Perforating, fracturing and mechanical packing integrated separate-layer fracturing tubular column and old well multi-stratum fracturing operation method

Abstract

The invention discloses a perforation fracturing mechanical packing integrated separate-layer fracturing pipe column and an old well multi-stratum fracturing operation method.The lower end of the pipe column is provided with a guiding shoe, the upper portion of the guiding shoe is sequentially connected with a damping centralizer, a supporting cylinder pressure meter and a screen pipe, and the lower end of an oil pipe is sequentially connected with a safety connector and a double-layer multi-stage filtering fracturing hydraulic anchor; a plurality of K344 packers and hydraulic ejectors are arranged between the screen pipe and the double-layer multi-stage filtering fracturing hydraulic anchor, the packers are respectively arranged on the inner wall of a casing pipe between adjacent stratums in a seat sealing mode, the hydraulic ejectors respectively correspond to stratums which are not perforated, and at least one side of each hydraulic ejector is provided with a centralizer special for ejection. Perforation fracturing is conducted on the stratum without perforation through the hydraulic ejectors in sequence; and the perforated stratum is fractured through the sliding sleeve sand blower. According to the tubular column, on the basis of reliable anchoring, sequential fracturing of a perforated section and an unperforated stratum can be met, the operation risk is low, safety and reliability are achieved, and the tubular column can be smoothly pulled out after fracturing is completed.

Description

Technical Field

[0001] The present invention relates to downhole fracturing and acidizing stimulation operations for oil and gas, and in particular to a perforating and fracturing mechanical packer integrated layered fracturing string, and also relates to a fracturing operation method for multiple formations in old wells, belonging to the technical field of hydraulic fracturing of oil and gas wells. Background Art

[0002] In recent years, layered fracturing technology has become the main means for the development of low-pressure and low-permeability oil and gas resources, and has been widely applied in oil and gas fields at home and abroad. Currently, for the transformation of thin interbedded formations, two types of layered fracturing processes, namely the sliding sleeve sandblaster + K344 packer combination and hydraulic jetting, are mainly adopted.

[0003] The layered fracturing technology of sliding sleeve sandblaster + K344 packer has the advantages of rapid construction, large fracturing sand addition volume, convenient and safe on-site operation, obvious mechanical packing effect, and reliable packing. However, it has the following problems: 1. Conventional perforation needs to be carried out in advance. Conventional perforation is easy to contaminate the oil and gas layers, reduce the permeability, damage the oil and gas layers, and requires scraping of the perforation holes, increasing the construction period and cost; 2. It is not applicable to near-water thin interlayers and is easy to fracture the water layer, affecting the fracturing effect; 3. During the construction process of the K344 packer, centralizers are installed at both the upper and lower ends. In horizontal wells, the outer diameter of the centralizer is about 112 mm, while the inner diameter of the 5½” casing is 124 mm. The packer is not centered, seriously affecting the pressure-bearing capacity and service life of the packer; 4. The sealing effect of the packer cannot be verified; 5. The anchoring effect of the hydraulic anchor is poor.

[0004] The hydraulic jetting layered fracturing technology relies on hydraulic perforation and packing, without mechanical packing, and is applicable to various well conditions. However, it has the following deficiencies: 1. It is difficult to achieve complete interlayer packing; Centralizers are installed at both ends of the hydraulic jetting tool. As mentioned above, there is a gap between the outer diameter of the centralizer and the inner diameter of the casing in horizontal wells, affecting the centrality of the hydraulic jetting tool, directly affecting the jetting effect, and due to the non-centralization of the hydraulic jetting tool, the back-splashing of the jetting fracturing sand causes great damage to the fracturing string close to the casing, and in severe cases, perforation or disconnection may occur, leading to complex downhole accidents; 2. For near-water thin interlayers, it is very crucial for the hydraulic jetting tool to accurately align with the thin interlayer, and it is very important to use a hydraulic anchor to anchor the string. However, in horizontal wells, the hydraulic anchor often fails to release stuck, resulting in downhole accidents; Therefore, the hydraulic jetting layered fracturing often does not use the hydraulic anchor, and the sand control and stuck release performance of the hydraulic anchor needs to be solved; 3. The nozzle wears greatly, has a limited service life, has a small sand addition volume, and a low sand ratio; 4. The frictional resistance is large, the construction wellhead pressure is high, and the application in deep wells is limited; By adopting the combination of hydraulic sandblasting perforation and mechanical sealing of K344 packers, the advantages of hydraulic jet fracturing technology can be utilized and its deficiencies can be addressed, enabling integrated perforating, fracturing, and mechanical sealing for layer-by-layer fracturing operations.

[0005] The Chinese invention patent with the publication number CN 103821489B discloses a horizontal well mechanical layer-by-layer and hydraulic jet fracturing and acidizing composite technology string, presenting the idea of a sliding sleeve sandblaster + K344 packer combination and hydraulic jetting. In fact, for unperforated formations in old wells, after perforation, a large displacement fracturing capacity of 5 - 6 m³ / min can be achieved; for unperforated and perforated formations in old wells, perforation can be carried out first, and simultaneous fracturing inside and outside the tubing can be achieved, reaching a large displacement fracturing capacity of 7 - 8 m³ / min. However, problems such as the difficulty of centering the packer and the hydraulic jetting device, the sand control problem of the hydraulic anchor, and the test of the pressure-bearing sealing effect of the K344 packer have not been solved.

[0006] The Chinese invention patent with the publication number CN 108166965B discloses a sandblasting perforation, fracturing, and sealing integrated device, belonging to the hydraulic sandblasting fracturing technology with a packer. The packer is hydraulic and operates with slips, and there may be problems with the slips not releasing. Moreover, this technology is not suitable for non-tubing movement layer-by-layer fracturing. With multiple packers with slips, the risk of the packers not releasing after construction is greatly increased.

[0007] The Chinese patent with the publication number CN 203161114U discloses a hydraulic centralizer applicable to multi-stage hydraulic jet fracturing. In principle, this hydraulic centralizer can achieve a centralizing effect. In actual application, the sand control is unreliable. Fracturing sand enters between the elastic sand control pipe and the centralizing block. After construction, the centralizing block does not have a spring forced recovery force, and the centralizing block cannot be restored, making it impossible to normally lift out the work string, and even causing major repairs to oil and water wells.

[0008] The Chinese patent with the publication number CN 212743930U discloses a slotted sand control hydraulic anchor. The gap of the sand control pipe is between 0.2 - 0.3. Under the influence of downhole pressure, the gap will increase, resulting in sand plugging. Moreover, the anchor teeth often cannot be normally recovered due to sand jamming during recovery, making it impossible to normally lift out the work string, and even causing major repairs to oil and water wells; and the anchor claws have only one direction, and the anchoring is unreliable. Summary of the Invention

[0009] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, but such simplifications or omissions shall not be used to limit the scope of the present invention.

[0010] The primary objective of the present invention is to overcome the problems existing in the prior art and provide a perforating and fracturing mechanical packer integrated layered fracturing string. On the basis of reliable anchoring, it can meet the fracturing requirements of the perforated section and the unperforated formation, with low operation risk, high safety and reliability, and the string can be smoothly retrieved after fracturing.

[0011] To solve the above technical problems, a perforating and fracturing mechanical packer integrated layered fracturing string of the present invention includes a guide shoe at the lower end of the string. Above the guide shoe, a shock-absorbing centralizer, a collar pressure gauge and a screen pipe are sequentially connected. At the lower end of the tubing, a safety joint and a double-layer multi-stage filtering fracturing hydraulic anchor are sequentially connected. Between the screen pipe and the double-layer multi-stage filtering fracturing hydraulic anchor, a plurality of K344 packers and hydraulic jetting devices are provided. Each packer is seated on the inner wall of the casing between adjacent formations, and each hydraulic jetting device corresponds to the unperforated formation. At least one side of each hydraulic jetting device is provided with a special jetting centralizer.

