Well completion apparatus, columnar earth anchors, and methods of boosting reservoir casing stress

Abstract

This invention relates to the field of oilfield thermal recovery well technology, and discloses a well completion process device, a column-type ground anchor, and a method for increasing the prestress of the oil layer casing. The well completion process device includes a surface casing (1) located below the surface, an oil layer casing (2), and a casing head body (3). The oil layer casing is connected to the inner surface of the casing head body via a connecting assembly (40). A column-type ground anchor (500) is connected to the bottom of the oil layer casing. The column-type ground anchor includes an anchor claw (502) and a plunger body (530). A liquid outlet (501) is formed on the column-type ground anchor. The anchor claw can extend out of the side wall of the plunger body and insert into the formation. Cement can be discharged from the liquid outlet to seal the annular gap between the oil layer casing and the formation. This invention uses hydraulic oil to insert the anchor claw into the formation, pulling the oil layer casing to a preset load. After the oil layer casing is pulled up, it is clamped to the inner wall of the casing head body via the connecting assembly, thus increasing the prestress.

Description

Technical Field

[0001] This invention relates to the field of oilfield thermal recovery well technology, specifically to a well completion process apparatus. Based on this, it also relates to a column-type ground anchor and a method for increasing the prestress of the oil reservoir casing. Background Technology

[0002] Wellbore integrity is fundamental to the normal development of an oilfield. However, with the continuous increase in production time, due to various factors such as geology and technology, a certain proportion of casing damage inevitably occurs in both injection and production wells, seriously affecting normal oilfield production. In production practice, due to the complex geological conditions, diverse oil properties, and multiple development methods in oilfields, the types of casing damage are diverse, making the analysis of the causes of casing damage extremely difficult. Since the 1990s, the applicant has been committed to the research on the mechanism analysis and prevention of casing damage in heavy oil thermal recovery wells, and has gradually developed distinctive technologies such as prestressed well completion, G-grade sand-added cementing system, and externally thickened casing, which have reduced the casing damage rate of thermal recovery wells to a certain extent and extended the service life of thermal recovery wells.

[0003] However, the current casing loss rate in oilfields remains high, averaging 22.3%. Production stoppages due to casing loss directly impact daily crude oil production. The casing loss rate for the first eight rounds of thermal recovery wells reached as high as 30%. This severely affects the production efficiency of thermal recovery wells and significantly increases well workover costs. The main reasons are: during field implementation, the low anchoring force of the completion anchor in heavy oil thermal recovery wells and the strict limitations on casing elongation imposed by the wellhead annular steel plate increase the difficulty of prestressing construction. During production, the casing is subjected to alternating hot and cold loads, resulting in large-area casing loss. Secondly, the strength of the currently used G-grade sand-added cement system begins to decrease significantly and permeability increases significantly after temperatures exceed 170℃. Under high-temperature alternating thermal stress, cementing quality deteriorates, cement sheath ruptures, and sand production causes the casing string to lose formation support. Compressive loads cause the casing string to undergo S-shaped bending deformation. Furthermore, traditional well completion string design methods do not adequately consider the thermal strain performance of the tubing. Temperature changes during injection and production cause alternating tensile and compressive stresses in the casing, leading to excessive plastic deformation and permanent damage. The trapezoidal threads of the casing cannot provide a steam seal; sealing performance can only be improved with thread sealant. However, when the injection temperature exceeds 200°C, the thread sealant fails, causing steam leakage into the mudstone layer, leading to water absorption and expansion. The drastic change in lateral load at the rock layer interface triggers casing shear / fracture. Increasing the casing steel grade and wall thickness can reduce the casing loss rate and has some effect on delaying casing deformation. However, once the steel grade and wall thickness reach a certain value, further increases in steel grade have a negligible effect on reducing casing loss, while significantly increasing costs. It is necessary to determine economic limits, especially given the current unfavorable oil price situation, and not simply increase steel grades indiscriminately.

[0004] Therefore, it is necessary to study thermal recovery completion technology that has good prestressing effect, high temperature resistance of cementing cement, and considerable economic benefits in well completion. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of low prestress in oil layer casing in the prior art, and to provide a well completion process device that can effectively improve the prestress of oil layer casing.

[0006] To achieve the above objectives, the present invention provides a well completion apparatus, comprising a surface casing located below the surface, an oil layer casing coaxially arranged with the surface casing, and a casing head body connected to the upper end of the surface casing. The oil layer casing is located at a greater depth below the surface than the surface casing. The oil layer casing is connected to the inner surface of the casing head body via a connecting assembly. A column-type ground anchor is connected to the bottom of the oil layer casing.

[0007] The post-type ground anchor includes an anchor claw, a plunger body for accommodating the anchor claw, an outer tube assembly, and a piston assembly coaxially arranged inside the outer tube assembly. The outer tube assembly and the piston assembly are both located above the plunger body. The space enclosed by the inner wall of the outer tube assembly and the outer wall of the piston assembly is a liquid channel. A liquid outlet communicating with the liquid channel is formed on the outer tube assembly.

[0008] The piston assembly has a hydraulic oil chamber, and the plunger body has a receiving cavity for accommodating the anchor claw and a hydraulic flow channel communicating with the hydraulic oil chamber and the receiving cavity. The piston assembly enables the hydraulic oil in the hydraulic oil chamber to flow sequentially through the hydraulic flow channel and the receiving cavity so that the anchor claw extends out of the side wall of the plunger body and inserts into the formation. Cement entering through the oil layer casing can be discharged from the liquid outlet to seal the annular gap between the column anchor and / or the oil layer casing and the formation.

[0009] Optionally, the upper end of the casing head body is formed with a mounting hole that tapers inward from top to bottom, and the connecting component is snapped into the inner wall of the mounting hole and sealed to the outer wall of the oil layer casing.

[0010] Optionally, the connecting assembly includes a hanger having a receiving cavity and a slip located within the receiving cavity, the outer surface of the slip engaging with the inner surface of the receiving cavity, the outer surface and the inner surface being respectively configured to slope inward from top to bottom, and the inner surface of the slip having barbs formed for preventing the oil layer casing from moving downward.

[0011] Optionally, the connecting assembly includes a connecting rod that passes through the suspension and connects to the top of the chuck.

[0012] A second aspect of the present invention provides a post-type ground anchor, the post-type ground anchor comprising an anchor claw, a plunger body, an outer tube assembly, and a piston assembly coaxially arranged inside the outer tube assembly, wherein the plunger body has a receiving cavity formed inside for accommodating the anchor claw.

[0013] Both the outer tube assembly and the piston assembly are located above the plunger body. The space enclosed by the inner wall of the outer tube assembly and the outer wall of the piston assembly is a liquid channel. A liquid outlet communicating with the liquid channel is formed on the outer tube assembly so that the liquid in the liquid channel can be discharged from the liquid outlet.

[0014] The piston assembly has a hydraulic oil chamber, and the plunger body has a hydraulic flow channel that communicates with the hydraulic oil chamber and the receiving cavity. The piston assembly enables the hydraulic oil in the hydraulic oil chamber to flow sequentially through the hydraulic flow channel and the receiving cavity, so that the anchor claw extends out of the side wall of the plunger body and inserts into the formation.

[0015] Optionally, a first one-way valve assembly is provided in the liquid channel and is sealed to the inner wall of the outer tube assembly and the outer wall of the piston assembly. The first one-way valve assembly allows the liquid in the liquid channel to flow out in one direction.

