Polyester hot melt glue spraying process for inner wall of downhole casing

Abstract

The present invention discloses a polyester hot-melt adhesive spraying process for the inner wall of downhole casing, which includes the following steps: setting a bridge plug → removing oil stains, dirt, and corrosion products on the inner wall of the casing → sucking the wellbore liquid and drying the wellbore casing → spraying 0.3 mm of surface-tolerant epoxy resin coating on the inner wall of the casing and curing it at 25-60°C for 24 hours → spraying 1-3 mm of high-strength copolyester hot-melt adhesive reinforcing material under high pressure and curing the coating at 60°C for 24 hours at the wellbore temperature → conducting a water pressure test of 15 MPa, and if the pressure drop is less than 0.5 MPa in 30 minutes, it is qualified, and then running the pump to complete the well. The present invention meets the requirements of old wellbore operations, realizes the internal anti-corrosion and strengthening of the existing casing, greatly improves the anti-corrosion ability of the wellbore inner wall, and can also plug the casing perforations to prevent formation water from flowing back into the wellbore.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of downhole repair of casing damage wells, and relates to a polyester hot melt adhesive spraying process for the inner wall of a downhole casing. BACKGROUND

[0002] With the increase of the exploitation years of multi-reservoir oil fields, and the influence of geological conditions and engineering factors, casing damage and fluid channeling often occur, and the corrosion of formation produced liquid on the inner wall of the casing causes hundreds of meters of perforation and pitting damage, the casing deformation of oil and water wells is aggravated, and the cost of workover production operations is increased; moreover, the inner wall of the wellbore is affected by scaling and pitting, which affects the smooth implementation of the stable production and development plan of the oil field, and even causes production to stop, which seriously affects the effective water injection of the reservoir and the improvement of the ultimate recovery rate.

[0003] At present, the commonly used channeling and leakage plugging technology mainly uses cement, resin and organic materials for chemical plugging. The cement and resin casing damage well plugging and patching and expansion pipe plugging processes can only be carried out in sections for casing damage sections with a length of more than 20 meters, and the repair is carried out by combining conventional metal expansion pipes with sealing rubber rings, adopting multiple expansion pipe threads, and expanding and patching through the metal expansion cone. The downhole operation process is complex, the risk of sticking is high, the material cost is high, and the expansion pipe thread and the outer rubber ring sealing are prone to failure. In view of the problems of the casing damage well metal expansion pipe patching, the difficulty of mechanical isolation and production, the low success rate, the short effective period and the small range of chemical plugging treatment, it is necessary to carry out research on the anticorrosion process technology of the in-use casing to prevent corrosion on the inner wall of the casing, isolate the corrosion medium from the inner wall of the casing, avoid internal corrosion of the casing, and re-spray anticorrosion and reinforcement for the casing that has been corroded and damaged downhole, so as to fundamentally solve the casing damage and casing breakage problems and improve the compressive strength and sealing effective period of the repaired casing. SUMMARY

[0004] The purpose of the present application is to provide a polyester hot melt adhesive spraying process for the inner wall of a downhole casing, which solves the problems of severe corrosion of the inner wall of the casing, difficulty in metal expansion pipe patching of casing damage wells, and low success rate in mechanical isolation and production.

[0005] The technical solution adopted by the present application is a polyester hot melt adhesive spraying process for the inner wall of a downhole casing, which is implemented according to the following steps:

[0006] Step 1, bridge plug, a fishable bridge plug is lowered into the casing at 10m-30m below the pitting perforation section, and sand is filled to 5m below the perforation section.

[0007] Step 2, lower the coiled tubing with high-pressure rotating nozzle, lower the coiled tubing with high-pressure rotating nozzle to 1 meter below the corrosion section, the ground pump truck injects cleaning fluid through the coiled tubing, the water pump injection pressure is 5-10 MPa, pressurize while lifting the tubing, clean the oil stains, scale and corrosion products in the casing inner wall.

[0008] Step 3, after the coiled tubing is lowered to suck the wellbore liquid, the cable in the coiled tubing is laid to connect the electric heating pipe, the well section is slowly lowered and heated, and the temperature is heated to 60-100 degrees, the wellbore casing is dried to ensure that the inner wall of the wellbore is dry.

[0009] Step 4, after the high-pressure spraying of the surface-tolerant epoxy resin coating on the inner wall of the casing, curing;

[0010] Step 5, high-pressure spraying of copolyester hot melt adhesive reinforcing material, curing;

[0011] Step 6, after the high-strength copolyester hot melt adhesive reinforcing material coating in step 5 is cured, pressure test, after the pressure test is qualified, the bridge plug is fished out, and the pump is used for well completion.

