A method for wellbore reconstruction and refracturing of a cased well
By using a wellbore reconstruction method, the wellbore is reconstructed using expansion tubing and variable-diameter expansion cones, and ultra-small diameter bridge plugs are installed. This solves the problems of casing deformation and difficulty in installing bridge plugs, achieving low-cost and high-efficiency repeated fracturing effects.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTHWEST PETROLEUM UNIV
- Filing Date
- 2023-05-17
- Publication Date
- 2026-07-10
AI Technical Summary
In existing technologies, the borehole plugging method cannot accurately control the flow of fracturing fluid and has poor plugging effect. Cement plugging is costly, leading to severe casing deformation, which affects shale gas downhole operations. In addition, conventional bridge plugs cannot be installed, making it difficult to achieve repeated fracturing.
By detecting casing deformation, the wellbore is reconstructed using expansion tubing and variable diameter expansion cones. Ultra-small diameter bridge plugs and bridge plug setting tools are then installed to achieve wellbore reconstruction and repeated fracturing, ensuring that the bridge plugs can be successfully set.
It reduced construction costs, improved the success rate of repeated fracturing, solved the problems of casing deformation and difficulty in running bridge plugs, and provided excellent wellbore conditions.
Smart Images
Figure CN116556914B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for wellbore reconstruction and repeated fracturing in casing-type wells, belonging to the field of oil and gas extraction technology. Background Technology
[0002] Shale gas and other unconventional oil and gas resources have been rapidly developed through hydraulic fracturing. However, as production time increases, the original fractures gradually close, leading to a rapid decline in production. Repeat fracturing is currently an effective technical solution to address the low production and inefficiency of unconventional oil and gas, and it also shows significant production enhancement effects on previously fractured wells. In repeat fracturing technology, the choice of different plugging methods has a significant impact on the repeat fracturing operation. Borehole plugging cannot plug long well sections and has the drawback of not being able to precisely control the flow of fracturing fluid, resulting in poor plugging effectiveness. Cement plugging is expensive and has low economic applicability. Therefore, there is an urgent need to develop a new plugging method that can overcome the shortcomings of current borehole and cement plugging methods to achieve the continuous and stable development of unconventional oil and gas resources. The fracturing process in shale gas wells easily leads to casing deformation. As the production depth gradually increases, the degree of casing deformation becomes more severe, making it increasingly difficult to run tools such as bridge plugs, seriously affecting shale gas well downhole operations.
[0003] To address the above issues, this paper proposes a wellbore reconstruction and repeated fracturing method for casing-type wells. This method can compensate for the deficiencies of borehole plugging and cement plugging, solve the problem that conventional bridge plugs cannot be installed, reduce construction costs, and improve the success rate of repeated fracturing operations, which has significant practical production implications. Summary of the Invention
[0004] In order to overcome the defects and limitations of the above-mentioned related technologies, the purpose of this invention is to provide a wellbore reconstruction and repeated fracturing method for casing-type wells. The method involved in this invention has a good sealing effect and provides high-quality wellbore conditions for subsequent perforation and repeated fracturing.
[0005] Therefore, the present invention provides a method for wellbore reconstruction and repeated fracturing in casing-type wells, comprising the following steps:
[0006] Step 1: Determine the deformation of the casing in the modified well using detection methods, locate the original perforated section of the casing, and clean the inner wall of the casing at the same time.
[0007] Step 2: Determine the dimensions of the expansion tube and the variable diameter expansion cone based on the casing deformation, and lower the expansion tube and the variable diameter expansion cone into the original perforation section casing position;
[0008] Step 3: Pressurize the casing to close the variable diameter expansion cone, and expand the expansion tube to the inner wall of the original perforated section of the casing to complete the wellbore reconstruction;
[0009] Step 4: Insert an ultra-small diameter bridge plug and a bridge plug setting tool into the reconstructed casing wellbore to complete the bridge plug setting;
[0010] Step 5: Perform perforation and repeated fracturing in the reconstructed wellbore.