[0016] Optionally, the first one-way valve assembly includes an upper stop and a lower stop with inclined surfaces in contact. The upper stop is sealed to the inner wall of the outer tube assembly, and the lower stop is slidably and sealed to the outer wall of the piston assembly. A first inclined surface connects the inner wall and the bottom wall of the upper stop, and a second inclined surface connects the outer wall and the top wall of the lower stop. The liquid can drive the lower stop to move downward relative to the upper stop, so that a flow channel is formed between the first inclined surface and the second inclined surface, allowing the liquid to pass through.

[0017] Optionally, the first one-way valve assembly includes a flow guide ring located below the lower plug seat, with a first spring connecting the lower plug seat and the flow guide ring, and / or, the first one-way valve assembly includes a retaining ring located on the top or bottom surface of the upper plug seat to restrict axial movement of the upper plug seat.

[0018] Optionally, the piston assembly includes a hydraulic cylinder, a piston slidably and sealingly connected to the inner wall of the hydraulic cylinder, and a sealing plug sealingly connected to the bottom of the piston. The inner wall of the hydraulic cylinder, the bottom wall of the piston, and / or the bottom wall of the sealing plug form the hydraulic oil chamber. The piston can drive the sealing plug to move axially downward relative to the hydraulic cylinder so that the hydraulic oil in the hydraulic oil chamber is discharged into the hydraulic flow channel.

[0019] Optionally, a second check valve assembly is provided at the bottom of the hydraulic oil chamber and is sealed to the inner wall of the cylinder. The second check valve assembly allows the hydraulic oil in the hydraulic oil chamber to flow unidirectionally into the hydraulic passage.

[0020] Optionally, the second one-way valve assembly includes a valve seat with a flow channel, a valve core located within the flow channel and in contact with the inclined surface of the valve seat, and an inner guide seat located within the flow channel and sleeved on the outside of the valve core. A third inclined surface is provided on the inner wall of the valve seat, and a fourth inclined surface is provided on the head of the valve core. A first through hole is formed on the inner guide seat. A second spring is connected between the bottom surface of the head and the top surface of the inner guide seat. The hydraulic oil in the hydraulic oil chamber can drive the valve core to move downward relative to the valve seat, so that a gap is formed between the third inclined surface and the fourth inclined surface to allow the hydraulic oil to pass through. The hydraulic oil flows into the hydraulic flow channel through the first through hole.

[0021] Optionally, the piston is configured as a uniform wall thickness structure with a second through hole, and the piston assembly includes an upper and a lower centering frame for restricting the radial movement of the piston. The upper and lower centering frames are located within the liquid channel and arranged around the piston. The upper centering frame is located on top of the piston and blocks the second through hole, and the lower centering frame is located on top of the cylinder.

[0022] Optionally, the outer tube assembly includes an upper outer tube and a lower outer tube arranged coaxially. A coupling is connected to the top of the upper outer tube, and a receiving tube is connected between the upper outer tube and the lower outer tube. A protrusion is provided on the top of the plunger body, and the piston assembly is connected to the inner wall of the protrusion. The lower outer tube is connected to the outer wall of the protrusion through a receiving rotating head, and the liquid outlet is formed on the side wall of the lower outer tube.

[0023] Optionally, the anchor claw is sealed to the inner wall of the receiving cavity, and a retainer for limiting the axial movement of the anchor claw is provided in the receiving cavity, and / or, an injection hole communicating with the hydraulic flow channel is formed on the plunger body, and an injection plug is sealed in the injection hole.

[0024] Optionally, the plunger body has multiple receiving cavities at different heights, and the axes of the different receiving cavities point to different horizontal directions. The hydraulic flow channel includes a first horizontal flow channel group arranged laterally, a first vertical flow channel group connected above the first horizontal flow channel group, and a second vertical flow channel group connected below the horizontal flow channel group. The first vertical flow channel group and the second vertical flow channel group each have multiple vertical flow channels located at different circumferential positions of the plunger body. Each vertical flow channel is connected to only one receiving cavity, so that the hydraulic oil can flow into the corresponding receiving cavity through the vertical flow channel.

[0025] Optionally, the hydraulic flow channel includes a second horizontal flow channel group that is parallel and spaced apart above the first horizontal flow channel group and communicates with the first vertical flow channel group. The hydraulic oil in the hydraulic oil chamber passes sequentially through the second horizontal flow channel group, the first vertical flow channel group, the first horizontal flow channel group, the second vertical flow channel group, and the receiving cavity, so that the anchor claw extends out of the side wall of the plunger body and inserts into the formation.

[0026] A third aspect of the present invention provides a method for increasing the prestress of oil reservoir casing, the method comprising the following steps:

[0027] S1: Drilling a well on the surface, running a surface casing into the well, and cementing the surface casing;

[0028] S2: Install the casing head body above the surface casing, install bypass pipes on both sides of the casing head body, and install valves on the bypass pipes;

[0029] S3: Install a conversion joint on the upper end of the casing head body, and connect a large crossover and a blowout preventer assembly in sequence on the top of the conversion joint. The drilling tool passes through the large crossover and the blowout preventer assembly to drill in the well.

[0030] S4: After drilling to the preset depth, retrieve the drilling tool and use the tool to lower the cylindrical ground anchor with multiple oil layer casings connected to its top into the well.

[0031] S5: When lowering to the last oil layer casing, the connecting assembly is sleeved on the outer surface of the last oil layer casing;

[0032] S6: The insertion tool is placed around the outer surface of the last oil layer casing and positioned above the connecting assembly;

[0033] S7: Lower the last oil layer casing using the top joint, and press the connecting assembly into the casing head body using the coupling of the last oil layer casing;

[0034] S8: After opening the valve, cement is injected into the oil layer casing, and then a rubber plug is placed into the oil layer casing. The cement is discharged from the liquid outlet on the column anchor through the rubber plug to seal the annular gap between the column anchor and / or the oil layer casing and the formation.

[0035] S9: After all the cement is discharged from the liquid outlet, the rubber plug continues to push the piston assembly inside the column anchor. The piston assembly pushes the hydraulic oil so that the anchor claw extends out of the side wall of the plunger body and inserts into the stratum, and then the rubber plug is retracted.

[0036] S10: Use a lifting tool to lift the oil layer casing upward to a preset load or raise it to a predetermined height;

[0037] S11: After lifting the insertion tool to a predetermined distance above the connecting assembly using a rope, release the rope to allow the insertion tool to fall freely, and strike the connecting assembly to make the oil layer casing clamped to the casing head body through the connecting assembly, then remove the lifting tool.

[0038] Optionally, the method for increasing the prestress of the casing further includes the following steps:

[0039] S12: Disassemble the top joint, the large four-way connector, the blowout preventer assembly, the delivery tool, and the adapter, and cut the last oil layer casing at a certain distance from the upper surface of the connecting assembly;

[0040] S13: Connect the flange joint to the top of the last oil layer sleeve, weld the flange joint to the last oil layer sleeve to seal, install the gland on both sides of the flange joint and tighten the flange joint.

[0041] Optionally, the cement includes Grade G oil well cement, silica fume, microsilica, strength stabilizer, high-temperature cracking resistant agent, expansion agent, suspension stabilizer, fluid loss reducing agent, early strength agent, and water.