[0012] The application is also characterized in that,

[0013] The surface-tolerant epoxy resin coating in step 4 includes the following components by mass ratio: 70-80 parts of coating, 10-20 parts of cross-linking reinforcing agent, and 5-15 parts of skeleton supporting agent. The coating includes the following components: epoxy resin, temperature-sensitive cross-linking initiator, diluent, and water sensitivity remover. The mass ratio of the epoxy resin, temperature-sensitive cross-linking initiator, diluent, and water sensitivity remover is: 12-24: 1-3: 1-2: 1. The epoxy resin is the main agent in the coating, the temperature-sensitive cross-linking initiator is a mixture of polyamide, 2-ethyl-4-methyl imidazole, and tetraethylene pentamine; the diluent is a mixture of 4-hydroxybutyl vinyl ether or 1,4-butanediol divinyl ether; and the water sensitivity remover is carbosulfan.

[0014] The cross-linking reinforcing agent uses silicon dioxide or titanium dioxide nanoparticles, and the silicon bond or titanium bond is polymerized with the epoxy coating; the skeleton supporting agent uses graphite nanoparticles to fill the intermolecular voids of the polymer molecules to provide skeleton support.

[0015] Step 5: after the surface-tolerant epoxy resin coating in step 4 is cured, the coiled tubing is lifted to replace the special polyester resin nozzle, which is lowered to 10 meters above the fishable bridge plug, and the coiled tubing is used to spray 1-3 millimeters of copolyester hot melt adhesive reinforcing material at a wellbore temperature of 60°C, and the coating is cured for 24 hours.

[0016] The copolyester hot melt adhesive reinforcing material in step 5 includes the following components: terephthalic acid, 1,4-butanediol, dimethyl terephthalate, titanium tetrabutoxide, dimer acid, and hydrogenated liquid polybutadiene diol. The above components are synthesized into copolyester hot melt adhesive reinforcing material according to the conventional hot melt adhesive.

[0017] Phthalic acid, 1,4-butanediol, see phthalic acid dimethyl ester, titanium acid tetra-n-butyl ester, dimer acid, hydrogenated liquid polybutadiene diol are synthesized according to the mass ratio of 30:110-11400:10-15:0.01-0.05:10-30:8-18.

[0018] The liquid viscosity of the normal-temperature copolyester hot melt adhesive reinforcing material is 800-1000 mPa·s, it is a soft viscous solid in the range of normal temperature--65 DEG C, it is not miscible with water, it is crosslinked and solidified at the temperature of 60 DEG C, and the adhesive strength of the solidified body is not less than 15 MPa.

[0019] In step 6, 15 MPa clean water is used for pressure test, if the pressure drop is less than 0.5 MPa in 30 min, the pressure test is qualified, otherwise, the pressure test is unqualified, and the wellbore is subjected to re-spraying and reinforcing treatment until the pressure test is qualified.

[0020] The specific step 4 is: the coiled tubing is pulled out to replace the coating nozzle, and is lowered to the position of 10 meters along the upper fishable bridge plug, the surface tolerant epoxy resin coating is sprayed on the coiled tubing by high pressure, the coating is sprayed on the inner wall of the casing from bottom to top by 0.3 mm, and the coiled tubing and the nozzle are pulled out; the surface tolerant epoxy resin coating is cured for 24 hours in the range of 25-60 DEG C of the wellbore temperature.

[0021] The beneficial effects of the present application are that, in the present application, the coiled tubing is lowered into the high-pressure rotary nozzle, the ground pump truck injects the cleaning liquid through the coiled tubing, and the oil stains, scales and corrosion products in the inner wall of the casing are cleaned. The surface tolerant epoxy resin coating is sprayed on the inner wall of the casing by 0.3 mm, and the coiled tubing sprays the high-strength copolyester hot melt adhesive reinforcing material by high pressure after curing for 24 hours, and the coating is cured for 24 hours at the temperature of 60 DEG C of the wellbore, so that the large-section corrosion and damage casing is repaired at one time; the process of the present application is simple and feasible, the film layer can be protected from being easily damaged, the film surface is smooth and straight, has no defects, and the pore distribution is uniform; the downhole operation cost and risk are reduced, and the present application is a high-efficiency treatment process for the casing damage well with point corrosion in the wellbore of more than 100 meters. DETAILED DESCRIPTION

[0022] The present application will be described in detail below in combination with the specific embodiments.

