Layered acidizing and layered flowback efficient operation pipe column and construction method

Abstract

This invention discloses a high-efficiency running string and method for layered flowback and layered acidizing, comprising a plug, tubing, anchor packer, several layered packers, and several integrated flowback and acidizing devices located within the casing. The plug is located at the bottom of the tubing. An integrated flowback and acidizing device is installed at each oil layer location on the tubing, and layered packers are located above and below each oil layer on the tubing. The anchor packer is located above the uppermost layered packer on the tubing. This invention achieves integrated flowback and acidizing operations in one step through an integrated design, simplifying the operation process and reducing operating costs.

Description

Technical Field

[0001] This patent relates to the field of efficient oil well maintenance, specifically a high-efficiency operation string and construction method for layered flowback and layered acidizing. Background Technology

[0002] The Shengli Oilfield has entered a high water-cut stage, which has increased the difficulty of extraction. Some high-permeability reservoirs have low pressure coefficients and large reservoir damage invasion radii. Simultaneously, particulate migration can clog near-wellbore areas and perforations, reducing permeability and production capacity. Furthermore, long-term precipitation from producing formations causes near-wellbore blockage. Given the significant increase in production and fluid output from operational wells, improving the unclogging effect and operational efficiency of low-fluidity wells is particularly important.

[0003] Currently, low-fluidity well treatment primarily relies on chemical acidizing for unclogging, a relatively simplistic approach. Based on thorough research, Shengli Oilfield has gradually adopted nitrogen foam negative pressure flowback unclogging technology. This involves using a combination of general flowback and general acidizing, or two runs of general flowback followed by two runs of stratified acidizing, with a construction period of approximately 2-4 days. Especially for offshore operations, platform operation costs are generally around 300,000 yuan per day, making the process quite expensive. Furthermore, during general flowback, significant differences in inter-layer properties can lead to uneven improvement across reservoirs, severely impacting the improvement effect on some layers. To further simplify the operational procedures and improve the improvement degree of each layer, a high-efficiency stratified flowback and stratified acidizing work string has been designed and invented.

[0004] Patent CN204299556U discloses an integrated tubing string for stratified acidizing and downhole water injection, consisting of a downhole tubing string and a stratified water distribution string. The stratified water distribution string is formed by sequentially connecting a water distributor, a packer, a water distributor, a ball seat, a screen pipe, and a plug. A reciprocating switch is installed between the water distributor of the downhole tubing string and the stratified water distribution string. In principle, this invention achieves stratified acidizing and downhole water injection in a single tubing run. However, this invention requires the insertion of a retrieveable plug during acidizing, and then the plug needs to be retrieved and replaced with a matching steel ball during subsequent water injection to implement stratified water injection, making the construction process rather cumbersome.

[0005] Patent CN1458388A discloses a three-in-one drainage system combining perforation, formation testing, and jet pump. This system comprises a perforator, formation testing device, jet pump, sand-supporting cup, testing pressure gauge, testing device, pressure gauge, pressure transmission connector, separator, screen pipe connector, shock absorber, ignition head, and perforation gun, all connected sequentially by tubing. This three-in-one system, enabling negative pressure perforation, formation testing, and jet pump drainage, saves workload and accelerates construction. However, this process only achieves perforation, testing, and drainage for a single reservoir, without effectively integrating it with acidizing for unblocking. Furthermore, as oilfields enter the later stages of development, the significant differences between reservoirs limit the effectiveness of this unblocking process.

[0006] The journal *Journal of Jianghan Petroleum Staff University* published a paper titled "Research and Application of Integrated Rapid Acid Removal Pipeline in Jianghan Oilfield." This technology enables the simultaneous installation of acid removal tools and acidizing tubing in a single run. It can be used with various packers to meet diverse processes and complex well conditions. Combined with optimized surface processes, it can achieve acid removal after any layer of acidizing in layered or multi-layered systems. This technology has been applied in seven wells in the field. Its main tool, the ZPS-l14 positive circulation jet acid removal device, uses high-pressure dynamic fluid (≥25MPa) pumped in to achieve continuous discharge using negative pressure. However, based on application experience, firstly, the 25MPa high-pressure dynamic fluid is too high for offshore operations, posing a significant risk. Secondly, the jet pump principle of this technology results in a low return efficiency of only about 30%, a long construction cycle, and the failure to promptly remove the returned material leads to secondary pollution of the formation and the borehole area. Summary of the Invention