[0042] Optionally, the silicon powder accounts for 20%-40% of the mass; the microsilica accounts for 15%-20% of the mass; the strength stabilizer accounts for 8%-13% of the mass; the anti-high temperature embrittlement agent accounts for 4%-6% of the mass; the expansion agent accounts for 1.2%-2% of the mass; the suspension stabilizer accounts for 0.2%-0.5% of the mass; the water loss reducing agent accounts for 0.5%-1% of the mass; the water loss reducing agent accounts for 1%-2% of the mass; and the water accounts for 45%-60% of the mass.

[0043] In this invention, after the first drilling operation, the casing head body is connected to the surface casing. After the second drilling operation is completed, a column-type ground anchor is driven into the well. The anchor claws are vertically inserted into the formation by hydraulic oil. The operation is simpler, the anchoring is more reliable, and there is no slippage after the anchoring is completed. After the oil layer casing is lifted to the preset load or predetermined height, the oil layer casing is clamped to the inner wall of the casing head body by the connecting component, thereby increasing the prestress of the oil layer casing. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the well completion process apparatus in this invention;

[0045] Figure 2 This is a schematic diagram showing the connection between the two-section sleeve head body and the blowout preventer assembly in this invention;

[0046] Figure 3 This is a schematic diagram of the wellhead in this invention;

[0047] Figure 4 yes Figure 3 Enlarged view of point I in the middle;

[0048] Figure 5 This is a structural schematic diagram of one embodiment of the column-type ground anchor in this invention;

[0049] Figure 6 yes Figure 5 Enlarged view of point I in the middle;

[0050] Figure 7 yes Figure 5 Enlarged schematic diagram at point II;

[0051] Figure 8 yes Figure 5 Schematic diagram of the AA section;

[0052] Figure 9 yes Figure 5 Schematic diagram of the BB cross section;

[0053] Figure 10 yes Figure 5 Schematic diagram of the CC section;

[0054] Figure 11 yes Figure 5 Schematic diagram of the DD section;

[0055] Figure 12 yes Figure 5 Schematic diagram of the EE cross section;

[0056] Figure 13 yes Figure 5 Schematic diagram of the FF cross section.

[0057] Explanation of reference numerals in the attached figures

[0058] 1-Surface casing; 2-Oil layer casing; 3-Casing head body; 40-Connecting assembly; 41-Suspender; 42-Slipper; 43-Connecting rod; 500-Pin anchor; 501-Liquid outlet; 502-Anchor claw; 503-Liquid channel; 504-Sleeve; 505-Injection plug; 506-Baffle; 507-Fastener; 521-Hydraulic oil chamber; 530-Plunger body; 531-Hydraulic flow channel; 532-First horizontal flow channel group; 533-First vertical flow channel group; 534-Second vertical flow channel group; 535-Second horizontal flow channel group; 540-Outer tube assembly; 541-Upper outer tube; 542-Lower outer tube 543-Receiving pipe; 544-Coupling; 545-Receiving rotor; 550-Piston assembly; 551-Cylinder; 552-Piston; 553-Sealing plug; 554-Upper centering frame; 555-Lower centering frame; 560-First check valve assembly; 561-Upper plug seat; 562-Lower plug seat; 563-Guide ring; 564-First spring; 565-Snap ring; 570-Second check valve assembly; 571-Valve seat; 572-Valve core; 573-Inner guide seat; 574-Second spring; 6-Bypass pipe; 7-Converter; 8-Large four-way connector; 9-Blowout preventer assembly; 10-Flange joint; 11-Gland. Detailed Implementation

[0059] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0060] In this invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the orientation shown in the accompanying drawings, and "inner" and "outer" refer to the inner and outer sides relative to the outline of each component itself.

[0061] like Figure 1 and Figure 3 As shown, one aspect of the present invention provides a well completion process apparatus, which includes a surface casing 1 located below the surface, an oil layer casing 2 arranged coaxially with the surface casing 1, and a casing head body 3 connected to the upper end of the surface casing 1. The oil layer casing 2 is located at a greater depth below the surface than the surface casing 1. The oil layer casing 2 is connected to the inner surface of the casing head body 3 via a connecting assembly 40. A column-type ground anchor 500 is connected to the bottom of the oil layer casing 2.

[0062] The post-type ground anchor 500 includes an anchor claw 502, a plunger body 530 for accommodating the anchor claw 502, an outer tube assembly 540, and a piston assembly 550 coaxially arranged inside the outer tube assembly 540. The outer tube assembly 540 and the piston assembly 550 are both located above the plunger body 530. The space enclosed by the inner wall of the outer tube assembly 540 and the outer wall of the piston assembly 550 is a liquid channel 503. A liquid outlet 501 communicating with the liquid channel 503 is formed on the outer tube assembly 540.

[0063] The piston assembly 550 has a hydraulic oil chamber 521, and the plunger body 530 has a receiving cavity for accommodating the anchor claw 502 and a hydraulic flow channel 531 communicating with the hydraulic oil chamber 521 and the receiving cavity. The piston assembly 550 enables the hydraulic oil in the hydraulic oil chamber 521 to flow sequentially through the hydraulic flow channel 531 and the receiving cavity so that the anchor claw 502 extends out of the side wall of the plunger body 530 and inserts into the formation. Cement entering through the oil layer casing 2 can be discharged from the liquid outlet 501 to seal the annular gap between the column anchor 500 and / or the oil layer casing 2 and the formation.

[0064] In this invention, after the first drilling operation, the casing head body 3 is connected to the surface casing 1. After the second drilling operation, a column-type ground anchor 500 is lowered into the well. Hydraulic oil is used to vertically insert the anchor claw 502 into the formation. This method is simpler to operate, more reliable in anchoring, and prevents slippage after initial anchoring. After the oil layer casing 2 is pulled to a preset load or predetermined height, it is tightened to the inner wall of the casing head body 3 via the connecting component clamp 40, thus increasing the prestress of the oil layer casing 2. Furthermore, this completion process device, through existing oil layer casing material and physical testing evaluation, high-temperature thermal cycle bearing capacity (anti-extrusion, anti-tension) tests, and high-temperature thermal cycle integrity tests of casing threads and sealing grease, establishes the selection of oil layer casing and threads, as well as the applicable temperature and gas injection pressure range. Ultimately, it forms a recommended technical solution for block casing selection, achieving the goal of reducing the casing loss rate of thermal recovery wells without increasing the cost of the completion string.

[0065] Specifically, during the production of heavy oil thermal recovery wells, the casing is subjected to alternating hot and cold loads, causing alternating tensile and compressive stresses that lead to excessive plastic deformation and permanent damage, resulting in large-area casing loss. Therefore, inserting the bottom of the casing into the ground using a column-type anchor, then lifting the upper part of the casing to a preset load or predetermined height using a tool, and finally locking the top of the casing can effectively increase the prestress of the casing, reduce casing deformation during subsequent production in heavy oil thermal recovery wells, improve the reliability of the thermal recovery wells, and reduce production costs.

