A naked eye anchor

Abstract

The present invention provides a naked hole anchor, comprising: a core shaft, which is provided with a pressure transmission hole; an upper joint; an expansion cylinder sleeved on the core shaft; a hydraulic drive assembly sleeved on the core shaft, which comprises a hydraulic cylinder sleeve and a piston cylinder sleeved on the core shaft, the piston cylinder being installed between the hydraulic cylinder sleeve and the core shaft, and a hydraulic cavity is formed between the hydraulic cylinder sleeve, the core shaft and the piston cylinder, the hydraulic cavity is connected with the internal flow channel of the core shaft through the pressure transmission hole, and the pressure in the hydraulic cavity can be increased by throwing a ball and holding up the pressure, pushing the piston cylinder upward, thereby squeezing the expansion cylinder to expand radially until the expansion cylinder is anchored to the well wall; wherein, the expansion cylinder is constructed to include a first cylinder and a second cylinder, the inner wall surface of the first cylinder is provided with a plurality of cutting grooves, a plurality of cutting seams penetrating the side wall are provided on the axial inner side of the first cylinder at the cutting groove, and a plurality of circumferentially uniformly distributed stress grooves are provided on the outer surface of the connection between the first cylinder and the second cylinder, and the stress grooves can guide the radial expansion of the expansion cylinder.

Description

Technical Field

[0001] The invention belongs to the technical field of open hole segmentation in oil and natural gas completion engineering, and particularly relates to an open hole anchor. Background Art

[0002] Currently, staged fracturing in horizontal openhole wells has become an important means of increasing reserve utilization and recovery rates in low- and ultra-low-permeability reservoirs. This technology not only increases oil and gas well production but also significantly reduces the costs and risks associated with cementing and perforating operations, while also mitigating formation contamination and damage. It is a trend in low-permeability reservoir development.

[0003] In the open hole segmentation process, in order to protect the packer and its pipe string, the existing technology generally uses hydraulic anchors or hangers to anchor them in the casing near the front end of the open hole section. However, for the open hole section, due to the irregularities of the open hole well wall, the hydraulic anchors or slips are prone to accidentally opening during the installation process, causing drill sticking accidents, and their adaptability is poor. The open hole packers are completely anchored by the friction force of the rubber sleeve, and generally there is no other anchoring device.

[0004] During high-pressure fracturing, the string expands due to the high pressure exerted on it, causing it to stretch. For example, for 88.9mm tubing, the elongation during fracturing can reach 2‰. This elongation can cause axial movement of the packer rubber sleeve, already seated on the openhole wellbore, which can be damaged by the wellbore rock and cause the packer seal to fail. Furthermore, during fracturing, the hydraulically induced elongation of the string creates tension that directly acts on the tubing and its threads, easily leading to tubing breakage or thread unthreading. To ensure the sealing effectiveness of the openhole packer and the safety of the string, existing openhole segmented tubing should be equipped with anchoring devices suitable for the process. For example, a centralizing anchoring device is used. However, existing centralizing anchoring devices present several challenges in practical application. For example, the anchor bolts must be embedded in the openhole wellbore, which is highly destructive and can easily cause wellbore collapse. Furthermore, the reliability of the centralizing anchoring device does not meet application requirements. Summary of the Invention

[0005] In response to the technical problems described above, the present invention aims to propose an open hole anchor that can greatly reduce damage to the open hole well wall, anchor the tubing, protect the tubing, and prevent the tubing from creeping during high-pressure construction and causing the packer to fail.

