A segmented prestressed cementing method and tool

Abstract

The present invention belongs to the technical field of cementing and completion, and specifically relates to a segmented prestressed cementing method and tool. The purpose of the present invention is to provide a segmented prestressed cementing method and tool in response to the problems existing in the prior art, including a pressure tube, a cementing casing, a segmented anchor, a sealing pressure device, and a casing plug; the sealing pressure device and the casing plug are respectively installed at the lower ends of the pressure tube and the cementing casing; the cementing casing is provided with a plurality of axially arranged segmented anchors; the pressure tube is slidably installed in the cementing casing. The segmented prestressed cementing method and tool of the present invention can apply different prestressing forces to the casing of different sections according to the different well conditions of each section of the thermal recovery well, thereby avoiding the deficiency that the conventional prestressed cementing operation can only provide a single prestressing force, and can more accurately offset the thermal stress of the casing of different sections, and more effectively prevent casing failure.

Description

Technical Field

[0001] The invention belongs to the technical field of cementing and completion, and in particular relates to a segmented pulling prestressed cementing method and a tool. Background Art

[0002] Prestressed cementing is to apply a certain tensile stress to the casing, so that the casing is cemented in this state. When the temperature rises, it can offset part of the compressive stress generated by the casing due to heat, thereby increasing the temperature resistance limit of the casing and slowing down or avoiding casing damage caused by steam injection. Prestressed cementing technology is a technology commonly used in heavy oil production at home and abroad. In recent years, prestressed cementing technology has been widely used in oil fields. However, as the main tool of prestressed cementing technology, the prestressing tool still has some shortcomings. At present, the prestressing tool can only provide a single prestressing force, and different well sections will produce different casing thermal stresses, which will make it impossible to offset the casing thermal stresses of different well sections. Summary of the invention

[0003] The purpose of the present invention is to provide a segmented prestressed cementing method and tool to solve the problems existing in the prior art.

[0004] The technical solution provided by the present invention to solve the above technical problems is: a segmented pull prestressed cementing tool, including a pressure pipe, a cementing casing, a segmented anchor, a sealing pressure device, and a casing plug;

[0005] The isolation and pressure device and the casing plug are respectively installed at the lower ends of the pressure pipe and the cementing casing; the cementing casing is provided with a plurality of axially arranged segmented anchors; the pressure pipe is slidably installed in the cementing casing.

[0006] A further technical solution is that the segmented ground anchor comprises a shear pin, a fixing pin, a ground anchor connecting pipe, and a sliding wedge sleeve, an anchor claw sleeve, and a fixing wedge sleeve which are sequentially sleeved on the ground anchor connecting pipe from top to bottom;

[0007] The ground anchor connection pipe is connected to the sliding wedge sleeve and the fixed wedge sleeve by using shear pins and fixed pins respectively;

[0008] The lower end of the sliding wedge sleeve has a sliding wedge groove, the upper end of the fixed wedge sleeve has a fixed wedge groove, the upper and lower ends of the anchor claw sleeve are both provided with wedge surfaces, the outside is provided with a toothed structure, and the two ends are respectively located in the sliding wedge groove and the fixed wedge groove;

[0009] A hydraulic cavity a is provided between the outer wall of the ground anchor connection pipe and the inner wall of the sliding wedge sleeve, and a hydraulic hole a communicating with the hydraulic cavity a is radially provided on the ground anchor connection pipe;

[0010] A locking pin with a spring is radially arranged on the outer wall of the upper end of the anchor connection pipe, and a positioning hole matching with the locking pin is arranged on the inner wall of the upper end of the sliding wedge sleeve, and the positioning hole is located above the locking pin;

[0011] The two ends of the ground anchor connecting pipe are respectively provided with internal threads and external threads, and are connected with the cementing casing.

[0012] A further technical solution is that sealing rings a and b are provided on the inner walls of the upper and lower ends of the sliding wedge sleeve respectively.