[0012] Furthermore, a sliding sleeve sandblasting device corresponding to the perforated formation is also provided between the screen pipe and the double-layer multi-stage filtering fracturing hydraulic anchor.

[0013] Furthermore, a ball seat, a non-sliding-sleeve hydraulic jetting device, a first special jetting centralizer, a first sliding-sleeve seat, a second special jetting centralizer, a first packer, a sliding sleeve sandblasting device, a second sliding-sleeve seat, a second packer, a first sliding-sleeve hydraulic jetting device, a third special jetting centralizer, a second sliding-sleeve hydraulic jetting device, a fourth special jetting centralizer, a third sliding-sleeve seat, a third packer and a third sliding-sleeve hydraulic jetting device are sequentially arranged between the screen pipe and the double-layer multi-stage filtering fracturing hydraulic anchor from bottom to top.

[0014] Furthermore, the non-sliding-sleeve hydraulic jetting device corresponds to the first formation, the sliding sleeve sandblasting device corresponds to the second formation, the first sliding-sleeve hydraulic jetting device and the second sliding-sleeve hydraulic jetting device correspond to the third formation, and the third sliding-sleeve hydraulic jetting device corresponds to the fourth formation.

[0015] Furthermore, the outer diameter of the sliding sleeve inside the first packer, the outer diameter of the sliding sleeve inside the second packer, and the outer diameter of the sliding sleeve inside the sliding sleeve sandblasting device are the same as the inner diameter of the second sliding-sleeve seat.

[0016] Furthermore, the outer diameter of the sliding sleeve inside the first sliding-sleeve hydraulic jetting device, the outer diameter of the sliding sleeve inside the second sliding-sleeve hydraulic jetting device, the outer diameter of the sliding sleeve inside the second sliding-sleeve hydraulic jetting device, and the outer diameter of the sliding sleeve inside the third packer are the same as the inner diameter of the third sliding-sleeve seat, and the inner diameter of the third sliding-sleeve seat is the same as that of the second sliding-sleeve seat.

[0017] Further, the sliding sleeves used in the second packer, the sliding sleeve sandblaster, and the first packer include a sliding sleeve body, a sealing ring, and a shear pin groove, and the shear pin groove is between the upper and lower sealing rings; a sliding sleeve blocking step is provided at the lower end of the central hole of the first sliding sleeve seat to block the sliding sleeve body.

[0018] Further, the sliding sleeves in the first sliding sleeve hydraulic jet and the second sliding sleeve hydraulic jet include a sliding sleeve body, a sealing ring, a shear pin groove, and a circlip. The shear pin groove is in the middle of the upper and lower sealing rings, and the circlip is embedded in the lower outer wall of the sliding sleeve body; the second sliding sleeve seat and the third sliding sleeve seat have the same shape, and an enlarged circlip groove is provided in the middle section of their central holes to lock the circlip of the second sliding sleeve.

[0019] Further, the special jet centralizer includes a centralizer body. A plurality of body radial holes communicating with the central hole of the body are provided in the middle section of the centralizer body. Sealing pistons are respectively provided in the body radial holes. A rectangular spring is embedded in the counterbore at the center of the outer end face of the sealing piston. The outer end of the rectangular spring abuts against the inner wall of the middle part of the gland. The outer circumference of the gland is screwed into the screw hole at the outer port of the body radial hole; a soluble support rod is embedded in the central through hole of the gland. The inner end of the soluble support rod is screwed into the screw hole at the center of the outer end face of the sealing piston; a jacket is embedded in the central hole of the body, an inner sleeve is nested in the jacket, the upper and lower ends of the inner sleeve respectively extend beyond the ports of the jacket, an upper body sealing ring is embedded at the upper end of the central hole of the body to seal the upper outer wall of the jacket, and a lower body sealing ring is embedded at the lower end of the central hole of the body to seal the lower outer wall of the inner sleeve.

[0020] Further, the double-layer multi-stage filtering fracturing hydraulic anchor includes a hydraulic anchor body. A plurality of anchor claw cavities communicating with the central hole are provided in the middle section of the hydraulic anchor body. Anchoring mechanisms are respectively installed in the anchor claw cavities. A jacket is embedded in the central hole of the hydraulic anchor body, an inner sleeve is nested in the jacket, the upper and lower ends of the inner sleeve respectively extend beyond the ports of the jacket, an upper body sealing ring is embedded at the upper end of the central hole of the hydraulic anchor body to seal the upper outer wall of the jacket, and a lower body sealing ring is embedded at the lower end of the central hole of the hydraulic anchor body to seal the lower outer wall of the inner sleeve. A plurality of inner sleeve wire cutting slots are evenly provided on the upper circumference of the inner sleeve to communicate with the inner wall gap of the jacket, and a plurality of jacket wire cutting slots are evenly provided on the lower circumference of the jacket to communicate with the inner wall gap of the central hole of the hydraulic anchor body.

[0021] Further, the lower end of the inner sleeve abuts against the inner step of the central hole of the hydraulic anchor body. The outer diameter of the upper end outer wall of the inner sleeve is enlarged to form a large end of the inner sleeve. An outer conical surface of the large end of the inner sleeve is pressed against the flared opening at the upper end of the central hole of the hydraulic anchor body. Each inner sleeve wire cutting slot extends to the top of the large end of the inner sleeve; the top of the large end of the inner sleeve is a plane and a circlip is pressed above it. The circlip is embedded in the inner wall ring groove of the central hole of the hydraulic anchor body.

[0022] Further, the upper part of the outer sleeve abuts against the lower part of the root of the large end of the inner sleeve, and the lower end of the outer sleeve abuts against the inner step of the central hole of the hydraulic anchor body.

[0023] Further, the anchoring mechanism includes an anchoring piston, a pressing strip and a rectangular spring. The anchoring piston is embedded in the corresponding anchor claw cavity and is sealed with each other. Anchor claw teeth are arranged on both sides of the outer end surface of the anchoring piston. A rectangular spring is embedded in the central sunken hole of the outer end surface of the anchoring piston. The outer end of the rectangular spring abuts against the inner wall of the middle part of the pressing strip. The upper and lower ends of the pressing strip are respectively fixed on the hydraulic anchor body by fastening screws; Hard alloy teeth are welded on each of the anchor claw teeth.

[0024] Further, three groups of the anchoring mechanisms are arranged along the height direction of the hydraulic anchor body. The anchor claw teeth of the three groups of anchoring mechanisms face upward, centered and downward from top to bottom.

[0025] Further, the fit clearance between the inner sleeve and the outer sleeve and the fit clearance between the outer sleeve and the central hole of the hydraulic anchor body are both H10 / d10 or H10 / c10; The slit widths of the wire cut slit of the inner sleeve and the wire cut slit of the outer sleeve are 0.2-0.3mm respectively.

[0026] Another object of the present invention is to overcome the problems existing in the prior art and provide a perforating and fracturing mechanical packer integrated layered fracturing string, which can meet the fracturing of the perforated section and the unperforated formation on the basis of reliable anchoring, and has low operation risk and is safe and reliable.

