Bridge plug capable of quickly flowback

Abstract

The utility model relates to a bridge plug capable of fast flowback, 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 base, and a plurality of flowback holes are arranged on 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] A bridge plug is a downhole plugging tool used in oilfields. It's used to seal the lower well section during stratified fracturing, acidizing, and well testing in oil and gas wells during exploration and development. Currently, bridge plugs used in oil and gas fields undergo flowback after construction. Flowback is a crucial step in oil and gas production, and its success directly impacts production progress. Therefore, optimizing the bridge plug structure and improving flowback efficiency are crucial to oil and gas production.

[0003] In existing technologies, flowback fluid is simply returned through the cavity in the center of the bridge plug, resulting in low flowback efficiency. Furthermore, the structure connecting the central tube of existing bridge plugs to the components at both ends is primarily based on ordinary threads, which offer the advantages of simple processing and assembly. However, the disadvantage is that when the threads are subjected to high loads, they can cause the threaded connection to fail, resulting in thread slippage at the assembly. This slippage indicates structural failure, failure to properly launch the well, and increased time and financial costs. Furthermore, during use, the slip components of existing bridge plugs expand unevenly during seating, making them unable to withstand high-pressure operating environments and often failing.

[0004] For example, the Chinese patent application with application number 202210072257.2 discloses a bridge plug sealing mechanism, in which the disclosed split-claw type fixed sleeve includes a second locking block, a fixed sleeve ring and a fixed sleeve split-claw, the upper end of the fixed sleeve split-claw is connected to the fixed sleeve ring, and the lower end of the fixed sleeve split-claw is connected to the second locking block. The fixed sleeve split-claw is in the form of an opening facing one side. The problem caused 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. Utility Model Content

[0005] The purpose of this application is to provide a bridge plug that can quickly return flow, which can improve the efficiency of the bridge plug's downhole return fluid operation and has high stability and reliability.

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

[0007] The other end of the central tube is connected to the conical seat, and a plurality of slip petals are arranged at intervals on the slip, and a separation groove is provided between adjacent slip petals, and the separation groove opens toward the direction of the conical seat. A weakened groove opening toward the base is also provided on each slip petal.

[0008] Wherein, each of the slip petals is further provided with an inlay hole, in which slip teeth are 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 teeth 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 teeth and the radial line of the slip is 18°.

[0010] 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 threads or 90° one-way threads; the outside of the conical seat is provided with a first expansion ring and a second expansion ring; 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 slip flap does not coincide with the center of the slip.

[0012] A bridge plug capable of rapid flowback according to the present application has the following technical advantages:

[0013] (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;

[0014] (2) The center tube and the cone seat are designed to be connected with an interference fit, which avoids the defect of thread slippage causing bridge plug failure;

[0015] (3) The slips are optimized and adjusted. By setting staggered slip teeth, the slip teeth are optimized under different stress conditions at different depths, so that the force on the slip teeth rises 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;

[0016] (4) This bridge plug design structure perfectly solves the above-mentioned shortcomings of slow flowback and uneven slip expansion, improves the qualified rate of bridge plug entry into the well and the flowback efficiency, thereby saving time and construction costs;

[0017] (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 by the design value of the expansion force. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a cross-sectional view of the bridge plug capable of rapid flowback of the present application.

[0019] Figure 2 It is a structural schematic diagram of the slips of the bridge plug of this application.

[0020] Figure 3 This is a partial detail view of the bridge plug of this application.

[0021] Figure 4 It is a schematic diagram of the base of the bridge plug of this application.

[0022] Figure 5 It is a schematic diagram of angle A in this application.

[0023] Figure 6 It is a three-dimensional diagram of the base of the bridge plug of this application.

[0024] Figure 7 It is a schematic diagram of the thread structure on the center tube and base of the bridge plug of this application.

[0025] Figure 8 It is a cross-sectional view of the slips of the bridge plug of the present application.

[0026] Figure 9 This is a schematic diagram of a single-card single-tube bridge plug using the structure of the present application. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions and advantages of this application more clear, the embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be noted that, unless there is a conflict, the embodiments and features in the embodiments of this application can be combined with each other in any way.

