Safety detection and replacement tubular column and using method thereof

Abstract

The invention discloses a safety inspection and replacement tubular column and a using method thereof. The safety inspection and replacement tubular column comprises an oil pipe, at least three water distributors are arranged on the oil pipe, a packer is arranged between every two water distributors, each water distributor corresponds to a water injection layer, the lowest packer is a second-type packer, and the remaining packers are first-type packers; the first type packer is provided with a first back-off safety part, and the second type packer is provided with a second back-off safety part. The packer is provided with a back-off safety mechanism, back-off unscrewing can be carried out when a pipe column is clamped in the later period, anchoring parts are made of cast iron materials, later milling and drilling are facilitated, safety accidents of the underground pipe column are reduced, and safe inspection and replacement of the pipe column are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of water injection pipe columns in oil production wells, in particular to a safe pipe column inspection and replacement and a use method thereof. Background Art

[0002] Water injection through water injection wells is an important means for oil fields to reasonably maintain formation pressure and improve oil reservoir recovery. At present, most of my country's oil fields have shifted from the initial natural energy development stage to the water injection development stage. In the early stage of water injection development, water injection was carried out in general according to the natural water absorption capacity of oil layers of different properties (i.e., multiple oil layers were injected with water at the same time). However, since there are multiple oil layers underground, the water absorption of oil layers with different permeabilities varies greatly, resulting in a sudden water injection, which affects the development effect. In order to solve this contradiction, it is necessary to put layered water injection strings into the water injection wells to increase the utilization of various oil layers.

[0003] For low permeability reservoirs, due to the low permeability of the oil layer and the high water injection pressure, in order to prevent tubing creep, anchoring tools such as hydraulic anchors, hydraulic slips or anchored packers are generally used.

[0004] Publication (Announcement) No.: CN112709557B, discloses a safe and long-term water injection string and construction method for offshore oil fields, including: a sand control string and a water injection string, wherein the water injection string is arranged inside the sand control string; the sand control string includes at least two sand filter pipes arranged on the casing from top to bottom and corresponding to different oil layers, and Y341 packers are arranged between the two sand filter pipes, above the top sand filter pipe, and below the bottom sand filter pipe; the water injection string includes at least two adjustable water distributors arranged on the oil pipe from top to bottom and corresponding to different oil layers, and each adjustable water distributor is connected to a sealing switch below, and a hydraulically controlled stratified packer is arranged above and below each sealing switch. The invention can not only realize the one-time lowering of the sand control string and the water injection string, saving the construction time of a single well, but also realize the reliable independent maintenance of the offshore oil field and extend the service life of the sand control string.

[0005] The prior art uses a pull sleeve switch for forced release, and if one packer fails and gets stuck, all packers need to be abandoned.

[0006] Publication (Announcement) No.: CN108999576B, discloses an integrated pipe column and process for sand control by water injection. The integrated pipe column is located in the casing, and includes at least one section of water injection sand control pipe column connected from the wellhead downward through the oil pipe; the water injection sand control pipe column includes a water distributor, an upper sand retaining packer, a sand control pipe and a lower sand retaining packer connected in sequence from top to bottom; wherein the water distributor is connected to the upper sand retaining packer through the oil pipe; the sand control pipe includes a central pipe, an outer pipe and a metal felt mesh located outside the outer pipe, an annular cavity is provided between the central pipe and the outer pipe, and a flow hole is provided on the outer pipe; the upper sand retaining packer and the lower sand retaining packer are both provided with a flow channel for connecting the annular cavity of the sand control pipe with the annulus of the oil casing; the upper sand retaining packer and the lower sand retaining packer are respectively located at the upper and lower ends of the oil layer, and a closed sand control space can be formed between the upper sand retaining packer, the lower sand retaining packer, the outer pipe of the sand control pipe and the casing. The use of the pipe string can effectively prevent the water injection pipe string from being buried by sand, thereby increasing the working life of the water injection pipe string.

[0007] The prior art uses a reverse buckle safety joint for forced release, and if one packer fails and gets stuck, all packers need to be abandoned.

[0008] Publication (Announcement) No.: CN111173483B, discloses a time-sharing water injection string and a time-sharing water injection method, the time-sharing water injection string includes an indoor control system, a wellhead control cabinet, a hydraulic control pipeline, an oil pipe, a hydraulic control layered packer and a hydraulic control water distribution device, the hydraulic control layered packer and the hydraulic control water distribution device have multiple, each hydraulic control layered packer seals its corresponding hydraulic control water distribution device in different oil layers, the hydraulic control water distribution device is ground stepped pressure, realizes the switch of water distributors in different oil layers, the wellhead control cabinet monitors and records the injection volume of the oil layer, and transmits it to the indoor control system, and dynamically monitors the pressure of the hydraulic control pipeline to ensure that the pressure is within a reasonable range, and the indoor control system controls the wellhead control cabinet by wired or wireless means. The time-sharing water injection string and the time-sharing water injection method open the corresponding water distribution device according to the ground pressure situation, and the ground flow device measures the flow of the injection layer to realize the stratified intermittent injection of the water injection well.

[0009] The prior art does not have a safety release mechanism, and there is a problem that the pipe string cannot be released due to packer failure.

[0010] In summary, the technical solutions of the above-disclosed technologies, the technical problems to be solved, and the beneficial effects produced are all different from the present invention. Regarding more technical features, technical problems to be solved, and beneficial effects of the present invention, the above-disclosed technical documents do not provide any technical inspiration. Summary of the invention

[0011] In view of the above-mentioned defects in the prior art, the purpose of the present invention is to provide a safe inspection and replacement of pipe strings and a method of using the same, so that when the pipe string is stuck, it can be unscrewed by reverse screwing, and the anchoring parts are made of cast iron materials, which is convenient for subsequent grinding and drilling, reducing the safety accidents of downhole pipe strings and realizing safe inspection and replacement of pipe strings.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] A safe replacement pipe string and a method for using the same, comprising an oil pipe, wherein at least three water distributors are arranged on the oil pipe, a packer is arranged between every two water distributors, each water distributor corresponds to a water injection layer, the lowest packer is a type II packer, and the remaining packers are type I packers; the type I packer is provided with a first inverted safety portion, and the type II packer is provided with a second inverted safety portion.

[0014] A well flushing valve is arranged at the bottom of the oil pipe, and a compensator is arranged above the uppermost water distributor of the oil pipe.

[0015] The type I packer comprises a first undercut safety portion, a first anchoring release portion, a first sealing and backwashing well portion which are connected in sequence.