[0027] To solve the above technical problems, an old well multi-stratum fracturing operation method of the present invention successively includes the following steps: S1. Run a string with a gauge through the well and wash the well. S2. After the multi-functional fracturing process string is lowered to the designed position, perform reverse circulation well washing. S3. Put a soluble ball one into the tubing. The soluble ball one falls into the ball seat and is seated. Pressurize the wellhead to open the non-sliding sleeve hydraulic jet. The double-layer multi-stage filtering fracturing hydraulic anchor anchors the string. The support rods of all jet special centralizers support on the inner wall of the casing; Then, perforate the first formation through the non-sliding sleeve hydraulic jet and complete the fracturing of the first formation. S4. Put a soluble ball two into the tubing. Cut the shear pins of each sliding sleeve in the second packer, the sliding sleeve sandblaster and the first packer in sequence; The three sliding sleeves jointly fall into the first joint sliding sleeve seat and are seated. The rubber cylinders of the second packer and the first packer cut off the upper and lower annuli of the second formation, and then perform high-volume fracturing on the second formation. S5. Put soluble ball three into the tubing. Sequentially cut the shear pins of the inner sleeves in the second sliding-sleeve hydraulic jet perforator and the first sliding-sleeve hydraulic jet perforator. The falling inner sleeves are locked by the second sliding-sleeve seat, sealing the central channel of the lower tubing string. The second sliding-sleeve hydraulic jet perforator and the first sliding-sleeve hydraulic jet perforator perform perforation simultaneously, increasing the displacement until the perforation of the third formation is completed. S6. Put soluble ball four into the tubing. Cut the shear pins of the inner sleeve in the third packer. After the inner sleeve drops, it seats and seals on the second sliding-sleeve seat, sealing the central channel of the lower tubing string. The third packer and the second packer are set. High-displacement fracturing is carried out through the second sliding-sleeve hydraulic jet perforator and the first sliding-sleeve hydraulic jet perforator until the fracturing of the third formation is completed. S7. Put soluble ball five into the tubing. Cut the shear pins of the inner sleeve in the second sliding-sleeve hydraulic jet perforator. After the inner sleeve drops, it seats and seals on the third sliding-sleeve seat, sealing the central channel of the lower tubing string. Then, use the second sliding-sleeve hydraulic jet perforator to perform hydraulic sandblasting perforation on the fourth formation. After the perforation construction is completed, sand addition and fracturing are carried out simultaneously in the tubing and the annulus between the tubing and the casing. After the fracturing is completed, close the wellhead. S8. Inject fracturing fluid from the annulus between the tubing and the casing to retrieve each packer. S9. Wait for the pressure to spread. During this process, the soluble metal support rods of the special jetting centralizer slowly dissolve. S10. Depressurize the central hole channel, release the anchoring of the double-layer multi-stage filtration fracturing hydraulic anchor, pull out the tubing string, and the fracturing is completed.

[0028] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. It combines the advantages of the combination of sliding-sleeve sandblasting perforator + K344 packer and hydraulic jetting technologies. It solves the problems that the stratified fracturing technology of sliding-sleeve sandblasting perforator + K344 packer is not applicable to near-water thin interlayers and is prone to fracturing the water layer, resulting in poor fracturing effects. It also solves the problems that it is difficult to achieve complete interlayer isolation and difficult to test the seal of the hydraulic jetting technology. It not only fully exerts the technical characteristics of hydraulic perforation and fixed-point transformation of the hydraulic jetting technology but also ensures the sealing effect of the stratified fracturing tubing string, can verify the sealing performance of the packer, and ensure the success rate of releasing the packer, realizing one-trip tubing string perforation, fracturing, and mechanical isolation integrated stratified fracturing operation.

[0029] 2. For unperforated formations in old wells, after perforation, it can achieve a high-displacement fracturing capacity of 5 - 6 m³ / min, doubling the traditional displacement. For unperforated and perforated formations in old wells, it can first perform perforation, and fracturing is carried out simultaneously inside and outside the tubing, achieving a high-displacement fracturing capacity of 7 - 8 m³ / min. It solves the problems of conventional mechanical stratified fracturing methods that require prior conventional perforation and scraping of the perforation hole positions after perforation, with a long construction period and increased perforation and scraping costs.

[0030] 3. It solves the problem of poor conventional fracturing effect in near-water thin interlayers. The perforation effect of the hydraulic jetting tool is obvious and the packer has reliable performance. A single trip string can achieve the construction purposes of hydraulic perforation and mechanical isolation, reduce the construction risk, simplify on-site operation, and the packer can be automatically released after fracturing, making the construction safe and reliable.

[0031] 4. A double-layer multi-stage filtering fracturing hydraulic anchor is designed at the uppermost end of the tool. Two layers and four channels of filtration are realized by using an inner sleeve and an outer sleeve for sand control. The fit clearance between the inner sleeve and the outer sleeve and between the outer sleeve and the hydraulic anchor body is H10 / d10 or H10 / c10. During the fracturing construction process, as the pressure increases, the liquid enters the gap between the inner sleeve and the outer sleeve from the wire-cutting slots of the inner sleeve, and then enters the gap between the inner wall of the hydraulic anchor body and the outer sleeve through the wire-cutting slots of the outer sleeve and enters the anchor piston cavity. The liquid acts to push the anchor piston and anchor the casing. The double-layer filtration of the inner sleeve and the outer sleeve has good sand control effect and can effectively solve the problem of the retraction of the anchor claws. The anchoring mechanism is designed into three groups, and the anchor claw teeth face upward, centered, and downward from top to bottom respectively, with better anchoring effect. For high-pressure fracturing wells, in order to further improve the anchoring force of the hydraulic anchor, cemented carbide is welded on the outer part of the anchor claws. Due to the high hardness of the cemented carbide, the anchoring force intensity is greatly improved, ensuring that the pipe string does not creep.

[0032] 5. By solving the problem of the centering of the packer and the hydraulic jetting tool, the pressure-bearing capacity of the packer is improved and the service life of the hydraulic jetting tool is extended; by installing a pressure gauge with a support cylinder below the ball seat at the lowermost end, dynamic monitoring of the fracturing at the lowermost end can be realized. During construction, the changes in pressure and temperature can also be used to test the pressure-bearing and sealing effect of the packer; at the same time, the shock absorber and centralizer can effectively reduce the vibration of the pressure gauge with the support cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings. The drawings are only for reference and explanation, and are not used to limit the present invention. Among them: Figure 1 is a schematic diagram of the perforating and fracturing mechanical isolation integrated layered fracturing string of the present invention; Figure 2 is a cross-sectional view of the shock absorber and centralizer in the present invention; Figure 3 is Figure 2 the top view of; Figure 4 is a schematic diagram of the structure of the first joint sliding sleeve seat and its matching sliding sleeve in the present invention; Figure 5 is a schematic diagram of the structure of the second joint sliding sleeve seat and its matching sliding sleeve in the present invention; Figure 6 This is a cross-sectional view of the double-layer multi-stage filtering fracturing hydraulic anchor in the present invention; Figure 7 This is a cross-sectional view of the double-layer multi-stage filtering fracturing hydraulic anchor in the present invention; Figure 8 is Figure 7 a cross-sectional view of the anchoring mechanism therein; In the figure: 1. Guide shoe; 2. Shock-absorbing centralizer; 2a. Limit pin; 2b. Shock-absorbing rubber; 2c. Protective sleeve; 3. Torus pressure gauge; 4. Screen pipe; 5. Ball seat; 6. Hydraulic ejector without sliding sleeve; 7. First special ejecting centralizer: 7a. Ejecting centralizer body; 7a1. Upper seal ring on the body; 7a2. Lower seal ring on the body; 7b. Circlip; 7c. Outer sleeve; 7c1. Wire cut slot on the outer sleeve; 7d. Inner sleeve; 7d1. Wire cut slot on the inner sleeve; 7e. Sealing piston; 7e1. Piston seal ring; 7f. gland; 7g. Rectangular spring; 7h. Soluble support rod; 8. First sliding sleeve connection seat; 8a. Step for blocking the sliding sleeve; 9. Second special ejecting centralizer; 10. First packer; 11. Sliding sleeve sandblaster; 12. Second sliding sleeve connection seat; 12a. Circlip expansion groove; 13. Second packer; 13a. Sliding sleeve body; 13b. Shearing pin slot; 14. First hydraulic ejector with sliding sleeve; 15. Third special ejecting centralizer; 16. Second hydraulic ejector with sliding sleeve; 17. Fourth special ejecting centralizer; 18. Third sliding sleeve connection seat; 19. Third packer; 20. Third hydraulic ejector with sliding sleeve; 21. Double-layer multi-stage filtering fracturing hydraulic anchor: 21a. Hydraulic anchor body; 21a1. Upper seal ring on the body; 21a2. Lower seal ring on the body; 21b. Circlip; 21c. Outer sleeve; 21c1. Wire cut slot on the outer sleeve; 21d. Inner sleeve; 21d1. Wire cut slot on the inner sleeve; 21e. Fastening screw; 21f. Press strip; 21g. Rectangular spring; 21h. Anchoring piston; 21j. Anchor claw teeth; 22. Safety joint; 23. Oil pipe; 24. Soluble ball; 25. Casing. Detailed implementation manners