[0013] A further technical solution is that the isolation and pressure device comprises an isolation and pressure device connecting pipe, an isolation sliding sleeve, an isolation rubber ring, a pressure head, a retaining ring, and a fixed retaining sleeve;

[0014] The fixed stopper sleeve is fixed on the connecting pipe of the packer and the packer sleeve and the packer rubber ring are sequentially sleeved on the connecting pipe of the packer and the packer from top to bottom, and the packer head is installed at the lower end of the connecting pipe of the packer and the packer;

[0015] The baffle ring is provided with a spherical hole in the middle part and is installed between the lower end surface of the connection pipe of the packer and the inner cavity of the pressure head; a valve ball and a spring are installed inside the pressure head; one end of the spring is fixed to the inner wall of the pressure head, and the other end is connected to the valve ball, and the spring presses the valve ball to block it in the spherical hole in the middle part of the baffle ring; the lower end of the pressure head is provided with a pressure hole communicating with the inner cavity of the lower end;

[0016] A hydraulic cavity b is provided between the outer wall of the isolation and pressure device connecting pipe and the inner wall of the isolation and pressure device sliding sleeve, and a hydraulic hole b communicating with the hydraulic cavity b is radially provided on the isolation and pressure device connecting pipe.

[0017] A further technical solution is that a sealing ring c and a sealing ring d are respectively provided on the inner walls of the upper and lower ends of the isolation and pressure device connecting pipe.

[0018] A further technical solution is that the upper and lower ends of the isolation and pressure device connecting pipe are respectively provided with internal threads and external threads, and are respectively threadedly connected with the pressure pipe and the pressure head.

[0019] A segmented prestressed cementing method comprises the following steps:

[0020] S1. Determine the number of cementing casing stretching sections and the installation positions of segmented anchors in the well;

[0021] S2. Calculate the pulling force required to be applied to each section of casing at the wellhead during prestressed cementing;

[0022] S3, according to the number of cementing casing stretching sections determined in step S1 and the installation position of the segmented anchors in the well, connecting the segmented anchors, cementing casings, and casing plugs to form a cementing pipe string, and lowering the cementing pipe string into the wellbore of the oil well;

[0023] S4, connecting the pressure pipe and the isolation pressure device to form a pressure pipe string, and lowering the pressure pipe string into the cementing pipe string;

[0024] S5, anchoring the first section of cementing casing;

[0025] S6, lifting the first section of cementing string;

[0026] S7, anchoring the second section of cementing string;

[0027] S8, lifting the second section of the cementing string according to the method of lifting the first section of the cementing string in step S6;

[0028] S9, anchoring and lifting the remaining section of the cementing casing according to the method described in step S5 and step S6;

[0029] S10, after all pipe sections are lifted, the pressurized pipe string is taken out;

[0030] S11, drilling through the casing plug;

[0031] S12, injecting cement into the cementing string to cement the well.

[0032] A further technical solution is that the specific process of step S5 is:

[0033] S51, introducing drilling fluid into the pressure pipe string;

[0034] S52, raising the drilling fluid pressure in the pressure pipe string at the wellhead to p1, and setting the isolation pressure device;

[0035] S53, at the wellhead, the drilling fluid pressure in the pressure-reducing pipe string is continuously increased to p2, and the drilling fluid opens the valve of the packer pressure-reducing device and enters the first section cementing casing;

[0036] S54, the drilling fluid pressure in the pressure pipe string is maintained greater than p2, the drilling fluid enters the first segmented ground anchor, and under the pressure of the drilling fluid, the first segmented ground anchor anchors the well wall.

[0037] A further technical solution is that the specific process of step S6 is:

[0038] S61, keep the drilling fluid pressure in the pressure pipe string greater than p2, pull up the cementing casing end at the wellhead, and then release it, repeat the pulling and releasing 2-3 times to ensure that the first segmented ground anchor is reliably anchored to the well wall;

[0039] S62, reducing the drilling fluid pressure in the pressure pipe string to less than p1, and releasing the packer pressure device;

[0040] S63, pull up the end of the cementing casing with a pulling force at the wellhead and maintain it.

