A horizontal well bore reconstruction refracturing process method

Abstract

The present application relates to the technical field of well repair operation, in particular to a horizontal well wellbore reconstruction and repeated fracturing process method.The process method of the present application is integrated with fracture leakage reduction, wellbore reconstruction and soluble bridge plug multi-layer fracturing technology, and a new technology for precise repeated fracturing reconstruction of horizontal wells is proposed, which mainly injects leakage reduction agent into the original fracture through the tubing to temporarily block the original fracture, and then performs staged fracturing after cementing the wellbore reconstruction pipe column from the tubing, and one pipe column is used to complete all the layers that need to be reconstructed, which meets the requirements of horizontal well reconstruction, large displacement, large sand volume, large liquid volume and precise target layer fracturing, thereby improving the development effect of old oil fields.

Description

Technical Field

[0001] This invention relates to the field of well workover technology, specifically to a method for repeated fracturing and rebuilding of a horizontal wellbore. Background Technology

[0002] Horizontal wells are an important oilfield development technology. Unlike vertical wells, horizontal wells have a large drainage area and high single-well production. However, horizontal well profile testing (water finding) data is limited, and the water-producing layers are unclear, making water shut-off in horizontal wells quite difficult. This is especially true for early-stage horizontal wells, which initially employed hydraulic jet fracturing in stages. These stages were small, with low flow rates and limited scale, and were affected by poor reservoir properties and well-developed natural fractures, leading to an accelerated decline in formation energy. For water shut-off in ultra-low permeability reservoirs, water typically emerges from fractures. Polymer plugging and bridge plug staged water shut-off methods are used, resulting in a decrease in both fluid and oil production after shut-off. To improve the development efficiency of horizontal wells, a method of repeated fracturing tests using 4.5-inch uncoupled casing horizontal wells within 5.5-inch casing was proposed. This involved inter-cluster re-perforation at locations with high remaining potential between existing clusters, and in-situ re-perforation at locations where existing clusters were unused or had low utilization, achieving the goal of re-modifying both old and new clusters.

[0003] The conventional wellbore reconstruction and repeated fracturing construction method mainly involves running tubing into the original casing, using biodegradable plugging particles to physically and chemically seal the existing horizontal well fractures, then injecting a high-strength drillable plugging agent to seal the blast holes, and after curing, running drilling tools to drill and grind the plugging agent in the wellbore to restore the inner diameter of the wellbore.

[0004] During repeated fracturing, the first drillable bridge plug and perforating gun are pumped down to the location of the first new fracture. The perforating gun is controlled to perform perforation, while the perforating gun separates from the first drillable bridge plug and the first drillable bridge plug is set. Then the perforating gun is pulled out, and casing injection fracturing is performed. The above process is repeated to complete all the sections that need to be modified.

[0005] Patent application number 201910160999.9, entitled "Method for Repeated Fracturing and Wellbore Reconstruction in Horizontal Wells," discloses a construction method. This method involves first injecting water to replenish the deficient formation, then running tubing, inserting elastic particles into the fractures of the original perforated section, followed by cement, and finally inserting a drillable plugging material primarily composed of barite, fly ash, and calcareous clay. This solidifies and seals the fracture openings near the wellbore outside the casing and the locations of external casing run-out. After shut-in and allowing solidification, a drill plug is run in for drilling and grinding, and the material is circulated to the surface using fluid, at which point wellbore reconstruction is complete. The advantages of this method are: simple process, restoration of the wellbore's internal diameter, and effective prevention of tool burial due to casing run-out. The disadvantage is that it cannot meet the process requirements of repeated fracturing, where the fractured section withstands pressures of 40-50 MPa for multiple extended periods.

[0006] Patent No. 201710910603.9, the invention name is "a kind of horizontal well re-fracturing method", a construction method is disclosed, the difference between the outer diameter of the oil pipe and the inner diameter of the casing is 30-40mm, under the condition of ensuring that the wellbore can establish normal circulation, injection of temporary plugging agent in the annulus between oil pipe and casing, the oil casing annulus of horizontal section is cemented, the well is closed for condensation, then the oil pipe is tested at 15MPa, the pressure drop is not greater than 0.7MPa for 30 minutes, which is qualified. The first section of horizontal well is re-fractured in the oil pipe, and the interlayer packer and perforation combined technology is used for segmented fracturing after fracturing. After fracturing, break the gelatinous agent from the oil pipe and the oil casing annulus, and take out the oil pipe after the temporary plugging agent is broken to restore the production of horizontal well. The advantages of this scheme are simple process, wellbore diameter recovery, and the disadvantages are that it cannot prevent the tool from being buried by sand outside the casing, and the control degree of the fracture is low. This scheme cannot meet the process requirements of repeated fracturing for many times and long time pressure resistance of 40-50MPa.

