Pressure control hydraulic anchor

Abstract

The utility model discloses a pressure control hydraulic anchor which comprises a central pipe and an outer pipe detachably arranged on the peripheral side of the central pipe in a sleeving mode, a closed annular hydraulic cavity is formed between the central pipe and the outer pipe, and a communicating hole is formed in the pipe wall of the central pipe so that the annular hydraulic cavity can be communicated with the inner space of the central pipe. The switch part is arranged relative to the communicating hole and has a first state and a second state; in the first state, the switch part blocks the communicating hole so that the annular hydraulic cavity does not communicate with the inner space of the center pipe, and in the second state, the switch part does not block the communicating hole so that the annular hydraulic cavity communicates with the inner space of the center pipe. The anchoring part is arranged on the hydraulic anchor and can extend outwards for anchoring or return to release anchoring. The problem that a hydraulic anchor is anchored accidentally in a well is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of hydraulic anchors, in particular to a pressure-controlled hydraulic anchor. Background Art

[0002] The existing technology is a common hydraulic anchor, which relies on the oil-casing pressure difference to work. Oil-casing pressure difference: The difference between the internal pressure of the pipe string at a certain depth (referred to as oil pressure) and the pressure between the outside of the pipe string and the casing or between the pipe string and the open hole wall (referred to as casing pressure) is referred to as the oil-casing pressure difference. When the oil-casing pressure difference is greater than the pressure generated by the maximum elastic force of the hydraulic anchor retraction spring acting on the anchor claw (or slip) (referred to as the minimum anchoring pressure difference), the hydraulic anchor claw extends out to anchor the pipe string. When the oil-casing pressure difference is greater than zero and less than the pressure generated by the maximum elastic force of the retraction spring acting on the anchor claw (or slip), or when the oil-casing pressure difference is less than zero, the hydraulic anchor claw retracts to release the anchor (referred to as unanchoring). When the hydraulic anchor is anchored to the pipe string, it can effectively protect the sealing of the packer and other work. After the hydraulic anchor is unanchored, the normal sealing of the packer cannot be guaranteed. Even in the case of long-term creep, it may cause fatigue and breakage of the pipe string.

[0003] The existing common hydraulic anchor has the following defects: because the retraction direction of the retraction spring is in the radial direction of the pipe column, the space is limited, the diameter is no more than 20mm, the length is no more than 30mm, the total extension distance is less than 15mm, the maximum effective elastic force is no more than 1000N, the cross-sectional diameter of the anchor claw is 50mm, and the maximum pressure generated by the anchor claw is no more than 1000 / (3.14╳0.025╳0.025)=50930Pa=0.51Mpa, which is very small, equivalent to a slight oil-casing pressure difference in the well, which will cause the anchor claw to extend out of the anchor pipe column. Especially in the process of lifting and lowering the pipe column, the formation oil and gas will often enter the wellbore annulus under the conditions of pipe column suction or agitation, and mix with the well killing fluid, causing the oil-casing pressure difference at the hydraulic anchor to increase to exceed the minimum anchoring pressure difference, which will cause the hydraulic anchor to be accidentally anchored. If the string is accidentally anchored in advance during the process of lowering the pipe, the string will encounter resistance and the packer string will not be able to be lowered to the predetermined position; if it is lowered by strong pressure, it will cause damage to the hydraulic anchor and / or casing; if it is accidentally anchored during the process of lifting the string, it will cause a drill sticking accident and the string cannot be pulled out of the well; if it is forcibly lifted, it will cause damage to the anchor and / or casing, and even cause the string to break off and form fallen objects in the wellbore.

[0004] Therefore, how to provide a hydraulic anchor that can solve the above-mentioned drawbacks is a problem that needs to be solved urgently. Summary of the invention

[0005] The technical problem to be solved by the utility model is to provide a pressure-controlled hydraulic anchor to solve the problem of accidental anchoring of the hydraulic anchor in the well. The specific technical solution is as follows:

[0006] A pressure-controlled hydraulic anchor comprises a central tube and an outer tube detachably mounted on the outer circumference thereof, a closed annular hydraulic chamber being arranged between the central tube and the outer tube, a connecting hole being arranged on the tube wall of the central tube so that the annular hydraulic chamber can be connected to the internal space of the central tube, and a switch portion being arranged relative to the connecting hole, the switch portion having a first state and a second state, wherein in the first state, the switch portion blocks the connecting hole so that the annular hydraulic chamber is not connected to the internal space of the central tube, and in the second state, the switch portion does not block the connecting hole so that the annular hydraulic chamber is connected to the internal space of the central tube, and an anchor portion being arranged on the hydraulic anchor and capable of extending outward for anchoring or returning to release the anchoring.