[0016] The first undercut safety part includes a first upper joint, a first locking block, and a first central tube;

[0017] The inner wall of the upper end of the first central tube and the outer wall of the lower end of the first upper joint are connected by an inverted thread; the first locking block passes through the upper end of the first central tube and is inserted into the first upper joint;

[0018] The first central tube is sleeved with a first shear nail sleeve on the outer wall below the first upper joint;

[0019] The first shear nail sleeve is connected to the first central tube through the first shear nail, and the first central tube is provided with a first pressure transmission hole at a position corresponding to the upper end of the first shear nail sleeve;

[0020] The outer wall of the first shear nail sleeve is connected with a first locking block sleeve by threads, the first locking block sleeve covers the first locking block, and the inner wall of the first locking block sleeve above the first locking block is provided with a first accommodating groove.

[0021] The first anchoring release part includes a second central tube, an anchor tooth, and a first anchor body;

[0022] The upper end of the first anchor body is connected to the lower end of the first center tube by threads, and the two ends of the anchor teeth are fixed to the outer wall of the first anchor body;

[0023] The first anchor body is provided with a first through hole in a region corresponding to the anchor teeth, and the second central tube is sleeved in the first anchor body;

[0024] A first piston is disposed in the first through hole, and a first spring is disposed between the first piston and the anchor tooth;

[0025] The anchor teeth, the first through hole, the first piston and the first spring are arranged in at least two groups.

[0026] The first sealing and backwashing part includes an upper outer sleeve, an upper support body, a first rubber cylinder, a lower support body, a third central tube, and a lower outer sleeve;

[0027] The upper sleeve is connected to the first anchor body by threads, and the upper end of the third central tube is connected to the inner wall of the upper end of the upper sleeve by threads;

[0028] The outer wall of the upper sleeve is provided with a protrusion extending downward, the upper end of the annulus between the protrusion and the third center tube is provided with a second spring, the lower end of the second spring is provided with a second piston, the lower end surface of the second piston is an outer cone, and the third center tube is provided with a second pressure transmission hole at a position corresponding to the upper end of the second spring;

[0029] The inner wall of the lower end of the protrusion is threadedly connected with an upper support body, the upper end surface of the upper support body is an inner conical surface, and the lower end surface of the second piston is in contact with the upper end surface of the upper support body;

[0030] The upper support body is not in contact with the third central tube, and the protrusion is provided with a first water inlet hole above the upper end surface of the upper support body;

[0031] The inner wall of the lower end of the upper support body is threadedly connected with a first rubber cylinder seat, the first rubber cylinder seat is not in contact with the third central tube, at least two first rubber cylinders are mounted on the first rubber cylinder seat, a spacer ring is arranged between every two first rubber cylinders, and a lower support body is arranged on the outer wall of the lower end of the first rubber cylinder seat, and the lower support body can slide relative to the second rubber cylinder seat;

[0032] The upper end of the lower support body is in contact with the first rubber cylinder, and the outer wall of the lower end of the lower support body is threadedly connected with a lower outer sleeve, and the lower outer sleeve is provided with a first water outlet hole below the lower support body, and the first rubber cylinder seat is provided with a first drainage hole at a corresponding position of the lower support body, and when the lower support body moves upward to squeeze the first rubber cylinder to complete the sealing, the first water outlet hole coincides with the first drainage hole.

[0033] The inner wall at the lower end of the lower outer sleeve is threadedly connected with a first lower joint, and the lower end of the third central tube is inserted into the inner wall at the upper end of the first lower joint;

[0034] The inner wall of the lower outer sleeve is provided with a convex ring, and the third central tube is provided with a groove in the corresponding area of ​​the lower outer sleeve;

[0035] A spring body is arranged between the third center tube and the lower outer sleeve, a first clamping portion is arranged on the outer wall of the spring body and is seated on the upper end surface of the convex ring, a second clamping portion is arranged on the inner wall of the spring body, and the upper end surface of the second clamping portion contacts the upper end surface of the groove.

[0036] The second type packer comprises a fourth central tube, and a second undercut safety part, a second anchoring release part, a second sealing and backwashing well part, and a supporting and setting part which are sequentially arranged on the fourth central tube.

[0037] The second undercut safety part comprises a second upper joint, a second locking block sleeve, a second locking block, and a second shear nail sleeve;

[0038] The inner wall of the upper end of the fourth central tube is connected to the outer wall of the lower end of the second upper joint by an inverted thread, and the second locking block passes through the upper end of the fourth central tube and is inserted into the second upper joint;

[0039] The fourth central tube is sleeved with a second shear nail sleeve on the outer wall below the second upper joint, the second shear nail sleeve is connected to the fourth central tube through the second shear nail, and the fourth central tube is provided with a third pressure transmission hole at a position corresponding to the upper end of the second shear nail sleeve;

[0040] The outer wall of the second shear nail sleeve is threadedly connected with a second locking block sleeve, the second locking block sleeve covers the second locking block, and the inner wall of the second locking block sleeve above the second locking block is provided with a second accommodating groove.

[0041] The second anchoring release part includes an anchor claw and a second anchor body;

[0042] The second anchor body is sleeved on the fourth central tube, the two ends of the fluke are fixed to the outer wall of the second anchor body, the second anchor body is provided with a second through hole in the area corresponding to the fluke, a third piston is provided in the second through hole, and a third spring is provided between the third piston and the fluke; the fluke, the second through hole, the third piston and the third spring are provided in at least two groups;

[0043] The fourth central tube is provided with a pressure groove in a region corresponding to the anchor claw, and a fourth pressure transmission hole is provided in the pressure groove.

[0044] Two second through holes are arranged in the corresponding area of ​​the anchor claw, and the middle of the anchor claw is also fixed to the outer wall of the second anchor body.

[0045] The second sealing and backwash well part includes a water inlet jacket, an upper retaining ring, and a cone;

[0046] The outer wall of the lower end of the second anchor body is threadedly connected with a water inlet sleeve, a fourth spring is arranged above the annulus between the water inlet sleeve and the fourth central tube, a fourth piston is arranged at the lower end of the fourth spring, and the lower end surface of the fourth piston is an outer conical surface;

[0047] The upper retaining ring is threadedly connected to the inner wall of the lower end of the water inlet sleeve, the upper retaining ring is not in contact with the fourth center tube, the upper end surface of the upper retaining ring is an inner conical surface, and the lower end surface of the fourth piston is in contact with the upper end surface of the upper retaining ring;

[0048] The water inlet sleeve is provided with a second water inlet hole above the upper end surface of the upper retaining ring, and the fourth center tube is provided with a fifth pressure transmission hole at a position corresponding to the upper end of the fourth spring;

[0049] The inner wall of the lower end of the upper retaining ring is threadedly connected with a second rubber cylinder seat, the second rubber cylinder seat is not in contact with the fourth central tube, at least two second rubber cylinders are sleeved on the outer surface of the second rubber cylinder seat, and a separation ring is arranged between every two second rubber cylinders;

[0050] The cone is arranged on the outer wall of the lower end of the second rubber cylinder seat and can slide relatively with the second rubber cylinder seat. An outer cone is arranged at the lower end of the cone, and the outer cone contacts the fourth central tube. A second water outlet is arranged above the outer cone.

