A preflush suitable for wellbore integrity casing cement sheath repair

Abstract

The application discloses a pre-treatment fluid suitable for wellbore integrity casing cement sheath repair. The pre-treatment fluid is prepared by emulsification of bisphenol A type epoxy resin, catalyst A, catalyst B, solvent, alkoxylation reagent and pH regulator; the catalyst A is one or more of tetrabutylammonium chloride, triethanolamine, sodium hydroxide, magnesium hydroxide and boron trifluoride ether; and the catalyst B is one or more of sodium acetate, ammonium chloride, boron trifluoride and tin tetrachloride. The application can perform cyclic treatment on the broken point before pumping the repair material, and improve the wettability of the surface of the broken point, thereby promoting the repair effect.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well plugging and oil and gas extraction technology, and relates to a pretreatment fluid suitable for repairing the cement sheath of the casing to ensure wellbore integrity. Background Technology

[0002] In the petroleum industry, numerous factors (such as large-scale acid fracturing, geology, plastic creep and corrosion of salt rock, etc.) can cause varying degrees of deformation in the casing cement sheath, especially in formations prone to collapse, with severe plastic creep and poor cementing quality. This not only seriously affects the safety and profitability of oil and gas fields but also causes huge economic losses to major oil fields. Currently, commonly used technologies for casing cement sheath repair include casing patching technology, casing replacement technology, small casing secondary cementing technology, and plugging technology. Among these, plugging technology is the most commonly used. By injecting the plugging agent into the broken section of the casing and allowing it to solidify, the broken point is sealed. It has good pressure resistance and a large diameter, and is suitable for repairs under various damage conditions. The other three technologies are not suitable for repairing micro-cracks in the casing cement sheath due to high construction costs, implementation difficulties, and high equipment requirements.

[0003] The ash-filling and sealing process repairs leaks by injecting material into the leak point. However, if the repair material cannot bond tightly to the surface of the leak point after curing, the repair effect will be severely affected. Summary of the Invention

[0004] To address the problem that existing repair technologies are not effective in repairing casing / cement sheath gaps, the purpose of this invention is to provide a pretreatment fluid suitable for repairing casing / cement sheath gaps that can indirectly promote the repair effect of casing / cement sheath gaps.

[0005] This invention can perform a circulation treatment on the broken point before pumping in the repair material, which improves the wettability of the surface of the broken point and promotes the improvement of the repair effect.

[0006] This invention provides a pretreatment fluid suitable for repairing the cement sheath of casing with wellbore integrity. It is made by emulsification of bisphenol A type epoxy resin, catalyst A, catalyst B, solvent, alkoxylation agent and pH adjuster.

[0007] The catalyst A is one or more of tetrabutylammonium chloride, triethanolamine, sodium hydroxide, magnesium hydroxide, and boron trifluoride diethyl ether;

[0008] The catalyst B is one or more of sodium acetate, ammonium chloride, boron trifluoride, and tin tetrachloride.

[0009] In the aforementioned pretreatment solution, the weight ratio of the bisphenol A type epoxy resin, catalyst A, solvent, catalyst B, and alkoxylation reagent is 1:0.001~0.005:1~3:0.0008~0.009:0.5~1.5.

[0010] In the pretreatment solution of the present invention, the weight ratio of the bisphenol A type epoxy resin, catalyst A, solvent, catalyst B and alkoxylation reagent can be specifically 1:0.002:1.4:0.001:1.2 or 1:0.0016:1.6:0.0008:1.

[0011] In the above-mentioned pretreatment solution, the pH adjuster adjusts the pH of the pretreatment solution to 6-7.

[0012] In the above-mentioned pretreatment solution, the solvent is one or more of stearic acid, isostearic acid, lauric acid, and palmitic acid.

[0013] In the above-mentioned pretreatment solution, the alkoxylating agent is one or more of ethylene oxide, propylene oxide, and butane oxide.

[0014] In the above-mentioned pretreatment solution, the pH adjuster is one or more of hydrochloric acid, sulfuric acid, propionic acid, and dodecylbenzenesulfonic acid.

[0015] In the aforementioned pretreatment solution, the viscosity is 0–50 cP and the density is 1–1.05 g / cm³. 3 .

[0016] The present invention also provides a method for preparing the above-mentioned pretreatment solution, comprising the following steps: 1) stirring and mixing the bisphenol A type epoxy resin and the catalyst A, heating and adding the solvent to react, testing the epoxy value of the system, and stopping the reaction when the epoxy value no longer changes;

[0017] 2) Add the catalyst B to the reaction system of step 1), and under vacuum conditions, after heating, continue to add the alkoxylating agent and continue the reaction until the system pressure is negative and the pressure no longer changes, then stop the reaction;

[0018] 3) Cool the reaction system in step 2) to 50-70℃ (specifically 65℃), add the pH adjuster to adjust the pH of the system, and the pretreatment solution is obtained.