[0007] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a high-efficiency working string for layered runoff and acidizing. Through an integrated string design, layered runoff and acidizing operations can be achieved without moving the string, thereby improving operational efficiency and runoff effectiveness while reducing the high operating costs at sea.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] A high-efficiency working string for layered flowback and layered acidizing includes a plug, tubing, anchor packer, several layered packers, and several integrated flowback and acidizing devices located inside the casing; the plug is located at the bottom of the tubing; an integrated flowback and acidizing device is installed at each oil layer on the tubing, and layered packers are installed above and below each oil layer on the tubing; the anchor packer is located above the uppermost layered packer on the tubing.

[0010] As a preferred technical solution, the anchoring packer is one of the Y441 packer, Y221 packer, and Y211 packer.

[0011] As a preferred technical solution, the layered packer is a Y341 packer.

[0012] As a preferred technical solution, the integrated backflow acidification device includes an upper jacket, a sealing tube, a lower jacket, an upper connector, a central tube, a corrosion-resistant sealing sleeve, and a lower connector, all with their inner bores aligned on a straight line.

[0013] The outer diameter of the lower end of the upper jacket is larger than the outer diameter of the rest of the jacket, and the inner diameter of the lower end of the upper jacket is larger than the inner diameter of the rest of the jacket; the outer diameter of the upper end of the lower jacket is larger than the outer diameter of the rest of the jacket, and the inner diameter of the upper end of the lower jacket is larger than the inner diameter of the rest of the jacket; the radial inner circumferential surface of the upper end of the upper jacket and the radial inner circumferential surface of the lower end of the lower jacket are threadedly connected to the radial outer circumferential surface of the sealing tube; the lower end of the upper jacket and the upper end of the lower jacket are threadedly connected, thereby forming a sealing cavity between the upper jacket, the lower jacket and the sealing tube; one or more sets of return flow components are vertically arranged inside the sealing cavity.

[0014] Each return assembly, from top to bottom, includes a battery, circuit, motor, sealing sleeve, and lower ball seat; the bottom end of the lower ball seat contacts the top surface of the part where the inner diameter of the inner hole of the lower outer sleeve increases; the lower end of the motor is provided with a liftable sealing rod, the lower end of which is inserted into the inner hole of the sealing sleeve; each lower ball seat has a first sealing ball on its inner hole.

[0015] The lower end of the upper connector is threaded to the lower end of the central tube; the upper end of the upper connector is threaded to the radial outer circumferential surface of the upper end of the lower sleeve; the radial inner circumferential surface of the top of the lower connector is threaded to the radial outer circumferential surface of the lower end of the central tube.

[0016] An adjusting sleeve is threaded onto the radial outer circumferential surface at the bottom of the upper connector, and a valve is installed below the adjusting sleeve on the radial outer circumferential surface of the central tube.

[0017] A spring ring and a washer ring are fitted on the outer circumferential surface of the central tube. The bottom end of the spring ring contacts the top of the valve, the top surface of the washer ring contacts the adjusting sleeve, and the bottom surface of the washer ring contacts the spring ring.

[0018] The radial inner circumferential surface at the top of the corrosion-resistant sealing sleeve contacts the radial outer circumferential surface at the bottom of the valve, and the radial inner circumferential surface at the bottom of the corrosion-resistant sealing sleeve is threadedly connected to the radial outer circumferential surface at the top of the lower connector.

[0019] An acid injection through hole is provided below the valve on the central tube. An upper ball seat is fixed to the radial inner circumferential surface of the central tube with a shear pin. The upper ball seat seals the acid injection through hole, thereby forming a sealed space between the corrosion-resistant sealing sleeve, the valve, the central tube, and the lower connector.

[0020] The top of the adjusting sleeve is equipped with an anti-rotation pin. After the adjusting sleeve is adjusted by rotating to adjust the preload of the spring ring, it is fixed to the upper connector by the anti-rotation pin.

[0021] The lower ball seat of the lower outer sleeve is provided with several first return drain holes; the lower ball seat of each sealing tube is provided with a second return drain hole directly below the motor; and each sealing sleeve is provided with a third return drain hole that is connected to the nearest second return drain hole.

[0022] As a preferred technical solution, the inner diameter of the upper ball seat in each integrated return acidification unit gradually decreases from top to bottom.