[0034] In order to make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be further described below with reference to specific drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention.

[0036] As Figure 1 shown, the perforating and fracturing integrated mechanical packer zonal fracturing string of the present invention sequentially includes, from bottom to top: a guide shoe 1, a shock-absorbing centralizer 2, a carrier barrel pressure gauge 3, a screen pipe 4, a ball seat 5, a non-sliding sleeve hydraulic jet 6, a first jet special centralizer 7, a first sliding sleeve connection seat 8, a second jet special centralizer 9, a first packer 10, a sliding sleeve sandblaster 11, a second sliding sleeve connection seat 12, a second packer 13, a first sliding sleeve hydraulic jet 14, a third jet special centralizer 15, a second sliding sleeve hydraulic jet 16, a fourth jet special centralizer 17, a third sliding sleeve connection seat 18, a third packer 19, a third sliding sleeve hydraulic jet 20, a double-layer multi-stage filtering fracturing hydraulic anchor 21, a safety joint 22, a tubing 23, a dissolvable ball 24, and a casing 25. Each packer herein is a K344 packer.

[0037] The carrier barrel pressure gauge 3 can record and store pressure and temperature data and has three functions: 1. Store the pressure and temperature data during the first stage of fracturing; 2. Verify the sealing performance of the packer. If the packer is not sealed, the stored pressure and temperature of the carrier barrel pressure gauge 3 will change; 3. After the fracturing is completed and the string is not pulled out, record the changes in pressure and temperature.

[0038] As Figure 2 、 Figure 3 shown, the shock-absorbing centralizer 2 can effectively reduce the vibration of the carrier barrel pressure gauge and improve the service life and accuracy of the pressure gauge. The shock-absorbing centralizer 2 includes a shock-absorbing centralizer body, a limit pin 2a, shock-absorbing rubber 2b, and a protective sleeve 2c. The shock-absorbing rubber 2b and the protective sleeve 2c are vulcanized together to form a combination. After use, as long as the limit pin 2a is removed, the combination of the shock-absorbing rubber and the protective sleeve can be replaced, and then the limit pin 2a is still screwed in from the end face. The inner end of the limit pin 2a is embedded in the protective sleeve 2c to lock it, and the shock-absorbing centralizer can be reused.

[0039] The outer diameter of the inner sliding sleeve of the first packer 10, the outer diameter of the inner sliding sleeve of the second packer 13, the outer diameter of the inner sliding sleeve of the sliding sleeve sandblaster 11 are the same as the inner diameter of the second sliding sleeve connection seat 12.

[0040] The outer diameter of the inner sliding sleeve of the first sliding sleeve hydraulic jet 14, the outer diameter of the inner sliding sleeve of the second sliding sleeve hydraulic jet 16, the outer diameter of the inner sliding sleeve of the second sliding sleeve hydraulic jet 20, the outer diameter of the inner sliding sleeve of the third packer 19 are the same as the inner diameter of the third sliding sleeve connection seat 18.

[0041] The outer diameter of the built-in sliding sleeve of the first packer 10, the outer diameter of the built-in sliding sleeve of the second packer 13, the outer diameter of the built-in sliding sleeve of the sliding sleeve sandblaster 11 are the same as the inner diameter of the second sliding sleeve seat 12.

[0042] The outer diameter of the built-in sliding sleeve of the first sliding sleeve hydraulic jet 14, the outer diameter of the built-in sliding sleeve of the second sliding sleeve hydraulic jet 16, the outer diameter of the built-in sliding sleeve of the second sliding sleeve hydraulic jet 20, the outer diameter of the built-in sliding sleeve of the third packer 19 are the same as the inner diameter of the third sliding sleeve seat 18. The inner diameter of the third sliding sleeve seat 18 is the same as the inner diameter of the second sliding sleeve seat 12.

[0043] As Figure 4 shown, the first type of sliding sleeve is used in the second packer 13, the sliding sleeve sandblaster 11 and the first packer 10. The first type of sliding sleeve includes a sliding sleeve body, a sealing ring and a shear pin groove. Taking the sliding sleeve of the second packer 13 as an example, it includes a sliding sleeve body 13a, and the shear pin groove 13b is between the upper and lower sealing rings to ensure the sealing performance of the shear pin groove 13b. The first sliding sleeve seat 8 is matched with the first type of sliding sleeve. A sliding sleeve blocking step 8a is provided at the lower end of the central hole of the first sliding sleeve seat 8 to block the sliding sleeve body 13a by the sliding sleeve blocking step.

[0044] As Figure 5 shown, the sliding sleeves in the first sliding sleeve hydraulic jet 14 and the second sliding sleeve hydraulic jet 20 are the second type of sliding sleeve. Taking the second type of sliding sleeve built in the first sliding sleeve hydraulic jet 14 as an example, it includes a sliding sleeve body 14a, a sealing ring, a shear pin groove 14b and a circlip 14c. The shear pin groove 14b is in the middle of the upper and lower sealing rings to ensure the sealing performance of the shear pin groove. The circlip 14c is embedded in the lower outer wall of the sliding sleeve body.

[0045] The second sliding sleeve seat 12 and the third sliding sleeve seat 18 have the same shape. Taking the second sliding sleeve seat 12 as an example, an enlarged circlip groove 12a with an expanded diameter is provided in the middle section of its central hole, which is matched with the second type of sliding sleeve, and the circlip 14c of the second type of sliding sleeve is locked through the enlarged circlip groove 12a.

[0046] As Figure 6 shown, taking the first special jetting centralizer 7 as an example, each special jetting centralizer includes: a jetting centralizer body 7a, a circlip 7b, an outer sleeve 7c, an inner sleeve 7d, a sealing piston 7e, a rectangular spring 7g, a soluble support rod 7h and a gland 7f. The jetting centralizer body 7a serves as the basic framework of the entire device and is used to install and fix other components.

[0047] The outer sleeve 7c is located in the central hole of the body, and the lower end of the outer sleeve 7c abuts against the inner step of the central hole of the body. The upper part of the central hole of the body is embedded with an upper body sealing ring 7a1 and the upper outer wall of the outer sleeve 7c to achieve sealing between the outer wall of the outer sleeve 7c, prevent liquid leakage and ensure the sealing performance of the device.