[0066] Further, the connecting assembly 40 includes a hanger 41 with a receiving cavity and slips 42 located within the receiving cavity. The outer surface of the slips 42 fits into the inner surface of the receiving cavity. The outer surface and the inner surface are respectively configured to slope inward from top to bottom. The inner surface of the slips 42 has barbs formed to prevent the oil layer casing 2 from moving downward. Multiple sheet-like slips 42 can be installed within the hanger 41. In one embodiment, as... Figure 3 As shown, the barbs include a plane extending horizontally inward from the inner wall of the slip 42, and an inclined surface connected below the plane, the inclined surface being sloping outward from top to bottom. Furthermore, a receiving groove is formed between the outer wall of the oil layer sleeve 2 and the inner wall of the receiving cavity, and the slip 42 is installed in this receiving groove. The minimum thickness of the slip 42 is greater than the minimum size of the receiving groove, so that after the slip 42 moves downward, it can clamp the oil layer sleeve 2 into the hanger 41.

[0067] Furthermore, the upper end of the casing head body 3 has a mounting hole that tapers inward from top to bottom. The connecting assembly 40 is engaged with the inner wall of this mounting hole and sealed to the outer wall of the oil layer casing 2. In one embodiment, the outer surface of the hanger 41 is an arc surface with equal diameters from top to bottom. It is understood that the large-diameter end of the mounting hole is larger than the outer diameter of the hanger 41, and the small-diameter end of the mounting hole is smaller than the outer diameter of the hanger 41. Therefore, the connecting assembly 40 can be secured within the mounting hole of the casing head body 3 by the hanger 41. Furthermore, the inner surface of the hanger 41 has a groove for installing a seal, and the connecting assembly 40 can include a seal installed in this groove, thereby sealingly connecting to the outer wall of the oil layer casing 2. In another embodiment, the outer surface of the hanger 41 also has a groove for installing a seal, and the connecting assembly 40 can include a seal installed in this groove, thereby sealingly connecting to the inner wall of the casing head body 3.

[0068] Furthermore, the connecting assembly 40 may also include a connecting rod 43, which passes through the hanger 41 and connects to the top of the slip 42. It is understood that the top of the hanger 41 has a through hole for the connecting rod 43 to pass through, and the upper surface of the slip 42 also has a corresponding connecting hole, through which the connecting rod 43 is installed. Moreover, the upper surface of the connecting rod 43 can be tapped using the following insertion tool, causing the slip 42 to move downwards, thereby securing the oil layer casing 2 inside the hanger 41.

[0069] The prestress can be pulled up at any height at the wellhead using the aforementioned connecting component 40, and the locking force of the connecting component 40 can reach 100t.

[0070] like Figure 5As shown, another aspect of the present invention provides a post-type ground anchor 500, which includes an anchor claw 502, a plunger body 530, an outer tube assembly 540, and a piston assembly 550 coaxially arranged inside the outer tube assembly 540. The plunger body 530 has a receiving cavity formed inside for accommodating the anchor claw 502.

[0071] Both the outer tube assembly 540 and the piston assembly 550 are located above the plunger body 530. The space enclosed by the inner wall of the outer tube assembly 540 and the outer wall of the piston assembly 550 is a liquid channel 503. A liquid outlet 501 communicating with the liquid channel 503 is formed on the outer tube assembly 540 so that the liquid in the liquid channel 503 can be discharged from the liquid outlet 501.

[0072] A hydraulic oil chamber 521 is formed inside the piston assembly 550, and a hydraulic flow channel 531 is formed on the plunger body 530, which communicates with the hydraulic oil chamber 521 and the receiving cavity. The piston assembly 550 enables the hydraulic oil in the hydraulic oil chamber 521 to flow sequentially through the hydraulic flow channel 531 and the receiving cavity, so that the anchor claw 502 extends out of the side wall of the plunger body 530 and inserts into the formation.

[0073] The anchor claw 502 is a columnar body with a conical surface, which extends into the stratum. This columnar ground anchor 500 has a large effective length extending into the stratum, making anchoring more reliable and preventing slippage after a single anchoring.

[0074] like Figure 5 As shown, a first one-way valve assembly 560 is provided in the liquid channel 503 and is sealed to the inner wall of the outer tube assembly 540 and the outer wall of the piston assembly 550. The first one-way valve assembly 560 allows the liquid in the liquid channel 503 to flow out in one direction.

[0075] Specifically, such as Figure 6As shown, the first one-way valve assembly 560 includes an upper stopper 561 and a lower stopper 562 with inclined surfaces in contact. The upper stopper 561 is sealed to the inner wall of the outer tube assembly 540, and the lower stopper 562 is slidably and sealed to the outer wall of the piston assembly 550. A first inclined surface is connected between the inner wall and the bottom wall of the upper stopper 561, and a second inclined surface is connected between the outer wall and the top wall of the lower stopper 562. The liquid can drive the lower stopper 562 to move downward relative to the upper stopper 561, so that a flow channel is formed between the first inclined surface and the second inclined surface, allowing the liquid to pass through. Further, the first one-way valve assembly 560 includes a flow guide ring 563 located below the lower plug seat 562, and a first spring 564 is connected between the lower plug seat 562 and the flow guide ring 563. Alternatively, the first one-way valve assembly 560 includes a retaining ring 565 located on the top or bottom surface of the upper plug seat 561 to restrict the axial movement of the upper plug seat 561. The first spring 564 provides an upward force to the lower plug seat 562, closing the flow channel between the first and second inclined surfaces when there is no liquid in the liquid channel 503, preventing liquid from flowing into the liquid channel 503 from the outer tube assembly 540. It is understood that multiple liquid flow channels are formed on the flow guide ring 563, and a groove for accommodating the retaining ring 565 is formed on the inner wall of the outer tube assembly 540. A non-metallic material is installed on the second inclined surface of the lower plug seat 562 to reduce wear when the second inclined surface contacts the first inclined surface. Furthermore, the inner surface of the lower plug seat 562 is formed with a groove for installing a seal, and the lower plug seat 562 is sealed to the outer wall of the hydraulic cylinder 551 through the seal in the groove.

[0076] In one embodiment, two sets of the first one-way valve assemblies 560 arranged axially may be provided within the liquid channel 503. In the upper first one-way valve assembly 560, a retaining ring 565 is located on the top surface of the upper stopper 561 to restrict the upper stopper 561 from moving upward; in the lower first one-way valve assembly 560, a retaining ring 565 is located on the bottom surface of the upper stopper 561 to restrict the upper stopper 561 from moving downward.

[0077] Further, the piston assembly 550 includes a hydraulic cylinder 551, a piston 552 slidably and sealingly connected to the inner wall of the hydraulic cylinder 551, and a sealing plug 553 sealingly connected to the bottom of the piston 552. The inner wall of the hydraulic cylinder 551, the bottom wall of the piston 552, and / or the bottom wall of the sealing plug 553 form the hydraulic oil chamber 521. The piston 552 can drive the sealing plug 553 to move axially relative to the hydraulic cylinder 551, so that the hydraulic oil in the hydraulic oil chamber 521 is discharged to the hydraulic flow channel 531. The inner wall of the hydraulic cylinder 551 has a groove for installing a seal, and the hydraulic cylinder 551 is sealingly connected to the outer wall of the piston 552 through the seal in the groove. Similarly, the outer wall of the sealing plug 553 has a groove for installing a seal, and the sealing plug 553 is sealingly connected to the inner wall of the piston 552 through the seal in the groove. In one embodiment, the piston 552 and the sealing plug 553 can be manufactured as a single component, and the piston 552 can move axially downward relative to the hydraulic cylinder 551 when the top of the piston is subjected to downward pressure.

[0078] Furthermore, a second one-way valve assembly 570 is provided at the bottom of the hydraulic oil chamber 521 and is sealed to the inner wall of the hydraulic cylinder 551. The second one-way valve assembly 570 allows the hydraulic oil in the hydraulic oil chamber 521 to flow unidirectionally into the hydraulic flow channel 531.