[0019] In the above method, in step 1), the temperature is raised to 140-160°C, specifically 150°C.

[0020] In the above method, in step 2), the temperature is 170–190℃, specifically 180℃.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The pretreatment fluid of this invention can not only clean the surface of the cement sheath gap in the casing, change the surface wettability, and improve the repair effect of the gap surface, but also form a protective film by adsorbing on the inner surface of the well casing, thereby improving the corrosion resistance of the inner surface of the casing and preventing the fluids used in subsequent well operations from causing corrosion damage. Detailed Implementation

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0024] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0025] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0026] This invention provides a pretreatment fluid suitable for repairing the cement sheath of casing with wellbore integrity. It is made by emulsification of bisphenol A type epoxy resin, catalyst A, catalyst B, solvent, alkoxylating agent and pH adjuster.

[0027] Furthermore, in the pretreatment solution, the weight ratio of the bisphenol A type epoxy resin, the catalyst A, the solvent, the catalyst B, and the alkoxylating agent is 1:0.001~0.005:1~3:0.0008~0.009:0.5~1.5.

[0028] The present invention also provides a method for preparing the above-mentioned pretreatment solution, comprising the following steps: 1) stirring and mixing the bisphenol A type epoxy resin and the catalyst A, heating to 140-160°C, adding the solvent to react, testing the epoxy value of the system, and stopping the reaction when the epoxy value no longer changes;

[0029] 2) Add the catalyst B to the reaction system of step 1), heat to 170-190°C under vacuum, continuously add the alkoxylation reagent, and continue the reaction until the system pressure is negative and no longer changes, then stop the reaction;

[0030] 3) Cool the reaction system in step 2) to 50-70℃, add the pH adjuster to adjust the pH of the system, and the pretreatment solution is obtained.

[0031] Example 1

[0032] In a reactor, 500g of bisphenol A epoxy resin and 1g of triethanolamine were stirred and mixed evenly. The mixture was heated to 150℃, and 700g of palmitic acid was added to the reactor for reaction. The epoxy value of the system was tested, and it no longer changed. Then, 0.5g of sodium acetate was added to the reactor, and a vacuum was applied. The temperature was raised to 180℃, and 600g of ethylene oxide was continuously added. The reaction continued until the pressure inside the reactor was negative and no longer changed. The heating was turned off, and the reactor was circulated and cooled. The system temperature dropped to 65℃, and sulfuric acid was added to the reactor to adjust the pH of the system to 7, thus obtaining the pretreatment solution A1.

[0033] The surface tension of the pretreatment fluid was tested according to GB / T 5549-2010 "Determination of Surface Tension of Surfactants by Pull-up Liquid Film Method", and the result was 35.14 mN / m. The viscosity of the pretreatment fluid at 25℃ was tested according to GB / T 11145-2014 "Determination of Low-Temperature Viscosity of Lubricants by Brockfeld Viscometer Method", and the result was 45 cP.

[0034] Example 2

[0035] In a reactor, 500g of bisphenol A epoxy resin, 0.5g of tetrabutylammonium chloride, and 0.5g of triethanolamine were stirred and mixed evenly. The mixture was heated to 150℃, and 800g of lauric acid was added to the reactor to carry out the reaction. The epoxy value of the system was tested, and it no longer changed. Then, 0.4g of ammonium chloride and 0.3g of tin tetrachloride were added to the reactor, and a vacuum was applied. The temperature was raised to 180℃, and 500g of ethylene oxide was continuously added. The reaction continued until the pressure inside the reactor was negative and no longer changed. The heating was turned off, and the reactor was circulated and cooled. The system temperature dropped to 65℃, and propionic acid was added to the reactor to adjust the pH of the system to 7, thus obtaining the pretreatment solution A2.

[0036] The surface tension of the pretreatment fluid was tested according to GB / T 5549-2010 "Determination of Surface Tension of Surfactants by Pull-up Liquid Film Method", and the result was 30.56 mN / m. The viscosity of the pretreatment fluid at 25℃ was tested according to GB / T 11145-2014 "Determination of Low-Temperature Viscosity of Lubricants by Brockfeld Viscometer Method", and the result was 42 cP.