[0007] Preferably, a first space and a second space are formed between the central tube and the outer tube, which are arranged in an annular direction from bottom to top, the communicating hole is toward the first space, the second space forms the annular hydraulic chamber, the first space and the second space are connected through a vertical through hole, and also include a strong spring, a piston ring and a short piston rod, the strong spring is located in the first annular space and its fixed end is located at the lower position of the first space, and the free end is connected to the lower end of the piston ring, the upper end of the piston ring is connected to the fixed end of the short piston rod, the short piston rod can seal and pass through the vertical through hole and its free end can extend into the second space, the strong spring The force spring has an initial state and a compressed state. In the initial state, the piston ring is located at a lower position of the connecting hole, the short piston rod seals and passes through the vertical through hole and its free end extends into the second space. In the compressed state, the short piston rod does not seal and passes through the vertical through hole so that the first space is connected to the second space. The first space, the strong spring, the piston ring, the short piston rod and the vertical through hole form the switch part, so that the strong spring forms the first state of the switch part in the initial state and the second state of the switch part in the compressed state, and the anchoring part is arranged at a position corresponding to the second space.

[0008] Preferably, it also includes an iron washer, which is fixed at a lower position of the first space and fixedly connected to the fixed end of the strong spring.

[0009] Preferably, the first space and the second space are also connected through three guide through holes, and also include three long piston rods, the fixed end of each long piston rod is fixedly connected to the upper end of the piston ring, each long piston rod corresponds to one of the guide through holes and can be sealed and penetrated through the corresponding guide through hole, the length of each long piston rod is set so that when the strong spring is in the compressed state, the long piston rod still seals and penetrates the corresponding guide through hole, and the three long piston rods and one short piston rod are evenly spaced along the circumferential direction of the piston ring.

[0010] Preferably, it also includes a chamber for installing a pressure relief valve located above the second space and outside the central tube, the pressure relief valve including a small pressure relief valve spring and a valve plate, the axial direction of the chamber is perpendicular to the axis of the central tube, a pressure relief through hole is provided on the central tube corresponding to the chamber, the small pressure relief valve spring is arranged in the chamber along the horizontal direction and its fixed end is fixed on the outer wall of the central tube, and the free end is fixedly connected to the valve plate, a top hole connected to the second space is provided at the top of the chamber, the small pressure relief valve spring has a closed state and a pressure relief state, in the closed state, the valve plate blocks the top hole under the action of the small pressure relief valve spring, and in the pressure relief state, the valve plate does not block the top hole so that the second space is connected to the chamber.

[0011] Preferably, the pressure relief through hole is opened below the fixed end of the small spring of the pressure relief valve.

[0012] Preferably, the anchoring portion comprises four groups of anchoring units evenly spaced apart along the circumferential surface of the body of the hydraulic anchor, each of the anchoring units comprises three groups of anchor shoes arranged along the vertical direction, and an anchor shoe retraction spring is provided corresponding to each anchor shoe.

[0013] Preferably, the upstream end of the central tube forms an upper joint provided with a female buckle, and the downstream end forms a lower joint provided with a male buckle.

