Method for improving repeated fracturing efficiency of horizontal well and fracturing pipe column structure

Abstract

The present application belongs to the field of oil production engineering, and specifically discloses a method for improving the efficiency of repeated fracturing of horizontal wells and a fracturing pipe string structure, comprising: a wellhead, a first oil pipe, a second oil pipe, a safety joint, a hydraulic anchor, a releasing packer and a check valve; the fracturing pipe string structure is lowered into a perforated section in the horizontal well, and step-by-step fracturing construction is performed, the releasing packer in the fracturing pipe string structure is used to release the horizontal well after repeated fracturing, the upper pipe string is pulled out, the post-fracturing blowout link is avoided, the construction efficiency is greatly improved, the fracturing fluid can more fully supplement the formation energy, the effective period of repeated fracturing of the horizontal well is prolonged, and the problems of long single-stage blowout pressure relief time and large liquid volume in the repeated fracturing process are solved.

Description

Technical Field

[0001] This invention belongs to the field of oil production engineering, specifically relating to a method for improving the efficiency of repeated fracturing in horizontal wells and a fracturing tubing structure. Background Technology

[0002] Ultra-low permeability reservoirs have low matrix permeability (<1.0×10⁻⁶). -3 um 2 Horizontal well staged fracturing has been applied on a large scale in ultra-low permeability blocks, improving single-well production. However, with the extension of horizontal well development time, some horizontal wells experience low production, mainly due to factors such as low initial stimulation and reduced conductivity of the fracture system. Repeated fracturing is necessary to restore single-well production and improve development results. Currently, repeated fracturing technology for horizontal wells is challenging and the process is immature. The main process is the double-seal single-pack repeated fracturing process, which uses tubing and packers to seal the target section and achieves targeted fracturing through tubing injection. The disadvantage is that the tubing string is dragged during operation, and after fracturing one section, pressure must be released before dragging the tubing string to construct the next section. As the parameters of repeated fracturing operations increase, the disadvantages of the double-seal single-card process are further amplified. Currently, the blowout time after a single-stage operation is more than 24 hours, causing the pressure to drop to 0 MPa. Then, the tubing is pulled up to the next modification stage. During the blowout process, the high-speed sand-carrying fluid will severely erode the tubing and tools, forming erosion damage. After completing two stages of fracturing operations, it is necessary to pull out the drill and replace the fracturing tools. The labor intensity is high, and it takes an average of 4 days to complete one stage of fracturing, resulting in low construction efficiency. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method and fracturing string structure for improving the efficiency of repeated fracturing of horizontal wells, so as to solve the problem of low construction efficiency due to the need for blowout relief after repeated fracturing of horizontal wells.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] In a first aspect, the present invention provides a fracturing tubing string structure, comprising: a wellhead, a first tubing, a second tubing, a safety joint, a hydraulic anchor, a release packer, and a check valve; the wellhead is connected to one end of the first tubing, the other end of the first tubing is connected to one end of the second tubing via a variable coupling, the other end of the second tubing is connected to one end of the safety joint via a variable coupling, the other end of the safety joint is connected to one end of the hydraulic anchor, the other end of the hydraulic anchor is connected to one end of the release packer, and the other end of the release packer is connected to the check valve.

[0006] Furthermore, the wellhead is a KQ1050 type wellhead, the first tubing is a 4" couplingless tubing, and the second tubing is a 3" type. 1 / 2″ couplingless oil pipe.

[0007] Furthermore, the release packer is an erosion-resistant release packer; the check valve is a sliding flap check valve.

[0008] Secondly, the present invention provides a method for improving the efficiency of repeated fracturing in horizontal wells, comprising the following steps:

[0009] S1: Pull out the production tubing from the horizontal well, circulate the well to the bottom of the artificial well, and perform reverse circulation well flushing;

[0010] S2: Densify the fabric seams and use a casing scraper to scrape down to the bottom of the artificial well.

[0011] S3: The fracturing string structure as described in any one of claims 1-3 is inserted into the first perforation section. The fracturing string structure, from top to bottom, consists of: wellhead, first tubing, second tubing, safety joint, hydraulic anchor, drop packer, and check valve.

[0012] S4: Sliding water is injected through the tubing for low displacement, the packer is released and set, and pre-fracturing fluid, sand-carrying fluid and displacement fluid are injected to complete the first stage of fracturing construction;

[0013] S5: A resin ball is dropped into the wellhead. The resin ball falls into the erosion-resistant ball seat. The pressure is increased, and the packer is released to release the tubing string above the packer. The upper tubing string is then pulled out.