[0051] The supporting and setting part includes a limiting shell;

[0052] The limiting shell is sleeved on the fourth central tube and arranged below the cone. The upper end of the limiting shell is provided with at least two slip grooves and the middle part is provided with at least two straightening grooves.

[0053] A slip is arranged in each slip groove, an inner cone is arranged at the upper end of the slip, slip teeth are arranged on the outer wall of the inner cone, and the lower end of the slip is fixed in the slip groove;

[0054] A straightening block is arranged in each straightening groove, and the outer walls of the upper and lower ends of the straightening groove protrude inwards to prevent the straightening block from escaping from the limiting shell. A spring sheet is arranged between the straightening block and the straightening groove, and inclined surfaces are arranged at the upper and lower ends of the straightening block.

[0055] The supporting and setting part also includes a reversing sleeve and a second lower joint;

[0056] The upper end of the reversing sleeve is threadedly connected to the outer wall of the lower end of the limit housing, the inner wall of the upper end of the second lower joint is threadedly connected to the outer wall of the lower end of the fourth center tube, and the inner wall of the reversing sleeve is provided with a "7"-shaped groove, and the "7"-shaped groove is divided into a short groove and a long groove;

[0057] A reversing block is arranged on the outer wall of the upper end of the second lower joint, and the reversing block is quickly embedded in the short slot or the long slot. When the reversing block is embedded in the short slot, the second lower joint moves synchronously with the reversing sleeve, and when the reversing block is embedded in the long slot, the second lower joint and the reversing sleeve can slide relative to each other.

[0058] The undercut thread is a left-hand thread, and the thread is a right-hand thread.

[0059] The anchor teeth are made of cast iron and can be processed by grinding or drilling.

[0060] The fluke is made of cast iron and can be milled or drilled.

[0061] The first locking block sleeve and the first shear nail sleeve are made of cast iron and can be processed by grinding or drilling.

[0062] The second locking block sleeve and the second shear nail sleeve are made of cast iron and can be processed by grinding or drilling.

[0063] A method for safely inspecting and replacing a pipe string comprises the following steps:

[0064] S1. Assemble the pipe string and lower it into the well. According to the designed construction depth, use different lengths of tubing to assemble the compensator, water distributor, type I packer, type II packer, and well flushing valve and lower them into the well to the designed depth, so that one water distributor corresponds to one water injection layer.

[0065] S2, Sealing: After reaching the designed depth, first complete the sealing of the lower type II packer, "lift up" - "right-hand" the pipe string, the second lower joint reversing block is in the long groove of the "7"-shaped groove on the inner wall of the reversing sleeve, lower the pipe string, at this time, the slips are pushed out and stuck on the inner wall of the casing, continue to lower the pipe string, the slips are tightened, and the cone compresses the second rubber cylinder to achieve sealing;

[0066] After the bottom type-2 packer is sealed, continue to lower the tubing string to seal the upper type-1 packer. The type-1 packer will use the lower type-2 packer as a support point. At this time, continue to lower the tubing string, the first lower joint is fixed, the first inverted safety part, the first anchor release part, the third center pipe, the upper outer sleeve, and the upper support body move downward, and the upper support body compresses the first rubber cylinder to achieve sealing; at this time, the first water outlet hole coincides with the first drainage hole.

[0067] S3, water injection: open the water distributors at all levels, adjust the water distributors to the appropriate opening according to the injection volume requirements, and inject water into the oil pipes;

[0068] After the oil pipe is pressurized, the oil pipe pressure passes through the gap between the second center pipe and the first anchor body to push the first piston to extend the anchor teeth, and the oil pipe pressure enters the pressure groove through the fourth pressure transmission hole to push the third piston to extend the anchor claws;

[0069] The oil pipe pressure passes through the second pressure transmission hole to make the second piston sit on the upper support body, and the oil pipe pressure passes through the fifth pressure transmission hole to make the fourth piston sit on the upper retaining ring, and the backwash channel is closed;

[0070] S4, backwash well: stop water injection, after the oil pipe is depressurized, backwash well fluid is injected from the casing annulus, and the backwash well fluid enters from the first water inlet, so that the second piston pushes the second spring to move under the backwash pressure, the first backwash channel is opened, and the backwash well fluid is discharged from the first water outlet and passes through a type I packer;

[0071] The backwash fluid enters from the second water inlet, so that the fourth piston pushes the fourth spring under the backwash pressure, the second backwash channel is opened, and the backwash fluid is discharged from the second water outlet and passes through the second type packer;

[0072] The backwash fluid enters the oil pipe through the well flushing valve and returns to the ground.

[0073] S5, unsealing: After the tubing is depressurized, the anchor teeth and claws of the type 1 and type 2 packers are recovered, and the pipe string is "lifted up" to drive the upper support body of the type 1 packer to move upward, and the first rubber cylinder is recovered to realize the unsealing of the type 1 packer;

[0074] Continue to "lift" the tubing string, the reversing block of the second lower joint of the type II packer moves from the lower end of the long groove of the reversing sleeve to the upper end, the slips are recovered, the cone is recovered, the second rubber cylinder loses compression, the second rubber cylinder is recovered, and the second packer is unsealed.

[0075] S6. Dropping, drilling and milling: If the pipe string is stuck, use the tubing "boosting pressure" - "forward rotation" to drop the pipe string from the safe part of the packer, and use grinding or drilling and milling to process the remaining part of the well.

[0076] When the type-1 packer is stuck: the tubing rises to the shearing pressure of the first shearing nail, the first shearing nail sleeve of the type-1 packer cuts off the first shearing nail, drives the locking block sleeve to move downward, the first locking block pops out to the first receiving groove, the first upper joint is disengaged from the first central pipe by right-hand rotation and is taken out, and the wellbore processing tool is used to grind or drill the remaining well part;

[0077] When the second type packer is stuck: the tubing rises to the shearing pressure of the second shear nail, the second shear nail sleeve of the second type packer cuts the second shear nail, drives the outer sleeve to move downward, the second locking block pops out to the second receiving groove, the second upper joint is disengaged from the fourth center pipe by right rotation and taken out, and the wellbore processing tool is used to mill or drill the remaining well part;

[0078] The second shear nail shearing pressure is less than the first shear nail shearing pressure.

[0079] Compared with the prior art, the present invention has the following beneficial effects:

[0080] 1. The two-stage packer in the string is set by the weight of the tubing itself. It is mechanically set, simple to operate and reliable. The sealing track of the type-1 packer support sealing mechanism is set on the inner wall of the reversing jacket to avoid direct contact with the wellbore fluid, eliminate the risk of affecting the track reversal, and improve the reliability of the tool sealing. The type-1 packer uses the type-2 packer after setting as the support point, and relies on the weight of the upper string to compress the rubber cylinder to achieve setting. The setting is simple and reliable.