[0014] The technical effects of the equipment provided are:

[0015] A switch part is provided to control the anchoring pressure. In one embodiment, the main component is a strong spring, the lower end of which is connected to the step of the central tube, and the other end is connected to a set of piston valve components. The piston valve is a ring-mounted piston ring to connect 4 piston rods, which are divided into long piston rods (3) and short piston rods (1). The long piston rod is used to fix the orientation, and the short piston rod is used to switch the vertical through hole for liquid to enter the anchoring annular hydraulic cavity. Furthermore, the position of the strong spring can be adjusted by placing or removing the iron gasket in the annular space, and the anchoring starting pressure can be quantitatively controlled, that is, the anchoring starting pressure value is set (the value range is between the anchor shoe retraction spring and the internal pressure resistance of the pipe string, and is less than the hydraulic setting type packer setting pressure -5MPa, the range is very wide), so that the initial anchoring pressure is completely controllable. For example, the anchoring starting pressure can be set to 10MPa, 15MPa, 20MPa, 25Mpa or 30MPa, etc. The hydraulic anchor can only be anchored when the oil casing pressure difference is ≥10MPa, 15MPa, 20MPa, 25Mpa or 30MPa, etc.

[0016] Preferably, a pressure relief valve is provided to only allow the anchor hydraulic chamber to flow toward the center of the pipe string, and is used to release the high-pressure liquid in the anchor hydraulic chamber when releasing the anchor, reduce the pressure in the hydraulic chamber, and allow the anchor claw to retract into the hydraulic chamber, thereby achieving a controllable anchor release device. When the oil pressure ≥ the anchor hydraulic chamber pressure - the pressure caused by the small spring force of the pressure relief valve (≈0.01MPa), the small spring of the pressure relief valve pushes the valve plate toward the outside of the pipe string, and the valve plate isolates the anchor hydraulic chamber from the inner cavity of the pipe string, and the valve is in a closed state. When the anchor hydraulic chamber pressure > the oil pressure + the pressure caused by the small spring force of the pressure relief valve (≈0.01MPa), the hydraulic chamber pressure acts on the valve plate and pushes back to cause the spring to contract, the valve opens, and the fluid in the hydraulic chamber flows toward the center of the pipe string, thereby achieving the purpose of pressure relief. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of the pressure-controlled hydraulic anchor provided by the utility model;

[0018] Figure 2 Simulation analysis diagram of uncontrolled hydraulic anchor pressure and working status.

[0019] Figure 1 The accompanying drawings are denoted as follows:

[0020] 1 center tube, 2 outer tube, 3 connecting hole, 4 first space, 5 second space, 6 strong spring, 7 piston ring, 8 short piston rod, 9 vertical through hole, 10 guide through hole, 11 long piston rod, 12 chamber, 13 small spring of pressure relief valve, 14 valve plate, 15 top hole, 16 pressure relief through hole, 17 anchor shoe, 18 anchor shoe retraction spring. DETAILED DESCRIPTION

[0021] The utility model will be described in further detail below.

[0022] The present invention will be described in more detail below with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown. It should be understood that those skilled in the art can modify the present invention described herein and still achieve the beneficial effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art and not as a limitation to the present invention.

[0023] For the sake of clarity, not all features of the actual embodiments are described. In the following description, well-known functions and structures are not described in detail because they would make the utility model confusing due to unnecessary details. It should be recognized that in the development of any actual embodiment, a large number of implementation details must be made to achieve the specific goals of the developer.

[0024] In order to make the purpose and features of the utility model more obvious and easy to understand, the specific implementation of the utility model is further described below in conjunction with the accompanying drawings. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise ratios, which are only used to conveniently and clearly assist in explaining the purpose of the embodiment of the utility model.

[0025] Combination Figure 1 , which is a schematic diagram of the structure of the pressure-controlled hydraulic anchor provided by the utility model; it includes a central tube 1 and an outer tube 2 detachably sleeved on its outer circumference, a closed annular hydraulic chamber is arranged between the central tube 1 and the outer tube 2, a connecting hole 3 is arranged on the tube wall of the central tube 1 so that the annular hydraulic chamber can be connected to the internal space of the central tube 1, and also includes a switch part arranged relative to the connecting hole 3, the switch part has a first state and a second state, in the first state, the switch part blocks the connecting hole 3 so that the annular hydraulic chamber is not connected to the internal space of the central tube 1, and in the second state, the switch part does not block the connecting hole 3 so that the annular hydraulic chamber is connected to the internal space of the central tube 1, and also includes an anchoring part arranged on the hydraulic anchor that can extend outward for anchoring or return to release the anchoring.