[0041] A further technical solution is that the specific process of step S7 is:

[0042] S71, lifting the pressure pipe string, so that the isolation pressure device is located between the second segment anchor and the third segment anchor;

[0043] S72, maintaining the pulling force applied to the first section of the cementing string at the end of the cementing casing in step S6;

[0044] S73, anchoring the second section of the pipe string according to the method for anchoring the first section of cementing casing described in step S5.

[0045] The present invention has the following beneficial effects: the present invention can apply different pulling prestresses to the casings of different sections according to the different well conditions of each section of the thermal recovery well, thereby avoiding the deficiency that conventional pulling prestressed cementing operations can only provide a single pulling prestress, and can more accurately offset the thermal stress of the casings of different sections, and more effectively prevent casing failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural schematic diagram of the segmented prestressed cementing tool and the pipe string;

[0047] Figure 2 This is a schematic diagram of the anchoring process of the first segmented ground anchor;

[0048] Figure 3 This is a schematic diagram of the first stage casing pulling process;

[0049] Figure 4 This is a schematic diagram of the anchoring process of the second segmented ground anchor;

[0050] Figure 5 This is a schematic diagram of the second stage casing pulling process;

[0051] Figure 6 It is a structural schematic diagram of a segmented ground anchor;

[0052] Figure 7 It is a schematic diagram of the structure of the packer and pressure relief device;

[0053] As shown in the figure: 1-oil wellbore, 2-pressure pipe, 3-cementing casing, 4-segmented anchor, 5-packer pressure device, 6-casing plug; 7-packer pressure hydraulic pressure, 8-anchor pressure hydraulic pressure; 9-casing lifting force;

[0054] 401-sealing ring a, 402-locking pin, 403-sealing ring b, 404-fixed wedge sleeve, 405-fixed pin, 406-anchor claw, 407-sliding wedge sleeve, 408-shear pin, 409-ground anchor connecting pipe, 4091-hydraulic cavity a, 4071-sliding wedge groove, 4041-fixed wedge groove, 4092-hydraulic hole a, 4072-positioning hole;

[0055] 501-isolator connecting pipe, 502-sealing ring c, 503-isolator sliding sleeve, 504-isolator rubber ring, 505-pressure head, 506-valve ball, 507-spring, 508-retaining ring, 509-fixed retaining sleeve, 510-sealing ring d, 5051-pressure hole, 5011-hydraulic hole b, 5012-hydraulic chamber b. DETAILED DESCRIPTION

[0056] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the invention, not all of them. 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.

[0057] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0058] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0060] like Figure 1 As shown, a segmented pull prestressed cementing tool includes a pressure pipe 2, a cementing casing 3, a segmented anchor 4, a sealing pressure device 5, and a casing plug 6;

[0061] The isolation and pressure device 5 and the casing plug 6 are respectively installed at the lower ends of the pressure tube 2 and the cementing casing 3; the cementing casing 3 is provided with a plurality of axially arranged segmented anchors 4; the pressure tube 2 is slidably installed in the cementing casing 3.

[0062] In this embodiment, Figure 6As shown, the specific implementation of the segmented ground anchor 4 is as follows: it includes a shear pin 408, a fixing pin 405, a ground anchor connecting pipe 409, and a sliding wedge sleeve 407, an anchor claw sleeve 406, and a fixing wedge sleeve 404 which are sequentially sleeved on the ground anchor connecting pipe 409 from top to bottom;

[0063] The ground anchor connection pipe 409 is connected to the sliding wedge sleeve 407 and the fixed wedge sleeve 404 by a shear pin 408 and a fixed pin 405 respectively;

[0064] The lower end of the sliding wedge sleeve 407 has a sliding wedge groove 4071, the upper end of the fixed wedge sleeve 404 has a fixed wedge groove 4041, the upper and lower ends of the anchor claw sleeve 406 are provided with wedge surfaces, the outer surface is provided with a toothed structure, and the two ends are respectively located in the sliding wedge groove 4071 and the fixed wedge groove 4041;