[0007] An expansion pipe re-fracturing technology is also discussed in the existing literature. The expansion pipe fracturing technology is a secondary well completion using expansion pipe (corrugated pipe) and pipe external packer, which realizes similar new well segmented multi-cluster reconstruction by means of small bridge plug. Its advantages are that it can repair the original wellbore, and the re-fracturing can realize accurate control of the fracture. Its technical defects are: the downhole tool of expansion pipe is complex, the technical difficulty is high, and the operation risk is high. There is also a permanent plugging fracturing technology in the existing literature, which is aimed at insufficient primary reconstruction, especially for horizontal wells with large interlayer distance. The common operation mode is to plug the old hole with cement, then drill the cement plug, and then implement the bridge plug and perforation combined operation from the toe to the heel of the horizontal section. Its advantages are that it can plug the original fracture and perforation hole, and the re-fracturing can realize accurate control of the fracture. Its technical defects are: the control difficulty of secondary cementing technology is high, and the operation risk of cementing and drilling plug is high. SUMMARY

[0008] The purpose of the present application is to overcome the defects of conventional wellbore reconstruction secondary cementing technology, such as high control difficulty, low control degree of fracture and low wellbore pressure capacity, and to provide a horizontal wellbore reconstruction re-fracturing process method.

[0009] In order to achieve the above purpose, the technical scheme provided by the present application is:

[0010] A horizontal wellbore reconstruction re-fracturing process method, which is specifically carried out according to the following steps:

[0011] S1. clean the wellbore of the horizontal well which needs to be cased and cemented and completed;

[0012] S2. lower the oil pipe into the first casing;

[0013] S3. pump hydrophobic polymer leak-off agent into the wellbore to ensure normal circulation;

[0014] S4. The lower end of the tubing is connected to the running-in head to clean the horizontal section of the wellbore;

[0015] S5. The annulus between the tubing and the first casing is positively circulated to pump in the metal drag-reducing agent to fill the wellbore with the metal drag-reducing agent;

[0016] S6. The float shoe and the pressure-encountering seat are connected, a plurality of second casings with an outer diameter smaller than an inner diameter of the first casing and an expansion hanger are connected through variable-diameter connection, and then the wellbore is re-cased by running the re-casing string to a position 300-500 m above the vertical section through the 89 mm diameter drill pipe;

[0017] S7. The string is pulled up to the neutral point of the string, i.e. the running-in drill pipe weight, the drill pipe is positively rotated, and the inner central pipe thread and the expansion pipe of the expansion hanger are disconnected;

[0018] S8. The wellbore is positively circulated for one wellbore volume, the water-soluble resin cementing fluid is positively circulated, the plug is put in, the water is positively replaced, the pressure is suddenly increased, the plug is combined with the pressure-encountering seat, the water-soluble resin cementing fluid is in place;

[0019] S9. The pressure is continuously increased to 24-27 MPa, the expansion hanger is expanded, and the expansion cone and the expansion pipe of the expansion hanger are disconnected;

[0020] S10. The expansion is completed, the wellbore is positively circulated, the water-soluble resin cementing fluid in the wellbore is cleaned, and the well is shut in for curing;

[0021] S11. The drill plug string is run in to drill and grind the cured resin and circulate the ground resin powder out of the ground through the liquid, and the wellbore is pressure tested at 40 MPa;

[0022] S12. After the wellbore pressure test is qualified, the soluble bridge plug and the perforating combined string are run in to perform inter-stage isolation and staged fracturing;

[0023] S13. After the fracturing is completed, the pump is run in to restore the horizontal well production.

[0024] Further, the outer diameter of the tubing in step S2 is 73 mm, the tubing is run in to a depth of 300-500 m above the upper part of the horizontal section A, the active agent is positively circulated from the annulus between the tubing and the first casing into the wellbore, the active agent is sodium alkyl benzene sulfonate, and the active agent addition amount is 0.5-1.0% of the total mass of the circulating water.

[0025] Further, in step S3, the hydrophobic polymer leak-off agent is normally circulated when the leak-off amount is less than 50 L / min, and plugging operation is performed when the leak-off amount is greater than 50 L / min.

[0026] After the hydrophobic polymer leak-off agent is injected, the well needs to be shut in for curing for 4 days.

[0027] Further, the hydrophobic polymer leak reducer is a polymer synthesized from monomers of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, and cationic hydrophobic monomer 3-dodecoxy-2-acryloyloxypropyl trimethyl ammonium chloride;

[0028] The synthesis method is to add acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, and cationic hydrophobic monomer 3-dodecoxy-2-acryloyloxypropyl trimethyl ammonium chloride into a reaction container in a molar ratio of 84:15:1.0, add distilled water as a solvent, and prepare a solution with a total monomer mass concentration of 10% wt.

[0029] Seal the reaction container and stir with a stirrer until the reaction system is uniform. Place the reaction container in a 70°C water bath for constant temperature. Prepare a 5% wt solution of the initiator NaHSO3 and a 5% wt solution of the oxidizing agent K2S2O8.