[0026] In a specific implementation manner, Figure 1 As shown, a first space 4 and a second space 5 are formed between the central tube 1 and the outer tube 2 and are arranged in an annular direction from bottom to top. The communicating hole 3 is toward the first space 4, and the second space 5 forms the annular hydraulic chamber. The first space 4 and the second space 5 are connected through a vertical through hole 9. The central tube 1 and the outer tube 2 also include a strong spring 6, a piston ring 7 and a short piston rod 8. The strong spring 6 is located in the annular first space 4 and its fixed end is located at the lower position of the first space 4, and its free end is connected to the lower end of the piston ring 7. The upper end of the piston ring 7 is connected to the fixed end of the short piston rod 8. The short piston rod 8 can pass through the vertical through hole 9 in a sealing manner and its free end can extend into the second space 5. The strong spring 6 has an initial state and a compressed state. In the initial state, the piston ring 7 is located at a lower position of the connecting hole 3, the short piston rod 8 seals and penetrates the vertical through hole 9 and its free end extends into the second space 5. In the compressed state, the short piston rod 8 does not seal and penetrates the vertical through hole 9 so that the first space 4 is connected to the second space 5. The first space 4, the strong spring 6, the piston ring 7, the short piston 8 rod and the vertical through hole 9 form the switch part, so that the strong spring 6 forms the first state of the switch part in the initial state and the second state of the switch part in the compressed state, and the anchoring part is arranged at a position corresponding to the second space 5.

[0027] A switch is provided to control the anchoring pressure; in one embodiment, the main component is a strong spring 6, the lower end of which is connected to the step of the central pipe 1, and the other end is connected to a set of piston valve components, the piston valve is a ring-mounted piston ring 7 to connect 4 piston rods, which are divided into long piston rods 11 (3 rods) and short piston rods 8 (1 rod), the long piston rod 11 is used to fix the position, and the short piston rod 8 is used to switch the vertical through hole 9 for liquid to enter the annular hydraulic cavity of the anchoring direction. That is, the anchoring starting pressure value is set (the value range is between the anchor shoe retraction spring and the internal pressure resistance of the pipe string, and is less than the hydraulic setting type packer setting pressure -5MPa, the range is very wide), so that the initial anchoring pressure is fully controllable, for example, the anchoring starting pressure can be set to 10MPa, 15MPa, 20MPa, 25Mpa or 30MPa, etc., and the hydraulic anchor can only be anchored when the oil-casing pressure difference is ≥10MPa, 15MPa, 20MPa, 25Mpa or 30MPa, etc.

[0028] Furthermore, it also includes an iron washer, which is fixed at a lower position of the first space 4 and fixedly connected to the fixed end of the strong spring 6.

[0029] Furthermore, the position of the strong spring 6 can be adjusted by placing or removing the iron washer in the annular space, and the anchoring starting pressure can be quantitatively controlled.

[0030] In a specific embodiment, the first space 4 and the second space 5 are also connected through three guide through holes 10, and also include three long piston rods 11, the fixed end of each long piston rod 11 is fixedly connected to the upper end of the piston ring 7, each long piston rod 11 corresponds to one of the guide through holes 10 and can be sealed and penetrated through the corresponding guide through hole 10, the length of each of the long piston rods 11 is set so that when the strong spring 6 is in the compressed state, the long piston rod 11 is still sealed and penetrates the corresponding guide through hole 10, and the three long piston rods 11 and one short piston rod 8 are evenly spaced along the circumferential direction of the piston ring 7.

[0031] In a specific embodiment, it also includes a chamber 12 for installing a pressure relief valve located above the second space 5 and outside the central tube 1, the pressure relief valve includes a small pressure relief valve spring 13 and a valve plate 14, the axial direction of the chamber 12 is perpendicular to the axis of the central tube 1, and a pressure relief through hole 16 is opened on the central tube 1 corresponding to the chamber 12, the small pressure relief valve spring 13 is arranged in the chamber 12 along the horizontal direction and its fixed end is fixed on the outer wall of the central tube 1, and the free end is fixedly connected to the valve plate 14, and a top hole 15 connected to the second space 5 is opened at the top of the chamber 12, the small pressure relief valve spring 13 has a closed state and a pressure relief state, in the closed state, the valve plate 14 blocks the top hole 15 under the action of the small pressure relief valve spring 13, and in the pressure relief state, the valve plate 14 does not block the top hole 15 so that the second space 5 is connected to the chamber 12.