[0081] 2. Lift the pipe string to unseal the two-stage packer. There is no additional load for unsealing. The operation is simple, safe and reliable. Both the two-stage packers are designed with an inverted safety mechanism. When the pipe string is stuck later, it can be unscrewed by inverting. The anchoring parts are made of cast iron materials, which is convenient for later milling and drilling, reducing the safety accidents of the downhole pipe string and realizing the safe inspection and replacement of the pipe string.

[0082] 3. Both the two-stage packers are designed with backwash well channels, and the pipe string can meet the needs of backwash wells in the later stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1 This is a structural schematic diagram of a safe pipe string replacement according to the present invention;

[0084] Figure 2 It is a structural schematic diagram of a type of packer for safely inspecting and replacing a pipe string according to the present invention;

[0085] Figure 3 It is a structural schematic diagram of a second type packer for safely inspecting and replacing a pipe string according to the present invention;

[0086] Figure 4 It is a structural schematic diagram of the second anchoring and releasing part of a second type packer for safely inspecting and replacing a pipe string according to the present invention;

[0087] Figure 5 It is a schematic diagram of the second seal and backwash well structure of a second type packer for safely replacing a pipe string according to the present invention;

[0088] In the figure: 1. compensator; 2. water distributor; 3. type 1 packer; 4. type 2 packer; 5. well flushing valve;

[0089] 6. First undercut safety part; 601. First upper joint; 602. First locking block; 603. First shear nail; 604. First center tube;

[0090] 7. First anchoring release part; 701. Second center tube; 702. Anchor teeth; 703. First anchor body;

[0091] 8. First sealing and backwash well part; 801. Upper outer sleeve; 802. Second spring; 803. Second piston; 804. Upper support body; 805. First rubber cylinder; 806. Lower support body; 807. Third central tube; 808. Lower outer sleeve; 809. First lower joint;

[0092] 9. Second undercut safety part; 901. Second upper joint; 902. Outer sleeve; 903. Second locking block; 904. Fourth center tube; 905. Second shear nail sleeve;

[0093] 10. Second anchor release part; 1001. Anchor claw; 1002. Second anchor body;

[0094] 11. Second sealing and backwash well part; 1101. Fourth spring; 1102. Fourth piston; 1103. Second rubber cylinder; 1104. Cone;

[0095] 12. Supporting and sealing part; 1201. Slips; 1202. Righting block; 1203. Reversing sleeve; 1204. Second lower joint. DETAILED DESCRIPTION

[0096] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0097] Embodiment 1:

[0098] See also Figure 1 A safe replacement string provided by the present invention comprises an oil pipe, on which at least three water distributors 2 are arranged, a packer is arranged between every two water distributors 2, each water distributor corresponds to a water injection layer, the lowest packer is a type II packer 4, and the remaining packers are type I packers 3, a well flushing valve 5 is arranged at the bottom of the oil pipe, and a compensator 1 is arranged above the uppermost water distributor 2 of the oil pipe.

[0099] See also Figure 2 The type 1 packer 3 comprises a first undercut safety part 6, a first anchoring release part 7, and a first sealing and backwashing well part 8 which are connected in sequence;

[0100] The first inverted safety part 6 includes a first upper joint 601, a first locking block 602, and a first center tube 604; the inner wall of the upper end of the first center tube 604 and the outer wall of the lower end of the first upper joint 601 are connected by inverted threads, the first locking block 602 passes through the upper end of the first center tube 604 and is inserted into the first upper joint 601, the first center tube 604 is provided with a first shear nail sleeve on the outer wall below the first upper joint 601, the first shear nail sleeve is connected to the first center tube 604 through the first shear nail 603, the first center tube 604 is provided with a first pressure transmission hole at a corresponding position on the upper end of the first shear nail sleeve, the outer wall of the first shear nail sleeve is connected with the first locking block sleeve by threads, the first locking block sleeve covers the first locking block 602, and the first locking block sleeve is provided with a first accommodating groove on the inner wall above the first locking block 602.

[0101] The first anchoring and releasing part 7 includes a second central tube 701, an anchor tooth 702, and a first anchor body 703; the upper end of the first anchor body 703 is connected to the lower end of the first central tube 604 by a thread, and the two ends of the anchor tooth 702 are fixed to the outer wall of the first anchor body 703, and the first anchor body is provided with a first through hole in the corresponding area of ​​the anchor tooth 702, the second central tube 701 is sleeved in the first anchor body 703, and a first piston is arranged in the first through hole, and a first spring is arranged between the first piston and the anchor tooth 702; the anchor tooth 702, the first through hole, the first piston, and the first spring are arranged in at least two groups.

[0102] The first sealing and backwashing part 8 comprises an upper outer sleeve 801, an upper support body 804, a first rubber cylinder 805, a lower support body 806, a third center tube 807, and a lower outer sleeve 808; the upper outer sleeve 801 is connected to the first anchor body 703 by threads, the upper end of the third center tube 807 is connected to the inner wall of the upper end of the upper outer sleeve 801 by threads, the outer wall of the upper outer sleeve 801 is provided with a protrusion extending downward, the upper end of the annulus between the protrusion and the third center tube 807 is provided with a second spring 802, the lower end of the second spring is provided with a second piston 803, the lower end surface of the second piston 803 is an outer cone, and the third center tube 807 is provided with a second pressure transmission hole at a position corresponding to the upper end of the second spring 802;

[0103] The inner wall at the lower end of the protrusion is threadedly connected to an upper support body 804, the upper end surface of the upper support body 804 is an inner conical surface, the lower end surface of the second piston 803 is in contact with the upper end surface of the upper support body 804, the upper support body 804 does not contact the third center tube 807, and the protrusion is provided with a first water inlet hole above the upper end surface of the upper support body 804; the inner wall at the lower end of the upper support body 804 is threadedly connected to a first rubber cylinder seat, the first rubber cylinder seat does not contact the third center tube 807, and at least two first rubber cylinders 805 are mounted on the first rubber cylinder seat, and each two first rubber cylinders 805 A spacer ring is arranged between them, a lower support body 806 is arranged on the outer wall of the lower end of the first rubber cylinder seat, the lower support body 806 can slide relatively with the first rubber cylinder seat, the upper end of the lower support body 806 contacts the first rubber cylinder 805, the lower end outer wall of the lower support body 806 is threadedly connected with a lower outer sleeve 808, the lower outer sleeve 808 is provided with a first water outlet hole below the lower support body 806, the first rubber cylinder seat is provided with a first drainage hole at a corresponding position of the lower support body 806, and when the lower support body 806 moves up to squeeze the first rubber cylinder 805 to complete the sealing, the first water outlet hole coincides with the first drainage hole;

[0104] The inner wall at the lower end of the lower sleeve 808 is threadedly connected with the first lower joint 809, the lower end of the third center tube is inserted into the inner wall at the upper end of the first lower joint 809, the inner wall of the lower sleeve 808 is provided with a convex ring, the third center tube 807 is provided with a groove in the corresponding area of ​​the lower sleeve 808, a spring body is provided between the third center tube 807 and the lower sleeve 808, the outer wall of the spring body is provided with a first clamping portion, which is seated on the upper end face of the convex ring, the inner wall of the spring body is provided with a second clamping portion, and the upper end face of the second clamping portion contacts the upper end face of the groove.