[0014] S6: Insert the fracturing tubing structure as described in any one of claims 1-3 into the second perforation section;

[0015] S7: Second stage of fracturing operation, repeat steps S3-S5, fracturing the remaining perforation section;

[0016] S8: Well pressure enhancement for 30-40 days;

[0017] S9: Remove the packer from the wellbore and flush the well with sand down to the bottom of the artificial well;

[0018] S10: Run the production tubing and complete the well.

[0019] Furthermore, the specific steps of the reverse circulation well washing are as follows: inject clean water in a large volume through the casing, reverse circulation well washing, until the water quality at the inlet and outlet is consistent.

[0020] Furthermore, the specific steps for densifying the fracturing pattern and scraping to the bottom of the artificial well using a casing scraper are as follows: based on the location of the initial fracturing section of the horizontal well, densify the fracturing pattern to ensure that the spacing between each section after densification is more than 20m, perform hole filling operation, and scrape to the bottom of the artificial well using a casing scraper.

[0021] Furthermore, the injection rates of the pre-fluid, sand-carrying fluid, and displacement fluid in S4 are 8m. 3 / min.

[0022] Furthermore, the diameter of the resin ball in S5 is 40 mm.

[0023] Furthermore, the resin balls fall into the erosion-resistant ball seat, the pressure is increased, and the upper tubing of the release packer is released. The specific steps for removing the upper tubing are as follows: using a 0.5-1.0m... 3 The resin balls are pumped at a displacement of / min, and the balls fall into the erosion-resistant ball seat. The pressure is increased to more than 7MPa, and the packer and the upper tubing are released, allowing the upper tubing to be removed.

[0024] Furthermore, the time for well pressure expansion in S8 is 30-40 days.

[0025] The present invention has at least the following beneficial effects:

[0026] 1. This invention involves running a fracturing tubing string into the perforated section of a horizontal well for segmented fracturing. By using a release packer in the fracturing tubing string, the upper tubing string can be retrieved after repeated fracturing of the horizontal well, avoiding the post-fracturing blowout stage and greatly improving construction efficiency. At the same time, it allows the fracturing fluid to more fully replenish formation energy, extending the effective period of repeated fracturing of the horizontal well. This solves the problems of long single-stage blowout pressure relief time and large fluid volume in repeated fracturing processes.

[0027] 2. The present invention involves suffocating the well and expanding the pressure for 30-40 days, so that the fluid flow pattern changes from linear flow in the fracture to linear flow or radial flow in the formation, thereby minimizing the amount of fluid returned from the formation during the sand flushing process after suffocation.

[0028] 3. This invention employs a erosion-resistant drop-out packer. The inner side of the drop-out packer's ball seat is treated with a tungsten carbide alloy coating to enhance its erosion resistance. A sliding-sleeve flap-type single-flow valve is used to prevent the backflow of fluid injected into the fracture. It has broad application prospects in repeated fracturing of low-yield horizontal wells in low-permeability reservoirs, improving the development effect of horizontal wells, and enhancing oil recovery. Attached Figure Description

[0029] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1 This is a schematic diagram of a fracturing tubing string structure;

[0031] Figure 2 This is a production curve diagram for Example 1.

[0032] Attached reference numerals: 1. Wellhead; 2. First tubing; 3. Second tubing; 4. Safety joint; 5. Hydraulic anchor; 6. Release packer; 7. Check valve. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0034] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0035] A method for improving the efficiency of repeated fracturing in horizontal wells includes the following steps:

[0036] S1: Pull out the production tubing of the horizontal well, open the well to the bottom of the artificial well, inject clean water through the casing at a large flow rate, reverse circulation to flush the well, and flush the well until the water quality at the inlet and outlet is consistent;

[0037] S2: Based on the location of the initial fracturing section of the horizontal well, the fracturing density is increased to ensure that the spacing between each section after the density is increased is more than 20m. The hole filling operation is carried out by using a casing scraper to scrape down to the bottom of the artificial well.

[0038] S3: As Figure 1 As shown, the fracturing string structure is lowered to the first perforation section. The fracturing string structure from top to bottom is: wellhead 1, first tubing 2 (20m above the build-up point), variable thread, second tubing 3, variable thread, safety joint 4, hydraulic anchor 5, drop packer 6, check valve 7.

[0039] S4: Slippery water is injected through the oil pipe to replace the low displacement, and the packer 6 is set at 8m. 3 Inject pre-fracturing fluid, proppant-carrying fluid, and displacement fluid at an injection rate of / min to complete the first stage of fracturing construction;

[0040] S5: Insert 40mm resin balls into the wellhead, using a depth of 0.5-1.0m. 3 The resin balls are pumped at a displacement of / min, and the balls fall into the erosion-resistant ball seat. The pressure is increased to more than 7MPa, and the release packer 6 or more tubing is released, and the upper tubing is removed.