[0032] A pressure relief valve is provided to only allow the anchor hydraulic chamber to flow toward the center of the pipe column. It is used to release the high-pressure liquid in the anchor hydraulic chamber when releasing the anchor, reduce the pressure in the hydraulic chamber, and allow the anchor claw (i.e., anchor shoe 17) to retract into the hydraulic chamber, thus achieving a controllable anchor release device. When the oil pressure ≥ the anchor hydraulic chamber pressure - the pressure caused by the small spring force of the pressure relief valve (≈0.01MPa), the small spring 13 of the pressure relief valve pushes the valve plate 14 toward the outside of the pipe column, and the valve plate 14 isolates the anchor hydraulic chamber from the inner cavity of the pipe column, and the valve is in a closed state. When the anchor hydraulic chamber pressure > the oil pressure + the pressure caused by the small spring force of the pressure relief valve (≈0.01MPa), the hydraulic chamber pressure acts on the valve plate 14 and pushes back to cause the spring to contract, the valve opens, and the fluid in the hydraulic chamber flows toward the center of the pipe column, thus achieving the purpose of pressure relief.

[0033] like Figure 1 As shown, the pressure relief through hole 16 is opened below the fixed end of the pressure relief valve small spring 13 .

[0034] In a specific embodiment, the anchoring part includes four groups of anchoring units evenly spaced along the circumferential surface of the body of the hydraulic anchor, each of the anchoring units includes three groups of anchor shoes 17 arranged in the vertical direction, and an anchor shoe retraction spring 18 is provided corresponding to each anchor shoe 17. The anchoring part (common hydraulic anchors all have, briefly described): a slip-shaped device (referred to as anchor shoe or anchor claw) used to fix the pipe column on the casing wall. One end of the cylinder is processed into a cylindrical surface that fits the inner surface of the casing, and the engaging teeth are milled out. When subjected to a pressure difference, it extends out of the pipe column and engages with the inner wall of the casing (or the wall of the open hole). The other end is a plane perpendicular to the axial direction of the column, which serves as the anchor hydraulic force surface in the hydraulic cavity inside the pipe column. Functional features: When the hydraulic chamber pressure > casing pressure + anchor shoe retraction spring pressure, the spring is compressed, the anchor shoe extends out of the pipe string and bites on the well wall to achieve the purpose of anchoring the pipe string; when the casing pressure > hydraulic chamber pressure - anchor shoe retraction spring pressure, the spring extends, the anchor shoe retracts into the hydraulic chamber to achieve the purpose of unanchoring the pipe string.

[0035] In a specific implementation manner, the upstream end of the central tube 1 forms an upper joint provided with a female buckle, and the downstream end forms a lower joint provided with a male buckle.

