Hydraulic anchor

Abstract

The invention belongs to an oil field downhole operation tool, and discloses a hydraulic anchor. The hydraulic anchor comprises a body, a pressing plate, a spring, an anchor fluke and a sealing ring. An anchor fluke hole is formed in the body, the anchor fluke is installed in the anchor fluke hole of the body through a pressing plate, and a sealing ring is arranged between the anchor fluke and the wall of the anchor fluke hole. The anchor flukes are sleeved with springs, and the springs are located between the pressing plates and the anchor flukes. Anchor teeth are arranged on the outer end sides of the anchor flukes, are spherical round protrusions and are used for being meshed into a sleeve under the action of the pressure difference between the interior and the exterior of a pipe column, and after pressure relief, the anchor teeth are rebounded and shrunk to be released through a spring. According to the hydraulic anchor provided by the invention, the spherical round convex anchor teeth are adopted, so that the hydraulic anchor fluke can be easily retracted into the hydraulic anchor body under an abnormal condition, underground operation accidents caused by accidental recovery of the hydraulic anchor fluke are reduced, and meanwhile, the anchor fluke cannot bite a sleeve and the sleeve damage risk is reduced.

Description

Technical Field

[0001] The invention belongs to an oil field downhole operation tool, in particular to a hydraulic anchor. Background Art

[0002] Hydraulic anchor is a very common downhole operation tool. It can enter the working state when there is a pressure difference between the pipe string and the annulus, providing a more reliable anchor for the pipe string. It is often used in pipe strings for measures such as fracturing and acidizing, but generally not used in production pipe strings. This is because the anchor claws of the hydraulic anchor will be difficult to retract into the hydraulic anchor body due to scaling, rusting or excessive load on the anchor claw body during operation. The anchor claws cannot be recovered normally, which is the biggest safety hazard of the pipe string after use. Since the structural strength of the anchor claws is very high, once this situation occurs, it will cause an operation accident of "stuck pipe string", which cannot be handled by general minor repairs. This is also the reason why hydraulic anchors are generally used in the fields of fracturing, acidizing and other measures, but are not suitable for production pipe strings and cannot be placed underground for a long time.

[0003] If the disadvantage of accidental recovery of hydraulic anchor claws can be overcome, it will not only improve the safety of pipe string operations such as fracturing and acidizing, but also expand the application scope of hydraulic anchors to production pipe strings.

[0004] Utility model patent CN201148851Y discloses a non-metallic hydraulic anchor used in conjunction with a hydraulic packer, which has the functions of not damaging casing and controlling water and stabilizing oil, and comprises a body, an anchor claw installed in the anchor claw hole of the body through a pressure plate and a fastening screw, a spring is mounted on the anchor claw, and the spring is located between the pressure plate and the anchor claw. The anchor claw comprises an anchor claw core and vulcanized rubber arranged on the anchor claw core. The anchor claw core is a cylindrical structure, and vulcanized rubber is arranged in the cylinder. A sealing ring is arranged between the anchor claw and the wall of the anchor claw hole. However, the hydraulic anchor of the patent adopts vulcanized rubber teeth, which cannot bite into the casing wall, and only relies on the friction between the teeth and the casing wall to fix the pipe column. The fixing strength of the anchor claw is unreliable and impractical. Summary of the invention

[0005] The present invention aims to solve at least one technical problem existing in the background technology and provides a hydraulic anchor which adopts spherical convex anchor teeth so that under abnormal circumstances, the hydraulic anchor claws can be easily retracted into the hydraulic anchor body, thereby reducing downhole operation accidents caused by accidental recovery of the hydraulic anchor claws. At the same time, the anchor claws will not bite through the casing, thereby reducing the risk of casing damage.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] A hydraulic anchor comprises a body, a pressure plate, a spring, an anchor claw and a sealing ring; the body is provided with an anchor claw hole, the anchor claw is installed in the anchor claw hole of the body through the pressure plate, and a sealing ring is arranged between the anchor claw and the wall of the anchor claw hole; the anchor claw is sleeved with a spring, and the spring is located between the pressure plate and the anchor claw; the outer end side of the anchor claw is provided with an anchor tooth, which is a spherical convex and is used to bite into the casing under the action of the pressure difference between the inside and outside of the pipe column, and after the pressure is released, the spring rebounds and contracts to release the jam.

[0008] Furthermore, the fluke is a piston structure, and comprises a first circular shaft and a second circular shaft from the inside to the outside, and the shaft diameter of the first circular shaft is greater than the shaft diameter of the second circular shaft.

[0009] Furthermore, the spherical convex anchor tooth is provided at the end of the second circular shaft.

[0010] Furthermore, the outer end surface of the second circular axis of the fluke is a matching curved surface, and the curvature of the matching curved surface is consistent with the wall of the matching sleeve.

[0011] Furthermore, the spring is sleeved on the periphery of the second circular shaft.

[0012] Furthermore, a sealing groove is provided on the first circular shaft for installing the sealing ring.