[0079] Specifically, such as Figure 7 As shown, the second one-way valve assembly 570 includes a valve seat 571 with a flow channel, a valve core 572 located in the flow channel and in contact with the inclined surface of the valve seat 571, and an inner guide seat 573 located in the flow channel and sleeved on the outside of the valve core 572. A third inclined surface is provided on the inner wall of the valve seat 571, and a fourth inclined surface is provided on the head of the valve core 572. A first through hole is formed on the inner guide seat 573. A second spring 574 is connected between the bottom surface of the head and the top surface of the inner guide seat 573. The hydraulic oil in the hydraulic oil chamber 521 can drive the valve core 572 to move downward relative to the valve seat 571, so that a gap is formed between the third inclined surface and the fourth inclined surface to allow the hydraulic oil to pass through. The hydraulic oil flows into the hydraulic flow channel 531 through the first through hole.

[0080] Furthermore, the valve core 572 includes a head and a rod coaxially arranged. A non-metallic material is installed on the fourth inclined surface of the head to reduce wear when the fourth inclined surface contacts the third inclined surface. Additionally, the inner guide seat 573 is sleeved on the outside of the rod. The second spring 574 provides an upward force for the valve core 572 to prevent hydraulic oil from flowing back into the hydraulic oil chamber 521. The outer surface of the valve seat 571 has a groove for installing a seal, and the valve seat 571 is sealed to the inner wall of the cylinder 551 through the seal within this groove.

[0081] In one embodiment, to reduce the weight and manufacturing cost of the piston assembly 550, the piston 552 is configured as a constant wall thickness structure with a second through hole. The piston assembly 550 includes an upper centering frame 554 and a lower centering frame 555 for restricting the radial movement of the piston 552. The upper centering frame 554 and the lower centering frame 555 are located within the liquid channel 503 and arranged around the piston 552. The upper centering frame 554 is located on top of the piston 552 and blocks the second through hole, while the lower centering frame 555 is located on top of the hydraulic cylinder 551. Multiple liquid flow channels are formed on the upper centering frame 554 and the lower centering frame 555, with the upper centering frame 554 used to increase the force-bearing area of ​​the piston 552.

[0082] In addition, such as Figure 5 As shown, the outer tube assembly 540 includes an upper outer tube 541 and a lower outer tube 542 arranged coaxially. A coupling 544 is connected to the top of the upper outer tube 541. A receiving tube 543 connects the upper outer tube 541 and the lower outer tube 542. A protrusion is provided on the top of the plunger body 530. The piston assembly 550 is connected to the inner wall of the protrusion. The lower outer tube 542 is connected to the outer wall of the protrusion via a receiving rotor 545. The liquid outlet 501 is formed on the side wall of the lower outer tube 542. Specifically, the outer wall of the hydraulic cylinder 551 has a groove for installing a seal. The hydraulic cylinder 551 is sealed to the plunger body 530 via the seal within the groove. In one embodiment, the lower outer tube 542 is threaded to the outside of the receiving rotor 545, and the protrusion is threaded to the inside of the receiving rotor 545. It is understandable that the coupling 544 can be threaded to the outside of the upper outer tube 541, and the receiving tube 543 can also be threaded to the outside of the upper outer tube 541 and the lower outer tube 542.

[0083] like Figures 8 to 13As shown, the anchor claw 502 is sealed to the inner wall of the receiving cavity. A retainer 504 is provided within the receiving cavity to restrict the axial movement of the anchor claw 502. Alternatively, the plunger body 530 has an injection hole communicating with the hydraulic flow channel 531, and an injection plug 505 is sealed within this injection hole. Specifically, the bottom of the anchor claw 502 has a protrusion approximately the same diameter as the inner diameter of the receiving cavity. The outer wall of this protrusion has a groove for installing a seal. The anchor claw 502 is sealed to the inner wall of the receiving cavity through the seal within this groove. Furthermore, the anchor claw 502 also includes a columnar body coaxially arranged with the protrusion. The outer diameter of the columnar body is smaller than the outer diameter of the protrusion, and the inner diameter of the retainer 504 is approximately the same as the outer diameter of the columnar body. In addition, the anchor claw 502 has a receiving state within the plunger body 530 and an extended state extending out of the side wall of the plunger body 530. When the anchor claw 502 changes from the contained state to the extended state under the drive of hydraulic oil, the movement of the anchor claw 502 is restricted because the inner diameter of the sleeve 504 is smaller than the outer diameter of the protrusion.

[0084] Furthermore, the anchor claw 502 also has an original state in which a baffle 506 is installed on the outer wall of the plunger body 530. The baffle 506 is connected to the plunger body 530 by a fastener 507 to restrict the anchor claw 502 from moving out of the receiving cavity. Before the column anchor 500 is lowered into the well, the baffle 506 and the fastener 507 are removed, and the anchor claw 502 changes from the original state to the receiving state.

[0085] like Figures 8 to 13 As shown, the plunger body 530 has multiple receiving cavities at different heights, and the axes of the different receiving cavities point in different horizontal directions. The hydraulic flow channel 531 includes a first horizontal flow channel group 532 arranged laterally, a first vertical flow channel group 533 connected above the first horizontal flow channel group 532, and a second vertical flow channel group 534 connected below the horizontal flow channel group 532. The first vertical flow channel group 533 and the second vertical flow channel group 534 each have multiple vertical flow channels located in different circumferential directions of the plunger body 530. Each vertical flow channel communicates with only one receiving cavity, so that the hydraulic oil can flow into the corresponding receiving cavity through the vertical flow channel. As one embodiment, in the original state, the hydraulic flow channel 531 can be filled with hydraulic oil.

[0086] Furthermore, the hydraulic flow channel 531 includes a second horizontal flow channel group 535 that is parallel to and spaced apart above the first horizontal flow channel group 532 and communicates with the first vertical flow channel group 533. The hydraulic oil in the hydraulic oil chamber 521 passes sequentially through the second horizontal flow channel group 535, the first vertical flow channel group 533, the first horizontal flow channel group 532, the second vertical flow channel group 534, and the receiving cavity, so that the anchor claw 502 extends out of the side wall of the plunger body 530 and inserts into the formation.

[0087] In one embodiment of the invention, the plunger body 530 has six receiving cavities at different heights, and the axes of the different receiving cavities point in different horizontal directions, namely the 1st, 2nd, ..., 6th from top to bottom. In this embodiment, a first horizontal flow channel group 532 is located between the 3rd and 4th receiving cavities. The first horizontal flow channel group 532 is symmetrically arranged about the longitudinal axis of the plunger body 530, and includes three horizontally extending horizontal flow channels. The centers of the three horizontal flow channels intersect at a point located on the longitudinal axis of the plunger body 530, and the included angle between two adjacent horizontal flow channels is 60°. One end of each horizontal flow channel is connected to the first vertical flow channel group 533, and the other end is connected to the second vertical flow channel group 534. Preferably, in order to ensure uniform distribution of hydraulic oil, the ends of two adjacent horizontal flow channels that are close to each other are connected to different vertical flow channel groups.

[0088] Furthermore, in this embodiment, the second horizontal flow channel group 535 includes three intersecting horizontal flow channels, with an included angle of 120° between two adjacent horizontal flow channels.