[0011] As described above, in step one, a mechanical multi-arm caliper or an electromagnetic flaw detection logging tool is used to obtain the inner diameter of the casing, to understand the casing deformation in the casing-changing well, and to determine the location of the original perforated casing section using an electromagnetic flaw detection logging tool.
[0012] As described above, in step one, a casing scraper is used to scrape and clean the inner wall of the original perforation section of the casing multiple times to ensure that the expansion tube has sufficient suspension force after expansion.
[0013] As described above, in step two, the dimensions of the expansion tube and the variable diameter expansion cone are determined based on the minimum inner diameter of the casing in the original perforated section and the section to be opened first. After the expansion tube is connected, an anchoring device is installed on the expansion tube. The expansion tube and the variable diameter expansion cone are then lowered into the original perforated section casing position using drill pipe or tubing, and the expansion tube is anchored using the anchoring device.
[0014] As described in step two above, before the expansion operation, ensure that the drill pipe or tubing is filled with pressurized fluid. If there is air in the drill pipe or tubing, pressurized fluid is pumped into the drill pipe or tubing through a hydraulic pump to expel the air.
[0015] As described above, in step three, pressure is applied to the drill pipe or tubing to fully close the male and female cones of the variable diameter expansion cone. Then, the variable diameter expansion cone is driven to expand the expansion tube, suspending it on the cleaned inner wall of the casing, sealing the original perforated section, completing the wellbore reconstruction, and testing the original perforated section of the casing. If the casing can maintain stable pressure, the expansion and sealing operation is considered successful.
[0016] As described above, in step three, the male and female cones of the variable-diameter expansion cone achieve diameter change through a sliding groove structure. The ends of the male and female cones and the upper and lower ring caps are in contact with each other through inclined grooves. Before pressure expansion, the male and female cones are not fully closed, and the ends of the male and female cones are located at the lower part of the inclined groove. After pressure expansion, the male and female cones are fully closed along the sliding groove, and at the same time, the ends of the male and female cones slide from the lower part of the inclined groove to the upper part.
[0017] As described above, in step four, based on the casing deformation characteristics and repeated fracturing locations, an ultra-small diameter bridge plug and a bridge plug setting tool are inserted into the corresponding location in the reconstructed wellbore. The maximum outer diameter of the ultra-small diameter bridge plug is between 40 mm and 50 mm, ensuring that the bridge plug can pass through the location with the greatest casing deformation and smoothly reach the bridge plug setting position.
[0018] As described in step four above, after the ultra-small diameter bridge plug reaches the setting position, the bridge plug setting tool is used to set the bridge plug. The bridge plug setting structure opens and sits on the inner wall of the casing, and the bridge plug sealing structure expands to the inner wall of the casing, thus completing the bridge plug setting. The ultra-small diameter bridge plug material has soluble properties, so there is no need to drill or grind the bridge plug after fracturing.
[0019] As described in step five above, perforation and repeated fracturing are performed at the new location of the reconstructed wellbore.
[0020] As described above, in step two, the expansion tube is vulcanized and bonded with 6-12 sealing rubber rings. After the expansion tube is expanded, the sealing rubber rings are compressed and contact the inner wall of the sleeve to provide suspension force for the expansion tube.
[0021] As described above, the ultra-small diameter bridge plug in step four can adopt a double-cone expansion method. The first expansion cone enters and pushes the second expansion cone, and the second expansion cone enters and pushes the bridge plug sealing structure. The second expansion cone and the bridge plug sealing structure are expanded to achieve an ultra-large annular seal. The second expansion cone can adopt an integral structure or an incompletely divided structure. An incompletely divided structure refers to dividing the integral structure into blocks. The integral structure requires a larger expansion force than the incompletely divided structure.
[0022] As described above, the sealing structure of the ultra-small diameter bridge plug in step four can adopt a spiral sealing structure. After expansion, the spiral metal strips slip and stack radially, resulting in a large thickness change and achieving an ultra-large annular seal.