[0105] The spring body prevents the type 1 packer 3 from being accidentally set.

[0106] See also Figures 3 to 5 The second type packer 4 includes a fourth central pipe 904, and a second undercut safety portion 9, a second anchoring release portion 10, a second sealing and backwashing well portion 11, and a supporting and setting portion 12 which are sequentially arranged on the fourth central pipe 904;

[0107] The second inverted safety part 9 includes a second upper joint 901, a second locking block sleeve 902, a second locking block 903, and a second shear nail sleeve 905; the inner wall of the upper end of the fourth center tube 904 is connected to the outer wall of the lower end of the second upper joint 901 by an inverted thread, the second locking block 903 passes through the upper end of the fourth center tube 904 and is inserted into the second upper joint 901, the fourth center tube 904 is sleeved with a second shear nail sleeve 905 on the outer wall below the second upper joint 901, the second shear nail sleeve 905 is connected to the fourth center tube 904 through the second shear nail, the fourth center tube 904 is provided with a third pressure transmission hole at a corresponding position on the upper end of the second shear nail sleeve 905, the outer wall of the second shear nail sleeve 905 is threadedly connected with the second locking block sleeve 902, the second locking block sleeve 902 covers the second locking block 903, and the second locking block sleeve 902 is provided with a second accommodating groove on the inner wall above the second locking block 903.

[0108] The second anchoring and releasing part 10 comprises an anchor claw 1001 and a second anchor body 1002; the second anchor body 1002 is sleeved on the fourth center tube 904, both ends of the anchor claw 1001 are fixed to the outer wall of the second anchor body 1002, the second anchor body 1002 is provided with a second through hole in the area corresponding to the anchor claw 1001, a third piston is provided in the second through hole, and a third spring is provided between the third piston and the anchor claw 1001; the anchor claw 1001, the second through hole, the third piston and the third spring are provided in at least two groups; two second through holes are provided in the area corresponding to the anchor claw 1001, the middle of the anchor claw 1001 is fixed to the outer wall of the second anchor body 1002, the fourth center tube 904 is provided with a pressure groove in the area corresponding to the anchor claw 1001, and a fourth pressure transmission hole is provided in the pressure groove.

[0109] The second sealing and backwash well part 11 includes a water inlet sleeve, an upper retaining ring, and a cone 1104; the outer wall of the lower end of the second anchor body 1002 is threadedly connected with the water inlet sleeve, a fourth spring 1101 is arranged above the annulus between the water inlet sleeve and the fourth center pipe 904, a fourth piston 1102 is arranged at the lower end of the fourth spring 1101, and the lower end face of the fourth piston 1102 is an outer cone surface, the upper retaining ring is threadedly connected with the inner wall of the lower end of the water inlet sleeve, the upper retaining ring is not in contact with the fourth center pipe 904, the upper end face of the upper retaining ring is an inner cone surface, the lower end face of the fourth piston 1102 is fitted with the upper end face of the upper retaining ring, the water inlet sleeve is provided with a second water inlet hole above the upper end face of the upper retaining ring, and the fourth center pipe 904 is provided with a fifth pressure transmission hole at a position corresponding to the upper end of the fourth spring 1101;

[0110] The inner wall at the lower end of the upper retaining ring is threadedly connected to a second rubber cylinder seat, and the second rubber cylinder seat does not contact the fourth center tube 904. At least two second rubber cylinders 1103 are mounted on the outer sleeve of the second rubber cylinder seat, and a separator ring is arranged between every two second rubber cylinders 1103. The cone 1104 is arranged on the outer wall of the lower end of the second rubber cylinder seat and can slide relative to the second rubber cylinder seat. An outer cone is arranged at the lower end of the cone 1104, and the outer cone is in contact with the fourth center tube 904. The cone 1104 is provided with a second water outlet above the outer cone.

[0111] The supporting sealing part 12 includes a limiting shell, a reversing sleeve 1203, and a second lower joint 1204; the limiting shell is sleeved on the fourth center tube 904 and is arranged below the cone 1104, and at least two slip grooves are arranged at the upper end of the limiting shell and at least two straightening grooves are arranged in the middle; a slip 1201 is arranged in each slip groove, an inner cone is arranged at the upper end of the slip 1201, and slip teeth are arranged on the outer wall of the inner cone, and the lower end of the slip 1201 is fixed in the slip groove, and a straightening block 1202 is arranged in each straightening groove, and the outer walls of the upper and lower ends of the straightening groove protrude inward to prevent the straightening block 1202 from detaching from the limiting shell, and a spring sheet is arranged between the straightening block and the straightening groove to make the straightening block extend out of the limiting shell, and inclined surfaces are arranged at the upper and lower ends of the straightening block;

[0112] The upper end of the reversing sleeve 1203 is threadedly connected to the outer wall of the lower end of the limit shell, the inner wall of the upper end of the second lower joint 1204 is threadedly connected to the outer wall of the lower end of the fourth center tube 904, the inner wall of the reversing sleeve 1203 is provided with a "7"-shaped groove, and the "7"-shaped groove is divided into a short groove and a long groove. The outer wall of the upper end of the second lower joint 1204 is provided with a reversing block, and the reversing block is embedded in the short groove or the long groove. When the reversing block is embedded in the short groove, the second lower joint 1204 moves synchronously with the reversing sleeve 1203. When the reversing block is embedded in the long groove, the second lower joint 1204 slides relative to the reversing sleeve 1203.

[0113] The undercut thread is a left-hand thread, and the thread is a right-hand thread.

[0114] The anchor teeth 702 and the anchor claws 1001 are made of cast iron and can be processed by grinding or drilling.

[0115] The first locking block sleeve, the first shear nail sleeve, the second locking block sleeve 902 and the second shear nail sleeve 905 are made of cast iron and can be processed by grinding or drilling.