[0036] Working mechanism: (1) Before the tubing enters the well, the external pressure (casing pressure), internal pressure (oil pressure), and pressure in the anchor hydraulic chamber (chamber pressure for short) of the hydraulic anchor are all equal to the standard atmospheric pressure (≈0.1MPa) in a balanced state, and the hydraulic anchor is in an unanchored state. (2) As the tubing enters the wellbore until the tubing is in place and before positive pressure is applied, the oil-casing pressure gradually increases after entering the wellbore liquid surface, and the oil pressure ≈ casing pressure. As the depth increases, the oil-casing pressure difference may continue to increase due to the invasion of formation oil and gas into the wellbore pressure fluid (affected by the bottom plug and other tubing tools, the fluidity of the oil-casing annulus is generally stronger than that of the tubing, and the oil and gas invasion is more serious, and the density is lower, resulting in the oil pressure being greater than the casing pressure at the depth of the hydraulic anchor). However, due to the action of the strong spring 6, when the oil-casing pressure difference is less than the set anchoring starting pressure, firstly, the short piston rod 8 is in the vertical through hole 9, and the first space 4 and the second space 5 are not connected; secondly, the oil pressure is also greater than the pressure in the hydraulic chamber, and the pressure relief valve is in a closed state; thirdly, the casing pressure is greater than the pressure in the hydraulic chamber, and under the action of the anchor shoe retraction spring 18, the anchor shoe 17 is at the bottom of the hydraulic chamber toward the center of the pipe string, and the hydraulic anchor is in an unanchored state. (3) Before the hydraulic packer (such as Y341, K344, K343, etc.) is set, and after the packer (such as Y221, Y211, etc.) is set, the pipe string is slowly positively pressurized to gradually make the oil-casing pressure difference greater than the set anchoring start pressure. At this time, the piston ring 7 and the long and short piston rods connected to the strong spring 6 move toward the spring end, causing the spring to shorten. When the end of the short piston rod 8 withdraws from the vertical through hole 9, the hydraulic chamber is connected to the inside of the pipe string. The fluid quickly enters the hydraulic chamber from the inside of the pipe string. The pressure in the hydraulic chamber rises rapidly to be equal to the oil pressure and greater than the set anchoring start pressure. Since the pressure in this hydraulic chamber is much greater than the casing pressure, the force-bearing surface of the anchor shoe is pushed and moves from the center of the pipe string to the outer end, extending out of the pipe string until the anchor shoe 17 bites into the well wall (the inner wall of the casing or the wall of the open hole), completing the work of anchoring the pipe string. (4) After the anchoring work is completed, when the tubing string performs other processes without moving the tubing string (including packer setting, acidizing, fracturing, wellbore leak detection, water injection, oil pumping, gas production, etc.), as long as the oil pressure (variable) is greater than the pressure (variable) in the hydraulic chamber - the pressure (constant) caused by the small spring, and the casing pressure (variable) is less than the pressure (variable) in the hydraulic chamber - the pressure (constant) caused by the anchor shoe retraction spring, the hydraulic chamber remains stable and the tubing string remains anchored. (5) When the casing annulus is pressurized and / or the pressure in the tubing is relieved, ① the strong spring 6 is in its longest state and the short piston rod 8 is at the top of the hydraulic chamber; ② the oil pressure is less than the pressure in the hydraulic chamber - the small spring of the pressure relief valve causes the pressure (constant), the pressure relief valve opens, and the pressure in the hydraulic chamber drops; ③ the casing pressure (variable) is greater than the pressure in the hydraulic chamber (variable) - the anchor shoe retraction spring causes the pressure (constant), the anchor shoe moves horizontally into the hydraulic chamber and retracts into the tubing, and the tubing changes from an anchored state to an unanchored state.

[0037] The pipe string in the unanchored state can move freely up and down according to the construction needs. The pipe string in the anchored state cannot move freely up and down. If it must move, it will cause damage to the well wall, casing damage, or anchor shoe wear.

[0038] The pressure-controlled hydraulic anchor adds a pressure-control device and a pressure relief valve device on the basis of the ordinary hydraulic anchor, and acts on the anchor hydraulic cavity together with the anchor device, and realizes repeated anchoring and unanchoring by using the increase and decrease of the casing pressure. Its characteristics are: 1. Before the hydraulic anchor is put into the well, the anchoring start pressure can be quantitatively adjusted to a relatively high fixed value to prevent the pipe string from being accidentally anchored in the well; 2. The pressure-controlled strong spring has a large diameter and high strength, and is highly corrosion-resistant. The diameter of its steel bar is much larger than the thickness of the pipe string, and its underground service life is much longer than the life of the pipe string; 3. The anchor shoe retraction spring is sealed in the anchor hydraulic cavity, and the liquid exchange opportunity is very small. The corrosion resistance time is slightly longer than the service life of the pipe string; 4. Although the small spring of the pressure relief valve device has a small strength, it is a single-flow valve device, and a single-flow cover plate is set between it and the inner cavity of the pipe string. Only at the moment of unanchoring can liquid flow through this part, and it can also achieve a longer service life than the pipe string. Therefore, the invention cleverly solves the problem of accidental anchoring of the packer pipe string and achieves the purpose of safe and efficient underground operation and construction. On average, solving each accidental anchoring problem can avoid economic losses of about 100,000 to 200,000 yuan and save 1 to 3 days of construction time.