[0023] The downhole casing inner wall polyester hot melt adhesive spraying process of the present application is implemented according to the following steps:

[0024] Step 1, bridge plug is set, the fishable bridge plug is lowered into the position of 10-30 meters below the casing corrosion perforation section, and the sand is filled to the position of 5 meters below the perforation section.

[0025] Step 2, lower the coiled tubing with high-pressure rotating nozzle, lower the coiled tubing with high-pressure rotating nozzle to 1 meter below the lower edge of the corrosion section, the ground pump truck injects cleaning fluid through the coiled tubing, the water pump injection pressure is 5-10 MPa, press while lifting the tubing, clean the oil, dirt, corrosion products in the casing inner wall.

[0026] Step 3, after lowering the coiled tubing to pump the wellbore liquid, the coiled tubing is laid with a cable connected to an electric heating tube, slowly lower the cleaning well section and heat, heat to 60-100 degrees, dry the wellbore casing, ensure the dryness of the inner wall of the wellbore.

[0027] Step 4, high-pressure spraying of surface-tolerant epoxy resin coating on the inner wall of the casing after curing;

[0028] Step 4, the specific steps are: pulling out the coiled tubing to replace the coating nozzle, lowering to 10 meters above the retrievable bridge plug, high-pressure spraying of surface-tolerant epoxy resin coating on the coiled tubing, spraying 0.3 mm on the inner wall of the casing from bottom to top, pulling out the coiled tubing and the nozzle; the surface-tolerant epoxy resin coating is cured for 24 hours at a wellbore temperature of 25-60℃.

[0029] The surface-tolerant epoxy resin coating includes the following components by mass ratio: 70-80 parts of coating, 10-20 parts of cross-linking enhancer, 5-15 parts of skeleton supporting agent, wherein the coating includes the following components: epoxy resin, temperature-sensitive cross-linking initiator, diluent, water sensitivity remover; wherein the mass ratio of epoxy resin, temperature-sensitive cross-linking initiator, diluent, and water sensitivity remover is: 12-24: 1-3: 1-2: 1.

[0030] Among them, the epoxy resin in the coating is the main agent, the temperature-sensitive cross-linking initiator is a mixture of polyamide, 2-ethyl-4-methyl imidazole and tetraethylene pentamine; the diluent is a mixture of 4-hydroxybutyl vinyl ether or 1,4-butanediol divinyl ether; the water sensitivity remover is carbosulfan.

[0031] The cross-linking enhancer uses silicon dioxide or titanium dioxide nanoparticles, and the silicon bond or titanium bond reacts with the epoxy coating to enhance the compressive strength of the coating; the skeleton supporting agent uses graphite nanoparticles to fill the intermolecular voids of the polymer to provide skeletal support, further improving the compressive strength of the coating; the prepared surface-tolerant epoxy resin coating is a low VOC content, high solid, multi-component surface-tolerant epoxy coating, suitable for repairing and protecting any rusted steel surface and rusted paint film surface. Compared with ordinary coatings, it has the advantages of strong wetting of the base material, good permeability, strong rust particle wrapping, normal temperature drying, excellent durability, etc.

[0032] Step 5, high-pressure spraying of copolyester hot melt adhesive reinforcing material after curing;

[0033] The specific steps of step 5 are as follows: after the surface-tolerant epoxy resin coating in step 4 is cured, the coiled tubing dedicated polyester resin spray head is lifted out, and the coiled tubing high-pressure spraying is performed to 10 meters above the fishable bridge plug, and 1-3 millimeters of copolyester hot melt adhesive reinforcing material is sprayed, and the coating is cured at a wellbore temperature of 60 DEG C for 24 hours.

[0034] The copolyester hot melt adhesive reinforcing material comprises the following components: terephthalic acid, 1,4-butanediol, dimethyl terephthalate, titanium tetrabutyl titanate, dimer acid, and hydrogenated liquid polybutadiene diol, and the above components are synthesized into copolyester hot melt adhesive according to conventional hot melt adhesive; wherein the terephthalic acid, 1,4-butanediol, dimethyl terephthalate, titanium tetrabutyl titanate, dimer acid, and hydrogenated liquid polybutadiene diol are synthesized according to a mass ratio of 30:110-11400:10-15:0.01-0.05:10-30:8-18.