[0116] Embodiment 2:

[0117] Based on Example 1, the present invention provides a method for safely replacing a pipe string, comprising the following steps:

[0118] S1, assemble the pipe string and lower it into the well. According to the designed construction depth, use different lengths of tubing to assemble the compensator 1, water distributor 2, type I packer 3, type II packer 4, and well flushing valve 5 and lower them into the well to the designed depth, so that one water distributor corresponds to one water injection layer;

[0119] S2. Sealing: After reaching the designed depth, first complete the sealing of the lower type II packer 4, "lift up" - "rotate right" the tubing, the reversing block of the second lower joint 1204 is in the long groove of the "7"-shaped groove on the inner wall of the reversing sleeve 1203, lower the tubing, at this time, the slip 1201 is stretched out and stuck on the inner wall of the casing, continue to lower the tubing, the slip 1201 is tightened, the cone 1104 compresses the second rubber cylinder 1103, and sealing is achieved.

[0120] After the lowermost type II packer is set, the pipe string is lowered to set the upper type I packer. The type I packer will use the lower type II packer as a support point. At this time, the pipe string is lowered, the first lower joint 809 is fixed, the first inverted safety part 6, the first anchor release part 7, the third central pipe 807, the upper sleeve 801, and the upper support body 804 move downward, and the upper support body 304 compresses the first rubber cylinder 805 to achieve setting; at this time, the first water outlet hole coincides with the first drainage hole;

[0121] S3, water injection: open the water distributors 2 at all levels, adjust the water distributors to appropriate openings according to the injection volume requirements, and inject water into the oil pipes;

[0122] After the oil pipe is pressurized, the oil pipe pressure passes through the gap between the second center pipe 701 and the first anchor body 703, pushing the first piston to extend the anchor teeth 602, and the oil pipe pressure enters the pressure groove through the fourth pressure transmission hole, pushing the third piston to extend the anchor claw 1001;

[0123] The oil pipe pressure passes through the second pressure transmission hole to make the second piston 903 sit on the upper support body 804, and the oil pipe pressure passes through the fifth pressure transmission hole to make the fourth piston 1102 sit on the upper retaining ring, and the backwash channel is closed;

[0124] S4, backwash well: stop water injection, after the oil pipe is depressurized, backwash well fluid is injected from the casing annulus, and the backwash well fluid enters from the first water inlet, so that the second piston 803 pushes the spring force of the second spring 802 to move under the backwash pressure, the backwash channel is opened, and the backwash well fluid is discharged from the first water outlet and passes through the type 1 packer 3;

[0125] The backwash fluid enters from the second water inlet, so that the fourth piston 1102 pushes the fourth spring 1101 under the backwash pressure, the backwash channel is opened, and the backwash fluid is discharged from the second water outlet and passes through the second type packer 3;

[0126] The backwash fluid enters the oil pipe through the well-washing valve 5 and returns to the ground;

[0127] S5, unsealing: After the tubing is depressurized, the anchor teeth 702 and the anchor claws 1001 of the type 1 packer 3 and the type 2 packer 4 are recovered, and the pipe column is "lifted up", driving the upper support body 804 of the type 1 packer 3 to move upward, and the first rubber cylinder 805 is recovered, so that the type 1 packer is unsealed;

[0128] Continue to "lift" the pipe string, the reversing block of the second lower joint 1204 of the second type packer 4 moves from the lower end of the long groove of the reversing sleeve 403 to the upper end, the slip 1201 is recovered, the cone 1104 is recovered, the second rubber cylinder 1103 loses compression, the second rubber cylinder 1103 is recovered, and the second packer is unsealed;

[0129] S6, release, drilling and milling: If the pipe string is stuck in the later stage, the tubing can be "pressurized" and "rotated forward" to release the pipe string from the packer, and the remaining part can be processed by milling or drilling and milling;

[0130] After the tubing is pressurized, the first shear nail sleeve of the type 1 packer 3 cuts off the first shear nail 603, driving the locking block sleeve to move downward, and the first locking block 602 pops out to the first receiving groove, and the first upper joint 601 is disengaged from the first central pipe 104 by right-hand rotation and then pulled out, and the wellbore processing tool is used to mill or drill the remaining well portion;

[0131] After the tubing is pressurized, the second shear nail sleeve 905 of the second type packer cuts off the second shear nail, driving the outer sleeve 902 to move downward, the second locking block 903 pops out to the second receiving groove, the second upper joint 901 is disengaged from the fourth center pipe 904 by right-hand rotation and pulled out, and the remaining well portion is milled or drilled using a wellbore processing tool.

[0132] The shearing pressure of the second shearing nail is smaller than the shearing pressure of the first shearing nail 603. When there are at least two first shearing nails, the deeper the position, the smaller the shearing pressure.

[0133] All components and connection methods of components not discussed in this application belong to the known technologies in this technical field and can be directly applied without further explanation.

[0134] In the present invention, the term "plurality" refers to two or more than two, unless otherwise clearly defined. The terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0135] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “front” and “back” are based on the directions or positional relationships shown in the accompanying 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 unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, cannot be understood as a limitation on the present invention.

[0136] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A safe replacement string, comprising an oil pipe, wherein at least three water distributors are arranged on the oil pipe, a packer is arranged between every two water distributors, and each water distributor corresponds to a water injection layer, characterized in that: The lowest packer is a type II packer, and the remaining packers are type I packers; The type-one packer is provided with a first undercut safety portion, and the type-two packer is provided with a second undercut safety portion.

2. A safe pipe replacement system according to claim 1, characterized in that: A well flushing valve is arranged at the bottom of the oil pipe, and a compensator is arranged above the uppermost water distributor of the oil pipe.

3. A safe pipe replacement string according to claim 1, characterized in that: The type I packer comprises a first undercut safety portion, a first anchoring release portion, a first sealing and backwashing well portion which are connected in sequence.

4. A safe pipe replacement string according to claim 3, characterized in that: The first undercut safety part includes a first upper joint, a first locking block, and a first central tube; The inner wall of the upper end of the first central tube and the outer wall of the lower end of the first upper joint are connected by an inverted thread; the first locking block passes through the upper end of the first central tube and is inserted into the first upper joint; The first central tube is sleeved with a first shear nail sleeve on the outer wall below the first upper joint; The first shear nail sleeve is connected to the first central tube through the first shear nail, and the first central tube is provided with a first pressure transmission hole at a position corresponding to the upper end of the first shear nail sleeve; The outer wall of the first shear nail sleeve is connected with a first locking block sleeve by threads, the first locking block sleeve covers the first locking block, and the inner wall of the first locking block sleeve above the first locking block is provided with a first accommodating groove.

5. A safe pipe replacement string according to claim 4, characterized in that: The first anchoring release part includes a second central tube, an anchor tooth, and a first anchor body; The upper end of the first anchor body is connected to the lower end of the first center tube by threads, and the two ends of the anchor teeth are fixed to the outer wall of the first anchor body; The first anchor body is provided with a first through hole in a region corresponding to the anchor teeth, and the second central tube is sleeved in the first anchor body; A first piston is disposed in the first through hole, and a first spring is disposed between the first piston and the anchor tooth; The anchor teeth, the first through hole, the first piston and the first spring are arranged in at least two groups.