[0028] 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, descriptions such as "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, features defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0029] According to the present application, a fast flowback bridge plug comprises a base 6, a central tube 4 and a conical seat 1. A slip 5 is provided between the base 6 and the conical seat 1. The slip 5 is provided on the outside of the central tube 4. One end of the central tube 4 is interference fit with the conical seat 1, and the other end of the central tube 4 is connected to the base 6 via a thread. A second expansion ring 3 and a first expansion ring 2 are provided on the outside of the conical 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 7 As 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 this 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 material of the slips of the present application can be all-metal slips or rubber-tube slips. The slip-type bridge plug of the present application is preferably an all-metal soluble bridge plug.

[0030] In terms of structure, considering the fracture between the petals of the slip 5, the structure between the partitions of the slip 5 is weakened by "U" shape and slits. Figure 2 As shown, a plurality of slip lobes are spaced apart on the circumference of the slip 5, and a separation groove 12 is provided between adjacent slip lobes, and the separation groove 12 opens upward, that is, toward the direction of the cone seat. Each slip lobe is also provided with a weakening groove 11 opening downward to facilitate the expansion of the slip. The slip structure of the present application not only can expand evenly and has good stability, but also has better anti-fracture ability. Figure 8 As shown, the intersection of the extended lines of the two sides of each slip flap is not at the center of the slip, but rather on a circle around the slip center. 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 inserting the slip teeth. Preferably, the inlay holes 7 are staggered on each slip flap to ensure more uniform insertion of the slip teeth.

[0031] In this application, the threads mating with the base 6 utilize ACME threads or 90° one-way threads, which offer superior anti-slip and anti-threading properties compared to conventional 60-degree threads, while maintaining effective setting performance. The threaded connection between the center tube and the tapered seat has been modified to an undercut and interference fit, eliminating the risk of thread failure and improving the stability of the bridge plug's operation. Furthermore, the switch from threaded assembly to insert-type assembly simplifies and expedites processing and assembly, saving costs.

[0032] The bridge plug assembly process of this application is as follows: Figure 1 As shown, first pass the center pipe 4 downward through the cavity of the cone seat 1 and abut against the step surface of the cone seat 1, then install the first expansion ring 2 and the second expansion ring 3 on the outside of the cone seat 1, then install the slip 5 on the cone seat 1, and finally install the base 6 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. The slip 5 has a guiding role, which can prevent the cone seat 1 from having a gap that causes sealing failure. After the sealing is completed, the structural design with the return hole can improve the return efficiency and wellbore stability, while reducing the construction cost.

[0033] The bridge plug in this application preferably uses a soluble bridge plug, a temporary isolation bridge plug made of a water-soluble material. During operation, the soluble bridge plug setting connector is connected to the setting tool, and the soluble bridge plug is delivered to the designed setting position using a cable or coiled tubing. Once the position is determined, the plug delivery tool is ignited or liquid is pumped in from the surface. The cone seat 1 is pushed by the gas pressure generated by the pyrotechnic column or the hydraulic pressure generated by the pumped liquid, causing the setting rod and the components mounted on the setting rod to move relative to each other. The base 6 pushes the first and second expander rings 2 and 3 toward the end of the cone seat 1, causing these components to deform radially. When the base moves a certain distance, the rubber ring on the base contacts the casing and, supported by the first expander ring 2, clings to the inner wall of the casing, providing a seal. Simultaneously, the slips 5 deform radially and contact the inner diameter of the casing, embedding the slips on the slips 5 into the casing wall, anchoring the bridge plug. When the thrust reaches a certain level, the setting rod shears off the release thread on the base, and the setting rod is removed along with the setting tool. Pump soluble balls of corresponding sizes to plug the central tube 4 of the bridge plug and perform fracturing on the upper layer. After fracturing, the fluid in the lower layer can flow through the single flow channel, thereby performing 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.

[0034] In conventional bridge plugs, the taper angle of the slip 5 is generally set to 10-20 degrees. The taper angle described in this 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 this application, based on the coordination of its various components and the design concept of improving the efficiency of the return fluid, has been optimized to have a taper angle of 5-8 degrees, with the best being 7 degrees; and as Figure 5 As shown, the angle between the axis of the slip teeth and the radial line of the slip 5 is preferably 10-20°, with the optimal angle A being 18°. Table 1 reports the test results for various angle combinations, recording the distance the bridge plug retreated within the casing. The test data in Table 1 indicates that a 7° taper angle of the slip 5 body and an 18° angle A achieve the best setting effect, enabling the bridge plug to achieve self-locking.