[0035] The liquid viscosity of the normal-temperature copolyester hot melt adhesive reinforcing material is 800-1000 mPa·s, and it is a soft viscous solid in the range of normal temperature to -65 DEG C, is not miscible with water, and is cross-linked and cured at a temperature of 60 DEG C, and the cured body has a bonding strength of not less than 15 MPa.

[0036] Step 6, after the high-strength copolyester hot melt adhesive reinforcing material coating in step 5 is cured, pressure test is performed, and after the pressure test is qualified, the bridge plug is fished out, and the well is completed by pumping.

[0037] In step 6, 15 MPa fresh water pressure test is used, and if the pressure drop is less than 0.5 MPa for 30 min, the pressure test is qualified; otherwise, the pressure test is unqualified, and the wellbore is re-sprayed and reinforced until the pressure test is qualified.

[0038] The downhole casing inner wall polyester hot melt adhesive spraying process of the present application, in step 4, the coiled tubing spraying surface-tolerant epoxy resin coating is directly sprayed on the rust layer on the inner wall of the casing to form a film, solving the problem of sandblasting and rust removal surface treatment of the inner wall of the downhole casing, and in step 5, the copolyester hot melt adhesive reinforcing material is directly sprayed on the surface-tolerant coating, realizing one-time reinforcement and repair of the downhole long section casing, and improving the corrosion resistance and compressive strength of the inner wall of the casing.

[0039] Example 1

[0040] The construction object is Z192-108 well put into production in July 2013, the perforated section is 2082-2086 m, the dynamic liquid level is 1382 m, and MTT+MIT engineering logging is performed in July 2018, showing that there is a long section of corrosion in the casing at 1586-1861 m.

[0041] In this embodiment, the downhole casing inner wall polyester hot melt adhesive spraying process is used for reinforcement and repair, and the following steps are implemented:

[0042] Step 1, at 2161m below the casing corrosion perforation section, a fishable bridge plug is lowered, and sand is filled to 1866m below the corrosion section.

[0043] Step 2, coiled tubing with high-pressure rotating nozzle is lowered, the coiled tubing with high-pressure rotating nozzle is lowered to 1m below the lower edge of the corrosion section, the ground pump truck injects cleaning fluid through the coiled tubing, the water pump injection pressure is 5MPa, the pressure is pressed while the tubing is pulled up, and the casing inner wall is cleaned of oil stains, scale and corrosion products.

[0044] Step 3, coiled tubing is lowered to suck wellbore liquid, an electric heating pipe is laid in the coiled tubing, the well section is slowly lowered and heated to 60 degrees to ensure that the wellbore inner wall is dry.

[0045] Step 4, the coiled tubing is pulled out to replace the coating nozzle, which is lowered to 10m above the fishable bridge plug, and a surface-tolerant epoxy resin coating is sprayed through the coiled tubing high-pressure nozzle, with a thickness of 0.3mm from bottom to top on the casing inner wall. The coiled tubing and nozzle are pulled out, and the resin coating is cured for 24 hours at a wellbore temperature of 25 degrees.

[0046] Among them, the cross-linking reinforcing agent uses 15 parts of silicon dioxide nanoparticles; the skeleton proppant graphite nanoparticles are 5 parts; the epoxy resin is 71 parts; the temperature-sensitive cross-linking initiator mixed from polyamide, 2-ethyl-4-methyl imidazole and tetraethylenepentamine is 3 parts; the diluent mixed from 4-hydroxybutyl vinyl ether or 1,4-butanediol divinyl ether is 3 parts; and the water sensitivity remover carbosulfan is 3 parts.

[0047] Step 5, after the surface-tolerant epoxy resin coating is cured, the coiled tubing is pulled out to replace the special polyester resin nozzle, and 1mm of copolyester hot melt adhesive reinforcing material is sprayed through the coiled tubing high-pressure nozzle, and the coating is cured for 24 hours at 60 degrees.

[0048] The copolyester hot melt adhesive formula is terephthalic acid, 1,4-butanediol, dimethyl terephthalate, titanium tetrabutyl titanate, dimer acid, and hydrogenated liquid polybutadiene diol, with a mass ratio of 30:10000:10:0.04:15:9.

[0049] Step 6, water pressure test 15MPa, 30min pressure drop less than 0.5MPa is qualified, salvage the bridge plug, and down the pump to complete the well.

[0050] Example 2

[0051] The implementation object is H192-100 well put into production in July 2013, the perforation section is 2001-2008m, the dynamic liquid level is 1300m, and the MTT+MIT engineering logging in July 2018 shows that there is a long corrosion section in the casing at 1580-1860m.