[0039] Simulation setting conditions: (1) The oil pressure, casing pressure, and cavity pressure near the ground are standard atmospheric pressure ≈ 0 MPa; (2) The anchoring starting pressure value is set, that is, the oil-casing pressure difference of 10 MPa is the critical value of the switch; (3) The maximum pressure of the anchor shoe retraction spring is 2 MPa; (4) The maximum pressure of the small spring of the pressure relief valve is 1 MPa; (5) The pressure-controlled hydraulic anchor is lowered from the ground to a certain depth, and the casing pressure rises to 6 MPa and remains unchanged. After the oil pressure rises to 6 MPa at this depth, the pumping equipment continues to increase the pressure at a uniform speed to 35 MPa, and then the pressure is uniformly released to 0 MPa, and then pumped again to increase the pressure to 35 MPa.

[0040] Observe and analyze the changes in chamber pressure and the working conditions of the pressure control valve (i.e. switch), pressure relief valve, and anchor shoe Figure 2As shown: (1) Pressure control valve status: initially, it is in the closed state when the pressure control spring is extended. When the set oil-casing pressure difference reaches 10, that is, when the oil pressure rises to 16MPa, the pressure control valve opens. When the oil pressure rises to 35MPa and then drops to less than 16MPa, the pressure control valve closes again. When the oil pressure continues to drop and then rises to 16MPa again, the pressure control valve opens again. It can be opened and closed repeatedly for many times; (2) Anchor shoe status: initially, when the pressure control spring is extended and the hydraulic chamber is filled with air, it is the unanchoring state. When the set oil-casing pressure difference reaches 10, that is, when the oil pressure rises to 16MPa, the pressure control valve opens, and the well fluid enters the hydraulic chamber. The pressure quickly rises to 16MPa, which is much greater than the retraction spring, causing the pressure plus the casing pressure (2+6MPa). The anchor shoe quickly extends out of the anchor string. When the oil pressure rises to 35MPa, the pressure is released, and then drops below 7MPa. The pressure in the hydraulic chamber drops below 8MPa through the pressure relief valve. At this time, the anchor shoe retraction spring causes the pressure (2MPa) to retract the anchor shoe, and the pipe is The string is unanchored. When the oil pressure continues to drop and then rises to 16MPa again, the pressure control valve opens again and the string is anchored again. It can be anchored and unanchored repeatedly. (3) Pressure relief valve state: The initial state is closed. When the oil pressure rises from zero to the original wellbore pressure of 6MPa, and then continues to rise to 16MPa until the pressure control valve opens, the pressure in the hydraulic chamber rises to 35MPa at the same time as the oil pressure, and then continues to release the pressure after the pressure is released to 34MPa. The oil pressure plus the small spring causes the pressure (1MPa) to be less than or equal to At the pressure in the hydraulic cavity (cavity pressure), the pressure relief valve opens until the pressure is relieved to 7MPa oil pressure and 8MPa cavity pressure, and the hydraulic anchor is released until the oil pressure drops to zero MPa again. The pressure relief valve is always in the open state, but in general actual well conditions, the pressure relief limit is reached when the natural pressure is released to the oil casing pressure balance (6MPa). At this time, the well is shut down and stationary, the pressure relief valve is closed, and the anchor shoe is in the released anchor state. If the string is pressurized again, the oil pressure will be greater than the cavity pressure, and the pressure relief valve is always in the closed state. The specific process is also referred to the following table:

[0041] Table 1 Simulation analysis of pressure and working status of pressure-controlled hydraulic anchor

[0042]

[0043] The above shows and describes the basic principles, main features and advantages of the utility model, so the above is only an embodiment of the utility model. Those skilled in the art should understand that the utility model is not limited by the above embodiments. The above embodiments and the description only describe the principles of the utility model. Without departing from the spirit and scope of the utility model, the utility model also includes various equivalent changes and improvements, which will fall within the scope of the utility model to be protected. The scope of protection claimed by the utility model is defined by the attached claims and their equivalents.