[0013] Furthermore, the pressing plate is fixed to the outer wall of the body by means of fastening screws, and the fluke is restricted in the fluke hole of the body.

[0014] Furthermore, there are multiple flukes.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] (1) The hydraulic anchor provided by the present invention has spherical teeth (spherical convex) and a shallow depth of biting into the casing. When unstuck, a greater load is applied to force the anchor claw to be retracted, so that the hydraulic anchor claw can be easily retracted into the hydraulic anchor body under abnormal conditions, thereby reducing underground operation accidents caused by accidental retraction of the hydraulic anchor claw. At the same time, the anchor teeth of traditional hydraulic anchors are sharp and pointed, which can bite through the casing wall. The bitten casing wall can easily cause electrochemical corrosion of the casing, affecting the service life of the casing and the safety of operation. The anchor claws of the embodiment of the present invention use spherical teeth, and the bite mark of the spherical teeth on the casing is a pit, which will not bite or bite through the casing wall, thereby avoiding the occurrence of corrosion, casing damage, etc.

[0017] (2) In the hydraulic anchor provided by the present invention, the outer end surface of the second circular shaft of the anchor claw is a matching curved surface, and the curvature of the matching curved surface is consistent with the matching sleeve wall, so that the outer end surface of the second circular shaft and the sleeve wall are just matched and connected, so that the anchor teeth can bite deeper into the sleeve wall, and the anchoring is more firm and reliable; at the same time, in order to prevent the situation where the anchor cannot be anchored, the number of anchor claws can be increased. Specifically, a reasonable number of anchor claws can be selected according to the force on the pipe column and the operating parameters during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the three-dimensional structure of a hydraulic anchor according to an embodiment of the present invention;

[0019] Figure 2 It is a schematic diagram of the main structure of a hydraulic anchor according to an embodiment of the present invention;

[0020] Figure 3 A schematic diagram of the structure of the anchor claw of a hydraulic anchor according to an embodiment of the present invention;

[0021] Figure 4 It is a structural schematic diagram of the anchor teeth biting into the casing when the anchor teeth of the embodiment of the present invention are at an acute angle θ1;

[0022] Figure 5 It is a structural schematic diagram of the anchor teeth biting into the casing when the anchor teeth of the embodiment of the present invention are at an acute angle θ2;

[0023] Figure 6 It is a structural schematic diagram of the anchor teeth biting into the casing when the anchor teeth of the embodiment of the present invention are at an acute angle θ3;

[0024] Markings in the figure: 1-main body; 2-fastening screw; 3-pressure plate; 4-spring; 5-anchor claw, 501-first circular axis, 502-second circular axis, 503-anchor tooth, 504-matching curved surface, 505-sealing groove; 6-sealing ring. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0027] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "screw-on" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0028] Example 1

[0029] Combination Figure 1-3 As shown, an embodiment of the present invention provides a hydraulic anchor, including a body 1, a fastening screw 2, a pressure plate 3, a spring 4, an anchor claw 5 and a sealing ring 6.

[0030] The main body 1 is provided with an anchor claw hole for installing the anchor claw; the upper and lower ends of the main body 1 are provided with internal threads for threaded connection with a pipe column or other tools.

[0031] The fluke 5 is installed in the fluke hole of the body 1 through the fastening screw 2 and the pressing plate 3, that is, the fastening screw 2 fixes the pressing plate 3 on the outer wall of the body 1, and the fluke 5 is restricted in the fluke hole of the body 1 through the pressing plate 3.

[0032] The fluke 5 is sleeved with a spring 4, which is located between the pressure plate 3 and the fluke 5. The spring 4 is pre-compressed by the pressure plate 3 and is further compressed when the hydraulic anchor is working, providing a resilience force for the fluke 5 to retract.

[0033] A sealing ring 6 is arranged between the anchor claw 5 and the wall of the anchor claw hole, and an anchor tooth 503 is arranged on the outer end side of the anchor claw 5. The anchor tooth 503 is a spherical convex and is used to bite into the casing under the pressure difference between the inside and outside of the pipe column, and after the pressure is relieved, the spring 4 rebounds and contracts to release the jam.

[0034] Specifically, the fluke 5 is a piston structure, and comprises a first circular shaft 501 and a second circular shaft 502 from the inside to the outside. The shaft diameter of the first circular shaft 501 is greater than the shaft diameter of the second circular shaft 502 .

[0035] The first circular shaft is provided with a sealing groove 505 for installing a sealing ring 6 so that the fluke 5 forms a piston and slides in a sealed manner in the fluke hole of the body 1 .

[0036] The outer periphery of the second circular shaft 502 is sleeved with a spring 4, and the end of the second circular shaft 502 is provided with the spherical convex anchor tooth 503. The anchor tooth 503 is used to bite into the casing under the pressure difference between the inside and outside of the pipe column after the oil pipe is pressurized, and to rebound and contract to release the jam due to the spring 4 after the pressure is released.