[0065] A hydraulic cavity a4091 is provided between the outer wall of the ground anchor connection pipe 409 and the inner wall of the sliding wedge sleeve 407, and a hydraulic hole a4092 communicating with the hydraulic cavity a4091 is radially provided on the ground anchor connection pipe 409;

[0066] A locking pin 402 with a spring is radially arranged on the outer wall of the upper end of the anchor connection pipe 409, and a positioning hole 4072 cooperating with the locking pin 402 is arranged on the inner wall of the upper end of the sliding wedge sleeve 407, and the positioning hole 4072 is located above the locking pin 402;

[0067] The two ends of the anchor connection pipe 409 are respectively provided with internal threads and external threads, and are connected to the cementing casing 3. The inner walls of the upper and lower ends of the sliding wedge sleeve 407 are respectively provided with sealing rings a401 and b403;

[0068] In this embodiment, Figure 7 As shown, the specific implementation of the packer 5 is as follows: it includes a packer connecting pipe 501, a packer sliding sleeve 503, a packer rubber ring 504, a packer head 505, a retaining ring 508, and a fixed retaining sleeve 509;

[0069] The fixed stopper sleeve 509 is fixed on the isolation and pressure device connecting pipe 501, the isolation sliding sleeve 503 and the isolation rubber ring 504 are sequentially sleeved on the isolation and pressure device connecting pipe 501 from top to bottom, and the pressure head (505) is installed at the lower end of the isolation and pressure device connecting pipe 501;

[0070] The retaining ring 508 is provided with a spherical hole in the middle part and is installed between the lower end surface of the packer pressure device connecting pipe 501 and the inner cavity of the pressure head 505; a valve ball 506 and a spring 507 are installed inside the pressure head 505; one end of the spring 507 is fixed on the inner wall of the pressure head 505, and the other end is connected to the valve ball 506, and the spring 507 presses the valve ball 506 to block the spherical hole in the middle part of the retaining ring 508; the lower end of the pressure head 505 is provided with a pressure hole 5051 that communicates with the inner cavity of the lower end;

[0071] A hydraulic cavity b5012 is provided between the outer wall of the isolation and pressure device connecting pipe 501 and the inner wall of the isolation and pressure device sleeve 503. The isolation and pressure device connecting pipe 501 is radially provided with a hydraulic hole b5011 communicating with the hydraulic cavity b5012. The inner walls at the upper and lower ends of the isolation and pressure device connecting pipe 501 are respectively provided with sealing rings c502 and sealing rings d510.

[0072] The upper and lower ends of the isolation and pressure device connecting pipe 501 are respectively provided with internal threads and external threads, and are respectively threadedly connected with the pressure pipe 2 and the pressure head 505.

[0073] like Figure 1 As shown, the specific use process of this embodiment is: the cementing casing 3, the segmented anchor 4 and the casing plug 6 are connected to form a cementing pipe string, which is lowered into the oil well bore 1; the pressure pipe 2 is connected to the isolation pressure device 5 to form a pressure pipe string, which is lowered into the cementing pipe string;

[0074] like Figure 2 , Figure 7 As shown, drilling fluid is introduced into the percussion pipe string; the drilling fluid enters the hydraulic chamber b5012 through the hydraulic hole b5011; the drilling fluid pressure in the percussion pipe string is increased to p1 at the wellhead, and the hydraulic pressure pushes the isolation sleeve 503 downward to squeeze the isolation rubber ring 504, which is radially deformed to contact and squeeze the inner wall of the cementing casing 3 to isolate the casing section.

[0075] Continue to increase the drilling fluid pressure in the pressure pipe string at the wellhead to p2. When the fluid pressure is higher than the elastic force generated by the spring 507, the drilling fluid lowers the valve ball 506 and enters the isolated pipe section of the cementing casing 3 through the pressure hole 5051 on the pressure head 505.