[0041] S6: Run the fracturing string structure to the second perforation section. The fracturing string structure from top to bottom is: wellhead 1, first tubing 2 (20m above the build-up point), changeover, second tubing 3, changeover, safety joint 4, hydraulic anchor 5, drop packer 6, check valve 7.

[0042] S7: Second stage of fracturing operation, repeat steps S3-S5, fracturing the remaining perforation section;

[0043] S8: Well pressure enhancement for 30-40 days;

[0044] S9: Remove the packer 6 from the wellbore and flush the well with sand down to the bottom of the artificial well;

[0045] S10: Run the production tubing and complete the well.

[0046] A fracturing tubing string structure includes: a wellhead 1, a first tubing 2, a second tubing 3, a safety joint 4, a hydraulic anchor 5, a release packer 6, and a check valve 7. The wellhead 1 is connected to one end of the first tubing 2, the other end of the first tubing 2 is connected to one end of the second tubing 3 via a variable coupling, the other end of the second tubing 3 is connected to one end of the safety joint 4 via a variable coupling, the other end of the safety joint 4 is connected to one end of the hydraulic anchor 5, the other end of the hydraulic anchor 5 is connected to one end of the release packer 6, and the other end of the release packer 6 is connected to the check valve 7.

[0047] Wellhead 1 is a KQ1050 type wellhead, the first tubing 2 is a 4" uncoupling tubing, and the second tubing 3 is a 3" type. 1 / 2″ couplingless oil pipe.

[0048] The drop-off packer 6 is an erosion-resistant drop-off packer. Conventional drop-off packers are insufficient for high-volume, high-proppant fracturing operations. This is primarily because the large volume of proppant-laden fracturing fluid passing through the packer's ball seat causes abrasion and erosion, resulting in an irregular ball seat, poor sealing, and ultimately, drop-off failure. To meet the requirement of over 200 cubic meters of proppant per stage of fracturing, the inner side of the drop-off packer's ball seat is treated with a tungsten carbide alloy coating to enhance erosion resistance.

[0049] The check valve 7 is a sliding flap check valve to prevent the liquid injected into the fracture from flowing back out.

[0050] After the ball is dropped, the packer 6 and the upper tubing string are released, and the upper tubing string is retrieved. This section of fracturing is completed. By using the packer 6, the post-fracturing blowout stage is avoided, which greatly improves the construction efficiency. At the same time, it allows the fracturing fluid to more fully replenish the formation energy and extends the effective period of repeated fracturing of the horizontal well.

[0051] "Break closure and pressure diffusion for 30-40 days" refers to the diffusion of formation pressure, and the fluid flow pattern changes from linear flow in the fractures to linear flow or radial flow in the formation, minimizing the amount of fluid returned from the formation during the sand flushing process after well closure.

[0052] Example 1

[0053] A method for improving the efficiency of repeated fracturing in horizontal wells includes the following steps:

[0054] S1: Pull out the production tubing of the horizontal well, open the well to the bottom of the artificial well, inject clean water through the casing at a large flow rate, reverse circulation to flush the well, and flush the well until the water quality at the inlet and outlet is consistent;

[0055] S2: The horizontal well was initially modified in 9 sections. Based on the location of the initial fracturing section of the horizontal well, the fracturing was densified to ensure that the spacing between each section after densification was more than 20m. 7 sections were repaired by using a casing scraper to scrape down to the bottom of the artificial well.

[0056] S3: As Figure 1 As shown, the fracturing string structure is run down to the first perforation section (2883.0m). The fracturing string structure from top to bottom is: KQ1050 wellhead, 4" couplingless tubing (20m above the build-up point), variable thread, 3 1 / 2″ couplingless oil pipe, variable coupling, safety joint 4, hydraulic anchor 5, erosion-resistant release packer, sliding flap check valve; the length of the 4" couplingless oil pipe is 1780.0m; the length of the erosion-resistant release packer is 2878.0m.

[0057] S4: From the oil pipe at a distance of 2m 3 / min displacement injection slickwater low displacement, erosion resistant drop packer setting, with 8m 3 Inject pre-fracturing fluid, sand-carrying fluid and displacement fluid at a displacement of / min to complete the first stage of fracturing construction;

[0058] S5: Insert 40mm resin balls into the wellhead, using a depth of 0.5-1.0m. 3 The resin balls are pumped at a displacement of / min. The balls fall into the erosion-resistant ball seat and the pressure is increased to 9MPa. The tubing above the erosion-resistant release packer is released and the upper tubing is removed.

[0059] S6: The fracturing string structure is lowered to the second perforation section (2861.0m). The fracturing string structure (from top to bottom) includes: KQ1050 wellhead, 4" couplingless tubing, variable thread, and 3... 1 / 2″ couplingless tubing, adapter, safety connector, hydraulic anchor, erosion-resistant release packer, sliding flap check valve; 4" couplingless tubing is 1780.0m long; erosion-resistant release packer is 2856.0m long.