[0023] As a preferred technical solution, the valve is sealed to the outside of the central tube by a number of first rubber rings; the lower connector is sealed to the corrosion-resistant sealing sleeve by a number of sixth rubber rings; the upper ball seat is sealed to the inner side of the central tube by a number of second rubber rings. The upper outer sleeve and the lower outer sleeve are sealed by a number of fourth rubber rings; and the upper outer sleeve and the sealing tube are sealed by a number of third rubber rings.

[0024] As a preferred technical solution, the radial outer circumferential surface of the sealing sleeve is provided with a number of fifth rubber rings that can contact the outer sleeve and the sealing tube.

[0025] As a preferred technical solution, a filter screen is welded to the radial outer peripheral surface of the lower jacket.

[0026] During the run-out construction, the run-out acidizing construction of the lowest formation is carried out first. A second sealing ball is inserted to seal the inner hole of the upper ball seat of the bottom run-out acidizing integrated device. The ground pressure pulse device sends a command to the circuit of the bottom run-out acidizing integrated device. Under the control of the circuit, the motor controls the sealing rod to move upward, so that the third run-out through hole is connected to the inner hole of the lower ball seat. Gas or liquid in the formation enters the sealing cavity between the upper and lower outer sleeves and the sealing tube through the first run-out through hole of the lower outer sleeve. At this time, the sealing ball separates from the lower ball seat, and the gas or liquid in the formation is run back to the ground through the inner hole of the lower ball seat of each run-out component, the inner hole of the sealing sleeve, the third run-out through hole, the second run-out through hole, the inner hole of the sealing tube, and the oil pipe.

[0027] After the backflow construction of this layer is completed, acidizing construction of this layer is carried out; the pressure pulse device on the ground sends a command to the circuit of the bottom acidizing integrated device. Under the control of the circuit, the motor controls the sealing rod to move downward, so that the third backflow through hole is no longer connected to the inner hole of the lower ball seat; acid is injected into the oil pipe by starting the pump on the ground. After reaching a certain pressure, the pin is sheared, the upper ball seat falls, and the acid injection through hole is opened. The injected acid enters through the acid injection through hole, pushes up the valve, and the acid enters the formation to start acidizing.

[0028] This process is repeated from bottom to top to complete the flowback acidizing and acidizing operations of the remaining strata.

[0029] As a preferred technical solution, the surface return flow method is either return flow using a return pump or return flow by injecting nitrogen to shut off the well.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1. This electrically controlled flowback method is simple and efficient. At the same time, the layered flowback improves the degree of transformation of each reservoir, especially reservoirs with large differences, and achieves balanced transformation, thus enabling oil wells to produce efficiently and for a long time.

[0032] 2. Layered backflow and layered acidification are integrated into a single design, allowing backflow and acidification operations to be carried out in one go, simplifying the operation process and reducing operating costs; ensuring that formation sand and other foreign objects enter the tubing during backflow construction.

[0033] 3. This technology, combined with oil saturation instruments and perforation guns, enables integrated testing and perforation of oil well layers, meeting the requirements for the integrated installation of various tubing strings and further improving operational efficiency.

[0034] 4. When the acid injection is finished, the spring ring returns to the valve to ensure that the liquid in the formation does not enter the integrated acid return unit. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a high-efficiency working column structure for layered return flow and layered acidification according to the present invention.

[0036] Figure 2 This is a schematic diagram of the integrated acidification and backflow treatment unit.

[0037] Figure 3 yes Figure 2 A magnified view of part A.

[0038] Figure 4 yes Figure 3 A magnified view of part D.

[0039] Figure 5 yes Figure 2 A magnified view of part B.

[0040] Figure 6 yes Figure 5 A magnified view of part E.

[0041] Figure 7 yes Figure 2 A magnified view of part C.

[0042] Figure 8 yes Figure 7 A magnified view of part F.

[0043] Figure 9 yes Figure 1 The diagram shows a state diagram of a high-efficiency working column structure for layered return and layered acidification.

[0044] Figure 10 yes Figure 9 A magnified view of part G.

[0045] Figure 11 yes Figure 9 A magnified view of part H.

[0046] Figure 12This is a state diagram of a high-efficiency working column for layered flowback and layered acidification according to the present invention.

[0047] Figure 13 yes Figure 12 A magnified view of part I.