[0076] like Figure 2 , Figure 6As shown in the figure, the drilling fluid pressure in the pressure pipe string is kept greater than p2, the drilling fluid enters the segmented anchor 4 of the isolated pipe section, and the drilling fluid enters the hydraulic chamber a4091 through the hydraulic hole a4092, generating a downward thrust on the sliding wedge sleeve 407. When the thrust is greater than the shear strength of the locking pin 402, the locking pin 402 is sheared off, and the sliding wedge sleeve 407 slides downward, pushing the anchor claw sleeve 406 to slide along the wedge groove 4071 and the wedge groove 4041, so that the anchor claw sleeve 406 as a whole generates a radial When the sliding wedge sleeve 407 moves downward, the toothed structure of the anchor claw sleeve 406 is pressed into the well wall of the oil well to anchor the cementing casing 3. When the downward displacement of the sliding wedge sleeve 407 reaches a set value, the positioning hole 4072 of the sliding wedge sleeve 407 is aligned with the locking pin 402 installed on the anchor connecting pipe 409. The locking pin 402 is inserted into the positioning hole 4072 under the action of the spring force. The position of the sliding wedge sleeve 407 is locked, and the radial position of the anchor claw sleeve 406 is also locked, so that the anchoring of the cementing casing 3 is in a locked state.

[0077] A segmented prestressed cementing method comprises the following steps:

[0078] S1. Determine the number of cementing casing stretching sections and the installation positions of segmented anchors in the well;

[0079] S2. Calculate the pulling force required to be applied to each section of casing at the wellhead during prestressed cementing;

[0080] S3, according to the number of cementing casing stretching sections and the installation position of the segmented anchors in the wellbore described in S1, the segmented anchors 4, the cementing casing 3, and the casing plug 6 are connected to form a cementing pipe string, and the cementing pipe string is lowered into the wellbore of the oil well;

[0081] S4, connect the pressure pipe 2 and the isolation pressure device 5 to form a pressure pipe string, and lower the pressure pipe string into the cementing pipe string;

[0082] S5, anchoring the first section of cementing casing, including the following sub-steps (such as Figure 2 shown):

[0083] a1. Introduce drilling fluid into the pressure pipe string;

[0084] b1. Raise the drilling fluid pressure in the wellhead pressure pipe string to p1, and seal the pressure packer 5;

[0085] c1. Continue to increase the drilling fluid pressure in the pressure pipe string at the wellhead to p2, and the drilling hydraulic pressure opens the valve of the packer pressure device and enters the first section of cementing casing;

[0086] d1. Keep the drilling fluid pressure in the pressure pipe string greater than p2, the drilling fluid enters the first segmented anchor, and under the pressure of the drilling fluid, the first segmented anchor anchors the well wall;

[0087] S6, pulling up the first section of cementing string, including the following sub-steps (such as Figure 3 shown):

[0088] a1. Keep the drilling fluid pressure in the pressure pipe string greater than p2, pull the cementing casing 3 end at the wellhead according to the pulling force calculated in step S2, and then relax, repeat the pulling and relaxation 2-3 times to ensure that the first segmented anchor is reliably anchored to the well wall;

[0089] b1. Reduce the drilling fluid pressure within the pressure pipe string to less than p1, and the packer pressure device 5 is unsealed;

[0090] c1. Pull the cementing casing 3 end portion at the wellhead according to the pulling force calculated in step S2 and maintain;

[0091] S7, anchoring the second section of cementing string, including the following sub-steps (such as Figure 4 shown):

[0092] a1. Lift the pressure pipe string so that the isolation pressure device is located between the second segment anchor and the third segment anchor;

[0093] b1. Maintain the pulling force applied to the first section of the cementing string at the end of the cementing casing 3 as described in S6;

[0094] c1. Anchor the second section of the tubing string according to the method of anchoring the first section of the cementing casing as described in S5;

[0095] S8, lift the second section of the cementing string according to the method of lifting the first section of the cementing string described in S6 (such as Figure 5 shown);

[0096] S9, anchoring and lifting the remaining section of the cementing casing according to the method described in S5 and S6;

[0097] S10, after all pipe sections are lifted, the pressurized pipe string is taken out;

[0098] S11, drilling through the casing plug;

[0099] S12, injecting cement into the cementing string to cement the well.