[0006] To this end, according to the present invention, a naked eye anchor is provided, comprising: a hollow tubular mandrel, the mandrel being provided with a pressure transmission hole penetrating the side wall; an upper joint fixedly connected to the upper end of the mandrel; an expansion cylinder sleeved on the mandrel; and a hydraulic drive assembly sleeved on the mandrel, the hydraulic drive assembly comprising a hydraulic cylinder sleeve and a piston cylinder sleeved on the mandrel, the piston cylinder being installed between the hydraulic cylinder sleeve and the mandrel, and a hydraulic cavity being formed between the hydraulic cylinder sleeve, the mandrel and the piston cylinder, the hydraulic cavity being connected to the internal flow channel of the mandrel through the pressure transmission hole, and the hydraulic pressure can be made by throwing a ball and holding up the pressure The pressure in the cavity increases and pushes the piston cylinder upward, thereby squeezing the expansion cylinder to expand radially until the expansion cylinder is anchored to the well wall; wherein, the expansion cylinder is constructed to include a first cylinder and a second cylinder connected to the first cylinder, the inner wall surface of the upper end of the first cylinder is provided with a plurality of cutting grooves extending in the axial direction, and the side wall area of ​​the first cylinder located on the axial inner side of the cutting groove is provided with a plurality of cutting seams penetrating the side wall, the cutting seams are extended in the axial direction, and the outer surface of the connection between the first cylinder and the second cylinder is provided with a plurality of circumferentially uniformly distributed stress grooves, and the stress grooves can guide the radial expansion of the expansion cylinder.

[0007] In one embodiment, the plurality of cutting grooves are evenly distributed in the circumferential direction, the plurality of cutting slits are evenly distributed in the circumferential direction, and the circumferential positions of the cutting grooves and the cutting slits correspond to each other.

[0008] In one embodiment, the outer wall of the lower end of the upper joint is configured as a first conical surface, and the inner wall of the expansion cylinder on the axial inner side of the cutting groove is configured as a second conical surface, and the second conical surface is adapted to be installed with the first conical surface.

[0009] In one embodiment, the hydraulic cylinder sleeve is fixedly connected to the spindle via a plurality of first fixing pins, and the plurality of first fixing pins are evenly distributed in the circumferential direction.

[0010] In one embodiment, the inner wall of the hydraulic cylinder sleeve is provided with a shoulder with an end surface facing upward, and the hydraulic cavity is formed between the inner wall of the hydraulic cylinder sleeve, the shoulder and the outer wall of the spindle.

[0011] In one embodiment, a shear ring is provided between the piston cylinder and the hydraulic cylinder sleeve. The shear ring is fixedly connected to the hydraulic cylinder sleeve and is fixedly connected to the piston cylinder via a first shear pin.

[0012] In one embodiment, the piston cylinder is fixedly connected to the expansion cylinder through a second shear pin. The shear value of the first shear pin is smaller than the shear value of the second shear pin. During the ball-throwing and pressure-holding process, the piston cylinder first shears the first shear pin and moves axially upward to axially compress the expansion cylinder, causing the expansion cylinder to radially expand until it contacts the wellbore wall and generates friction. The second shear pin is sheared when the friction force is greater than its shear value, thereby completing anchoring.

[0013] In one embodiment, a first ratchet is provided on the outer wall of the piston cylinder, a locking ring is provided on the inner wall of the hydraulic cylinder sleeve, and a second ratchet matched with the first ratchet is provided on the inner wall of the locking ring to prevent the piston cylinder from retreating.

[0014] In one embodiment, a mounting step with an upward end surface is provided on the inner wall of the hydraulic cylinder sleeve, the mounting step is located on the axial inner side of the shear ring, and the lock ring is mounted on the mounting step.

[0015] In one embodiment, a seal is provided between the connecting surface of the upper joint and the spindle, seals are provided between the piston cylinder and the spindle and the hydraulic cylinder sleeve respectively, and a seal is provided between the hydraulic cylinder sleeve and the spindle.

[0016] Compared with the prior art, the advantages of this application are:

[0017] The open-hole anchor according to the present invention is capable of adaptively anchoring open-hole segmented tubing with a 20% open-hole expansion rate. The open-hole anchor can be lowered into the open-hole section along with the open-hole packer, providing high safety. The open-hole anchor anchors the tubing through the friction between the first conical structure of the upper joint, the expansion cylinder, and the open-hole wall, significantly reducing damage to the open-hole wellbore wall. It also serves to anchor and protect the tubing, and prevent creep during high-pressure construction, which could cause the packer to fail. Furthermore, the expansion cylinder, by providing a cutting groove and cutting seam structure, can effectively prevent the open-hole anchor from accidentally opening during the open-hole run, thereby effectively avoiding the risk of drill sticking. This significantly improves the efficiency of lowering the open-hole anchor into the open-hole well and the anchoring efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be described below with reference to the accompanying drawings.

[0019] Figure 1 The structure of the open hole anchor according to the present invention is shown.