[0089] During the machining process, the hydraulic flow channel 531 requires a cutting tool to pass through the outer wall of the plunger body 530. After the hydraulic flow channel 531 is machined, the area communicating with the outer wall of the plunger body 530 is sealed inside the plunger body 530 by welding.

[0090] A third aspect of the present invention provides a method for increasing the prestress of oil reservoir casing, the method comprising the following steps:

[0091] S1: Drill a well on the surface, run the surface casing 1 into the well, and cement the surface casing 1.

[0092] S2: Install the sleeve head body 3 above the surface sleeve 1, install bypass pipes 6 on both sides of the sleeve head body 3, and install valves on the bypass pipes 6.

[0093] S3: Install a conversion joint 7 on the upper end of the casing head body 3, and connect a large cross 8 and a blowout preventer assembly 9 in sequence on the top of the conversion joint 7. The drilling tool passes through the large cross 8 and the blowout preventer assembly 9 to drill in the well.

[0094] S4: After drilling to the preset depth, retrieve the drilling tool and use the tool to lower the column anchor 500, which has multiple oil layer casings 2 connected to its top, into the well.

[0095] S5: When lowering to the last oil layer casing 2, the connecting component 40 is sleeved on the outer surface of the last oil layer casing 2;

[0096] S6: The insertion tool is placed around the outer surface of the last oil layer casing 2 and positioned above the connecting assembly 40;

[0097] S7: Lower the last oil layer casing 2 using the top joint, and press the connecting assembly 40 into the casing head body 3 using the coupling of the last oil layer casing 2;

[0098] S8: After opening the valve, cement is injected into the oil layer casing 2, and then a rubber plug is placed into the oil layer casing 2. The cement is discharged from the liquid outlet 501 on the column anchor 500 through the rubber plug to seal the annular gap between the column anchor 500 and / or the oil layer casing 2 and the formation.

[0099] S9: After all the cement is discharged from the liquid outlet 501, the rubber plug continues to push the piston assembly 550 inside the column anchor 500. The piston assembly 550 pushes the hydraulic oil so that the anchor claw 502 extends out of the side wall of the plunger body 530 and inserts into the stratum, and then the rubber plug is retracted.

[0100] S10: Use a lifting tool to lift the oil layer casing 2 upward to a preset load or to a predetermined height;

[0101] S11: After lifting the insertion tool to a predetermined distance above the connecting assembly 40 with a rope, release the rope to allow the insertion tool to fall freely, and strike the connecting assembly 40 so that the oil layer casing 2 is clamped to the casing head body 3 through the connecting assembly 40, and then remove the lifting tool.

[0102] Specifically, in S1, the upper surface of the top coupling of the surface casing 1 should be 30cm below the ground level, and the surface casing 1 should be perpendicular to the horizontal plane to prevent wellhead deviation. In S2, the threads on the casing head body 3 can be cleaned and coated with casing thread sealant. Then, bypass pipes 6 can be installed on both sides of the casing head body 3. The threads on the surface casing 1 can be cleaned and coated with casing thread sealant. Then, the casing head body 3 can be connected to the surface casing 1, and the threads should be tightened to the specified torque and installed in place.

[0103] In S5, in order to prevent the slip 43 in the connecting assembly 40 from falling into the oil layer casing 2 due to operational errors, the connecting assembly 40 needs to be put on from the bottom of the last oil layer casing 2 upwards, and it is forbidden to do this operation directly above the second to last oil layer casing 2, or to sit the connecting assembly 40 on the coupling of the second to last oil layer casing and insert the last oil layer casing 2 into the connecting assembly 40.

[0104] In S6, a set of the feeding tools consists of two mating irons that cooperate with each other. The teeth of the two mating irons are aligned and wrapped around the last oil layer sleeve 2. A pin is installed on the mating irons and the lower end of the pin is fixed with wire.

[0105] In one implementation, in S10, the oil layer casing 2 is slowly lifted upward using a lifting tool. After the suspended weight of the oil layer casing 2 increases to the designed tensile load, it is lifted an additional 22KN. Alternatively, the oil layer casing 2 is slowly lifted upward by 300mm using a lifting tool.

[0106] like Figure 2 As shown, the large four-way valve 8 is used for fluid circulation during the drilling process and for pressure relief or well control operations in case of emergencies. Furthermore, a clearance hole is formed on the delivery tool, which corresponds to the connecting rod 43 on the connecting assembly 40. This clearance hole prevents accidental operation when it is not necessary to strike the connecting assembly 40. In S11, the delivery tool can be rotated by a rope at a certain angle so that the clearance hole is no longer directly above the connecting rod 43, and the top surface of the connecting rod 43 is struck by the lower surface of the delivery tool. For example, after raising the delivery tool 300mm to 500mm above the connecting assembly 40 with a rope, the delivery tool is rotated 60°, the rope is released to allow the delivery tool to fall freely, and the connecting rod 43 is struck to suspend the oil layer casing 2. To ensure reliability, it can be struck several times.

[0107] Furthermore, the method for increasing the prestress of the casing also includes the following steps:

[0108] S12: Disassemble the top joint, the large four-way connector 8, the blowout preventer assembly 9, the delivery tool, and the adapter 7, and cut the last oil layer sleeve 2 at a certain position away from the upper surface of the connecting assembly 40;

[0109] S13: Connect the flange joint 10 to the top of the last oil layer sleeve 2, and weld the flange joint 10 to the last oil layer sleeve 2 to seal it. Install the gland 11 on both sides of the flange joint 10 and tighten the flange joint 10.

[0110] Preferably, in S12, the oil layer casing 2 can be cut at a distance of 45mm ± 2mm from the upper plane of the suspension connection assembly 40 to ensure a clean cut. Furthermore, when it is necessary to connect the venting line and pressure gauge, the corresponding components can be directly fitted onto the valve installed in S2.

[0111] Furthermore, the cement in S8 comprises Grade G oil well cement, silica fume, microsilica, strength stabilizer, anti-high temperature cracking agent, expansion agent, suspension stabilizer, fluid loss reducing agent, early strength agent, and water.

[0112] This high-temperature cementing formula utilizes the synergistic effect of various additives and base cement to ensure that the strength of the cement stone does not decrease or decreases only slightly under long-term alternating hot and cold temperatures of 350℃, thereby delaying casing damage. Due to its high temperature resistance, the formula is widely applicable to various thermal well cementing processes.

[0113] High-temperature cementing technology proposes a performance design method for cement stone in thermal recovery wells based on the cement stone sealing failure criteria and cement ring stress calculation model. This method optimizes the performance parameters of the cement stone in thermal recovery wells. According to the design requirements of key mechanical performance parameters of the cement stone and the requirements of the on-site cementing process, through hundreds of additive comparisons and compatibility tests, and considering cost, the optimal high-temperature cement additives and their optimal dosages are selected. A high-temperature resistant cement slurry system suitable for thermal recovery wells is developed. Through experiments on the basic properties of the cement slurry, the compressive strength and tensile strength of the cement stone, and the performance changes of the cement stone under temperature cyclic loading, the influence of multi-cycle temperature loading on the compressive strength, tensile strength, and microstructure of the cement stone is studied. This verifies whether the cement slurry meets the cementing process requirements and whether the cement stone meets the mechanical performance requirements. Furthermore, this study, for the first time, introduced the theory that the elastic modulus of the oil reservoir casing and cement sheath needs to be matched into cementing design. Using a wellbore thermal stress calculation model under 350℃ conditions, the stress state of the wellbore with multiple sets of cement sheaths with different elastic moduli was calculated. The study investigated the range of cement stone elastic modulus values ​​when neither the casing nor the cement stone fails. Based on this, the cement formula was designed and the tubing string assembly was optimized, achieving the goal of reducing the casing loss rate in thermal recovery wells without increasing the completion string cost. Finally, a high-temperature cementing formula resistant to 350℃ was developed. This high-temperature cementing slurry formula exhibits an average compressive strength greater than 20 MPa after 48 hours and an average compressive strength greater than 22 MPa after 168 hours, with no strength degradation at high temperatures, meeting the requirements for steam injection in oilfields.