[0048] The inner sleeve 7d abuts against the inner wall of the outer sleeve 7c. The lower end of the inner sleeve 7d extends out from the lower port of the outer sleeve 7c and abuts against the inner step of the central hole of the body. The upper part of the central hole of the body is fitted with a lower sealing ring 7a2 of the body to seal with the lower outer wall of the inner sleeve 7d. The outer wall of the upper end of the inner sleeve 7d has an enlarged diameter to form a large end of the inner sleeve. The lower part of the large end of the inner sleeve is provided with an outer conical surface of the large end of the inner sleeve. The outer conical surface of the large end of the inner sleeve presses on the flared opening at the upper end of the central hole of the body. The top of the large end of the inner sleeve is a plane and a snap ring 7b is pressed above it. The snap ring 7b is fitted in the annular groove below the upper tapered female thread of the injection centralizer body 7a. The upper part of the outer sleeve 7c abuts against the lower part of the root of the large end of the inner sleeve. In this way, both the inner sleeve 7d and the outer sleeve 7c are prevented from moving around, ensuring the stability of the assembly during operation.

[0049] A plurality of inner sleeve wire cutting slits 7d1 are evenly arranged on the upper circumference of the inner sleeve 7d. The slit width of each inner sleeve wire cutting slit 7d1 is 0.2 - 0.3 mm and extends all the way to the top of the large end of the inner sleeve, for guiding the liquid flow into the gap between the inner sleeve 7d and the outer sleeve 7c.

[0050] A plurality of outer sleeve wire cutting slits 7c1 are evenly arranged on the lower circumference of the outer sleeve 7c. The slit width of each outer sleeve wire cutting slit 7c1 is 0.2 - 0.3 mm, for guiding the liquid flow into the gap between the outer sleeve 7c and the inner wall of the central hole of the body. The wall thicknesses of the outer sleeve 7c and the inner sleeve 7d are preferably 2 mm respectively.

[0051] A plurality of body radial holes communicating with the central hole of the body are arranged on the circumference of the injection centralizer body 7a. Sealing pistons 7e are respectively fitted in each body radial hole. A piston sealing ring 7e1 is fitted on the circumferential wall of the sealing piston 7e to seal with the inner wall of the body radial hole. A counterbore is provided at the center of the outer end face of the sealing piston 7e. A rectangular spring 7g is fitted in the counterbore. The outer end of the rectangular spring 7g abuts against the middle inner wall of the gland 7f. The outer circumference of the gland 7f is screwed into the screw hole at the outer port of the body radial hole; A soluble support rod 7h is fitted in the central through hole of the gland 7f. The inner end of the soluble support rod 7h is screwed into the screw hole at the center of the outer end face of the sealing piston 7e.

[0052] The gland 7f is used to press the outer end of the rectangular spring 7g and provide positioning for the soluble support rod 7h; The rectangular spring 7g provides a resilience force for the sealing piston 7e to ensure that the soluble support rod 7h can retract in time when the pressure changes, facilitating the removal of the pipe string.

[0053] Jetting special centralizers are installed at both ends of the hydraulic ejector. The jetting special centralizers are lowered together with the fracturing string. After the string reaches the designed position, fracturing construction is carried out. During the construction process, when the pressure rises, the liquid action pushes the sealing piston 7e to move outward. The sealing piston 7e overcomes the elastic force of the rectangular spring 7g and pushes the soluble support rod 7h to extend radially, firmly supporting on the inner wall of the casing, realizing the centralization of the hydraulic ejector and ensuring the reliable centering of the hydraulic ejector.

[0054] After the construction is completed, when the pressure in the string is less than the sealing pressure of the hydraulic anchor seat, the sealing piston 7e retracts under the action of the elastic force of the rectangular spring 7g, driving the soluble support rod 7h to recover, that is, the outer end of the soluble support rod 7h retracts into the central hole of the gland, and the string can be smoothly lifted out.

[0055] The soluble support rod 7h is made of soluble metal. In case of abnormal conditions, if the sand control of the inner sleeve 7d and the outer sleeve 7c fails accidentally and the fracturing sand enters between the inner wall of the outer sleeve 7c and the jetting centralizer body 7a, and the sealing piston 7e cannot be recovered, the soluble support rod 7h can automatically dissolve. There is no rod body of the soluble support rod 7h outside the jetting special centralizer, and the centralizer returns to its normal outer diameter, ensuring that the string can be smoothly lifted out.

[0056] The jetting special centralizer is not only applicable to hydraulic jet fracturing, but also applicable to the technology of conventional fracturing sliding sleeve sandblasting tool + K344 packer, which can ensure the centering of the K344 packer, improve the pressure-bearing capacity and service life of the packer.

[0057] The tests in wells such as Chen XX et al. showed that during the fracturing construction at 60 MPa, the construction was smooth, the string was lifted out smoothly, and there was no sticking phenomenon. After disassembling the jetting special centralizer, there was a little fracturing sand between the inner sleeve 7d and the outer sleeve 7c, and there was no fracturing sand between the outer sleeve 7c and the jetting centralizer body 7a, and the soluble support rod 7h had dissolved.

[0058] As Figure 7 、 Figure 8 shown, the double-layer multi-stage filtering fracturing hydraulic anchor in the present invention includes: a hydraulic anchor body 21a, a snap ring 21b, an outer sleeve 21c, an inner sleeve 21d, fastening screws 21e, a pressing strip 21f, a rectangular spring 21g, an anchoring piston 21h, anchor claw teeth 21j and cemented carbide teeth. The hydraulic anchor body 21a serves as the basic framework of the entire device and is used to install and fix other components.

[0059] The outer sleeve 21c is located in the central hole of the hydraulic anchor body, and the lower end of the outer sleeve 21c abuts against the inner step of the central hole of the hydraulic anchor body. The upper part of the central hole of the hydraulic anchor body is fitted with an upper body sealing ring 21a1 and the upper outer wall of the outer sleeve 21c to achieve the seal between the outer wall of the outer sleeve 21c, preventing liquid leakage and ensuring the sealing performance of the device.

[0060] The inner sleeve 21d abuts against the inner wall of the outer sleeve 21c. The lower end of the inner sleeve 21d extends out from the lower port of the outer sleeve 21c and abuts against the inner step of the central hole of the hydraulic anchor body. The upper part of the central hole of the hydraulic anchor body is fitted with a lower body sealing ring 21a2 to seal with the lower outer wall of the inner sleeve 21d. The outer wall of the upper end of the inner sleeve 21d has an enlarged diameter to form a large end of the inner sleeve. The lower part of the large end of the inner sleeve is provided with an outer conical surface of the large end of the inner sleeve, and the outer conical surface of the large end of the inner sleeve presses on the flared opening at the upper end of the central hole of the hydraulic anchor body. The top of the large end of the inner sleeve is flat and a snap ring 21b is pressed above it. The snap ring 21b is fitted in the annular groove below the upper tapered female thread of the hydraulic anchor body 21a. The upper part of the outer sleeve 21c abuts against the lower part of the root of the large end of the inner sleeve. In this way, both the inner sleeve 21d and the outer sleeve 21c are prevented from moving around, ensuring the stability of the assembly during operation.

[0061] A plurality of inner sleeve wire cutting slits 21d1 are uniformly arranged on the upper circumference of the inner sleeve 21d. The slit width of each inner sleeve wire cutting slit 21d1 is 0.2 - 0.3 mm and extends all the way to the top of the large end of the inner sleeve, for guiding the liquid flow into the gap between the inner sleeve 21d and the outer sleeve 21c.

