sealing effect 10 10 qualified 10 12.5 qualified 10 15 Failure 12 10 qualified 12 12.5 Failure 12 15 Failure

[0053] Table 4 Test results of discharge time of return holes with different numbers, diameters and inclination angles under fixed water volume

[0054] Number of return holes Diameter of return hole (mm) Tilt angle (degrees) Emission time (seconds) 10 12.5 40 23 10 12.5 50 20 10 12.5 60 26

[0055] This application improves the return efficiency by optimizing the design of the number, angle, diameter and other dimensions of the return holes on the base; in addition, the unique cava structure design makes the force more uniform, improving the stability of the seal and the uniformity of the split; the interference fit between the center pipe and the cone seat and the use of ACME threads or 90° one-way threads between the center pipe and the base greatly reduce the risk of slipping threads, ensuring the stability and tightness of the connection. Combining the above-mentioned combined designs with various characteristics, this application can make the splitting and sealing of the bridge plug after it is lowered into the well more stable, and for the first time considers the return optimization work of the bridge plug after the sealing is completed, saving construction costs for subsequent return operations.

[0056] Although the implementation methods disclosed in this application are as above, the contents described are only implementation methods adopted for facilitating the understanding of this application, and are not intended to limit this application. Any technician in the technical field to which this application belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in this application, but the scope of patent protection of this application shall still be based on the scope defined in the attached claims.

Claims

1. A bridge plug capable of rapid flowback, characterized in that: It includes a base, a center tube and a cone seat, a slip is provided between the base and the cone seat, the slip is arranged outside the center tube, one end of the center tube is connected to the cone seat, the other end of the center tube is connected to the base, and a plurality of return holes are provided on the base.

2. The bridge plug according to claim 1, characterized in that: A plurality of slip flaps are arranged at intervals on the slip, and a separation groove is arranged between adjacent slip flaps, the separation groove opening is toward the direction of the cone seat, and a weakened groove opening toward the base is also arranged on each of the slip flaps.

3. The bridge plug according to claim 2, characterized in that: Each of the slip petals is also provided with an inlay hole, in which a slip tooth is inlaid, and the inlay holes are staggeredly arranged on the slip petals.

4. The bridge plug according to claim 3, characterized in that: The taper angle of the slip body is 5-8°, and the angle between the axis of the slip tooth and the radial line of the slip is 10-20°.

5. The bridge plug according to claim 4, characterized in that: The taper angle of the slip body is 7°, and the angle between the axis of the slip tooth and the radial line of the slip is 18°.

6. The bridge plug according to any one of claims 1 to 5, characterized in that: The return hole is arranged obliquely, and the angle between the axis of the return hole and the axis of the base is 45-55°.

7. The bridge plug according to any one of claims 1 to 5, characterized in that: The central tube and the base are connected by ACME threads or 90° one-way threads.

8. The bridge plug according to any one of claims 1 to 5, characterized in that: A first expansion ring and a second expansion ring are arranged outside the conical seat.

9. The bridge plug according to claim 8, characterized in that: The assembly process of the bridge plug is as follows: first, the center tube is passed through the cavity of the conical seat and installed on the conical seat, then the first expansion ring and the second expansion ring are installed on the outside of the conical seat, and then the slip is installed on the conical seat, and finally the base is installed under the slip, and the contact surface between the center tube and the conical seat is formed into an interference fit by tightening the spiral between the base and the center tube.

10. The bridge plug according to any one of claims 1 to 5 and 9, characterized in that: The expansion force F of the bridge plug T Calculate according to the following formula: F T =max[F P1 ,F P2 ], In the formula, F P1 is the radial breaking force of the slip connection, F P2 is the tangential fracture force of the slip connection, σ L1 is the tensile strength of the slip material, L K is the slip length, L C is the length of the separation slot, D KW is the maximum outer diameter of the slip, D KN is the maximum inner diameter of the slip, S is the number of slip petals, θ is the angle of each slip petal, γ is the cone angle of the slip body, and R1 is the diameter of the slip petal.

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