[0100] The segmented prestressed pulling cementing method and tool of the present invention can apply different prestressed pulling forces to the casing of different sections according to the different well conditions of each section of the thermal recovery well, thereby avoiding the deficiency that conventional prestressed pulling cementing operations can only provide a single prestressed pulling force, and can more accurately offset the thermal stress of the casing of different sections, and more effectively prevent casing failure.

[0101] The above description is not intended to impose any form of limitation on the present invention. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A segmented prestressed cementing tool, characterized in that: It comprises a pressure pipe (2), a cementing casing (3), a segmented ground anchor (4), a sealing pressure device (5), and a casing plug (6); The isolation and pressure device (5) and the casing plug (6) are respectively installed at the lower ends of the pressure tube (2) and the cementing casing (3); the cementing casing (3) is provided with a plurality of axially arranged segmented ground anchors (4); the pressure tube (2) is slidably installed in the cementing casing (3); The segmented ground anchor (4) comprises a shear pin (408), a fixing pin (405), a ground anchor connecting pipe (409), and a sliding wedge sleeve (407), an anchor claw sleeve (406), and a fixing wedge sleeve (404) which are sequentially sleeved on the ground anchor connecting pipe (409) from top to bottom; The ground anchor connection pipe (409) is connected to the sliding wedge sleeve (407) and the fixed wedge sleeve (404) by using a shear pin (408) and a fixed pin (405) respectively; The lower end of the sliding wedge sleeve (407) has a sliding wedge groove (4071), the upper end of the fixed wedge sleeve (404) has a fixed wedge groove (4041), the upper and lower ends of the anchor claw sleeve (406) are both provided with wedge surfaces, the outside is provided with a toothed structure, and the two ends are respectively located in the sliding wedge groove (4071) and the fixed wedge groove (4041); A hydraulic cavity a (4091) is provided between the outer wall of the ground anchor connection pipe (409) and the inner wall of the sliding wedge sleeve (407), and a hydraulic hole a (4092) communicating with the hydraulic cavity a (4091) is radially provided on the ground anchor connection pipe (409); A locking pin (402) with a spring is radially arranged on the outer wall of the upper end of the anchor connection pipe (409), and a positioning hole (4072) matching with the locking pin (402) is arranged on the inner wall of the upper end of the sliding wedge sleeve (407), and the positioning hole (4072) is located above the locking pin (402); The two ends of the ground anchor connection pipe (409) are respectively provided with internal threads and external threads, and are connected to the cementing casing (3).

2. A segmented prestressed cementing tool according to claim 1, characterized in that: The inner walls at the upper and lower ends of the sliding wedge sleeve (407) are respectively provided with a sealing ring a (401) and a sealing ring b (403).

3. The segmented prestressed cementing tool according to claim 1, characterized in that: The isolation and pressure device (5) comprises an isolation and pressure device connecting pipe (501), an isolation sliding sleeve (503), an isolation rubber ring (504), a pressure head (505), a retaining ring (508), and a fixed retaining sleeve (509); The fixed stopper sleeve (509) is fixed on the isolation and pressure device connecting pipe (501), the isolation sliding sleeve (503) and the isolation rubber ring (504) are sequentially sleeved on the isolation and pressure device connecting pipe (501) from top to bottom, and the pressure head (505) is installed at the lower end of the isolation and pressure device connecting pipe (501); The retaining ring (508) is provided with a spherical hole in the middle and is installed between the lower end surface of the sealing and pressing device connecting pipe (501) and the inner cavity of the pressing head (505); a valve ball (506) and a spring (507) are installed inside the pressing head (505); one end of the spring (507) is fixed on the inner wall of the pressing head (505), and the other end is connected to the valve ball (506), and the spring (507) presses the valve ball (506) to block it in the spherical hole in the middle of the retaining ring (508); the lower end of the pressing head (505) is provided with a pressing hole (5051) which is communicated with the inner cavity of the lower end; A hydraulic cavity b (5012) is provided between the outer wall of the isolation and pressure device connecting pipe (501) and the inner wall of the isolation and pressure device sliding sleeve (503), and a hydraulic hole b (5011) communicating with the hydraulic cavity b (5012) is radially provided on the isolation and pressure device connecting pipe (501).