[0062] A plurality of outer sleeve wire cutting slits 21c1 are uniformly arranged on the lower circumference of the outer sleeve 21c. The slit width of each outer sleeve wire cutting slit 21c1 is 0.2 - 0.3 mm, for guiding the liquid flow into the gap between the outer sleeve 21c and the inner wall of the central hole of the hydraulic anchor body. Inside and outside the outer sleeve 21c are the hydraulic anchor body 21a and the inner sleeve 21d respectively. When the liquid enters, due to the outer sleeve 21c being restricted inside and outside, it prevents the outer sleeve wire cutting slit 21c1 from expanding and restricts the entry of fracturing sand.

[0063] A plurality of anchor claw cavities communicating with the central hole are provided on the circumference of the hydraulic anchor body 21a. An anchor piston 21h is respectively fitted in each anchor claw cavity. The circumferential wall of the anchor piston 21h is fitted with a piston sealing ring to seal with the inner wall of the anchor claw cavity. A counterbore is provided at the center of the outer end face of the anchor piston 21h, and a rectangular spring 21g is fitted in the counterbore. The outer end of the rectangular spring 21g abuts against the inner wall of the middle part of the pressure bar 21f. The pressure bar 21f extends along the axial direction of the hydraulic anchor body 21a and is fixed to the hydraulic anchor body 21a at both the upper and lower ends through fastening screws 21e.

[0064] Anchor claw teeth 21j are provided on both sides of the outer end face of the anchor piston 21h. The pressure bar 21f is located between the two anchor claw teeth 21j. When the pipe string central channel is pressurized, after the liquid passes through multi - stage filtration, it pushes the anchor piston 21h to extend radially outwards, so that the anchor claw teeth 21j extend out from both sides of the pressure bar 21f and are anchored on the inner wall of the casing.

[0065] The pressure bar 21f is used to press the outer end of the rectangular spring 21g. The rectangular spring 21g provides a resilience force for the anchor piston 21h, ensuring that the anchor claw teeth 21j can retract in time when the pressure changes and release the anchoring.

[0066] For high-pressure fracturing wells, to further improve the anchoring force of the hydraulic anchor, cemented carbide teeth are welded externally on the anchor claw teeth 21j. Since cemented carbide has high hardness and good wear resistance, the friction between the anchor claw teeth and the inner wall of the casing is greatly enhanced, thereby significantly improving the anchoring ability of the hydraulic anchor and ensuring stable anchoring under high-pressure conditions.

[0067] The anchoring process is as follows: The sand control hydraulic anchor is lowered into the well together with the fracturing string. When the string reaches the designed position, the fracturing construction begins. During the construction process, when the pressure in the string reaches the setting pressure of the hydraulic anchor, the liquid acts to push the anchoring piston 21h to overcome the elastic force of the rectangular spring 21g and automatically extend radially. The anchor claw teeth 21j tightly grip the inner wall of the casing, and the string is anchored through the friction between the anchor claws and the casing, preventing relative displacement between the tubing string and the casing.

[0068] The releasing process is as follows: When the fracturing construction is completed and the pressure in the string drops below the setting pressure of the hydraulic anchor, the anchoring piston 21h retracts under the action of the rectangular spring 21g, the hydraulic anchor is released, and the string can be smoothly pulled out.

[0069] Double-layer multi-channel filtration is adopted with the inner sleeve 21d and the outer sleeve 21c. The fitting clearance between the inner sleeve 21d and the outer sleeve 21c is H10 / d10 or H10 / c10, and the fitting clearance between the outer sleeve 21c and the central hole of the hydraulic anchor body is also H10 / d10 or H10 / c10.

[0070] During the fracturing construction process, the pressure in the central channel rises. After the liquid passes through the first-stage filtration at the inner sleeve wire cutting slot 21d1, it enters the annular gap between the inner sleeve 21d and the outer sleeve 21c and flows downward for the second-stage filtration. After passing through the third-stage filtration at the lower outer sleeve wire cutting slot 21c1, it enters the annular gap between the outer sleeve 21c and the central hole of the hydraulic anchor body and flows upward for the fourth-stage filtration. Finally, it enters the anchor claw cavity to push the anchoring piston 21h and the anchor claw teeth 21j to extend. The above design ensures that the liquid passes through four-stage filtration before entering the anchor claw cavity, effectively preventing impurities such as sand grains from entering the anchor claw cavity and protecting the normal operation of the anchor claws.

[0071] The anchor claw directions of traditional hydraulic anchors are all perpendicular to the inner wall of the casing. However, in actual construction, the stress direction of the hydraulic anchor string may be upward or downward, resulting in unreasonable anchor claw directions. In this hydraulic anchor, the anchoring mechanism is designed into three groups, and the anchor claw teeth face upward, centered, and downward from top to bottom. This multi-directional design enables the anchor claws to be effectively anchored under different stress conditions, significantly improving the anchoring effect.

[0072] The method for multi-layer fracturing operation in old wells of the present invention successively includes the following steps: S1. Run a drift mandrel through the tubing string with the lower drift mandrel and conduct well flushing. S2. After the multi-functional fracturing string is lowered to the designed position, adjust the string by depth calibration so that the nozzles of each hydraulic jet perforator are respectively aligned with the positions of the well sections to be fractured, and ensure that all rubber cylinders are not at the positions of the casing collars. Conduct reverse circulation well flushing upward from the screen pipe and the guide shoe into the central hole. S3. Drop a soluble ball of corresponding size into the tubing. The soluble ball falls onto the ball seat and seals. Apply pressure at the wellhead to open the hydraulic jet perforator 6 without a sliding sleeve. The double-layer multi-stage filtration fracturing hydraulic anchor 21 anchors the string on the inner wall of the casing. The support rods of all jet special centralizers support on the inner wall of the casing to ensure that each hydraulic jet perforator is centered and reduce the vibration of the string. Then, conduct hydraulic sandblasting perforation of the first formation through the hydraulic jet perforator 6 without a sliding sleeve, and then complete the fracturing of the first formation. S4. Drop a soluble ball of corresponding size into the tubing, and successively cut the shear pins of each sliding sleeve in the second packer 13, the sliding sleeve sandblasting tool 11, and the first packer 10. The three sliding sleeves jointly fall into the first joint sliding sleeve seat 8 and seal, sealing the central channel of the lower string. The rubber cylinders of the second packer 13 and the first packer 10 cut off the upper and lower annuli of the second formation. Then, conduct high-rate fracturing of the second formation at a rate of 5 - 6 m³ / min to achieve the high-rate fracturing capacity of 5 - 6 m³ / min of the conventional sliding sleeve sandblasting tool + packer, and complete the fracturing of the second formation. The specific process of the soluble ball two sealing is as follows: The soluble ball two first falls onto the upper port of the inner sliding sleeve of the second packer 13. Apply pressure at the wellhead to cut the shear pin of the inner sliding sleeve in the second packer 13, and the rubber cylinder of the second packer 13 seals. The soluble ball two and the inner sliding sleeve of the second packer 13 fall and enter the sliding sleeve sandblasting tool 11, and continue to cut the shear pin of the inner sliding sleeve in the sliding sleeve sandblasting tool 11, and the sandblasting channel of the sliding sleeve sandblasting tool 11 is opened. The soluble ball two, the inner sliding sleeve of the second packer 13, and the inner sliding sleeve of the sliding sleeve sandblasting tool 11 fall and enter the first packer 10, and continue to cut the shear pin of the inner sliding sleeve in the first packer 10, and the rubber cylinder of the first packer 10 seals. The soluble ball two, the inner sliding sleeve of the second packer 13, the inner sliding sleeve of the sliding sleeve sandblasting tool 11, and the inner sliding sleeve of the first packer 10 jointly fall into the first joint sliding sleeve seat 8 and seal.