[0023] As can be seen from the technical solution provided by the present invention above, compared with the prior art, the present invention provides a method for wellbore reconstruction and repeated fracturing for casing-type wells, which can make up for the defects of borehole plugging and cement plugging, reduce construction costs, and improve the success rate of repeated fracturing operations, and has significant practical significance for production. Attached Figure Description
[0024] Figure 1 A flowchart of a wellbore reconstruction and repeated fracturing method for casing wells provided by the present invention;
[0025] Figure 2 This is a schematic diagram of the well conditions of the variable well.
[0026] Figure 3 This is a schematic diagram of the expansion tube installation.
[0027] Figure 4 This is a schematic diagram of the expansion operation;
[0028] Figure 5 Schematic diagram of the insertion of an ultra-small diameter bridge plug;
[0029] Figure 6 Schematic diagram of a small diameter bridge plug seat;
[0030] Figure 7 This is a schematic diagram of perforation and repeated fracturing.
[0031] Figure 8 This is a schematic diagram of a tapered expansion cone with a variable diameter.
[0032] Figure 9 This is a schematic diagram of an ultra-small diameter bridge plug; in the diagram: 1-formation, 2-original fracture, 3-casing, 4-expansion tube, 5-ultra-small diameter bridge plug, 6-new fracture, 7-upper ring cap, 8-male cone, 9-female cone, 10-lower ring cap, 11-expansion cone, 12-spiral sealing structure, 13-setting seal structure, 14-protective head. Detailed Implementation
[0033] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.
[0034] As shown in the accompanying drawings, the present invention provides a method for wellbore reconstruction and repeated fracturing in casing-type wells, comprising the following steps:
[0035] Step 1: Determine the deformation of the casing in the modified well using detection methods, locate the original perforated section of the casing, and clean the inner wall of the casing at the same time.
[0036] Step 2: Determine the dimensions of the expansion tube and the variable diameter expansion cone based on the casing deformation, and lower the expansion tube and the variable diameter expansion cone into the original perforation section casing position;
[0037] Step 3: Pressurize the casing to close the variable diameter expansion cone, and expand the expansion tube to the inner wall of the original perforated section of the casing to complete the wellbore reconstruction;
[0038] Step 4: Insert an ultra-small diameter bridge plug and a bridge plug setting tool into the reconstructed casing wellbore to complete the bridge plug setting;
[0039] Step 5: Perform perforation and repeated fracturing in the reconstructed wellbore.
[0040] In step one, specifically, the measuring arm of the mechanical multi-arm caliper contacts the inner wall of the casing to obtain the well circumference radius. The relationship between the change of the caliper measuring arm and the change of the inner wall of the casing is established to obtain the inner diameter of the casing, understand the damage such as misalignment, twisting, and deformation of the casing, and record the deformation of the original perforated section and the first section of the casing.
[0041] In step one, specifically, an electromagnetic flaw detection logging tool is used to determine the location of the original perforated section of the casing. The casing condition is studied based on the electromagnetic effect caused by the metal defects of the casing. For example, the thicker the casing, the slower the propagation speed and the smaller the amplitude of the electromagnetic wave, while the thinner the casing, the opposite is true. This allows us to understand the corrosion, pores, and cracks inside and outside the casing and record the accurate location of the casing fracturing section.
[0042] In step one, specifically, the casing of the expansion tube plugging section is scraped multiple times by lowering the coiled tubing and casing scraper. Well washing fluid with a displacement of 1.2-1.6 m3 / min is used as the medium for circulation, thereby achieving a comprehensive cleaning of the inner wall of the casing of the expansion tube plugging section, ensuring that the outer rubber ring of the expansion tube can be stably suspended on the inner wall of the casing after expansion.
[0043] In step two, specifically, based on the minimum inner diameter of the casing in the original perforated section and the section opened first, and the required suspension force of the expansion tube, the outer diameter of the expansion tube and the number, length, and thickness of the sealing rubber rings vulcanized on the outside of the expansion tube are determined.
[0044] In step two, specifically, the expansion tube material and wall thickness are selected based on the maximum wellbore pressure during subsequent perforation and repeated fracturing operations.