[0052] The embodiment adopts the polyester hot melt adhesive spraying process on the inner wall of the downhole casing for reinforcement repair, and is implemented according to the following steps:

[0053] Step 1, a fishable bridge plug is lowered at 1890 m below the casing corrosion perforation section, and sand is filled to 1865 m below the corrosion section.

[0054] Step 2, the coiled tubing with a high-pressure rotating nozzle is lowered. The coiled tubing with a high-pressure rotating nozzle is lowered to 1 m below the lower edge of the corrosion section, the ground pump truck injects cleaning fluid through the coiled tubing, the water pump injection pressure is 6 MPa, the pressure is punched at the same time, and the coiled tubing is lifted, so that the oil stains, dirt and corrosion products on the inner wall of the casing are cleaned.

[0055] Step 3, the coiled tubing is lowered to suck the wellbore liquid, the cable is laid in the coiled tubing to connect the electric heating pipe, the well section is slowly lowered and heated to 70 degrees to ensure that the inner wall of the wellbore is dry.

[0056] Step 4, the coiled tubing is lifted to replace the coating nozzle, and is lowered to 10 m above the fishable bridge plug. The surface-tolerant epoxy resin coating is sprayed through the coiled tubing high-pressure spraying, and the resin coating is sprayed on the inner wall of the casing at 0.3 mm from bottom to top. The coiled tubing and the nozzle are lifted, and the resin coating is cured for 24 hours at 30 degrees under the temperature of the wellbore.

[0057] In the formula, 10 parts of titanium dioxide nanoparticles are used as the cross-linking reinforcing agent; 3 parts of graphite nanoparticles are used as the skeleton supporting agent; 60 parts of epoxy resin are used; 15 parts of a temperature-sensitive cross-linking initiator composed of polyamide, 2-ethyl-4-methyl imidazole and tetraethylenepentamine are used; 10 parts of a diluent composed of 4-hydroxybutyl vinyl ether or 1,4-butanediol divinyl ether are used; and 2 parts of carbosulfan is used as the water sensitivity remover.

[0058] Step 5, after the surface-tolerant epoxy resin coating is cured, the coiled tubing is lifted to replace the special polyester resin nozzle, and the high-strength copolyester hot melt adhesive reinforcement material is sprayed through the coiled tubing high-pressure spraying at 2 mm, and the coating is cured for 24 hours at 60 degrees.

[0059] The high-strength copolyester hot melt adhesive is synthesized by terephthalic acid, 1,4-butanediol, dimethyl terephthalate, titanium tetrabutoxide, dimer acid and hydrogenated liquid polybutadiene diol (the mass ratio is 30:110:10:0.01:10:8.

[0060] Step 6, the water pressure test is 15 MPa, and the pressure drop is less than 0.5 MPa for 30 min, which is qualified. The bridge plug is fished out, and the pump is lowered for well completion.

[0061] Example 3

[0062] The implementation object is L192-110 well put into production in July 2013, perforation section 1580-1583m, dynamic liquid level 1210m, MTT+MIT engineering logging in July 2018, showing that there is a large section of corrosion in the casing at 1380-1360m.

[0063] This embodiment adopts downhole casing inner wall polyester hot melt adhesive spraying process for reinforcement repair, and is implemented according to the following steps:

[0064] Step 1, a fishable bridge plug is lowered into the casing at 1390m below the corrosion perforation section, and sand is filled to 1365m below the corrosion section.

[0065] Step 2, the coiled tubing with high-pressure rotating nozzle is lowered. The coiled tubing with high-pressure rotating nozzle is lowered to 1m below the lower edge of the corrosion section, the ground pump truck injects cleaning fluid through the coiled tubing, the water pump injection pressure is 7MPa, the tubing is lifted up at the same time of pressure, and the casing inner wall is cleaned of oil stains, scale and corrosion products.

[0066] Step 3, the coiled tubing is lowered to suck the wellbore liquid, the cable is laid in the coiled tubing to connect the electric heating pipe, the well section is slowly lowered and heated to 80 degrees, and the wellbore inner wall is ensured to be dry.

[0067] Step 4, the coiled tubing is lifted to replace the coating nozzle, and is lowered to 10m above the fishable bridge plug. The surface-tolerant epoxy resin coating is sprayed through the coiled tubing high-pressure spraying, and the resin coating is sprayed on the casing inner wall at 0.3mm from bottom to top. The coiled tubing and the nozzle are lifted, and the resin coating is cured at 45 degrees under the wellbore temperature for 24 hours.