[0030] After the constant temperature system is stirred uniformly, add the initiator NaHSO3 solution to the reaction system while stirring, add excess reducing agent Na2S2O4 to remove dissolved oxygen which has a polymerization inhibition effect, and then add the oxidizing agent K2S2O8 solution. Seal and stop stirring when the constant temperature system has a significant viscosity. Continue to maintain the constant temperature in the 70°C water bath for 6 hours.

[0031] Take 50% of the reaction product by mass and add it to a treatment container. Soak it in a large amount of anhydrous ethanol, and at the same time, cut the reaction product into rice grain size with scissors. After the surface becomes hard, squeeze out the water, and then repeatedly soak and wash it in anhydrous ethanol. Change the anhydrous ethanol multiple times until it becomes a hard white granular solid. Vacuum dry the white granular solid polymer to a constant weight to obtain the finished product for use.

[0032] Further, the step S4 removes impurities in the wellbore during the working process of the casing processor using a liquid to circulate the impurities to the ground.

[0033] Further, the metal drag reducer in step S5 is a mixture of sodium dodecyl sulfonate and sodium alkyldiphenyloxide disulfonate.

[0034] Further, the difference between the outer diameter and the inner diameter of the second casing in step S6 is 9.9-10.5 mm.

[0035] Further, the soluble bridge plug in step S11 is made of a soluble material and includes an intermediate tube, a ball seat fixed inside the intermediate tube, a fixing plate fixed outside the intermediate tube, a first sealing ring sitting on the upper end of the fixing plate, the first sealing ring being sleeved on the intermediate tube, a plurality of first liquid bladders and blades fixed on the upper end of the fixing plate inside the first sealing ring, a plurality of second liquid bladders fixed on the outer side of the intermediate tube above the fixing plate, a first channel communicating with the first liquid bladders being opened inside the fixing plate, a second channel being opened inside the wall of the intermediate tube, the second channel communicating with the first channel, a diaphragm being fixedly and sealed inside the second channel, a portion of the second channel on one side of the diaphragm communicating with the second liquid bladder, a portion of the second channel on the other side of the diaphragm communicating with the first channel, and a sealed cavity formed by the diaphragm, the portion of the second channel communicating with the first channel, the first channel and the first liquid bladder being filled with a dissolving liquid, and an anti-melting coating being coated on the inner wall of the sealed cavity;

[0036] A movable plug is slidably sleeved on the intermediate tube above the first sealing ring. Multiple second sealing rings are sleeved on the intermediate tube between the movable plug and the first sealing ring. The annular cavity at the lower end of the second sealing ring stores dissolving particles. From bottom to top, the diameters of the multiple second sealing rings decrease sequentially. The lower end of the upper second sealing ring is inserted into the upper end of the lower second sealing ring. The lower end of the movable plug is inserted into the upper end of the uppermost second sealing ring. The lower end of the lowermost second sealing ring is inserted into the upper end of the first sealing ring. A baffle is fixed to the upper end of the movable plug. Except for the lowermost second sealing ring, baffles are fixed to the upper ends of the other second sealing rings.

[0037] The lower end of the inner edge of the movable plug has a groove corresponding to the second liquid bladder. The outer edge of the middle tube above the fixed plate is machined with multiple lower locking teeth, and the inner edge of the movable plug is machined with multiple upper locking teeth for engaging with the lower locking teeth.

[0038] Furthermore, the inner side of the upper end of the second sealing ring of the soluble bridge plug is machined with an inner conical surface, and the outer side of the lower end of the second sealing ring is machined with an outer conical surface. The outer conical surface of the upper second sealing ring contacts the inner conical surface of the lower second sealing ring. The outer edge of the lower end of the movable plug is machined with a lower guide conical surface, which contacts the inner conical surface of the uppermost second sealing ring. The inner side of the upper end of the first sealing ring is machined with an upper guide conical surface, which contacts the outer conical surface of the lowermost second sealing ring.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The present application firstly carries out wellbore leakage reduction, provides normal wellbore environment for cementing circulation, and then carries out fine treatment and metal drag reduction of the wellbore, so that the frictional resistance of the second casing of four and a half inches without coupling is minimized. The present application uses drill pipe weighting to ensure the smooth running of the four and a half inch casing. During cementing, the solid-free resin plugging agent and expansion suspension are used to ensure the ability of 40MPa pressure bearing, so that a brand new wellbore of the horizontal well can be realized, and the tool sand burial caused by the communication between the upper and lower layers outside the casing due to poor cementing quality can be effectively prevented. According to the needs of reservoir engineering, the repeated reconstruction section can be freely selected to achieve the goal of accurately controlling the fracture and improving the stimulation effect. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 A schematic diagram for adding hydrophobic polymer leakage reduction agent into the wellbore through the tubing.

[0042] Figure 2 A schematic diagram for treating the horizontal section of the wellbore by the casing processor.

[0043] Figure 3 A schematic diagram for pumping the metal drag reduction agent into the tubing and casing annulus by the positive circulation.