[0020] Figure 2 yes Figure 1 Magnified view of area A in center.

[0021] Figure 3 yes Figure 1Magnified view of area B.

[0022] Figure 4 Shows Figure 1 The structure of the expansion tube in the open hole anchor is shown.

[0023] Figure 5 yes Figure 4 Cross-sectional view along line CC.

[0024] Figure 6 yes Figure 4 Cross-sectional view along line DD.

[0025] Figure 7 Shows Figure 1 The structure of the piston cylinder in the open hole anchor is shown.

[0026] Figure 8 yes Figure 7 Magnified view of area E in the middle.

[0027] Figure 9a and Figure 9b Shows Figure 1 The structure of the locking ring in the open hole anchor is shown.

[0028] Figure 10 yes Figure 9a Magnified view of region F.

[0029] In this application, all drawings are schematic drawings, which are only used to illustrate the principles of the present invention and are not drawn to scale. DETAILED DESCRIPTION

[0030] The present invention will be described below with reference to the accompanying drawings.

[0031] In the present application, it should be noted that the end of the open hole anchor according to the present invention lowered into the wellbore away from the wellhead is defined as the lower end or similar terms, and the end close to the wellhead is defined as the upper end or similar terms.

[0032] Figure 1 1 shows the structure of the open hole anchor 100 according to the present invention. Figure 1As shown, the open hole anchor 100 includes a hollow tubular mandrel 2, an upper joint 1 fixedly connected to the upper end of the mandrel 2, an expansion cylinder 3 sleeved on the mandrel 2, and a hydraulic drive assembly sleeved on the mandrel 2. The hydraulic drive assembly is configured to axially push the expansion cylinder 3 upward to achieve radial expansion, thereby contacting the wellbore wall and generating friction, thereby achieving anchoring. The open hole anchor 100 can be lowered into the open hole section together with the open hole packer. Its lowering is highly safe, and it anchors the tubing through friction, greatly reducing damage to the open hole wellbore wall. At the same time, it can anchor the tubing, protect the tubing, and prevent the tubing from creeping during high-pressure construction, causing the packer to fail.

[0033] like Figure 1 As shown, in one embodiment, the upper joint 1 is connected to the upper end of the spindle 2 by means of threads. The lower end of the upper joint 1 is configured as an inner step-shaped connecting buckle, and the upper end of the spindle 2 is adapted to connect with the step-shaped connecting buckle and is fixedly connected by means of threads. At the same time, symmetrically distributed second fixing pins 12 are provided at the connection between the upper end of the spindle 2 and the upper joint 1 to prevent the threads from loosening and causing the threads to rotate and unscrew, thereby ensuring the stability of the connection between the spindle 2 and the upper joint 1. For example, the upper joint 1 is provided with a pin hole for the second fixing pin 12 to pass through, and a corresponding pin groove is provided on the outer wall surface of the spindle 2.

[0034] Furthermore, to ensure a tight seal at the connection between the mandrel 2 and the upper connector 1, multiple sets of seals 11 are provided between the connecting surfaces of the mandrel 2 and the upper connector 1. For example, the lower inner wall of the upper connector 1 is provided with multiple sealing grooves, with the seals 11 installed in corresponding sealing grooves. Preferably, the seals 11 are positioned axially between the upper end surface of the mandrel 2 and the second fixing pin 12. This greatly helps ensure the tight seal of the open-hole anchor 100.

[0035] According to one embodiment of the present invention, the upper end inner wall surface of the upper sub 1 is provided with internal threads for connecting to the upper open hole segmented tubing or tools (not shown). In addition, the lower end outer wall surface of the mandrel 2 is provided with external threads for connecting to the tubing or other segmented tools (not shown) of the open hole segmented tubing string.