[0060] S7: Second stage of fracturing, repeat steps S3-S5, fracturing 14 stages remaining;

[0061] S8: Well pressure enhancement for 35 days;

[0062] S9: Remove the erosion-resistant drop packer from the wellbore, run in a slanted tip + Φ73mm tool tubing well washing string, flush the well with sand to the artificial bottom of the well;

[0063] S10: Pull out the well washing tubing, run in the production tubing, and complete the well production. (Example:) Figure 2 The figure shown is a production curve of Example 1.

[0064] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for improving the efficiency of repeated fracturing in horizontal wells, characterized in that, Includes the following steps: S1: Pull out the production tubing from the horizontal well, circulate the well to the bottom of the artificial well, and perform reverse circulation well flushing; S2: Densify the fabric seams and use a casing scraper to scrape down to the bottom of the artificial well. S3: Lower the fracturing tubing string into the first perforation section; The fracturing string structure includes a wellhead (1), a first tubing (2), a second tubing (3), a safety joint (4), a hydraulic anchor (5), a release packer (6), and a check valve (7); the wellhead (1) is connected to one end of the first tubing (2), the other end of the first tubing (2) is connected to one end of the second tubing (3) via a variable thread, the other end of the second tubing (3) is connected to one end of the safety joint (4) via a variable thread, the other end of the safety joint (4) is connected to one end of the hydraulic anchor (5), the other end of the hydraulic anchor (5) is connected to one end of the release packer (6), and the other end of the release packer (6) is connected to the check valve (7); S4: Inject slickwater into the tubing for low displacement, release the packer (6) to set, and inject pre-flush fluid, sand-carrying fluid and displacement fluid to complete the first stage of fracturing construction; S5: Resin balls are dropped into the wellhead and fall into the erosion-resistant ball seat. The pressure is increased and the packer (6) is released to release the tubing string above it. The upper tubing string is then removed. The fracturing operation of this section is completed. The release of the blowout after fracturing is avoided by using the packer (6). S6: Lower the fracturing tubing string to the second perforation section; S7: Second stage of fracturing operation, repeat steps S3-S5, fracturing the remaining perforation section; S8: Well pressure enhancement for 30-40 days; S9: Remove the packer (6) from the wellbore and flush the well with sand to the bottom of the artificial well; S10: Run the production tubing and complete the well.

2. The method for improving the efficiency of repeated fracturing in horizontal wells according to claim 1, characterized in that, The wellhead (1) is a KQ1050 type wellhead, the first tubing (2) is a 4" uncoupling tubing, and the second tubing (3) is a 3" type. 1 / 2″ couplingless oil pipe.

3. The method for improving the efficiency of repeated fracturing in horizontal wells according to claim 1, characterized in that, The release packer (6) is an erosion-resistant release packer; the one-way valve (7) is a sliding flap one-way valve.

4. The method for improving the efficiency of repeated fracturing in horizontal wells according to claim 1, characterized in that, The specific steps of the reverse circulation well washing are as follows: inject clean water in a large volume through the casing, reverse circulate the well, and wash the well until the water quality at the inlet and outlet is consistent.

5. The method for improving the efficiency of repeated fracturing in horizontal wells according to claim 1, characterized in that, The specific steps for densifying the fractures and scraping to the bottom of the artificial well using a casing scraper are as follows: based on the location of the initial fracturing section of the horizontal well, densify the fractures to ensure that the spacing between each section after densification is more than 20m, perform hole filling operation, and scrape to the bottom of the artificial well using a casing scraper.

6. The method for improving the efficiency of repeated fracturing in horizontal wells according to claim 1, characterized in that, In step S4, the injection rates of the pre-fluid, sand-carrying fluid, and displacement fluid are 8m. 3 / min.

7. The method for improving the efficiency of repeated fracturing in horizontal wells according to claim 1, characterized in that, The resin ball in S5 has a diameter of 40 mm.

8. The method for improving the efficiency of repeated fracturing in horizontal wells according to claim 1, characterized in that, The resin ball falls into the erosion-resistant ball seat, the pressure is increased, and the release packer (6) above the tubing is released. The specific steps for removing the upper tubing are as follows: using 0.5-1.0m 3 The resin ball is pumped at a displacement of / min. The resin ball falls into the erosion resistant ball seat and the pressure is increased to more than 7MPa. The packer (6) and the upper tubing are released and the upper tubing is removed.

9. The method for improving the efficiency of repeated fracturing in horizontal wells according to claim 1, characterized in that, The time for well pressure expansion in step S4 is 30-40 days.

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