[0044] Figure 4 A schematic diagram for the float shoe and pressure seat entering into the wellbore.

[0045] Figure 5 A schematic diagram for the water-soluble resin cementing fluid by positive circulation.

[0046] Figure 6 A schematic diagram for the wellbore reconstruction pipe string after forming.

[0047] Figure 7 A schematic diagram for perforating the wellbore reconstruction pipe string and opening a new fracture.

[0048] Figure 8 A schematic diagram after opening the new fracture.

[0049] Figure 9 A schematic diagram for dissolving the soluble bridge plug.

[0050] Figure 10 A structural schematic diagram of the soluble bridge plug.

[0051] Figure 11 A sectional view of the soluble bridge plug.

[0052] Figure 12 A Figure 11 An enlarged view of area A.

[0053] Figure 13 A structural schematic diagram of the fixed plate cooperating with the blade and the first liquid bag.

[0054] Figure 14 This is a schematic diagram of the movable plug.

[0055] The names of the components in the attached diagram are:

[0056] 1. Intermediate tube; 2. Ball seat; 3. Fixing plate; 4. First sealing ring; 5. Second sealing ring; 6. Baffle; 7. Solubilizing particles; 8. Movable plug; 9. Baffle; 10. Groove; 11. Upper locking tooth; 12. Lower locking tooth; 13. First liquid bladder; 14. Blade; 15. Second liquid bladder; 161. First channel; 162. Second channel; 17. Diaphragm; 101. Oil pipe; 102. Original crack; 1 03. Hydrophobic polymer leak reducer; 104. Casing processor; 105. Metal drag reducer; 106. Float shoe; 107. Pressure seat; 108. Variable thread; 109. Expandable hanger; 110. Water-soluble resin cementing fluid; 111. Rubber plug; 112. Wellbore reconstruction string; 113. Cable; 114. Perforation gun; 115. New fracture; 116. Soluble bridge plug; 117. Soluble bridge plug solvent. Detailed Implementation

[0057] A method for re-fracture and re-engineering a horizontal wellbore, comprising the following steps:

[0058] S1. Clean the wellbore of the horizontal well that requires casing cementing completion.

[0059] S2. Run tubing 101 into the first casing, which has an outer diameter of 139.7 mm. Tubing 101 has an outer diameter of 73 mm and is run to a depth of 300-500 m above the horizontal section A target. Then, circulate an activator (sodium alkylbenzene sulfonate) into the wellbore through the annulus between tubing 101 and the first casing. The activator dosage is 0.5-1.0% of the total mass of circulating water.

[0060] S3. Pump hydrophobic polymer leak-proof agent 103 into the wellbore to ensure proper circulation. See [link / reference]. Figure 1 . Figure 1 The arrows indicate the direction of movement of the hydrophobic polymer leak-preventing agent 103. During the pumping of the hydrophobic polymer leak-preventing agent 103, a leakage rate of less than 50 L / min indicates normal circulation, while a leakage rate greater than 50 L / min necessitates leak-sealing operations.

[0061] The hydrophobic polymer leak-proof agent 103 is a polymer synthesized from monomers acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and 3-dodecyloxy-2-acryloyloxypropenetrimethylammonium chloride;

[0062] The synthetic method is to add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and cationic hydrophobic monomer 3-dodecyloxy-2-acryloyloxypropyl trimethyl ammonium chloride into a reaction container in a molar ratio of 84:15:1.0, add distilled water as a solvent, and prepare a solution with a total monomer mass concentration of 10% wt; seal the reaction container, stir until the reaction system is uniform, place the reaction container in a 70°C water bath for constant temperature, prepare a 5% wt solution of initiator NaHSO3, and prepare a 5% wt solution of oxidizing agent K2S2O8; after the constant temperature system is stirred uniformly, add the initiator NaHSO3 solution to the reaction system dropwise while stirring, add excess reducing agent Na2S2O4 to remove dissolved oxygen that acts as a polymerization inhibitor, then add the oxidizing agent K2S2O8 solution dropwise, seal, stop stirring when the constant temperature system has a significant viscosity, and continue to maintain the constant temperature in the 70°C water bath for 6 hours; take 50% of the mass of the reaction product, add it to a processing container, soak in a large amount of anhydrous ethanol, and at the same time, cut the reaction product into rice grain size with scissors, squeeze out the water in it after the surface becomes hard, and then repeatedly soak and wash it in anhydrous ethanol, replace the anhydrous ethanol multiple times until it becomes a hard white granular solid; vacuum dry the white granular solid polymer to a constant weight to obtain a finished product for use.

[0063] After the hydrophobic polymer leak-off reducer 103 is injected, the well needs to be shut in for 4 days for condensation.

[0064] S4. The lower end of the tubing 101 is connected to the casing processor 104 to process the horizontal section of the wellbore completely, as shown in Figure 2 . The casing processor 104 is lowered into the wellbore to process it and circulate the generated impurities out of the ground through liquid, at which time the wellbore leak-off is completed.