[0114] Further, in the cement formulation, the silica fume accounts for 20%-40% by mass; the microsilica accounts for 15%-20% by mass; the strength stabilizer accounts for 8%-13% by mass; the anti-high-temperature cracking agent accounts for 4%-6% by mass; the expansion agent accounts for 1.2%-2% by mass; the suspension stabilizer accounts for 0.2%-0.5% by mass; the water loss reducing agent accounts for 0.5%-1% by mass; the water loss reducing agent accounts for 1%-2% by mass; and the water accounts for 45%-60% by mass.

[0115] As one implementation method, the mass of G-grade oil well cement can be 600g, and the mass of the remaining additives is the mass percentage of the additives multiplied by 600g.

[0116] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A well completion process apparatus, characterized in that, The well completion equipment includes a surface casing (1) located below the ground, an oil layer casing (2) arranged coaxially with the surface casing (1), and a casing head body (3) connected to the upper end of the surface casing (1). The depth of the oil layer casing (2) below the ground is greater than the depth of the surface casing (1) below the ground. The oil layer casing (2) is connected to the inner surface of the casing head body (3) through a connecting component (40). A column anchor (500) is connected to the bottom of the oil layer casing (2). The post-type ground anchor (500) includes an anchor claw (502), a plunger body (530) for accommodating the anchor claw (502), an outer tube assembly (540), and a piston assembly (550) coaxially arranged inside the outer tube assembly (540). The outer tube assembly (540) and the piston assembly (550) are both located above the plunger body (530). The space enclosed by the inner wall of the outer tube assembly (540) and the outer wall of the piston assembly (550) is a liquid channel (503). A liquid outlet (501) communicating with the liquid channel (503) is formed on the outer tube assembly (540). The piston assembly (550) has a hydraulic oil chamber (521) formed inside, and the plunger body (530) has a receiving cavity for accommodating the anchor claw (502) and a hydraulic flow channel (531) communicating with the hydraulic oil chamber (521) and the receiving cavity. The piston assembly (550) enables the hydraulic oil in the hydraulic oil chamber (521) to flow sequentially through the hydraulic flow channel (531) and the receiving cavity so that the anchor claw (502) extends out of the side wall of the plunger body (530) and inserts into the formation. Cement entering through the oil layer casing (2) can be discharged from the liquid outlet (501) to seal the annular gap between the column anchor (500) and / or the oil layer casing (2) and the formation.

2. The well completion process apparatus according to claim 1, characterized in that, The upper end of the casing head body (3) has an installation hole that tapers inward from top to bottom. The connecting component (40) is snapped into the inner wall of the installation hole and sealed to the outer wall of the oil layer casing (2).

3. The well completion process apparatus according to claim 1, characterized in that, The connecting assembly (40) includes a hanger (41) having a receiving cavity and a slip (42) located in the receiving cavity. The outer surface of the slip (42) fits into the inner surface of the receiving cavity. The outer surface and the inner surface are respectively configured to slope inward from top to bottom. The inner surface of the slip (42) is formed with barbs to prevent the oil layer casing (2) from moving downward.

4. The well completion process apparatus according to claim 3, characterized in that, The connecting assembly (40) includes a connecting rod (43) that passes through the hanger (41) and is connected to the top of the chuck (42).

5. A type of post-type ground anchor, characterized in that, The post-type ground anchor (500) includes an anchor claw (502), a plunger body (530), an outer tube assembly (540), and a piston assembly (550) coaxially arranged inside the outer tube assembly (540). The plunger body (530) has a receiving cavity formed inside to accommodate the anchor claw (502). The outer tube assembly (540) and the piston assembly (550) are both located above the plunger body (530). The space enclosed by the inner wall of the outer tube assembly (540) and the outer wall of the piston assembly (550) is a liquid channel (503). A liquid outlet (501) communicating with the liquid channel (503) is formed on the outer tube assembly (540) so that the liquid in the liquid channel (503) can be discharged from the liquid outlet (501). A hydraulic oil chamber (521) is formed inside the piston assembly (550), and a hydraulic flow channel (531) communicating with the hydraulic oil chamber (521) and the receiving cavity is formed on the plunger body (530). The piston assembly (550) enables the hydraulic oil in the hydraulic oil chamber (521) to flow sequentially through the hydraulic flow channel (531) and the receiving cavity so that the anchor claw (502) extends out of the side wall of the plunger body (530) and inserts into the formation.

6. The post-type ground anchor according to claim 5, characterized in that, The liquid channel (503) is provided with a first one-way valve assembly (560) that is sealed to the inner wall of the outer tube assembly (540) and the outer wall of the piston assembly (550), the first one-way valve assembly (560) allowing the liquid in the liquid channel (503) to flow out in one direction.

7. The post-type ground anchor according to claim 6, characterized in that, The first one-way valve assembly (560) includes an upper stop (561) and a lower stop (562) with inclined surfaces in contact. The upper stop (561) is sealed to the inner wall of the outer tube assembly (540), and the lower stop (562) is slidably and sealed to the outer wall of the piston assembly (550). A first inclined surface is connected between the inner wall and the bottom wall of the upper stop (561), and a second inclined surface is connected between the outer wall and the top wall of the lower stop (562). The liquid can drive the lower stop (562) to move downward relative to the upper stop (561), so that a flow channel is formed between the first inclined surface and the second inclined surface, allowing the liquid to pass through.

8. The post-type ground anchor according to claim 7, characterized in that, The first one-way valve assembly (560) includes a flow guide ring (563) located below the lower plug seat (562), a first spring (564) connecting the lower plug seat (562) and the flow guide ring (563), and / or, the first one-way valve assembly (560) includes a retaining ring (565) located on the top or bottom surface of the upper plug seat (561) to restrict axial movement of the upper plug seat (561).

9. The post-type ground anchor according to claim 5, characterized in that, The piston assembly (550) includes a hydraulic cylinder (551), a piston (552) slidably and sealingly connected to the inner wall of the hydraulic cylinder (551), and a sealing plug (553) sealingly connected to the bottom of the piston (552). The inner wall of the hydraulic cylinder (551), the bottom wall of the piston (552), and / or the bottom wall of the sealing plug (553) form the hydraulic oil chamber (521). The piston (552) can drive the sealing plug (553) to move axially downward relative to the hydraulic cylinder (551) so that the hydraulic oil in the hydraulic oil chamber (521) is discharged to the hydraulic flow channel (531).

10. The post-type ground anchor according to claim 9, characterized in that, The bottom of the hydraulic oil chamber (521) is provided with a second one-way valve assembly (570) that is sealed to the inner wall of the cylinder (551). The second one-way valve assembly (570) allows the hydraulic oil in the hydraulic oil chamber (521) to flow unidirectionally into the hydraulic flow channel (531).