6. A safe replacement pipe string according to claim 5, characterized in that: The first sealing and backwashing part includes an upper outer sleeve, an upper support body, a first rubber cylinder, a lower support body, a third central tube, and a lower outer sleeve; The upper sleeve is connected to the first anchor body by threads, and the upper end of the third central tube is connected to the inner wall of the upper end of the upper sleeve by threads; The outer wall of the upper sleeve is provided with a protrusion extending downward, the upper end of the annulus between the protrusion and the third center tube is provided with a second spring, the lower end of the second spring is provided with a second piston, the lower end surface of the second piston is an outer cone, and the third center tube is provided with a second pressure transmission hole at a position corresponding to the upper end of the second spring; The inner wall of the lower end of the protrusion is threadedly connected with an upper support body, the upper end surface of the upper support body is an inner conical surface, and the lower end surface of the second piston is in contact with the upper end surface of the upper support body; The upper support body is not in contact with the third central tube, and the protrusion is provided with a first water inlet hole above the upper end surface of the upper support body; The inner wall of the lower end of the upper support body is threadedly connected with a first rubber cylinder seat, the first rubber cylinder seat is not in contact with the third central tube, at least two first rubber cylinders are mounted on the first rubber cylinder seat, a spacer ring is arranged between every two first rubber cylinders, and a lower support body is arranged on the outer wall of the lower end of the first rubber cylinder seat, and the lower support body can slide relative to the second rubber cylinder seat; The upper end of the lower support body is in contact with the first rubber cylinder, and the outer wall of the lower end of the lower support body is threadedly connected with a lower outer sleeve, and the lower outer sleeve is provided with a first water outlet hole below the lower support body, and the first rubber cylinder seat is provided with a first drainage hole at a corresponding position of the lower support body, and when the lower support body moves upward to squeeze the first rubber cylinder to complete the sealing, the first water outlet hole coincides with the first drainage hole.

7. A safe pipe replacement string according to claim 6, characterized in that: The inner wall at the lower end of the lower outer sleeve is threadedly connected with a first lower joint, and the lower end of the third central tube is inserted into the inner wall at the upper end of the first lower joint; The inner wall of the lower outer sleeve is provided with a convex ring, and the third central tube is provided with a groove in the corresponding area of ​​the lower outer sleeve; A spring body is arranged between the third center tube and the lower outer sleeve, a first clamping portion is arranged on the outer wall of the spring body and is seated on the upper end surface of the convex ring, a second clamping portion is arranged on the inner wall of the spring body, and the upper end surface of the second clamping portion contacts the upper end surface of the groove.

8. The safe replacement pipe string according to claim 1, characterized in that: The second type packer comprises a fourth central tube, and a second undercut safety part, a second anchoring release part, a second sealing and backwashing well part, and a supporting and setting part which are sequentially arranged on the fourth central tube.

9. A safe pipe replacement string according to claim 8, characterized in that: The second undercut safety part comprises a second upper joint, a second locking block sleeve, a second locking block, and a second shear nail sleeve; The inner wall of the upper end of the fourth central tube is connected to the outer wall of the lower end of the second upper joint by an inverted thread, and the second locking block passes through the upper end of the fourth central tube and is inserted into the second upper joint; The fourth central tube is sleeved with a second shear nail sleeve on the outer wall below the second upper joint, the second shear nail sleeve is connected to the fourth central tube through the second shear nail, and the fourth central tube is provided with a third pressure transmission hole at a position corresponding to the upper end of the second shear nail sleeve; The outer wall of the second shear nail sleeve is threadedly connected with a second locking block sleeve, the second locking block sleeve covers the second locking block, and the inner wall of the second locking block sleeve above the second locking block is provided with a second accommodating groove.

10. A safe pipe replacement string according to claim 9, characterized in that: The second anchoring release part includes an anchor claw and a second anchor body; The second anchor body is sleeved on the fourth central tube, the two ends of the fluke are fixed to the outer wall of the second anchor body, the second anchor body is provided with a second through hole in the area corresponding to the fluke, a third piston is provided in the second through hole, and a third spring is provided between the third piston and the fluke; the fluke, the second through hole, the third piston and the third spring are provided in at least two groups; The fourth central tube is provided with a pressure groove in a region corresponding to the anchor claw, and a fourth pressure transmission hole is provided in the pressure groove.

11. A safe pipe replacement string according to claim 10, characterized in that: Two second through holes are arranged in the corresponding area of ​​the anchor claw, and the middle of the anchor claw is also fixed to the outer wall of the second anchor body.

12. A safe pipe replacement string according to claim 10, characterized in that: The second sealing and backwash well part includes a water inlet jacket, an upper retaining ring, and a cone; The outer wall of the lower end of the second anchor body is threadedly connected with a water inlet sleeve, a fourth spring is arranged above the annulus between the water inlet sleeve and the fourth central tube, a fourth piston is arranged at the lower end of the fourth spring, and the lower end surface of the fourth piston is an outer conical surface; The upper retaining ring is threadedly connected to the inner wall of the lower end of the water inlet sleeve, the upper retaining ring is not in contact with the fourth center tube, the upper end surface of the upper retaining ring is an inner conical surface, and the lower end surface of the fourth piston is in contact with the upper end surface of the upper retaining ring; The water inlet sleeve is provided with a second water inlet hole above the upper end surface of the upper retaining ring, and the fourth center tube is provided with a fifth pressure transmission hole at a position corresponding to the upper end of the fourth spring; The inner wall of the lower end of the upper retaining ring is threadedly connected with a second rubber cylinder seat, the second rubber cylinder seat is not in contact with the fourth central tube, at least two second rubber cylinders are sleeved on the outer surface of the second rubber cylinder seat, and a separation ring is arranged between every two second rubber cylinders; The cone is arranged on the outer wall of the lower end of the second rubber cylinder seat and can slide relatively with the second rubber cylinder seat. An outer cone is arranged at the lower end of the cone, and the outer cone contacts the fourth central tube. A second water outlet is arranged above the outer cone.

13. A safe pipe replacement string according to claim 12, characterized in that: The supporting and setting part includes a limiting shell; The limiting shell is sleeved on the fourth central tube and arranged below the cone. The upper end of the limiting shell is provided with at least two slip grooves and the middle part is provided with at least two straightening grooves. A slip is arranged in each slip groove, an inner cone is arranged at the upper end of the slip, slip teeth are arranged on the outer wall of the inner cone, and the lower end of the slip is fixed in the slip groove; A straightening block is arranged in each straightening groove, and the outer walls of the upper and lower ends of the straightening groove protrude inwards to prevent the straightening block from escaping from the limiting shell. A spring sheet is arranged between the straightening block and the straightening groove, and inclined surfaces are arranged at the upper and lower ends of the straightening block.