[0065] S5. The metal drag reducer 105 is pumped into the tubing 101 and the casing annulus in positive circulation, and the wellbore is filled with the metal drag reducer 105, as shown in Figure 3 .

[0066] Figure 3 The arrow direction in the figure is the flow direction of the metal drag reducer 105. The metal drag reducer 105 is a mixture of sodium dodecyl sulfonate and sodium fatty alcohol polyoxyethylene ether sulfonate.

[0067] S6. The float shoe 106 and the pressure bump seat 107 are connected, a plurality of second casings with an outer diameter smaller than the inner diameter of the first casing are connected through the variable pin 108 and the expansion hanger 109, and then the wellbore reconstruction string 112 is lowered to a position 300-500 m above the vertical section through a drill pipe with a diameter of 89 mm, as shown in Figure 4 . The difference between the outer diameter and the inner diameter of the second casing is 9.9-10.5 mm.

[0068] S7. Pull up the pipe string to the neutral point of the pipe string, that is, the running-in tool weight, rotate the drilling tool 25-30 circles, and expand the inner central pipe thread and the expansion pipe to be separated.

[0069] S8. Circulate the well, circulate the water-soluble resin cementing fluid 110, put the rubber plug 111, positively replace the water, the pressure suddenly rises, the rubber plug 111 is combined with the pressure seat 107, the water-soluble resin cementing fluid 110 is in place, and the rubber plug 111 is combined with the pressure seat 107. See Figure 5 .

[0070] S9. Continue to press to 24-27 MPa, expand the expansion hanger 109, and separate the expansion cone on the expansion hanger 109 and the expansion pipe.

[0071] S10. After the expansion is completed, the well is washed, the water-soluble resin cementing fluid 110 in the well is washed clean, and the well is closed for condensation.

[0072] S11. Drill the plug pipe string to drill and grind the cured resin, and circulate the ground resin powder out of the ground through the liquid, and test the wellbore pressure of 40 MPa. See Figure 6 .

[0073] S12. After the wellbore pressure test is qualified, the soluble bridge plug 116 is lowered with the perforating joint pipe string to carry out inter-stage isolation and staged fracturing. See Figure 7 and Figure 8 . The soluble bridge plug 116 and the perforating gun 114 are pumped down to the designed new fracture 115 position through the cable 113, the perforating gun 114 is controlled to perforate through the cable 113, the perforating gun 114 is separated from the soluble bridge plug 116, the soluble bridge plug 116 is completed, and then the cable 113 and the perforating gun 114 are pulled out. Thereafter, the casing injection fracturing is carried out.

[0074] S13. After the fracturing is completed, the pump is lowered to restore the horizontal well production.

[0075] The process method described in the application integrates fracture leakage reduction, wellbore reconstruction, and soluble bridge plug 116 multi-layer fracturing technology, and proposes a new technology that can be used for precise repeated fracturing reconstruction of horizontal wells. The main method is to temporarily block the original fracture 102 by injecting leakage reduction agent into the original fracture 102 from the tubing 101. The injection fracturing is carried out from the casing, and one pipe string is used to complete all the layers that need to be modified, which realizes the requirements of large displacement, large sand volume, large liquid volume, and precise purpose layer fracturing for horizontal well repeated modification, and improves the development effect of old oilfields. Conventional horizontal well repeated modification mostly uses double-sealing single-clamping fracturing process, or light pipe fracturing for blocking the old cracks of the original well. Due to the reasons such as lower pressure level of tubing 101, double packers, and blocking, it cannot realize large displacement modification, and often causes casing external stringing due to poor cementing quality, thereby increasing the risk of sticking.

[0076] This invention creates a completely new wellbore by temporarily plugging old fractures, running in a small casing, and cementing the annulus outside the casing, thus achieving the requirements of large displacement, large sand volume, large fluid volume, and precise target layer fracturing.

[0077] like Figures 10-14 As shown, the soluble bridge plug 116 in S11 is made of a soluble material and includes an intermediate tube 1, with a ball seat 2 fixed inside the intermediate tube 1. A fixing plate 3 is fixed to the outside of the intermediate tube 1. A first sealing ring 4 is seated on the upper end of the fixing plate 3 and is sleeved on the intermediate tube 1. Multiple first liquid bladders 13 and blades 14 are fixed to the upper end of the fixing plate 3 inside the first sealing ring 4. Multiple second liquid bladders 15 are fixed to the outside of the intermediate tube 1 above the fixing plate 3. A first channel 161 communicating with the first liquid bladders 13 is opened inside the fixing plate 3. A second channel 162 is opened inside the tube wall of the intermediate tube 1 and communicates with the first channel 161. A diaphragm 17 is fixedly and sealed inside the second channel 162. The second channel 162 on one side of the diaphragm 17 communicates with the second liquid bladders 15, and the second channel 162 on the other side of the diaphragm 17 communicates with the first channel 161. The sealed cavity formed by the diaphragm 17, the second channel 162 communicating with the first channel 161, the first channel 161, and the first liquid bladder 13 is filled with a dissolving liquid. The inner wall of the sealed cavity is coated with an anti-melting coating.