[0073] S5. Put soluble balls three of corresponding sizes into the tubing, and successively cut the shear pins of the inner sliding sleeves in the second sleeve-equipped hydraulic jet 16 and the first sleeve-equipped hydraulic jet 14. The inner sliding sleeve of the first sleeve-equipped hydraulic jet 14 is locked by the second sliding sleeve seat 12 to seal the central channel of the lower tubing string. The second sleeve-equipped hydraulic jet 16 and the first sleeve-equipped hydraulic jet 14 perforate simultaneously to increase the displacement and achieve hydraulic sandblasting perforation of the third formation. During this process, the second packer 13 remains set until the perforation construction of the third formation is completed; S6. Put soluble balls four of corresponding sizes into the tubing, cut the shear pins of the inner sliding sleeve in the third packer 19. After the inner sliding sleeve drops, it sets on the second sliding sleeve seat 12 to seal the central channel of the lower tubing string. The third packer 19 and the second packer 13 are set, and large-displacement fracturing is carried out through the second sleeve-equipped hydraulic jet 16 and the first sleeve-equipped hydraulic jet 14. The displacement can reach 5 - 6 m³ / minute, achieving the large-displacement fracturing capacity of 5 - 6 m³ / minute of the conventional sleeve sandblaster + packer, and completing the fracturing of the third formation; S7. Put soluble balls five of corresponding sizes into the tubing, cut the shear pins of the inner sliding sleeve in the second sleeve-equipped hydraulic jet. After the inner sliding sleeve drops, it sets on the third sliding sleeve seat 18 to seal the central channel of the lower tubing string. Then, the second sleeve-equipped hydraulic jet is used to carry out hydraulic sandblasting perforation of the fourth formation. At this time, the third packer 19 is set; after the perforation construction is completed, simultaneous sand addition fracturing is carried out in the tubing and the annulus between the tubing and the casing, reaching a large displacement of 7 - 8 m³ / minute. After the fracturing is completed, close the wellhead; S8. The central hole channel is in a closed state, and KCL fracturing fluid is injected from the annulus between the tubing and the casing to recover each packer; the injection volume of the fracturing fluid is 1.5 times the volume of the annulus between the tubing and the casing to accelerate the dissolution of the dissolvable metal support rod of the special jetting centralizer; S9. Wait for the pressure to spread. During this process, the dissolvable metal support rod of the special jetting centralizer slowly dissolves.

[0074] S10. Depressurize the central hole channel, the double-layer multi-stage filtration fracturing hydraulic anchor 21 releases its anchoring, pull out the tubing string, and the fracturing is completed.

[0075] The diameters of soluble balls one to five increase successively. Tests in Well Huaxx showed that the combination of sleeve sandblaster + K344 packer and hydraulic jetting technologies each have their own advantages, solving the problem that it is difficult for hydraulic jetting technology to achieve complete interlayer isolation, and solving problems such as poor conventional fracturing effects in near-water thin interlayers.

[0076] The above are only the preferred and feasible embodiments of the present invention, which show and describe the basic principles, main features and advantages of the present invention. It does not limit the patent protection scope of the present invention thereby. Those skilled in the art should understand that the present invention is not limited by the above embodiments. Except for the above embodiments, without departing from the spirit and scope of the present invention, the present invention may have other implementation manners. The present invention will also have various changes and improvements. All technical solutions formed by using equivalent replacements or equivalent transformations fall within the protection scope required by the present invention. The protection scope required by the present invention is defined by the appended claims and their equivalents. The technical features not described in the present invention can be realized by or adopted the prior art, and will not be elaborated herein.

Claims

1. A perforating and fracturing mechanical packer integrated layered fracturing string, comprising a guide shoe located at the lower end of the string, with a shock absorber centralizer, a collar pressure gauge and a screen pipe connected in sequence above the guide shoe, characterized in that: A safety joint and a double-layer multi-stage filtering fracturing hydraulic anchor are successively connected to the lower end of the tubing string. A plurality of K344 packers and hydraulic jetting tools are provided between the screen pipe and the double-layer multi-stage filtering fracturing hydraulic anchor. Each packer is seated on the inner wall of the casing between adjacent formations, and each hydraulic jetting tool corresponds to an unperforated formation. At least one side of each hydraulic jetting tool is provided with a special jetting centralizer.

2. The perforating and fracturing mechanical packer integrated layered fracturing string according to claim 1, wherein: A sliding sleeve sandblaster corresponding to the perforated formation is also provided between the screen pipe and the double-layer multi-stage filtering fracturing hydraulic anchor.

3. The perforating and fracturing integrated mechanical packer layered fracturing string according to claim 2, wherein: A ball seat, a non-sliding sleeve hydraulic jetting tool, a first special jetting centralizer, a first sliding sleeve seat, a second special jetting centralizer, a first packer, a sliding sleeve sandblaster, a second sliding sleeve seat, a second packer, a first sliding sleeve hydraulic jetting tool, a third special jetting centralizer, a second sliding sleeve hydraulic jetting tool, a fourth special jetting centralizer, a third sliding sleeve seat, a third packer and a third sliding sleeve hydraulic jetting tool are successively arranged between the screen pipe and the double-layer multi-stage filtering fracturing hydraulic anchor from bottom to top.

4. The perforating and fracturing integrated mechanical packer layered fracturing string according to claim 3, characterized in that: The non-sliding sleeve hydraulic jetting tool corresponds to the first formation, the sliding sleeve sandblaster corresponds to the second formation, the first sliding sleeve hydraulic jetting tool and the second sliding sleeve hydraulic jetting tool correspond to the third formation, and the third sliding sleeve hydraulic jetting tool corresponds to the fourth formation.

5. The perforating and fracturing integrated mechanical packer zonal fracturing string according to claim 3, characterized in that: The outer diameter of the sliding sleeve inside the first packer, the outer diameter of the sliding sleeve inside the second packer, and the outer diameter of the sliding sleeve inside the sliding sleeve sandblaster are the same as the inner diameter of the second sliding sleeve seat.

6. The perforating and fracturing mechanical packer integrated layered fracturing string according to claim 3, characterized in that: The outer diameter of the sliding sleeve inside the first sliding sleeve hydraulic jetting tool, the outer diameter of the sliding sleeve inside the second sliding sleeve hydraulic jetting tool, the outer diameter of the sliding sleeve inside the second sliding sleeve hydraulic jetting tool, and the outer diameter of the sliding sleeve inside the third packer are the same as the inner diameter of the third sliding sleeve seat, and the inner diameter of the third sliding sleeve seat is the same as that of the second sliding sleeve seat.

7. The perforating and fracturing mechanical packer integrated zonal fracturing string according to claim 3, wherein: The sliding sleeves used in the second packer, the sliding sleeve sandblaster and the first packer include a sliding sleeve body, a sealing ring and a shear pin groove, and the shear pin groove is between the upper and lower sealing rings; a sliding sleeve blocking step is provided at the lower end of the central hole of the first sliding sleeve seat to block the sliding sleeve body.