[0045] In step two, specifically, the outer diameter of the variable diameter expansion cone before diameter change is determined based on the minimum inner diameter of the expansion tube, and the outer diameter of the variable diameter expansion cone after diameter change is determined based on the expansion rate of the expansion tube.
[0046] In step two, specifically, after the expansion tube and its supporting equipment are installed, an anchoring device is installed on the expansion tube. Then, the expansion tube and the variable diameter expansion cone are lowered into the drill pipe or tubing to allow them to pass smoothly through the casing deformation section and into the original perforation section casing position. Finally, the expansion tube is anchored with the anchoring device.
[0047] In step three, specifically, before the expansion tube expansion operation, ensure that the drill pipe or tubing is filled with pressurized fluid. If there is air in the drill pipe or tubing, pressurized fluid is pumped into the drill pipe or tubing through a hydraulic pump to expel the air.
[0048] In step three, specifically, by pressurizing the drill pipe or tubing, the male and female cones of the variable diameter expansion cone are first fully closed, and then the variable diameter expansion cone is driven to expand the expansion tube, so that the expansion tube is suspended on the inner wall of the cleaned casing, sealing the original perforation section and completing the wellbore reconstruction.
[0049] In step three, specifically, there are 3-4 male and female cones of the variable diameter expansion cone. The male and female cones of the variable diameter expansion cone achieve diameter change through a sliding groove structure. The ends of the male and female cones contact the upper and lower ring caps through inclined grooves. Before pressure expansion, the male and female cones are not fully closed, and the ends of the male and female cones are located at the lower part of the inclined groove. After pressure expansion, the male and female cones are fully closed along the sliding groove, and at the same time, the ends of the male and female cones slide from the lower part of the inclined groove to the upper part.
[0050] In step three, specifically, after the expansion operation is completed, the original perforated section of the casing is pressure tested. If the casing can stabilize the pressure, the expansion and sealing operation is considered successful. The specific test qualification standard is that the pressure drop is less than 1 MPa for 30 minutes at 75 MPa.
[0051] In step four, specifically, based on the casing deformation characteristics and repeated fracturing locations, ultra-small diameter bridge plugs and bridge plug setting tools are inserted into the corresponding positions in the reconstructed wellbore. The maximum outer diameter of the ultra-small diameter bridge plug is between 40 mm and 50 mm, ensuring that the bridge plug can pass through the locations with large casing deformation and smoothly reach the bridge plug setting position.
[0052] In step four, specifically, after the ultra-small diameter bridge plug reaches the setting position, a bridge plug setting tool is used to set the bridge plug. The bridge plug setting structure opens and sits on the inner wall of the casing, and the bridge plug sealing structure spirals open to the inner wall of the casing, thus completing the bridge plug setting.
[0053] In step four, specifically, the ultra-small diameter bridge plug has soluble properties, so there is no need to drill or grind the bridge plug after fracturing;
[0054] In step four, specifically, the ultra-small diameter bridge plug can adopt a double-cone expansion method. The first expansion cone enters and pushes the second expansion cone, and the second expansion cone enters and pushes the bridge plug sealing structure. The second expansion cone and the bridge plug sealing structure are expanded to achieve an ultra-large annular seal. The second expansion cone of the ultra-small diameter bridge plug can adopt an integral structure or an incompletely divided structure. The incompletely divided structure refers to dividing the integral structure into 4-6 pieces. The integral structure requires a larger expansion force than the incompletely divided structure.
[0055] In step four, specifically, the sealing structure of the ultra-small diameter bridge plug can adopt a spiral sealing structure. After expansion, the spiral metal strips slide and stack radially, resulting in a large thickness change, thereby achieving an ultra-large annular seal. The number of spiral metal strips is 3-6.
[0056] In step five, specifically, the casing is perforated using a perforating gun at the new location of the reconstructed wellbore.