[0078] A movable plug 8 is slidably fitted onto the intermediate tube 1 above the first sealing ring 4. Multiple second sealing rings 5 ​​are fitted onto the intermediate tube 1 between the movable plug 8 and the first sealing ring 4. The annular cavity at the lower end of each second sealing ring 5 stores dissolving particles 7. The diameters of the multiple second sealing rings 5 ​​decrease sequentially from bottom to top. The lower end of the uppermost second sealing ring 5 is inserted into the upper end of the lowermost second sealing ring 5. The lower end of the movable plug 8 is inserted into the upper end of the uppermost second sealing ring 5. The lower end of the lowermost second sealing ring 5 is inserted into the upper end of the first sealing ring 4. A baffle 9 is fixed to the upper end of the movable plug 8. Except for the lowermost second sealing ring 5, all other second sealing rings 5 ​​have baffle plates 6 fixed to their upper ends.

[0079] The lower inner edge of the movable plug 8 has a groove 10 corresponding to the second liquid bladder 15. The outer edge of the intermediate tube 1 above the fixed plate 3 is machined with multiple lower locking teeth 12, and the inner edge of the movable plug 8 is machined with multiple upper locking teeth 11 for engaging with the lower locking teeth 12.

[0080] The second sealing ring 5 of the soluble bridge plug 116 has an inner conical surface machined on its upper inner side. The second sealing ring 5 has an outer conical surface machined on its lower outer side. The outer conical surface of the upper second sealing ring 5 contacts the inner conical surface of the lower second sealing ring 5. The lower outer edge of the movable plug 8 has a lower guide conical surface machined, which contacts the inner conical surface of the uppermost second sealing ring 5. The upper inner side of the first sealing ring 4 has an upper guide conical surface machined, which contacts the outer conical surface of the lowermost second sealing ring 5.

[0081] When the soluble bridge plug 116 is used, the soluble bridge plug 116 is placed downhole and adjusted to the set position. The anchoring device is started to push the movable plug 8 to move on the middle pipe 1 in the direction of the fixed plate 3. During the movement of the movable plug 8 in the direction of the fixed plate 3, under the guidance of the outer taper surface, the inner taper surface, the upper guide taper surface and the lower guide taper surface, the movable plug 8 is gradually inserted into the uppermost second sealing ring 5, the upper second sealing ring 5 is gradually inserted into the lower second sealing ring 5, and the lowermost second sealing ring 5 is gradually inserted into the first sealing ring 4. After the baffle plate 9 contacts the uppermost second sealing ring 5, the contact area between the movable plug 8 and the uppermost second sealing ring 5 increases. The movable plug 8 can effectively transmit the pushing force received by the anchoring device to the uppermost second sealing ring 5, so as to ensure that the uppermost second sealing ring 5 can move in the direction of the fixed plate 3 synchronously with the movable plug 8. When the baffle plate 6 contacts the second sealing ring 5 below it, the upper second sealing ring 5 can effectively transmit the pushing force received to the second sealing ring 5 below it, so as to ensure that the upper second sealing ring 5 can move in the direction of the fixed plate 3 synchronously with the upper second sealing ring 5. With the continuous movement of the movable plug 8 in the direction of the fixed plate 3, the second sealing ring 5 gradually expands outward. At the same time, the first sealing ring 4 also expands outward.

[0082] When the lower ends of the plurality of second sealing rings 5 are located in the same horizontal plane, the expansion of the first sealing ring 4 is completed. At this time, the first sealing ring 4 is in contact with the well wall and the anchoring is completed, the upper dog 11 and the lower dog 12 are engaged to prevent the movable plug 8 from moving away from the fixed plate 3, and the movable plug 8 is fixed.

[0083] When the lower ends of the plurality of second sealing rings 5 are located in the same horizontal plane, the blade 14 will cut the lower ends of the plurality of second sealing rings 5, so that the lower ends of the second sealing rings 5 are cut. The slit is in communication with the annular cavity at the lower end of the second sealing ring 5.