[0036] like Figure 4 As shown, the expansion cylinder 3 is cylindrical and is constructed to include a first cylinder 31 and a second cylinder 32 connected to the first cylinder 31. The inner wall surface of the upper end of the first cylinder 31 is provided with a plurality of cutting grooves 33 extending in the axial direction (see FIG. Figure 6 ), multiple cutting grooves 33 are evenly distributed in the circumferential direction. During the process of running the open hole anchor 100 into the open hole, the cutting grooves 33 are used to prevent the expansion cylinder 4 from accidentally opening, thereby avoiding the risk of drill jamming. A plurality of cutting slits 34 (see FIG. 34 ) penetrating the side wall of the first cylinder 31 on the axial inner side of the cutting grooves 33 are provided. Figure 5), the cutting slits 34 extend axially, with multiple cutting slits 34 evenly distributed circumferentially. Preferably, the circumferential positions of the cutting grooves 33 and the cutting slits 34 can be arranged to correspond to each other to facilitate radial expansion. A plurality of circumferentially evenly distributed stress grooves 35 are provided on the outer surface of the junction between the first cylinder 31 and the second cylinder 32. In one embodiment, the stress grooves 35 extend axially, with the center of the stress groove 35 being rectangular and the ends being semicircular, to guide the radial expansion of the expansion cylinder 3. Furthermore, the stress grooves 35 can effectively prevent stress concentration.

[0037] According to one embodiment of the present invention, the lower outer wall of the upper connector 1 is configured as a first conical surface. The expansion cylinder 3 is sleeved onto the mandrel 2 and positioned axially inward of the upper connector 1. The inner wall of the upper end of the expansion cylinder 3 is configured as a second conical surface, which mates with the first conical surface of the upper connector 1. This conical surface fit guides the axial movement of the expansion cylinder 3, thereby facilitating radial expansion of the expansion cylinder 3.

[0038] like Figure 2 and Figure 3 As shown, the hydraulic drive assembly includes a hydraulic cylinder sleeve 7 and a piston cylinder 4 that are sleeved on the spindle 2. The hydraulic cylinder sleeve 7 is constructed in a roughly cylindrical shape, and a shoulder 73 with an upward-facing end face is provided on the inner wall of the hydraulic cylinder sleeve 7. The inner wall of the hydraulic cylinder sleeve 7 at the lower end of the shoulder 73 is provided with an internal thread, and the outer wall surface of the spindle 2 is provided with a corresponding external thread. The hydraulic cylinder sleeve 7 is fixedly connected to the spindle 2 through the thread. At the same time, two symmetrically distributed first fixing pins 72 are provided at the threaded connection between the hydraulic cylinder sleeve 7 and the spindle 2. The first fixing pins 72 can prevent the threads from loosening and retreating, effectively ensuring a stable connection between the hydraulic cylinder sleeve 7 and the spindle 2.

[0039] In order to ensure the sealing between the hydraulic cylinder sleeve 7 and the spindle 2, multiple sets of sealing members 75 are provided between the connecting surfaces of the hydraulic cylinder sleeve 7 and the spindle 2. Preferably, the sealing members 75 are provided between the shoulder 73 of the hydraulic cylinder sleeve 7 and the axial direction of the first fixing pin 72. This is very helpful in ensuring the sealing of the open hole anchor 100.

[0040] like Figure 3As shown, the piston cylinder 4 is installed between the hydraulic cylinder sleeve 7 and the spindle 2, and a hydraulic cavity 8 is formed between the shoulder 73 of the hydraulic cylinder sleeve 7, the spindle 2 and the piston cylinder 4. At the same time, the spindle 2 is provided with a pressure transmission hole 21 that passes through the side wall. The pressure transmission hole 21 is connected to the hydraulic cavity 8, so that the hydraulic cavity 8 is connected to the internal flow channel of the spindle 2. The upper end of the piston cylinder 4 is fixedly connected to the expansion cylinder 3 through a plurality of second shear pins 36. For example, the lower end side wall of the expansion cylinder 3 is provided with a plurality of pin holes for the second shear pins 36 to pass through. The plurality of pin holes are evenly distributed circumferentially, and a corresponding pin groove is provided on the outer wall surface of the upper end of the piston cylinder 4. During operation, the liquid pressure in the spindle 2 can be increased by throwing the ball to hold the pressure, thereby increasing the pressure in the hydraulic cavity 8 and pushing the piston cylinder 4 upward, thereby axially pushing the expansion cylinder 3 to squeeze the expansion cylinder 3 to expand radially. In this way, the hydraulic drive function is realized.