11. The post-type ground anchor according to claim 10, characterized in that, The second one-way valve assembly (570) includes a valve seat (571) with a flow channel, a valve core (572) located in the flow channel and in contact with the inclined surface of the valve seat (571), and an inner guide seat (573) located in the flow channel and sleeved on the outside of the valve core (572). A third inclined surface is provided on the inner wall of the valve seat (571), and a fourth inclined surface is provided on the head of the valve core (572). A first through hole is formed on the inner guide seat (573). A second spring (574) is connected between the bottom surface of the head and the top surface of the inner guide seat (573). The hydraulic oil in the hydraulic oil chamber (521) can drive the valve core (572) to move downward relative to the valve seat (571), so that a gap is formed between the third inclined surface and the fourth inclined surface to allow the hydraulic oil to pass through. The hydraulic oil flows into the hydraulic flow channel (531) through the first through hole.

12. The post-type ground anchor according to claim 5, characterized in that, The piston (552) is configured as a uniform wall thickness structure with a second through hole. The piston assembly (550) includes an upper centering frame (554) and a lower centering frame (555) for restricting the radial movement of the piston (552). The upper centering frame (554) and the lower centering frame (555) are located within the liquid channel (503) and arranged around the piston (552). The upper centering frame (554) is located on top of the piston (552) and blocks the second through hole. The lower centering frame (555) is located on top of the cylinder (551).

13. The post-type ground anchor according to claim 5, characterized in that, The outer tube assembly (540) includes an upper outer tube (541) and a lower outer tube (542) arranged coaxially. A coupling (544) is connected to the top of the upper outer tube (541). A receiving tube (543) is connected between the upper outer tube (541) and the lower outer tube (542). A protrusion is provided on the top of the plunger body (530). The piston assembly (550) is connected to the inner wall of the protrusion. The lower outer tube (542) is connected to the outer wall of the protrusion through a receiving rotor (545). The liquid outlet (501) is formed on the side wall of the lower outer tube (542).

14. The post-type ground anchor according to claim 5, characterized in that, The anchor claw (502) is sealed to the inner wall of the receiving cavity, and a retainer (504) for restricting the axial movement of the anchor claw (502) is provided in the receiving cavity. Alternatively, an injection hole communicating with the hydraulic flow channel (531) is formed on the plunger body (530), and an injection plug (505) is sealed in the injection hole.

15. The post-type ground anchor according to claim 5, characterized in that, The plunger body (530) has a plurality of receiving cavities at different heights, and the axes of the different receiving cavities point to different horizontal directions. The hydraulic flow channel (531) includes a first horizontal flow channel group (532) arranged laterally, a first vertical flow channel group (533) connected above the first horizontal flow channel group (532), and a second vertical flow channel group (534) connected below the horizontal flow channel group (532). The first vertical flow channel group (533) and the second vertical flow channel group (534) each have a plurality of vertical flow channels located in different circumferential directions of the plunger body (530). Each vertical flow channel is connected to only one receiving cavity, so that the hydraulic oil can flow into the corresponding receiving cavity through the vertical flow channel.

16. The post-type ground anchor according to claim 15, characterized in that, The hydraulic flow channel (531) includes a second horizontal flow channel group (535) that is parallel and spaced above the first horizontal flow channel group (532) and communicates with the first vertical flow channel group (533). The hydraulic oil in the hydraulic oil chamber (521) passes sequentially through the second horizontal flow channel group (535), the first vertical flow channel group (533), the first horizontal flow channel group (532), the second vertical flow channel group (534), and the receiving cavity so that the anchor claw (502) extends out of the side wall of the plunger body (530) and inserts into the formation.

17. A method for increasing the prestress of oil reservoir casing, characterized in that, The method for increasing the prestress of the casing includes the following steps: S1: Drill a well on the surface, run a surface casing (1) into the well, and cement the surface casing (1); S2: Install the casing head body (3) above the surface casing (1), install bypass pipes (6) on both sides of the casing head body (3), and install valves on the bypass pipes (6); S3: Install a conversion joint (7) on the upper end of the casing head body (3), and connect a cross-connector (8) and a blowout preventer assembly (9) in sequence on the top of the conversion joint (7). The drilling tool passes through the cross-connector (8) and the blowout preventer assembly (9) to drill in the well. S4: After drilling to the preset depth, the drilling tool is retrieved, and the tool is used to lower the column anchor (500) with multiple oil layer casings (2) connected to the top into the well. S5: When lowering to the last oil layer casing (2), the connecting assembly (40) is fitted onto the outer surface of the last oil layer casing (2); S6: The insertion tool is placed around the outer surface of the last oil layer casing (2) and positioned above the connecting assembly (40); S7: Lower the last oil layer casing (2) using the top joint, and press the connecting assembly (40) into the casing head body (3) using the coupling of the last oil layer casing (2); S8: After opening the valve, cement is injected into the oil layer casing (2), and then a rubber plug is placed into the oil layer casing (2). The cement is discharged from the liquid outlet (501) on the column anchor (500) through the rubber plug to seal the annular gap between the column anchor (500) and / or the oil layer casing (2) and the formation. S9: After all the cement is discharged from the liquid outlet (501), the rubber plug continues to push the piston assembly (550) inside the column anchor (500). The piston assembly (550) pushes the hydraulic oil so that the anchor claw (502) extends out of the side wall of the plunger body (530) and inserts into the stratum, and then the rubber plug is retracted. S10: Use a lifting tool to lift the oil layer casing (2) upward to the preset load or to the predetermined height; S11: After lifting the insertion tool to a predetermined distance above the connecting assembly (40) with a rope, release the rope to let the insertion tool fall freely, and strike the connecting assembly (40) so that the oil layer casing (2) is clamped to the casing head body (3) through the connecting assembly (40), and then remove the lifting tool.

18. The method for increasing the prestress of the oil reservoir casing according to claim 17, characterized in that, The method for increasing the prestress of the casing also includes the following steps: S12: Disassemble the top joint, the large four-way connector (8), the blowout preventer assembly (9), the delivery tool and the adapter (7), and cut the last oil layer casing (2) at a certain position away from the upper surface of the connecting assembly (40); S13: Connect the flange joint (10) to the top of the last oil layer sleeve (2), and weld the flange joint (10) to the last oil layer sleeve (2) to seal it. Install the gland (11) on both sides of the flange joint (10) and press the flange joint (10) tightly.

19. The method for increasing the prestress of the oil reservoir casing according to claim 17, characterized in that, The cement comprises Grade G oil well cement, silica fume, microsilica, strength stabilizer, high-temperature cracking resistant agent, expansion agent, suspension stabilizer, water loss reducing agent, early strength agent, and water.

20. The method for increasing the prestress of the oil reservoir casing according to claim 19, characterized in that, The silicon powder accounts for 20%-40% of the total mass; the microsilicon accounts for 15%-20% of the total mass; the strength stabilizer accounts for 8%-13% of the total mass; the anti-high temperature embrittlement agent accounts for 4%-6% of the total mass; the expansion agent accounts for 1.2%-2% of the total mass; the suspension stabilizer accounts for 0.2%-0.5% of the total mass; the water loss reducing agent accounts for 0.5%-1% of the total mass; the water accounts for 1%-2% of the total mass; and the water accounts for 45%-60% of the total mass.

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