[0084] When the lower ends of the second sealing rings 5 are located in the same horizontal plane, the lower ends of the second sealing rings 5 will press the first liquid bag 13, so that the pressure of the closed cavity formed by the diaphragm 17, the second channel 162 communicating with the first channel 161, the first channel 161 and the first liquid bag 13 is increased. After the pressure in the closed cavity is increased, the diaphragm 17 is broken. The dissolving liquid will enter the second liquid bag 15. After the dissolving liquid enters the second liquid bag 15, the second liquid bag 15 expands. At this time, the expanded second liquid bag 15 is located in the groove 10. Since the inner side of the second liquid bag 15 is not provided with a release coating, after a period of time, the second liquid bag 15 will be dissolved. Then the dissolving liquid will directly contact the movable plug 8, so that the movable plug 8 is quickly dissolved. After the movable plug 8 is dissolved, the movable plug 8 loses the expansion support of the second sealing ring 5 outside it, and the second sealing ring 5 and the first sealing ring 4 quickly recover to the original state under the elastic action of themselves. At this time, the self-dissolvable bridge plug 116 loses the anchoring effect on the well wall. During the process of dissolving the movable plug 8, the dissolving liquid will contact the dissolving promoting particles 7 through the slits at the lower ends of the second sealing rings 5. After the dissolving promoting particles 7 are dissolved, the mineralization degree of the dissolving liquid can be improved, and then the dissolving speed of the movable plug 8 can be improved. When the self-dissolvable bridge plug 116 is dissolved as a whole, when the dissolvable bridge plug solvent 117 is injected into the well, after the dissolvable bridge plug solvent 117 contacts the dissolving promoting particles 7 through the slits, the dissolving promoting particles 7 can also improve the mineralization degree of the dissolvable bridge plug solvent 117, so as to improve the dissolving speed of the self-dissolvable bridge plug 116.

[0085] The above merely describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for repeated fracturing and rebuilding of a horizontal wellbore, characterized in that, This method is specifically carried out according to the following steps: S1. Clean the wellbore of the horizontal well that requires casing cementing completion; S2. Insert the oil pipe (101) into the first casing; S3. Pump hydrophobic polymer leak-proof agent (103) into the wellbore to ensure normal circulation is established; S4. The lower end of the tubing (101) is connected to the casing processor (104) to clean the horizontal section of the wellbore; S5. In the annulus between the tubing (101) and the first casing, a metal drag-reducing agent (105) is pumped in to fill the wellbore with the metal drag-reducing agent (105); S6. Connect the float shoe (106) and the pressure seat (107), and connect several second casings with an outer diameter smaller than the inner diameter of the first casing and the expansion hanger (109) through the variable buckle (108). Then, use the 89mm diameter drill pipe to lower the wellbore reconstructing string (112) to a position 300-500m above the vertical well section. S7. Raise the tubing string to the neutral point of the tubing string, then insert the drill pipe suspension weight, rotate the drill bit forward, and the central thread of the expansion hanger and the expansion tube will disengage. S8. For a wellbore volume of positive circulation, positive circulation water-soluble resin cementing fluid (110) is applied, rubber plug (111) is added, and clean water is applied. The pressure rises suddenly and combines with the rubber plug (111). The clean water is applied again and the pressure rises suddenly. The rubber plug (111) combines with the pressure seat (107). The water-soluble resin cementing fluid (110) is in place. S9. Continue pressurizing to 24-27MPa, the expansion hanger (109) expands, and the expansion cone and expansion tube on the expansion hanger (109) separate; S10. After expansion is complete, perform a well wash to clean the wellbore with water-soluble resin cementing fluid (110), then shut in the well and wait for it to set. S11. The drill plug string is lowered in to grind and cure the resin, and the ground resin powder is circulated to the surface through liquid. The wellbore is pressure tested at 40MPa. S12. After the wellbore pressure test is qualified, a soluble bridge plug (116) is run into the perforation connection string to carry out inter-segment isolation and segmented fracturing; S13. After fracturing is completed, the pump is lowered to restore the production level of the horizontal well.

2. The method for repeated fracturing and rebuilding of a horizontal wellbore according to claim 1, characterized in that, In step S2, the outer diameter of the tubing (101) is 73 mm, and the tubing (101) is lowered to a depth of 300-500 m above the horizontal section A target. An active agent is circulated into the wellbore through the annulus between the tubing (101) and the first casing. The active agent is sodium alkylbenzene sulfonate, and the amount of active agent added is 0.5-1.0% of the total mass of circulating water.

3. The method for repeated fracturing and rebuilding of a horizontal wellbore according to claim 1, characterized in that, In step S3, if the leakage rate of the hydrophobic polymer leak-proof agent (103) is less than 50L / min, it is considered normal circulation; if the leakage rate of the hydrophobic polymer leak-proof agent (103) is greater than 50L / min, a leak-sealing operation is performed. After the hydrophobic polymer leak reducer (103) is injected, the well needs to be shut in for 4 days to allow it to solidify.