[0057] In step five, specifically, after the perforation operation is completed, the formation is repeatedly fracturing. Fracturing refers to a method of creating fractures in oil and gas reservoirs by using hydraulic action during oil or gas production. It includes various fracturing methods such as flow-limited layered fracturing, packer layered fracturing, and selective fracturing with plugging balls.
[0058] The specific embodiments of the invention described herein are for illustrative purposes only and should not be construed as limiting the invention in any way. Under the teachings of this invention, those skilled in the art can conceive of any possible variations based on the invention, all of which should be considered within the scope of the invention. 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 application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
Claims
1. A method for wellbore reconstruction and repeated fracturing in casing-type wells, characterized in that, Includes the following steps: Step 1: Determine the deformation of the casing in the modified well using detection methods, locate the original perforated section of the casing, and clean the inner wall of the original perforated section of the casing. Step 2: Determine the dimensions of the expansion tube and the variable diameter expansion cone based on the deformation of the casing in the variable well, and lower the expansion tube and the variable diameter expansion cone into the original perforated section of the casing. Step 3: Pressurize the casing to close the variable diameter expansion cone, and expand the expansion tube to the inner wall of the original perforated section of the casing to complete the wellbore reconstruction; Step 4: Insert the ultra-small diameter bridge plug and bridge plug setting tool into the reconstructed wellbore to complete the bridge plug setting; Step 5: Perform perforation and repeated fracturing in the reconstructed wellbore; In step two, the dimensions of the expansion tube and the variable diameter expansion cone are determined based on the minimum inner diameter of the casing of the variable well. After the expansion tube is connected, an anchoring device is installed on the expansion tube. The expansion tube and the variable diameter expansion cone are lowered into the original perforated section casing position using drill pipe or tubing, and the expansion tube is anchored with the anchoring device. Before the expansion operation, step three ensures that the drill pipe or tubing is filled with pressurized fluid. If there is air in the drill pipe or tubing, pressurized fluid is pumped into the drill pipe or tubing through a hydraulic pump to expel the air. Step three involves pressurizing the drill pipe or tubing to first fully close the male and female cones of the variable diameter expansion cone, then driving the variable diameter expansion cone to expand the expansion tube, suspending the expansion tube on the inner wall of the original perforated section of the casing after cleaning, sealing the original perforated section, completing the wellbore reconstruction, and testing the original perforated section of the casing. If the casing can stabilize the pressure, the expansion and sealing operation is considered successful. In step four, based on the casing deformation characteristics and repeated fracturing locations of the modified well casing, an ultra-small diameter bridge plug and a bridge plug setting tool are inserted into the corresponding positions of the reconstructed wellbore. The maximum outer diameter of the ultra-small diameter bridge plug is between 40 mm and 50 mm, ensuring that the bridge plug can pass through the locations with large casing deformation and smoothly reach the bridge plug setting position. In step four, after the ultra-small diameter bridge plug reaches the setting position, the bridge plug setting tool is used to set the bridge plug. The bridge plug setting structure opens and sits on the inner wall of the reconstructed wellbore. The bridge plug sealing structure expands to the inner wall of the reconstructed wellbore, completing the bridge plug setting. The ultra-small diameter bridge plug material has soluble properties, so there is no need to drill or grind the bridge plug after fracturing.
2. The method for wellbore reconstruction and repeated fracturing for casing-type wells according to claim 1, characterized in that, Step one involves using a mechanical multi-arm caliper or an electromagnetic flaw detection logging tool to obtain the inner diameter of the casing in the casing-variable well, to understand the deformation of the casing in the casing-variable well, and to use an electromagnetic flaw detection logging tool to determine the location of the original perforated section of the casing.
3. The method for wellbore reconstruction and repeated fracturing in a casing-type well according to claim 1, characterized in that, In step one, a casing scraper is used to scrape and clean the inner wall of the original perforation section of the casing multiple times to ensure that the expansion tube has sufficient suspension force after expansion.
4. The method for wellbore reconstruction and repeated fracturing for casing-type wells according to claim 1, characterized in that, Step five involves perforation and repeated fracturing at the new location of the reconstructed wellbore.