[0048] Figure 14 yes Figure 12 A magnified view of part J.

[0049] Among them: 1-oil pipe, 2-anchor packer, 3-layer packer, 4-integrated acid return device, 5-plug, 6-casing; second sealing ball 7;

[0050] 401-Upper Outer Jacket, 402-Sealing Tube, 403-Battery, 404-Circuit Circuit, 405-Motor, 406-Sealing Rod, 407-Sealing Sleeve, 408-First Sealing Ball, 409-Lower Ball Seat, 410-Lower Outer Jacket, 411-Filter Screen, 412-Upper Connector, 413-Anti-rotation Pin, 414-Adjusting Sleeve, 415-Gasket Ring, 416-Spring Coil, 417-Center Tube, 418-First Rubber ring, 419-Valve, 420-Pin, 421-Upper ball seat, 422-Corrosion resistant sealing sleeve, 423-Lower connector, 424-First return drain hole, 425-Second return drain hole, 426-Third return drain hole, 427-Acid injection hole, 428-Second rubber ring, 429-Third rubber ring, 430-Fourth rubber ring, 431-Fifth rubber ring, 432-Sixth rubber ring, 433-Seventh rubber ring. Detailed Implementation

[0051] The present invention will now be further described in conjunction with the accompanying drawings and embodiments.

[0052] Example 1. As... Figure 1-8 As shown, a high-efficiency working string for layered run-out and layered acidizing is characterized by comprising: a plug 5 located within a casing 6, a tubing 1, an anchor packer 2, several layered packers 3, and several integrated run-out and acidizing devices 4; the plug 5 is located at the bottom of the tubing 1; one integrated run-out and acidizing device 4 is installed at each oil layer location on the tubing 1, and layered packers 3 are located above and below each oil layer on the tubing 1; the anchor packer 2 is located above the uppermost layered packer 3 on the tubing 1. Surface run-out is achieved using a run-out pump. In this embodiment, there are two oil layers, and the number of integrated run-out and acidizing devices 4 is two.

[0053] The anchoring packer 2 is a Y441 packer.

[0054] The layered packer 3 is a Y341 packer.

[0055] The integrated backflow acidification device 4 includes an upper outer sleeve 401, a sealing tube 402, a lower outer sleeve 410, an upper connector 412, a central tube 417, a corrosion-resistant sealing sleeve 422, and a lower connector 423, all with their inner bores aligned on the same straight line.

[0056] The outer diameter of the lower end of the upper jacket 401 is larger than the outer diameter of the rest of its parts, and the inner diameter of the lower end of the upper jacket 401 is larger than the inner diameter of the rest of its parts; the outer diameter of the upper end of the lower jacket 410 is larger than the outer diameter of the rest of its parts, and the inner diameter of the upper end of the lower jacket 410 is larger than the inner diameter of the rest of its parts; the radial inner circumferential surface of the upper end of the upper jacket 401 and the radial inner circumferential surface of the lower end of the lower jacket 410 are threadedly connected to the radial outer circumferential surface of the sealing tube 402; the lower end of the upper jacket 401 is threadedly connected to the upper end of the lower jacket 410, thereby forming a sealing cavity between the upper jacket 401, the lower jacket 410 and the sealing tube 402; a set of return flow components is vertically arranged inside the sealing cavity.

[0057] The return assembly includes, from top to bottom, a battery 403, a circuit 404, a motor 405, a sealing sleeve 407, and a lower ball seat 409. The bottom end of the lower ball seat 409 contacts the top surface of the inner diameter of the inner hole of the lower outer sleeve 410. The lower end of the motor 405 is provided with a liftable sealing rod 406, and the lower end of the sealing rod 406 is inserted into the inner hole of the sealing sleeve 407. Each lower ball seat 409 has a first sealing ball 408 on its inner hole.

[0058] The lower end of the upper connector 412 is threaded to the lower end of the central tube 417; the upper end of the upper connector 412 is threaded to the upper radial outer circumferential surface of the lower sleeve 410; the radial inner circumferential surface of the top of the lower connector 423 is threaded to the lower radial outer circumferential surface of the central tube 417.

[0059] An adjusting sleeve 414 is threaded onto the radial outer circumferential surface at the bottom of the upper connector 412, and a valve 419 is installed below the adjusting sleeve 414 on the radial outer circumferential surface of the central tube 417.