[0068] Among them, the cross-linking reinforcing agent adopts titanium dioxide nanoparticles 10 parts; the skeleton supporting agent adopts graphite nanoparticles 5 parts; the epoxy resin 48 parts; the temperature-sensitive cross-linking initiator mixed by polyamide, 2-ethyl-4-methyl imidazole and tetraethylenepentamine 10 parts; the diluent mixed by 4-hydroxybutyl vinyl ether or 1,4-butanediol divinyl ether 6 parts; and the water sensitivity remover carbosulfan 4 parts.

[0069] Step 5, after the surface-tolerant epoxy resin coating is cured, the coiled tubing is lifted to replace the special polyester resin nozzle, and the high-strength copolyester hot melt adhesive reinforcement material 3mm is sprayed through the coiled tubing high-pressure spraying, and the coating is cured at 60 degrees for 24 hours.

[0070] The high-strength copolyester hot melt adhesive formula is terephthalic acid, 1,4-butanediol, dimethyl terephthalate, titanium tetrabutoxide, dimer acid and hydrogenated liquid polybutadiene diol (the method is a conventional hot melt adhesive synthesis method, and the mass ratio is 30:1000:12:0.03:20:12.

[0071] Step 6, water pressure test 15 MPa, 30 min pressure drop less than 0.5 MPa is qualified, salvage the bridge plug, down the pump completion.

[0072] Example 4

[0073] The implementation object is H193-11 well put into production in July 2013, perforation section 1500-1520 m, dynamic liquid level 1200 m, MTT+MIT engineering logging in July 2020, showing that there is a large section of corrosion in the casing at 1380-1460 m.

[0074] This embodiment adopts downhole casing inner wall polyester hot melt adhesive spraying process for reinforcement repair, which is implemented according to the following steps:

[0075] Step 1, bridge plug: a retrievable bridge plug is lowered into the casing at 1490 m below the corrosion perforation section, and sand is filled to 1465 m below the corrosion section.

[0076] Step 2, remove oil stains, dirt, and corrosion products from the inner wall of the casing: lower the coiled tubing with high-pressure rotating nozzles. The coiled tubing with high-pressure rotating nozzles is lowered to 1 meter below the corrosion section, and the ground pump truck injects cleaning fluid through the coiled tubing. The water pump injection pressure is 8 MPa. The pressure is pressed while the tubing is lifted up, and the oil stains, dirt, and corrosion products in the inner wall of the casing are cleaned.

[0077] Step 3, lower the coiled tubing to suck the wellbore liquid and dry the wellbore casing: the cable is laid in the coiled tubing to connect the electric heating tube, slowly lower the cleaning well section and heat to 90 degrees to ensure the dryness of the inner wall of the wellbore.

[0078] Step 4, raise the coiled tubing to replace the coating nozzle, lower to 10 meters above the retrievable bridge plug, and spray the surface-tolerant epoxy resin coating through the coiled tubing high-pressure nozzle. Spray 0.3 mm on the inner wall of the casing from bottom to top. Raise the coiled tubing and the nozzle, and the resin coating is cured at 45 degrees under the temperature of the wellbore for 24 hours.

[0079] Among them, the cross-linking reinforcing agent uses titanium dioxide nanoparticles 11 parts; the skeleton supporting agent uses graphite nanoparticles 5 parts; the epoxy resin 55 parts; the temperature-sensitive cross-linking initiator mixed from polyamide, 2-ethyl-4-methyl imidazole and tetraethylene pentamine 10 parts; the diluent mixed from 4-hydroxybutyl vinyl ether or 1,4-butanediol divinyl ether 8 parts; and the water sensitivity remover carbosulfan 4 parts.

[0080] Step 5, after the surface-tolerant epoxy resin coating is cured, the coiled tubing is raised to replace the special polyester resin nozzle, and the high-strength copolyester hot melt adhesive reinforcement material is sprayed 3 mm through the coiled tubing high-pressure nozzle. The coating is cured at 60 degrees for 24 hours.

[0081] The high-strength copolyester hot melt adhesive formula is terephthalic acid, 1,4-butanediol, dimethyl terephthalate, titanium tetrabutylate, dimer acid, and hydrogenated liquid polybutadiene diol (the method is a conventional hot melt adhesive synthesis method, and the mass ratio is 30:11000:13:0.03:25:16).