[0035] Table 1 Test data of the distance the bridge plug retreats in the casing at various angle combinations

[0036] 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

[0037] 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 sealed prematurely, and 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 thread of the base, but how much 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 seat cone angle, because the release force is converted into expansion force through the cone seat cone pressure. In order to ensure expansion safety and avoid design waste, the expansion force F of the bridge plug of this application is T It can be calculated according to the following empirical formula:

[0038] F T =max[F P1 , F P2 ],

[0039]

[0040] Where, 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.

[0041] Conversely, the expansion force design value F of the bridge plug is known Tand the tensile strength σ of the slip material L1 , the designed slip size can be verified so that the bridge plug can meet the design requirements. As shown in Table 2, the calculation data of the bridge plug design are listed.

[0042] Table 2 Calculation example of bridge plug design

[0043] parameter unit Example 1 Example 2 Example 3 Example 4 <![CDATA[F T ]]> N 21758 22232 23787 34781 γ Rad 0.122173 0.122173 0.15 0.122173 <![CDATA[L K ]]> mm 74 78 74 74 <![CDATA[L C ]]> mm 66 60 66 66 <![CDATA[σ L1 ]]> Mpa 330 330 330 330 <![CDATA[D KW ]]> mm 102 102 102 106 <![CDATA[D KN ]]> mm 88.6 88.6 88.6 88.6 S piece 6 6 6 6 θ Rad π / 3 π / 3 π / 3 π / 3 <![CDATA[R1]]> mm 45.4 45.4 45.4 45.4

[0044] like Figure 4 The cross-sectional view of the base 6 shows that the discharge of conventional bridge plug flowback fluid is 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 this application has optimized 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 through 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, 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. It can be seen that when the number of return holes is 10 and the inclination angle is 50 degrees, the fastest discharge result can be obtained.

[0045] Table 3 Test results of flowback holes with different numbers and diameters

[0046] Number of return holes Diameter of flowback hole (mm) Sealing effect 10 10 qualified 10 12.5 qualified 10 15 Unqualified 12 10 qualified 12 12.5 Unqualified 12 15 Unqualified

[0047] Table 4 Test results of discharge time of flowback holes with different numbers, diameters and inclination angles at fixed water volume

[0048] Number of return holes Diameter of flowback hole (mm) Tilt angle (degrees) Discharge time (seconds) 10 12.5 40 23 10 12.5 50 20 10 12.5 60 26

[0049] This application improves the return flow efficiency by optimizing the number, angle, and diameter of the return flow holes on the base. In addition, the unique slip structure design makes the force more uniform, improving the stability of the setting and the uniformity of the splitting. 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 slippage, ensuring the stability and tightness of the connection. Combining the above-mentioned unique design features, this application can make the splitting and setting of the bridge plug more stable after it is lowered into the well, and for the first time considers the return flow optimization work of the bridge plug after the setting is completed, saving construction costs for subsequent return flow operations.

[0050] Although the embodiments disclosed in this application are as described above, the contents described are merely embodiments adopted to facilitate understanding of this application and are not intended to limit this application. Any person skilled in the art of the art to which this application belongs may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in this application. However, the scope of patent protection of this application shall still be based on the scope defined by the attached claims.

Claims

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

2. The bridge plug according to claim 1, wherein: The other end of the central tube is connected to the conical seat, and a plurality of slip petals are arranged at intervals on the slip, and a separation groove is provided between adjacent slip petals, and the separation groove opens toward the conical seat. A weakened groove opening toward the base is also provided on each slip petal.

3. The bridge plug according to claim 2, wherein: Each of the slip flaps is also provided with an inlay hole, in which slip teeth are inlaid, and the inlay holes are staggeredly arranged on the slip flaps.

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

5. The bridge plug according to claim 4, wherein: The taper angle of the slip body is 7°, and the angle between the axis of the slip teeth 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 degrees.

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 2 to 5, characterized in that: A first expansion ring and a second expansion ring are provided on the outside of the conical seat.

9. The bridge plug according to any one of claims 2 to 5, characterized in that: One end of the central tube is connected to the conical seat by interference fit.

10. The bridge plug according to any one of claims 1 to 5, characterized in that: The intersection of the extension lines of the two side edges of the slip petal does not coincide with the center of the slip.

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