[0060] A spring ring 416 and a washer ring 415 are fitted on the radial outer circumferential surface of the central tube 417. The bottom end of the spring ring 416 contacts the top end of the valve 419, the top surface of the washer ring 415 contacts the adjusting sleeve 414, and the bottom surface of the washer ring 415 contacts the spring ring 416.

[0061] The radial inner circumferential surface of the top of the corrosion-resistant sealing sleeve 422 contacts the radial outer circumferential surface of the bottom of the valve 419, and the radial inner circumferential surface of the bottom of the corrosion-resistant sealing sleeve 422 is threadedly connected to the radial outer circumferential surface of the top of the lower connector 423.

[0062] Below the valve 419 on the central tube 417, there is an acid injection through hole 427. On the radial inner circumferential surface of the central tube 417, a shear pin 420 fixes an upper ball seat 421. The upper ball seat 421 seals the acid injection through hole 427, thereby forming a sealed space between the corrosion-resistant sealing sleeve 422, the valve 419, the central tube 417, and the lower connector 423.

[0063] The top of the adjusting sleeve 414 is provided with an anti-rotation pin 413. After the adjusting sleeve 414 adjusts the preload of the spring ring 416 by rotation, it is fixed to the upper connector 412 by the anti-rotation pin 413.

[0064] The lower ball seat 409 of the lower outer sleeve 410 is provided with several first return drainage holes 424; the motor 405 above each lower ball seat 409 of the sealing tube 402 is provided with a second return drainage hole 425, and each sealing sleeve 407 is provided with a third return drainage hole 426 that communicates with the nearest second return drainage hole 425. The inner diameter of the upper ball seat 421 of each return acidification integrated device gradually decreases from top to bottom.

[0065] The valve 419 is sealed to the outside of the central tube 417 by a number of first rubber rings 418; the lower connector 423 is sealed to the corrosion-resistant sealing sleeve 422 by a number of sixth rubber rings 432; and the upper ball seat 421 is sealed to the inner side of the central tube 417 by a number of second rubber rings 428.

[0066] The upper outer sleeve 401 and the lower outer sleeve 410 are sealed by a number of fourth rubber rings 430; the upper outer sleeve 401 and the sealing tube 402 are sealed by a number of third rubber rings 429.

[0067] The outer radial circumferential surface of the sealing sleeve 407 is provided with a plurality of fifth rubber rings 431 that can contact the outer sleeve 410 and the sealing tube 402 for sealing. The outer sleeve 410 and the sealing tube 402 are sealed by a seventh rubber ring 433.

[0068] The corrosion-resistant sealing sleeve 422 and the valve 419, the sealing rod 406 and the sealing sleeve 407, and the sealing ball 408 and the sealing sleeve 407 are all sealed with metal surfaces.

[0069] The outer radial circumferential surface of the lower jacket 410 is welded with a filter screen 411.

[0070] The construction method for the layered flowback and layered acidification high-efficiency working tubing is as follows: (e.g.) Figure 12-14 As shown, during the backflow construction, the backflow acidification construction of the lowest layer is carried out first, and a second sealing ball 7 is put into the inner hole of the upper ball seat 421 of the integrated backflow acidification device 4 at the bottom.

[0071] After the ground pressure test completes the setting of the packers at each level, the ground pressure pulse device marks the location. After receiving the instruction, the bottom acid removal integrated device, under the control of circuit 404, motor 405 controls the sealing rod 406 to move upward, so that the third return through hole 426 connects with the inner hole of the lower ball seat 409. Gas or liquid in the formation enters the sealing cavity between the upper outer sleeve 401, the lower outer sleeve 410 and the sealing tube 402 through the first return through hole 424 of the lower outer sleeve 410. At this time, the sealing ball 408 separates from the lower ball seat 409, and the gas or liquid in the formation is returned to the ground through the inner hole of the lower ball seat 409 of each return component, the inner hole of the sealing sleeve 407, the third return through hole 426, the second return through hole 425, the inner hole of the sealing tube 402 and the oil pipe 1.