Claims

1. A pressure-controlled hydraulic anchor, characterized in that: The hydraulic anchor comprises a central tube and an outer tube detachably mounted on the outer circumference thereof, a sealed annular hydraulic chamber being arranged between the central tube and the outer tube, a connecting hole being arranged on the tube wall of the central tube so that the annular hydraulic chamber can be connected to the internal space of the central tube, and a switch portion being arranged relative to the connecting hole, the switch portion having a first state and a second state, in the first state the switch portion blocks the connecting hole so that the annular hydraulic chamber is not connected to the internal space of the central tube, and in the second state the switch portion does not block the connecting hole so that the annular hydraulic chamber is connected to the internal space of the central tube, and an anchor portion being arranged on the hydraulic anchor and capable of extending outward for anchoring or returning to release the anchoring.

2. The pressure-controlled hydraulic anchor according to claim 1, characterized in that: A first space and a second space are formed between the central tube and the outer tube, which are arranged in an annular direction from bottom to top. The communicating hole is toward the first space, and the second space forms the annular hydraulic chamber. The first space and the second space are connected through a vertical through hole. The central tube also includes a strong spring, a piston ring and a short piston rod. The strong spring is located in the first annular space, and its fixed end is located at the lower position of the first space, and the free end is connected to the lower end of the piston ring. The upper end of the piston ring is connected to the fixed end of the short piston rod. The short piston rod can seal and pass through the vertical through hole, and its free end can extend into the second space. The spring has an initial state and a compressed state. In the initial state, the piston ring is located at a lower position of the connecting hole, the short piston rod seals and passes through the vertical through hole and its free end extends into the second space. In the compressed state, the short piston rod does not seal and passes through the vertical through hole so that the first space is connected to the second space. The first space, the strong spring, the piston ring, the short piston rod and the vertical through hole form the switch part, so that the strong spring forms the first state of the switch part in the initial state and the second state of the switch part in the compressed state, and the anchoring part is arranged at a position corresponding to the second space.

3. The pressure-controlled hydraulic anchor according to claim 2, characterized in that: It also includes an iron washer, which is fixed at a lower position of the first space and is fixedly connected to the fixed end of the strong spring.

4. The pressure-controlled hydraulic anchor according to claim 3, characterized in that: The first space and the second space are also connected through three guide through holes, and also include three long piston rods. The fixed end of each long piston rod is fixedly connected to the upper end of the piston ring. Each long piston rod corresponds to one of the guide through holes and can be sealed and penetrated through the corresponding guide through hole. The length of each long piston rod is set so that when the strong spring is in the compressed state, the long piston rod still seals and penetrates the corresponding guide through hole. The three long piston rods and one short piston rod are evenly spaced along the circumferential direction of the piston ring.

5. The pressure-controlled hydraulic anchor according to claim 4, characterized in that: It also includes a chamber located above the second space and outside the central tube for installing a pressure relief valve, the pressure relief valve includes a small pressure relief valve spring and a valve plate, the axial direction of the chamber is perpendicular to the axis of the central tube, a pressure relief through hole is provided on the central tube corresponding to the chamber, the small pressure relief valve spring is arranged in the chamber along the horizontal direction and its fixed end is fixed on the outer wall of the central tube, and the free end is fixedly connected to the valve plate, a top hole connected to the second space is provided at the top of the chamber, the small pressure relief valve spring has a closed state and a pressure relief state, in the closed state, the valve plate blocks the top hole under the action of the small pressure relief valve spring, and in the pressure relief state, the valve plate does not block the top hole so that the second space is connected to the chamber.

6. The pressure-controlled hydraulic anchor according to claim 5, characterized in that: The pressure relief through hole is arranged below the fixed end of the small spring of the pressure relief valve.

7. The pressure-controlled hydraulic anchor according to claim 2, characterized in that: The anchoring part includes four groups of anchoring units evenly spaced along the circumferential surface of the body of the hydraulic anchor, each of the anchoring units includes three groups of anchor shoes arranged along the vertical direction, and an anchor shoe retraction spring is provided corresponding to each anchor shoe.

8. The pressure-controlled hydraulic anchor according to claim 1, characterized in that: The upstream end of the central tube forms an upper joint provided with a female buckle, and the downstream end forms a lower joint provided with a male buckle.

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