[0041] To ensure the sealing of hydraulic chamber 8, seals are provided between piston cylinder 4, spindle 2, and cylinder sleeve 7. For example, two sets of sealing grooves 45 are provided on the inner wall of the lower end of piston cylinder 4, while two sets of sealing grooves 46 are axially staggered on the outer wall of the lower end of piston cylinder 4. Seals 42 and 43 are installed in sealing grooves 45 and 46, respectively. This effectively ensures the sealing of chamber 8, thereby ensuring a tight seal and maintaining pressure.

[0042] According to one embodiment of the present invention, a shear ring 5 is provided between the piston cylinder 4 and the hydraulic cylinder sleeve 7. The outer surface of the piston cylinder 4 is provided with an annular protrusion 44 extending radially outward (see Figure 7 The shear ring 5 is fixedly connected to the hydraulic cylinder sleeve 7 and to the piston cylinder 4 via a plurality of first shear pins 51, which are evenly distributed around the circumference. Initially, the upper end surface of the shear ring 5 contacts the lower end surface of the annular protrusion 44. These first shear pins 51 effectively prevent accidental activation of the piston cylinder 4 during lowering of the tubing string due to operational errors or obstructions, pushing the expansion cylinder 3 to open unexpectedly and causing drill sticking.

[0043] The shear ring 5 is cylindrical in shape, with a downward-facing step on its outer surface and external threads. The upper inner wall of the hydraulic cylinder liner 7 also features an upward-facing step and internal threads. The shear ring 5 and the hydraulic cylinder liner 7 are fitted together using the step and fixedly connected via threads. Two symmetrically spaced fixing pins 71 are located at the connection between the shear ring 5 and the hydraulic cylinder liner 7. These pins prevent the threads from rotating and unthreading, effectively ensuring the stability of the connection between the shear ring 5 and the hydraulic cylinder liner 7.

[0044] According to the present invention, the shear value of the first shear pin 51 is less than the shear value of the second shear pin 36. During the ball injection and pressure-holding process, the piston cylinder 4 first shears the first shear pin 51 and then moves axially upward to axially compress the expansion cylinder 3, causing the expansion cylinder 3 to radially expand until it contacts the wellbore wall. After the expansion cylinder 3 expands to the open hole wall, the friction between the expansion cylinder 3 and the open hole wall increases under the further push of the hydraulic pressure. When the friction force exceeds the shear value of the second shear pin 36, the second shear pin 36 is sheared, and the expansion cylinder 3 is disconnected from the tubing string. Thus, the friction between the upper joint 1, the piston cylinder 4, and the open hole wall achieves the directional anchoring of the tubing string.

[0045] According to one embodiment of the present invention, Figure 7 and Figure 8 As shown, the outer wall of the piston cylinder 4 is provided with a first ratchet 41. The first ratchet 41 is preferably provided in the middle area of ​​the outer surface of the piston cylinder 4. A lock ring 6 is provided on the inner wall of the hydraulic cylinder sleeve 7. A mounting step 74 with an upward end face is provided on the inner wall of the hydraulic cylinder sleeve 7. The mounting step 74 is located axially inside the shear ring 5. The lock ring 6 is mounted on the mounting step 74. Figure 9a 、 9b and Figure 10 As shown, the locking ring 6 is an annular structure with an opening 62. The inner wall of the locking ring 6 is provided with a second ratchet 61 adapted to the first ratchet 41 to prevent the piston cylinder 7 from retreating. Preferably, the locking direction of the first ratchet 41 is set to be opposite to the movement direction of the piston cylinder 4, and the right-hand design is convenient for installation. In this way, in the event of accidental pressure relief during operation, the expansion cylinder 3 can always expand in the radial expansion direction without rebounding, thereby maintaining the expansion force. In addition, a feed groove and a back groove are provided at the front and rear ends of the first ratchet 41, respectively, for easy processing.