14. A safe replacement pipe string according to claim 13, characterized in that: The supporting and setting part also includes a reversing sleeve and a second lower joint; The upper end of the reversing sleeve is threadedly connected to the outer wall of the lower end of the limit housing, the inner wall of the upper end of the second lower joint is threadedly connected to the outer wall of the lower end of the fourth center tube, and the inner wall of the reversing sleeve is provided with a "7"-shaped groove, and the "7"-shaped groove is divided into a short groove and a long groove; A reversing block is arranged on the outer wall of the upper end of the second lower joint, and the reversing block is quickly embedded in the short slot or the long slot. When the reversing block is embedded in the short slot, the second lower joint moves synchronously with the reversing sleeve, and when the reversing block is embedded in the long slot, the second lower joint and the reversing sleeve can slide relative to each other.

15. A safe replacement pipe string according to claim 4 or 9, characterized in that: The undercut thread is a left-hand thread, and the thread is a right-hand thread.

16. A safe replacement pipe string according to claim 5, characterized in that: The first locking block sleeve and the first shear nail sleeve are made of cast iron and can be processed by grinding or drilling; The anchor teeth are made of cast iron and can be processed by grinding or drilling.

17. A safe replacement pipe string according to claim 10 or 11, characterized in that: The second locking block sleeve and the second shear nail sleeve are made of cast iron and can be processed by grinding or drilling; The fluke is made of cast iron and can be milled or drilled.

18. A method for safely replacing a pipe string, characterized in that: The following steps are involved: S1. Assemble the pipe string and lower it into the well. According to the designed construction depth, use different lengths of tubing to assemble the compensator, water distributor, type I packer, type II packer, and well flushing valve and lower them into the well to the designed depth, so that one water distributor corresponds to one water injection layer. S2, Sealing: "Lift up" - "rotate right" the string to seat the second type packer, then continue to "lower" the string to seat the first type packer, at this time the first water outlet and the first drainage hole coincide; S3, water injection: open the water distributors at all levels, adjust the water distributors to the appropriate opening according to the injection volume requirements, and inject water into the oil pipe; after the oil pipe is pressurized, the anchor teeth and the anchor claws extend; S4, backwash well: stop water injection, after the oil pipe is depressurized, backwash well fluid is injected from the casing annulus, and the backwash well fluid passes through the type 1 packer, type 2 packer, and the well washing valve into the oil pipe and returns to the ground; S5, unsealing: After the tubing is depressurized, the anchor teeth and claws are recovered, the pipe string is "lifted up", and the first type of packer is unsealed; the pipe string is "lifted up" again, and the second type of packer is unsealed; S6. Dropping, drilling and milling: If the pipe string is stuck, use the tubing "boosting pressure" - "forward rotation" to drop the pipe string from the safe part of the packer, and use grinding or drilling and milling to process the remaining part of the well.

19. A method for safely replacing a pipe string according to claim 18, characterized in that: The process of setting the seal is as follows: After reaching the designed depth, first complete the setting of the lower type II packer, "lift up" - "right-hand" the pipe string, the second lower joint reversing block is in the long groove of the "7"-shaped groove on the inner wall of the reversing sleeve, and the pipe string is lowered. At this time, the slips are pushed out and stuck on the inner wall of the casing, and the pipe string is continued to be lowered. The slips are tightened, and the cone compresses the second rubber cylinder to achieve setting; After the bottom type-2 packer is sealed, continue to lower the tubing string to seal the upper type-1 packer. The type-1 packer will use the lower type-2 packer as a support point. At this time, continue to lower the tubing string, the first lower joint is fixed, the first inverted safety part, the first anchor release part, the third center pipe, the upper outer sleeve, and the upper support body move downward, and the upper support body compresses the first rubber cylinder to achieve sealing; at this time, the first water outlet hole coincides with the first drainage hole.

20. The method for safely replacing a pipe string according to claim 18, characterized in that: When injecting water, open the water distributors at all levels, adjust the water distributors to the appropriate opening according to the injection volume requirements, and inject water into the oil pipes; After the oil pipe is pressurized, the oil pipe pressure passes through the gap between the second center pipe and the first anchor body to push the first piston to extend the anchor teeth, and the oil pipe pressure enters the pressure groove through the fourth pressure transmission hole to push the third piston to extend the anchor claws; The oil pipe pressure passes through the second pressure transmission hole to make the second piston sit on the upper support body, and the oil pipe pressure passes through the fifth pressure transmission hole to make the fourth piston sit on the upper retaining ring, and the backwash channel is closed.

21. A method for safely replacing a pipe string according to claim 18, characterized in that: The process of backwash fluid returning to the surface through type 1 and type 2 packers is as follows: After the water injection is stopped and the oil pipe is depressurized, the backwash fluid is injected from the annulus of the casing. The backwash fluid enters from the first water inlet, so that the second piston pushes the second spring to move under the backwash pressure, the first backwash channel is opened, and the backwash fluid is discharged from the first water outlet and passes through a type I packer; The backwash fluid enters from the second water inlet, so that the fourth piston pushes the fourth spring under the backwash pressure, the second backwash channel is opened, and the backwash fluid is discharged from the second water outlet and passes through the second type packer; The backwash fluid enters the oil pipe through the well flushing valve and returns to the ground.

22. A method for safely replacing a pipe string according to claim 18, characterized in that: During unsealing, after the tubing is depressurized, the anchor teeth and claws of the type 1 and type 2 packers are recovered, and the tubing string is "lifted up", driving the upper support body of the type 1 packer to move upward, and the first rubber cylinder is recovered, realizing the unsealing of the type 1 packer; Continue to "lift" the tubing string, the reversing block of the second lower joint of the second type packer moves from the lower end of the long groove of the reversing sleeve to the upper end, the slips are recovered, the cone is recovered, the second rubber cylinder loses compression, the second rubber cylinder is recovered, and the second packer is unsealed.

23. A method for safely replacing a pipe string according to claim 18, characterized in that: The S6, hand-off, drilling and milling, is divided into two situations; Type I packer is stuck: the tubing rises to the shearing pressure of the first shearing nail, the first shearing nail sleeve of the Type I packer cuts the first shearing nail, drives the locking block sleeve to move downward, the first locking block pops out to the first receiving groove, the first upper joint is disengaged from the first central pipe by right-hand rotation and is taken out, and the wellbore processing tool is used to mill or drill the remaining well part; The second type packer is stuck: the tubing rises to the shearing pressure of the second shear nail, the second shear nail sleeve of the second type packer cuts the second shear nail, drives the outer sleeve to move downward, the second locking block pops out to the second receiving groove, the second upper joint is disengaged from the fourth center pipe by right rotation and taken out, and the wellbore processing tool is used to mill or drill the remaining well part; The shearing pressure of the second shearing nail is smaller than the shearing pressure of the first shearing nail. When there are at least two first shearing nails, the deeper the position, the smaller the shearing pressure.

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