[0072] After the backflow construction of this layer is completed, acidizing construction of this layer is carried out; the pressure pulse device on the ground sends a command to the circuit 404 of the bottom acidizing integrated device 4. Under the control of the circuit 404, the motor 405 controls the sealing rod 406 to move downward, so that the third backflow through hole 426 is no longer connected to the inner hole of the lower ball seat 409; acid is injected into the oil pipe 1 by starting the pump on the ground. After reaching a certain pressure, the pin 420 is sheared, the upper ball seat 421 falls, realizing the opening of the acid injection through hole 427. The injected acid enters from the acid injection through hole 427, lifts the valve 419, and the acid enters the formation to start acidizing;

[0073] This process is repeated from bottom to top to complete the flowback acidizing and acidizing operations of the remaining strata.

[0074] Example 2. (As shown) Figure 9-11 As shown, the difference between this embodiment and Embodiment 1 is that the lower end of the upper outer sleeve 401 is threadedly connected to the upper end of the lower outer sleeve 410, thereby vertically arranging multiple sets of return assemblies within the sealed cavity formed between the upper outer sleeve 401, the lower outer sleeve 410, and the sealing tube 402. Each return assembly is arranged in a ring array around the central axis of the upper outer sleeve 401. The anchoring packer 2 is a Y221 packer.

[0075] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A layered flowback layered acidification high-efficiency operation pipe column, characterized in that: The application relates to a multilayered acidizing and flowback integrated device, which comprises a nipple (5) located in a sleeve (6), a tubing (1), an anchor packer (2), a plurality of layered packers (3) and a plurality of acidizing and flowback integrated devices (4). The acidizing and flowback integrated device (4) comprises an upper sleeve (401) with a same axis as the inner hole, a sealing pipe (402), a lower sleeve (410), an upper joint (412), a central pipe (417), a corrosion-resistant sealing sleeve (422) and a lower joint (423). The outer diameter of the lower end of the upper sleeve (401) is larger than that of the rest part, and the inner diameter of the lower end of the upper sleeve (401) is larger than that of the rest part; the outer diameter of the upper end of the lower sleeve (410) is larger than that of the rest part, and the inner diameter of the upper end of the lower sleeve (410) is larger than that of the rest part; the radial inner circumferential surface of the upper end of the upper sleeve (401) and the radial outer circumferential surface of the lower end of the lower sleeve (410) are threadedly connected with the radial outer circumferential surface of the sealing pipe (402); the lower end of the upper sleeve (401) is threadedly connected with the upper end of the lower sleeve (410), so that a sealing cavity is formed among the upper sleeve (401), the lower sleeve (410) and the sealing pipe (402); one or more groups of flowback assemblies are vertically arranged in the sealing cavity; Each flowback assembly comprises a battery (403), a circuit (404), a motor (405), a sealing sleeve (407) and a lower ball seat (409) from top to bottom; the bottom end of the lower ball seat (409) is in contact with the top surface of the enlarged inner hole of the lower sleeve (410); the lower end of the motor (405) is provided with a liftable sealing rod (406), and the lower end of the sealing rod (406) is inserted into the inner hole of the sealing sleeve (407); the inner hole of each lower ball seat (409) is provided with a first sealing ball (408); The lower end of the upper joint (412) is threadedly connected with the lower end of the central pipe (417); the upper end of the upper joint (412) is threadedly connected with the radial outer circumferential surface of the upper end of the lower sleeve (410); and the radial inner circumferential surface of the top end of the lower joint (423) is threadedly connected with the radial outer circumferential surface of the lower end of the central pipe (417); The radial outer circumferential surface of the bottom end of the upper joint (412) is threadedly connected with an adjusting sleeve (414); and the radial outer circumferential surface of the central pipe (417) is provided with a valve (419) below the adjusting sleeve (414); The radial outer circumferential surface of the central pipe (417) is provided with a spring ring (416) and a gasket ring (415); the bottom end of the spring ring (416) is in contact with the top end of the valve (419); the top surface of the gasket ring (415) is in contact with the adjusting sleeve (414); and the bottom surface of the gasket ring (415) is in contact with the spring ring (416). The radial inner circumferential surface of the top end of the corrosion-resistant sealing sleeve (422) is in contact with the radial outer circumferential surface of the bottom end of the valve (419), and the radial inner circumferential surface of the bottom end of the corrosion-resistant sealing sleeve (422) is threadedly connected with the radial outer circumferential surface of the top end of the lower joint (423); The upper ball seat (421) is fixed on the pin (420) on the radial inner circumferential surface of the center tube (417), and the upper ball seat (421) seals the acid injection through hole (427), so as to form a closed space among the corrosion-resistant sealing sleeve (422), the valve (419), the center tube (417) and the lower joint (423); The top end of the adjusting sleeve (414) is provided with an anti-rotation pin (413), and the adjusting sleeve (414) is fixed on the upper joint (412) through the anti-rotation pin (413) after the pre-tightening force of the spring ring (416) is adjusted by rotation; The lower ball seat (409) of the lower outer sleeve (410) is provided with a plurality of first backflow through holes (424) below; the motor (405) below each lower ball seat (409) of the sealing tube (402) is provided with a second backflow through hole (425) below, and each sealing sleeve (407) is provided with a third backflow through hole (426) which is in communication with the nearest second backflow through hole (425); The radial outer circumferential surface of the lower outer sleeve (410) is welded with a sand filter net (411).