[0082] Step 6, water pressure test 15 MPa, 30 min pressure drop less than 0.5 MPa is qualified, salvage the bridge plug, and lower the pump to complete the well.

[0083] Example 5

[0084] The implementation object is X35-58 well put into production in March 2017, the perforated section is 1500-1520 m, the dynamic liquid level is 1200 m, and the MTT+MIT engineering logging in July 2020 shows that there is a large section of corrosion in the casing at 1380-1460 m.

[0085] In this embodiment, the downhole casing inner wall polyester hot melt adhesive spraying process is used for reinforcement repair, and the implementation is specifically as follows:

[0086] Step 1, bridge plug: a fishable bridge plug is lowered into the casing at 1700 m below the corrosion perforated section, and sand is filled to 1675 m below the corrosion section.

[0087] Step 2, remove oil stains, dirt, and corrosion products from the inner wall of the casing: lower the coiled tubing with a high-pressure rotating nozzle into the corrosion section. The coiled tubing with a high-pressure rotating nozzle is lowered to 1 meter below the corrosion section, the ground pump truck injects cleaning fluid through the coiled tubing, the water pump injection pressure is 10 MPa, the pressure is pressed while the tubing is lifted, and the oil stains, dirt, and corrosion products on the inner wall of the casing are cleaned.

[0088] Step 3, lower the coiled tubing to suck the wellbore liquid, lay the cable in the coiled tubing to connect the electric heating tube, slowly lower the cleaning well section and heat to 100 degrees to ensure that the inner wall of the wellbore is dry.

[0089] Step 4, raise the coiled tubing to replace the coating nozzle, lower to 10 meters above the fishable bridge plug, spray surface-tolerant epoxy resin coating through the coiled tubing high-pressure nozzle, spray 0.3 mm on the inner wall of the casing from bottom to top, and raise the coiled tubing and the nozzle. The resin coating is cured for 24 hours at 60 degrees under the temperature of the wellbore.

[0090] Among them, the cross-linking reinforcing agent adopts titanium dioxide nanoparticles 8 parts; the skeleton supporting agent adopts graphite nanoparticles 5 parts; the epoxy resin 53 parts; the temperature-sensitive cross-linking initiator mixed by polyamide, 2-ethyl-4-methyl imidazole and tetraethylenepentamine 9 parts; the diluent mixed by 4-hydroxybutyl vinyl ether or 1,4-butanediol divinyl ether 7 parts; and the water sensitivity remover carbosulfan 3 parts.

[0091] Step 5, after the surface-tolerant epoxy resin coating is cured, the coiled tubing replacement special polyester resin spray head is taken out, and the high-strength copolyester hot melt adhesive reinforcing material 3 mm is sprayed through the coiled tubing high pressure, and the coating is cured for 24 hours at 60 degrees.

[0092] The high-strength copolyester hot melt adhesive formula is terephthalic acid, 1,4-butanediol, dimethyl terephthalate, titanium tetrabutoxide, dimer acid, and hydrogenated liquid polybutadiene diol, which is synthesized (the method is a conventional hot melt adhesive synthesis method, and the mass ratio is 30:11400:15:0.05:30:18.

[0093] Step 6, water pressure test 15 MPa, 30 min pressure drop less than 0.5 MPa is qualified, salvage the bridge plug, and down the pump to complete the well.

[0094] The field test of the above examples shows that the surface-tolerant epoxy resin coating can be constructed in a closed environment downhole, the formula has a wide range of adaptation, and the coating surface is suitable. After the well is completed for 6-12 months, the production data of the oil well is observed, the production fluid and water content are normal, the water quality analysis has no upper formation water backflow into the wellbore, which shows that the process is well applied in the field.

Claims

1. A process for the application of a polyester hot melt glue to the inside of a downhole casing, characterised in that, The method is implemented according to the following steps: Step 1, bridge plug, down to the fishable bridge plug at 10-30m below the casing corrosion perforation section, and fill sand to 5m below the perforation section; Step 2, down the coiled tubing with high-pressure rotating nozzle, the coiled tubing with high-pressure rotating nozzle is lowered to 1m below the lower edge of the corrosion section, the ground pump truck injects cleaning fluid through the coiled tubing, the water pump injection pressure is 5-10MPa, the pressure is pressed while the tubing is lifted, and the inner wall of the casing is cleaned of oil stains, scale and corrosion products; Step 3, after the coiled tubing is used to suck the wellbore liquid, the cable is laid in the coiled tubing to connect the electric heating pipe, the well section is slowly lowered and heated, the temperature is heated to 60-100 degrees, the wellbore casing is dried, and the inner wall of the wellbore is dried; Step 4, the surface tolerant epoxy resin coating is sprayed on the inner wall of the casing and then solidified; Step 5, high-pressure spraying of copolyester hot melt adhesive reinforcing material and then solidification; Step 6, after the high-strength copolyester hot melt adhesive reinforcing material coating in step 5 is solidified, pressure test is performed, after the pressure test is qualified, the bridge plug is fished out, and the pump is used for well completion.