[0046] During the actual installation process of the open-hole anchor 100 according to the present invention, a seal 11 is installed in the sealing groove provided on the inner wall at the lower end of the upper joint 1, and sealing oil is applied to the connection surfaces of the upper joint 1 and the spindle 2, and then the spindle 2 and the upper joint 1 are connected by threads and tightened. Afterwards, the expansion cylinder 3 is inserted upward from the lower end of the spindle 2, so that the upper end face of the expansion cylinder 3 abuts against the first conical surface of the upper joint 1. Then, the shear ring 5 is inserted upward from the lower end of the piston cylinder 4, so that the upper end face of the shear ring 5 abuts against the lower end face of the annular protrusion 44 of the piston cylinder 4. At the same time, the pin hole of the shear ring 5 is aligned with the pin groove provided on the lower part of the annular protrusion 44 of the piston cylinder 4, and the first shear pin 51 is tightened. Afterwards, the lock ring 6 is installed on the first ratchet 41 of the piston cylinder 4 using shear pliers from the lower end of the piston cylinder 4, and the upper end face of the lock ring 6 abuts against the lower end face of the shear ring 5. Next, seals 42 and 43 are installed in the sealing grooves 45 and 46 of the piston cylinder 4, respectively, and sealing oil is applied. Simultaneously, sealing oil is applied to the sealing surfaces of the spindle 2 corresponding to seals 42 and 43, thereby completing the assembly of the piston cylinder assembly. Next, the piston cylinder assembly is fitted onto the spindle 2 from the lower end upward, so that the pin groove on the upper portion of the annular protrusion 44 of the piston cylinder 4 aligns with the pin hole on the lower portion of the expansion cylinder 3, and the second shear pin 36 is tightened. Next, seal 75 is installed in the sealing groove provided on the inner wall of the hydraulic cylinder sleeve 7, and sealing oil is applied between the connecting surface of the hydraulic cylinder sleeve 7 and the spindle 2. The hydraulic cylinder sleeve 7 is then fitted upward from the lower end of the spindle 2 and the threads are tightened so that the upper end surface of the hydraulic cylinder sleeve 7 abuts the downward-facing stepped structure of the shear ring 5. Finally, the first fixing pin 72 is installed, thereby completing the assembly of the open-hole anchor 100.

[0047] The following is a brief description of the working process of the open hole anchor 100 according to the present invention. First, the open hole anchor 100 is connected to the open hole segmented tubing. In the initial state of the open hole anchor 100, the expansion tube 3 is not expanded. The outer diameter of the expansion tube 3 is basically the same as the outer diameter of the hydraulic cylinder sleeve 7, and is slightly smaller than the maximum outer diameter of the upper joint 1, which facilitates the lowering of the tool into the open hole section. Afterwards, the open hole anchor 100 is driven into the wellbore by the tubing until it reaches the predetermined position. Afterwards, by throwing the ball to hold the pressure, the liquid pressure in the core shaft 2 is continuously increased and enters the hydraulic chamber 8. The hydraulic pressure in the hydraulic chamber 8 acts on the lower end face of the piston cylinder 4 until the shear value of the first shear pin 51 is reached. The piston cylinder 4 shears the first shear pin 51 and pushes the expansion cylinder 3 to move axially, thereby squeezing the expansion cylinder 3 and expanding radially until the expansion cylinder 3 radially expands to contact the wellbore wall. When the expansion cylinder 3 expands to the open hole wall, the friction between the expansion cylinder 3 and the open hole wall continues to increase under the further push of the hydraulic pressure. When the friction force is greater than the shear value of the second shear pin 36, the second shear pin 36 is sheared off, and the expansion cylinder 3 is disconnected from the pipe string. At this time, under the action of the friction between the upper joint 1, the piston cylinder 4 and the open hole wall, the pipe string is anchored.

[0048] The open-hole anchor 100 according to the present invention is capable of adaptively anchoring open-hole segmented tubing with a 20% open-hole expansion rate. The open-hole anchor 100 can be lowered into the open-hole section along with the open-hole packer, ensuring high safety. The open-hole anchor 100 anchors the tubing through friction between the first conical structure of the upper connector 1, the expansion cylinder 3, and the open-hole wall, significantly reducing damage to the open-hole wellbore wall. It also serves to anchor and protect the tubing, preventing creep during high-pressure construction and the resulting packer failure. Furthermore, the expansion cylinder 3, by providing a cutting groove 33 and a cutting seam 34, effectively prevents the open-hole anchor 100 from accidentally opening during the open-hole run, thereby effectively avoiding the risk of drill bit sticking. This significantly improves the efficiency of lowering the open-hole anchor 100 into the open-hole well and its anchoring efficiency.