4. The method for repeated fracturing and rebuilding of a horizontal wellbore according to claim 1, characterized in that, The hydrophobic polymer leak-proof agent (103) is a polymer synthesized from monomers acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and 3-dodecoxy-2-acryloyloxypropenetrimethylammonium chloride; The synthesis method involves adding acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and the cationic hydrophobic monomer 3-dodecyloxy-2-acryloyloxypropenyltrimethylammonium chloride into a reaction vessel at a molar ratio of 84:15:1.0, and adding distilled water as a solvent to prepare a solution with a total mass concentration of the three monomers of 10%wt. Seal the reaction vessel and stir with a stirrer until the reaction system is homogeneous. Place the reaction vessel in a 70°C water bath to maintain a constant temperature. Prepare a 5% wt solution of initiator NaHSO3 and a 5% wt solution of oxidant K2S2O8. After the constant temperature system is stirred evenly, the initiator NaHSO3 solution is added dropwise to the reaction system while stirring. Excess reducing agent Na2S2O4 is added to remove dissolved oxygen that inhibits polymerization. Then, the oxidizing agent K2S2O8 solution is added dropwise. The system is sealed and stirring is stopped when the constant temperature system has obvious viscosity. The system is then kept at a constant temperature of 70℃ for 6 hours. Take 50% of the reaction product by mass into a processing container, add a large amount of anhydrous ethanol to soak it, and at the same time use scissors to cut the reaction product into the size of rice grains. After the surface hardens, squeeze out the water. Then repeatedly soak and wash with anhydrous ethanol, changing the anhydrous ethanol several times until it becomes a hard white granular solid. Vacuum dry the white granular solid polymer to constant weight to obtain the finished product for later use.

5. The method for repeated fracturing and rebuilding of a horizontal wellbore according to claim 1, characterized in that, In step S4, the casing processor (104) removes impurities from the wellbore during operation and uses liquid to circulate the impurities to the surface.

6. The method for repeated fracturing and rebuilding of a horizontal wellbore according to claim 1, characterized in that, The metal drag reducer (105) in step S5 is a mixture of sodium dodecyl sulfonate and sodium fatty alcohol polyoxyethylene ether sulfonate.

7. The method for repeated fracturing and rebuilding of a horizontal wellbore according to claim 1, characterized in that, The difference between the outer diameter and inner diameter of the second sleeve in step S6 is 9.9-10.5 mm.

8. The method for repeated fracturing and rebuilding of a horizontal wellbore according to claim 1, characterized in that, The soluble bridge plug (116) in step S11 is made of soluble material and includes an intermediate tube (1). A ball seat (2) is fixed inside the intermediate tube (1). A fixing plate (3) is fixed outside the intermediate tube (1). A first sealing ring (4) is located on the upper end of the fixing plate (3). The first sealing ring (4) is sleeved on the intermediate tube (1). Multiple first liquid bladders (13) and blades (14) are fixed on the upper end of the fixing plate (3) inside the first sealing ring (4). Multiple second liquid bladders (15) are fixed on the outer side of the intermediate tube (1) above the fixing plate (3). A first channel (161) communicating with the first liquid bladders (13) is opened inside the fixing plate (3). (1) A second channel (162) is provided in the inner wall of the tube. The second channel (162) is connected to the first channel (161). A diaphragm (17) is fixedly and sealed in the second channel (162). The second channel (162) on one side of the diaphragm (17) is connected to the second liquid bladder (15). The second channel (162) on the other side of the diaphragm (17) is connected to the first channel (161). The sealed cavity formed by the diaphragm (17), the second channel (162) connected to the first channel (161), the first channel (161) and the first liquid bladder (13) is filled with a dissolving liquid. The inner wall of the sealed cavity is coated with an anti-melting coating. A movable plug (8) is slidably sleeved on the intermediate tube (1) above the first sealing ring (4). Multiple second sealing rings (5) are sleeved on the intermediate tube (1) between the movable plug (8) and the first sealing ring (4). The annular cavity at the lower end of the second sealing ring (5) stores dissolving particles (7). From bottom to top, the diameter of the multiple second sealing rings (5) decreases sequentially. The lower end of the upper second sealing ring (5) is inserted into the upper end of the lower second sealing ring (5). The lower end of the movable plug (8) is inserted into the upper end of the uppermost second sealing ring (5). The lower end of the lowermost second sealing ring (5) is inserted into the upper end of the first sealing ring (4). A baffle (9) is fixed at the upper end of the movable plug (8). Except for the lowermost second sealing ring (5), the upper ends of the other second sealing rings (5) are all fixed with baffles (6). The lower end of the inner edge of the movable plug (8) is provided with a groove (10) corresponding to the second liquid bladder (15). The outer edge of the middle tube (1) above the fixed plate (3) is machined with multiple lower locking teeth (12), and the inner edge of the movable plug (8) is machined with multiple upper locking teeth (11) for engaging with the lower locking teeth (12).

9. The method for repeated fracturing and rebuilding of a horizontal wellbore according to claim 8, characterized in that, The second sealing ring (5) of the soluble bridge plug (116) has an inner conical surface machined on the inner side of its upper end and an outer conical surface machined on the outer side of its lower end. The outer conical surface of the upper second sealing ring (5) is in contact with the inner conical surface of the lower second sealing ring (5). The lower outer edge of the movable plug (8) has a lower guide conical surface machined on its lower end. The lower guide conical surface is in contact with the inner conical surface of the uppermost second sealing ring (5). The inner side of the upper end of the first sealing ring (4) has an upper guide conical surface machined on its upper end. The upper guide conical surface is in contact with the outer conical surface of the lowermost second sealing ring (5).

Images