2. The downhole in-casing wall polyester hot melt glue spray process of claim 1, wherein, The surface tolerant epoxy resin coating in step 4 comprises the following components in a mass ratio: 70-80 parts of coating, 10-20 parts of cross-linking reinforcing agent, and 5-15 parts of skeleton supporting agent.

3. The downhole in-casing wall polyester hot melt glue spray process of claim 2, wherein, The coating comprises the following components: epoxy resin, temperature-sensitive cross-linking initiator, diluent, and water sensitivity remover; the mass ratio of the epoxy resin, temperature-sensitive cross-linking initiator, diluent, and water sensitivity remover is 12-24:1-3:1-2:1; the epoxy resin is the main agent in the coating, the temperature-sensitive cross-linking initiator is a mixture of polyamide, 2-ethyl-4-methyl imidazole and tetraethylene pentamine, the diluent is a mixture of 4-hydroxybutyl vinyl ether and 1,4-butanediol divinyl ether, and the water sensitivity remover is carbosulfan.

4. The downhole in-casing wall polyester hot melt glue spray process of claim 2, wherein, The cross-linking reinforcing agent adopts silica or titanium dioxide nanoparticles, and the silicon bond or titanium bond is polymerized with the epoxy coating; the skeleton supporting agent adopts graphite nanoparticles to fill the intermolecular voids of the polymer, and plays a skeleton supporting role.

5. The downhole in-casing wall polyester hot melt glue spray process of claim 1, wherein, The specific steps of step 5 are as follows: after the surface tolerant epoxy resin coating in step 4 is solidified, the coiled tubing is lifted to replace the special polyester resin nozzle, the nozzle is lowered to 10m above the fishable bridge plug, and 1-3mm of copolyester hot melt adhesive reinforcing material is sprayed through the coiled tubing at high pressure, and the coating is solidified at 60℃ in the wellbore for 24 hours.

6. The downhole in-casing wall polyester hot melt glue spray process of claim 5, wherein, The copolyester hot melt adhesive reinforcing material in step 5 comprises the following components: terephthalic acid, 1,4-butanediol, dimethyl phthalate, titanium tetrabutyl titanate, dimer acid, and hydrogenated liquid polybutadiene diol, and the above components are synthesized into copolyester hot melt adhesive reinforcing material according to the conventional hot melt adhesive.

7. The downhole in-casing wall polyester hot melt glue spray process of claim 6, wherein, The terephthalic acid, 1,4-butanediol, dimethyl phthalate, titanium tetrabutyl titanate, dimer acid, and hydrogenated liquid polybutadiene diol are synthesized according to a mass ratio of 30:110-11400:10-15:0.01-0.05:10-30:8-18.

8. The downhole in-casing wall polyester hot melt glue spray process of claim 5, wherein, The liquid viscosity of the copolyester hot melt adhesive reinforcing material is 800-1000 mPa·s at normal temperature, it is a soft viscous solid in the range of normal temperature-65 DEG C, is not miscible with water, is crosslinked and solidified at 60 DEG C, and the bonding strength of the solidified body is not less than 15 MPa.

9. The downhole in-casing wall polyester hot melt glue spray process of claim 1, wherein, In step 6, 15 MPa water pressure test is used, if the pressure drop is less than 0.5 MPa in 30 min, the pressure test is qualified; otherwise, the wellbore is resprayed and reinforced until the pressure test is qualified.

10. The downhole in-casing wall polyester hot melt glue spray process of claim 1, wherein, The specific steps of step 4 are: the coiled tubing is pulled out to replace the coating nozzle, and is lowered to the 10-meter position along the fishable bridge plug; the coiled tubing is used to spray the surface-tolerant epoxy resin coating at high pressure; the coating is sprayed on the inner wall of the casing from bottom to top at a thickness of 0.3 mm; the coiled tubing and the nozzle are pulled out; and the surface-tolerant epoxy resin coating is cured for 24 hours at the wellbore temperature in the range of 25-60 DEG C.