[0049] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation to the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A naked hole anchor, characterized in that: include: A hollow tubular mandrel (2), wherein the mandrel is provided with a pressure transmission hole (21) penetrating the side wall; an upper joint (1) fixedly connected to the upper end of the spindle; an expansion cylinder (3) sleeved on the mandrel; and A hydraulic drive assembly is sleeved on the mandrel, the hydraulic drive assembly comprises a hydraulic cylinder sleeve (7) and a piston cylinder (4) sleeved on the mandrel, the piston cylinder is installed between the hydraulic cylinder sleeve and the mandrel, and a hydraulic cavity (8) is formed between the hydraulic cylinder sleeve, the mandrel and the piston cylinder, the hydraulic cavity is communicated with the internal flow channel of the mandrel through the pressure transmission hole, and the pressure in the hydraulic cavity can be increased by throwing a ball to hold the pressure and push the piston cylinder upward, thereby squeezing the expansion cylinder to expand radially until the expansion cylinder is anchored to the well wall; The expansion cylinder is constructed to include a first cylinder (31) and a second cylinder (32) connected to the first cylinder, the inner wall surface of the upper end of the first cylinder is provided with a plurality of cutting grooves (33) extending in the axial direction, and the side wall area of ​​the first cylinder located axially inside the cutting groove is provided with a plurality of cutting slits (34) penetrating the side wall, the cutting slits are arranged to extend in the axial direction, and the outer surface of the connection between the first cylinder and the second cylinder is provided with a plurality of circumferentially uniformly distributed stress grooves (35), and the stress grooves can guide the radial expansion of the expansion cylinder.

2. The open hole anchor according to claim 1, characterized in that: The plurality of cutting grooves are evenly distributed in the circumferential direction, the plurality of cutting slits are evenly distributed in the circumferential direction, and the circumferential positions of the cutting grooves and the cutting slits correspond to each other.

3. The open hole anchor according to claim 1 or 2, characterized in that: The outer wall of the lower end of the upper joint is configured as a first conical surface, and the inner wall of the expansion cylinder located axially inside the cutting groove is configured as a second conical surface, and the second conical surface is adapted to be installed with the first conical surface.

4. The open hole anchor according to claim 1, characterized in that The hydraulic cylinder sleeve is fixedly connected to the spindle via a plurality of first fixing pins (72), and the plurality of first fixing pins are evenly distributed in the circumferential direction.

5. The open hole anchor according to claim 1, characterized in that: The inner wall of the hydraulic cylinder sleeve is provided with a shoulder (73) with an end surface facing upward, and the hydraulic cavity is formed between the inner wall of the hydraulic cylinder sleeve, the shoulder and the outer wall of the spindle.

6. The open hole anchor according to claim 1, characterized in that: A shear ring (5) is provided between the piston cylinder and the hydraulic cylinder sleeve. The shear ring is fixedly connected to the hydraulic cylinder sleeve and is fixedly connected to the piston cylinder via a first shear pin (51).

7. The open hole anchor according to claim 6, characterized in that: The piston cylinder is fixedly connected to the expansion cylinder via a second shear pin (36), wherein the shear value of the first shear pin is smaller than the shear value of the second shear pin. During the ball-throwing and pressure-holding process, the piston cylinder first shears off the first shear pin and moves axially upward to axially compress the expansion cylinder, causing the expansion cylinder to radially expand until it contacts the wellbore wall and generates friction. The second shear pin is sheared off when the friction force is greater than its shear value, thereby completing anchoring.

8. The open hole anchor according to claim 6, characterized in that: The outer wall of the piston cylinder is provided with a first ratchet (41), the inner wall of the hydraulic cylinder sleeve is provided with a lock ring (6), and the inner wall of the lock ring is provided with a second ratchet (61) adapted to the first ratchet for preventing the piston cylinder from retreating.

9. The open hole anchor according to claim 8, characterized in that: An installation step (74) with an upward end face is provided on the inner wall of the hydraulic cylinder sleeve. The installation step is located on the axial inner side of the shear ring, and the lock ring is installed on the installation step.

10. The open hole anchor according to claim 6, characterized in that: A sealing member is provided between the connecting surface of the upper joint and the spindle, a sealing member is provided between the piston cylinder and the spindle and the hydraulic cylinder sleeve respectively, and a sealing member is provided between the hydraulic cylinder sleeve and the spindle.

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