[0037] Normally, if the hydraulic anchor claw is scaled or rusted, the anchor claw will not be able to be retracted into the hydraulic anchor due to the limited force of the spring. At this time, the upward force of the pipe string can act on the anchor claw, which is decomposed into an axial upward force and a radial recovery force. The radial recovery force will force the anchor claw to retract into the inside of the pipe string.

[0038] At the same time, the magnitude of the radial recovery force decomposed by the lifting force on the pipe string is positively correlated with the contact angle between the anchor teeth and the casing. The larger the contact angle, the greater the radial recovery force and the easier it is for the hydraulic anchor to unstuck.

[0039] The tooth shape of traditional hydraulic anchor claws is as follows Figure 4-5 As shown in the figure, the contact angle between the anchor teeth and the casing is a fixed value and remains unchanged during the whole unblocking process. Figure 4-5 As shown, Figure 5 The contact angle θ2 is Figure 4 The contact angle θ1 in the pipe increases. When the pipe string is lifted, Figure 5 The radial recovery force acting on the anchor claw is greater than Figure 4 The radial recovery force in Figure 5 The contact angle in remains a fixed value.

[0040] The anchor teeth 503 of the embodiment of the present invention use spherical teeth. Figure 6 As shown, the contact angle θ3 between the anchor tooth 5 and the casing is related to the spherical diameter D and the bite depth h of the anchor tooth; the larger the spherical diameter D and the shallower the bite depth h, the larger the contact angle θ3, and it is easier to recover the anchor claw 5. When the designed spherical diameter D and the initial bite depth h are determined, during the unblocking process, under the action of the lifting force on the pipe string, as the bite depth h decreases, the contact angle θ3 increases, and it is also easier to recover the anchor claw 5 and unblock it. Compared with the traditional contact angle that remains unchanged during the entire unblocking process, the contact angle θ3 of the anchor claw 5 in the embodiment of the present invention gradually increases during the unblocking process, which can significantly improve the success rate of unblocking the anchor claw 5 and reduce the occurrence of the anchor claw 5 encountering an accident and being unable to be recovered normally.

[0041] In addition, the anchor teeth of traditional hydraulic anchors are sharp and pointed, which will bite through the casing wall. The bitten casing wall is likely to cause electrochemical corrosion of the casing, affecting the service life of the casing and operational safety. Compared with traditional anchor claws, the anchor claws of the embodiment of the present invention use spherical teeth, and the bite mark of the spherical teeth on the casing is a pit, which will not bite or bite through the casing wall, thereby avoiding the occurrence of corrosion, casing damage, etc.

[0042] Example 2

[0043] The embodiment of the present invention is based on the embodiment 1 with the following improvements:

[0044] The outer end surface of the second circular shaft 502 of the anchor claw 5 is a matching curved surface 504, and the curvature of the matching curved surface 504 is consistent with the matching sleeve wall, so that the outer end surface of the second circular shaft 502 is just matched with the sleeve wall, so that the anchor teeth 503 can bite deeper into the sleeve wall, and the anchoring is more firm and reliable.

[0045] At the same time, in order to prevent the situation where the anchor cannot be anchored, the number of anchor claws can be increased. Specifically, a reasonable number of anchor claws can be selected according to the force on the pipe string and the operating parameters during use.

[0046] The above description is only an embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the application scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. A hydraulic anchor, comprising a body, a pressure plate, a spring, an anchor claw and a sealing ring; the body is provided with an anchor claw hole, the anchor claw is installed in the anchor claw hole of the body through the pressure plate, a sealing ring is arranged between the anchor claw and the wall of the anchor claw hole; the anchor claw is sleeved with a spring, the spring is located between the pressure plate and the anchor claw; the characteristics are: The outer end side of the anchor claw is provided with an anchor tooth, which is a spherical convex and is used to bite into the casing under the action of the pressure difference between the inside and outside of the pipe column, and to be unblocked by spring rebound after pressure relief.

2. The hydraulic anchor according to claim 1, characterized in that: The fluke is a piston structure, and comprises a first circular shaft and a second circular shaft from the inside to the outside, wherein the diameter of the first circular shaft is greater than the diameter of the second circular shaft.

3. The hydraulic anchor according to claim 2, characterized in that: The end of the second circular shaft is provided with the spherical convex anchor tooth.

4. The hydraulic anchor according to claim 3, characterized in that: The outer end surface of the second circular axis of the fluke is a matching curved surface, and the curvature of the matching curved surface is consistent with the wall of the matching sleeve.

5. The hydraulic anchor according to claim 2, characterized in that: The spring is sleeved on the periphery of the second circular shaft.

6. The hydraulic anchor according to claim 2, characterized in that: The first circular shaft is provided with a sealing groove for installing the sealing ring.

7. The hydraulic anchor according to any one of claims 1 to 6, characterized in that: The pressure plate is fixed to the outer wall of the body by means of fastening screws, and restricts the fluke in the fluke hole of the body.

8. The hydraulic anchor according to claim 7, characterized in that: The number of the flukes is multiple.

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