4. A segmented prestressed cementing tool according to claim 3, characterized in that: The inner walls of the upper and lower ends of the isolation and pressure device connecting pipe (501) are respectively provided with a sealing ring c (502) and a sealing ring d (510).

5. The segmented prestressed cementing tool according to claim 3, characterized in that: The upper and lower ends of the isolation and pressure device connecting pipe (501) are respectively provided with internal threads and external threads, and are respectively threadedly connected to the pressure pipe (2) and the pressure head (505).

6. A segmented prestressed cementing method using a segmented prestressed cementing tool according to any one of claims 3 to 5, comprising the following steps: S1. Determine the number of cementing casing stretching sections and the installation positions of segmented anchors in the well; S2. Calculate the pulling force required to be applied to each section of casing at the wellhead during prestressed cementing; S3, according to the number of cementing casing stretching sections determined in step S1 and the installation position of the segmented anchors in the well, connecting the segmented anchors (4), cementing casing (3), and casing plugs (6) to form a cementing pipe string, and lowering the cementing pipe string into the oil well borehole (1); S4, connecting the pressure-reducing pipe (2) and the isolation pressure-reducing device (5) to form a pressure-reducing pipe string, and lowering the pressure-reducing pipe string into the cementing pipe string; S5, anchoring the first section of cementing casing; S6, lifting the first section of cementing string; S7, anchoring the second section of cementing string; S8, lifting the second section of the cementing string according to the method of lifting the first section of the cementing string in step S6; S9, anchoring and lifting the remaining section of the cementing casing according to the method described in step S5 and step S6; S10, after all pipe sections are lifted, the pressurized pipe string is taken out; S11, drilling through the casing plug; S12, injecting cement into the cementing string to cement the well.

7. A segmented prestressed cementing method according to claim 6, characterized in that: The specific process of step S5 is: S51, introducing drilling fluid into the pressure pipe string; S52, raising the drilling fluid pressure in the pressure-relief pipe string at the wellhead to p1, and setting the isolation pressure-relief device (5); S53, the drilling fluid pressure in the pressure reducing pipe string is continuously increased to p2 at the wellhead, and the valve ball (506) of the drilling hydraulic pressure seal and pressure reducing device (5) is opened and enters the first section cementing casing; S54, the drilling fluid pressure in the pressure pipe string is kept greater than p2, the drilling fluid enters the first segmented ground anchor, and under the pressure of the drilling fluid, the first segmented ground anchor anchors the well wall.

8. The method for prestressed cementing by segmented pulling according to claim 7, characterized in that: The specific process of step S6 is: S61, maintaining the drilling fluid pressure in the pressure pipe string greater than p2, pulling up the end of the cementing casing (3) at the wellhead, and then loosening it, repeating the pulling up and loosening process 2-3 times to ensure that the first segmented ground anchor is reliably anchored to the well wall; S62, reducing the drilling fluid pressure in the pressure pipe string to less than p1, and releasing the packer pressure device (5); S63, pulling up the end of the cementing casing (3) with a pulling force at the wellhead and maintaining it.

9. The method for prestressed cementing by segmented pulling according to claim 8, characterized in that: The specific process of step S7 is: S71, lifting the pressure pipe string, so that the isolation pressure device is located between the second segment anchor and the third segment anchor; S72, maintaining the pulling force applied to the first section of the cementing string at the end of the cementing casing (3) in step S6; S73, anchoring the second section of the pipe string according to the method for anchoring the first section of cementing casing described in step S5.

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