8. The perforating and fracturing integrated mechanical packer layered fracturing string according to claim 3, characterized in that: The sliding sleeves in the first sliding sleeve hydraulic jetting tool and the second sliding sleeve hydraulic jetting tool include a sliding sleeve body, a sealing ring, a shear pin groove and a circlip, the shear pin groove is in the middle of the upper and lower sealing rings, and the circlip is embedded in the lower outer wall of the sliding sleeve body; the second sliding sleeve seat and the third sliding sleeve seat have the same shape, and an enlarged circlip groove is provided in the middle section of the central hole to lock the circlip of the second sliding sleeve.

9. The perforating and fracturing integrated mechanical packer layered fracturing string according to claim 1, characterized in that: The special jet centralizer includes a jet centralizer body. A plurality of body radial holes communicating with the central hole of the body are provided in the middle section of the jet centralizer body. Sealing pistons are respectively arranged in the body radial holes. A rectangular spring is embedded in a counterbore at the center of the outer end face of the sealing piston. The outer end of the rectangular spring abuts against the inner wall of the middle part of the gland. The outer periphery of the gland is screwed into a threaded hole at the outer port of the body radial hole. A soluble support rod is embedded in the central through hole of the gland. The inner end of the soluble support rod is screwed into a threaded hole at the center of the outer end face of the sealing piston. A jacket is embedded in the central hole of the body. An inner sleeve is nested in the jacket. The upper and lower ends of the inner sleeve respectively extend beyond the ports of the jacket. An upper body sealing ring is embedded at the upper end of the central hole of the body to seal the upper outer wall of the jacket. A lower body sealing ring is embedded at the lower end of the central hole of the body to seal the lower outer wall of the inner sleeve.

10. The perforating and fracturing integrated mechanical packer layered fracturing string according to claim 1, characterized in that: The double-layer multi-stage filtering fracturing hydraulic anchor includes a hydraulic anchor body. A plurality of anchor claw cavities communicating with the central hole are provided in the middle section of the hydraulic anchor body. Anchoring mechanisms are respectively installed in the anchor claw cavities. A jacket is embedded in the central hole of the hydraulic anchor body. An inner sleeve is nested in the jacket. The upper and lower ends of the inner sleeve respectively extend beyond the ports of the jacket. An upper body sealing ring is embedded at the upper end of the central hole of the hydraulic anchor body to seal the upper outer wall of the jacket. A lower body sealing ring is embedded at the lower end of the central hole of the hydraulic anchor body to seal the lower outer wall of the inner sleeve. A plurality of inner sleeve wire cutting slits are evenly arranged on the upper circumference of the inner sleeve and communicate with the inner wall gap of the jacket. A plurality of jacket wire cutting slits are evenly arranged on the lower circumference of the jacket and communicate with the inner wall gap of the central hole of the hydraulic anchor body.

11. The perforating and fracturing integrated mechanical packer layered fracturing string according to claim 10, characterized in that: The lower end of the inner sleeve abuts against an inner step in the central hole of the hydraulic anchor body. The outer diameter of the upper end outer wall of the inner sleeve expands to form a large end of the inner sleeve. An outer conical surface of the large end of the inner sleeve presses against the flared opening at the upper end of the central hole of the hydraulic anchor body. Each inner sleeve wire cutting slit extends to the top of the large end of the inner sleeve. The top of the large end of the inner sleeve is a plane and a circlip is pressed above it. The circlip is embedded in an inner wall annular groove of the central hole of the hydraulic anchor body.

12. The perforating and fracturing integrated mechanical packer stratified fracturing string according to claim 11, wherein: The upper part of the jacket abuts against the lower part of the root of the large end of the inner sleeve. The lower end of the jacket abuts against an inner step in the central hole of the hydraulic anchor body.

13. The perforating and fracturing integrated mechanical packer zonal fracturing string according to claim 10, wherein: The anchoring mechanism includes an anchoring piston, a pressure strip and a rectangular spring. The anchoring piston is embedded in the corresponding anchor claw cavity and is sealed with each other. Anchor claw teeth are provided on both sides of the outer end face of the anchoring piston. A rectangular spring is embedded in a counterbore at the center of the outer end face of the anchoring piston. The outer end of the rectangular spring abuts against the inner wall of the middle part of the pressure strip. The upper and lower ends of the pressure strip are respectively fixed on the hydraulic anchor body by fastening screws. Hard alloy teeth are respectively welded on each of the anchor claw teeth.

14. The perforating and fracturing integrated mechanical packer layered fracturing string according to claim 13, wherein: Three groups of the anchoring mechanisms are arranged along the height direction of the hydraulic anchor body. The anchor claw teeth of the three groups of anchoring mechanisms face upward, in the middle and downward from top to bottom.

15. The perforating and fracturing integrated mechanical packer layered fracturing string according to claim 10, wherein: The fit clearance between the inner sleeve and the jacket and the fit clearance between the jacket and the central hole of the hydraulic anchor body are both H10 / d10 or H10 / c10. The slit widths of the inner sleeve wire cutting slits and the jacket wire cutting slits are respectively 0.2 - 0.3 mm.

16. A fracturing operation method for multiple formations in old wells, characterized in that, Sequentially include the following steps: S1. Run a drift over the string with a lower drift collar and wash the well. S2. After the multi-functional fracturing string is lowered to the designed position, conduct reverse circulation well washing. S3. Drop soluble ball 1 into the tubing. The soluble ball 1 falls into the ball seat and seats. Apply pressure at the wellhead to open the non-sliding sleeve hydraulic jetting tool. The double-layer multi-stage filtering fracturing hydraulic anchor anchors the string. The support rods of all jetting special centralizers support on the inner wall of the casing. Then, perforate the first formation through the non-sliding sleeve hydraulic jetting tool and complete the fracturing of the first formation. S4. Drop soluble ball 2 into the tubing. Successively cut the shear pins of the sleeves in the second packer, sleeve sandblasting tool, and the first packer. The three sleeves jointly fall into the first slip sleeve seat and seat. The rubber barrels of the second packer and the first packer cut off the upper and lower annuli of the second formation. Then, conduct high-volume fracturing on the second formation. S5. Drop soluble ball 3 into the tubing. Successively cut the shear pins of the inner sleeves in the second sliding sleeve hydraulic jetting tool and the first sliding sleeve hydraulic jetting tool. The falling inner sleeve is locked by the second slip sleeve seat, sealing the central channel of the lower string. The second sliding sleeve hydraulic jetting tool and the first sliding sleeve hydraulic jetting tool perforate simultaneously, increase the displacement until the perforation of the third formation is completed. S6. Drop soluble ball 4 into the tubing. Cut the shear pin of the inner sleeve in the third packer. After the inner sleeve falls, it seats on the second slip sleeve seat, sealing the central channel of the lower string. The third packer and the second packer seat. Conduct high-volume fracturing through the second sliding sleeve hydraulic jetting tool and the first sliding sleeve hydraulic jetting tool until the fracturing of the third formation is completed. S7. Drop soluble ball 5 into the tubing. Cut the shear pin of the inner sleeve in the second sliding sleeve hydraulic jetting tool. After the inner sleeve falls, it seats on the third slip sleeve seat, sealing the central channel of the lower string. Then, conduct hydraulic sandblasting perforation on the fourth formation through the second sliding sleeve hydraulic jetting tool. After the perforation construction is completed, add sand and conduct fracturing simultaneously in the tubing and the tubing-casing annulus. After the fracturing is completed, close the wellhead. S8. Inject fracturing fluid from the annulus between the tubing and the casing to retrieve each packer. S9. Wait for the pressure to dissipate. During this process, the soluble metal support rods of the jetting special centralizers slowly dissolve. S10. Depressurize the central hole. The double-layer multi-stage filtering fracturing hydraulic anchor releases the anchoring. Pull out the string and the fracturing is completed.

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