2. The layered flowback and acidizing efficient operation string according to claim 1, characterized in that: The anchor packer (2) is one of Y441 packer, Y221 packer and Y211 packer.

3. The layered flowback and acidizing efficient operation string according to claim 1, characterized in that: The layered packer (3) is Y341 packer.

4. The layered flowback and acidizing efficient operation string according to claim 1, characterized in that: The inner hole diameters of the upper ball seats (421) of each backflow and acidification integrated device (4) gradually decrease from top to bottom.

5. The layered flowback and acidizing efficient operation string according to claim 1, characterized in that: The upper outer sleeve (401) and the lower outer sleeve (410) are sealed by a plurality of fourth rubber rings (430); the upper outer sleeve (401) and the sealing tube (402) are sealed by a plurality of third rubber rings (429); the valve (419) and the outer part of the center tube (417) are sealed by a plurality of first rubber rings (418); the lower joint (423) and the corrosion-resistant sealing sleeve (422) are sealed by a plurality of sixth rubber rings (432); the upper ball seat (421) and the inner side of the center tube (417) are sealed by a plurality of second rubber rings (428).

6. The layered flowback and acidizing efficient operation string according to claim 1, characterized in that: The radial outer circumferential surface of the sealing sleeve (407) is provided with a plurality of fifth rubber rings (431) which are in contact with the lower outer sleeve (410) and the sealing tube (402).

7. The construction method of the layered backflow and layered acidification efficient operation string according to any one of claims 1-6, characterized in that: When the flowback operation is performed, firstly, the flowback acidification operation of the lowermost formation is performed, a second sealing ball (7) is put into the inner hole of the upper ball seat (421) of the bottommost flowback acidification integrated device (4), the code of the pressure pulse device on the ground is hit to send an instruction to the circuit (404) of the bottommost flowback acidification integrated device (4), under the control of the circuit (404), the motor (405) controls the sealing rod (406) to move upward, so that the third flowback through hole (426) is communicated with the inner hole of the lower ball seat (409), the gas or liquid in the formation enters the sealing cavity between the upper outer sleeve (401), the lower outer sleeve (410) and the sealing pipe (402) through the first flowback through hole (424) of the lower outer sleeve (410), at this time, the first sealing ball (408) is separated from the lower ball seat (409), the gas or liquid in the formation flows back to the ground through the inner hole of the lower ball seat (409) of each flowback assembly, the inner hole of the sealing sleeve (407), the third flowback through hole (426), the second flowback through hole (425), the inner hole of the sealing pipe (402) and the oil pipe (1); After the flowback operation of the layer is completed, the acidification operation of the layer is performed; the code of the pressure pulse device on the ground is hit to send an instruction to the circuit (404) of the bottommost flowback acidification integrated device (4), under the control of the circuit (404), the motor (405) controls the sealing rod (406) to move downward, so that the third flowback through hole (426) is no longer communicated with the inner hole of the lower ball seat (409); the acid liquid is injected into the oil pipe (1) by opening the pump on the ground, after a certain pressure is reached, the pin (420) is cut off, the upper ball seat (421) falls off, the acid injection through hole (427) is opened, the injected acid liquid enters from the acid injection through hole (427), the valve (419) is lifted, the acid liquid enters the formation to start acidification; In this way, the flowback acidification operation and the acidification operation of the remaining formations from the bottom to the top are completed.

8. The construction method of claim 7, wherein: The flowback mode on the ground is flowback by a flowback pump or flowback by nitrogen injection.

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