[0037] Example 3

[0038] In a reactor, 500g of bisphenol A epoxy resin and 0.5g of boron trifluoride ether were stirred and mixed evenly. The mixture was heated to 150°C, and 600g of isostearic acid was added to the reactor for reaction. The epoxy value of the system was tested, and it no longer changed. Then, 0.4g of boron trifluoride was added to the reactor, and a vacuum was applied. The temperature was raised to 180°C, and 400g of propylene oxide was continuously added. The reaction continued until the pressure inside the reactor was negative and no longer changed. The heating was turned off, and the reactor was circulated and cooled. The system temperature dropped to 65°C, and hydrochloric acid was added to the reactor to adjust the pH of the system to 7, thus obtaining the pretreatment solution A3.

[0039] The surface tension of the pretreatment fluid was tested according to GB / T 5549-2010 "Determination of Surface Tension of Surfactants by Pull-up Liquid Film Method", and the result was 32.28 mN / m. The viscosity of the pretreatment fluid at 25℃ was tested according to GB / T 11145-2014 "Determination of Low-Temperature Viscosity of Lubricants by Brockfeld Viscometer Method", and the result was 44 cP.

[0040] Comparative Example 1

[0041] 500g of bisphenol A epoxy resin was stirred and mixed evenly in a reactor. The temperature was raised to 150℃, and 600g of palmitic acid was added to the reactor for reaction. The epoxy value of the system was tested. If the epoxy value no longer changed, 0.4g of sodium acetate was added to the reactor and the system was vacuumed. The temperature was raised to 180℃, and 400g of propylene oxide was continuously added. The reaction continued until the pressure inside the reactor was negative and no longer changed. The heating was turned off, and the reactor was circulated and cooled. The system temperature dropped to 65℃, and hydrochloric acid was added to the reactor to adjust the pH of the system to 7, thus obtaining the pretreatment solution A4.

[0042] The surface tension of the pretreatment fluid was tested according to GB / T 5549-2010 "Determination of Surface Tension of Surfactants by Pull-up Liquid Film Method", and the result was 20.58 mN / m. The viscosity of the pretreatment fluid at 25℃ was tested according to GB / T 11145-2014 "Determination of Low-Temperature Viscosity of Lubricants by Brockfeld Viscometer Method", and the result was 58 cP.

[0043] Comparative Example 2

[0044] In a reactor, 500g of bisphenol A epoxy resin and 0.5g of boron trifluoride ether were stirred and mixed evenly. The mixture was heated to 150°C, and 600g of isostearic acid was added to the reactor to carry out the reaction. The epoxy value of the system was tested, and the epoxy value no longer changed. The temperature was then increased to 180°C, and 400g of propylene oxide was continuously added. The reaction continued until the pressure inside the reactor was negative and no longer changed. The heating was then turned off, and the reactor was circulated and cooled. The system temperature dropped to 65°C, and hydrochloric acid was added to the reactor to adjust the pH of the system to 7, thus obtaining the pretreatment solution A5.

[0045] The surface tension of the pretreatment fluid was tested according to GB / T 5549-2010 "Determination of Surface Tension of Surfactants by Pull-up Liquid Film Method", and the result was 22.46 mN / m. The viscosity of the pretreatment fluid at 25℃ was tested according to GB / T 11145-2014 "Determination of Low-Temperature Viscosity of Lubricants by Brockfeld Viscometer Method", and the result was 52 cP.

[0046] (1) Wetting performance test

[0047] Cement block surface wettability: Cement slurry was prepared according to the formula (formula: water + 300g G grade cement). After preparation, it was poured into a mold and placed in a 60℃ water bath until it was completely cured. After that, it was taken out and soaked in the pretreatment solutions A1-A5 prepared in Examples 1-3 and Comparative Examples 1-2 and distilled water for 24 hours and then dried. Subsequently, the contact angle between distilled water and untreated cement blocks and cement blocks treated with pretreatment solutions was measured using a fully automatic contact angle measuring instrument. The specific test results are shown in Table 1.

[0048] Table 1 Contact Angle with Cement Block

[0049] Serial Number Types of solutions for soaking cement blocks Contact angle θ / ° 1 Pretreatment fluid A1 122.5 2 Pretreatment fluid A2 138.2 3 Pretreatment fluid A3 167.0 4 Pretreatment fluid A4 76.9 5 Pretreatment fluid A5 57.6 6 distilled water 29.1 7 Unsoaked 26.8

[0050] Simulated sleeve surface wettability: Commonly used J-55 sleeve material was processed into test pieces (30 mm in length, 30 mm in width, and 2 mm in height). After grinding and removing rust, the test pieces were cleaned with ethanol and then immersed in the pretreatment solutions A1-A5 prepared in Examples 1-3 and Comparative Examples 1-2, as well as distilled water, for 24 hours and then dried. Subsequently, the contact angles between distilled water and untreated test pieces and test pieces treated with pretreatment solutions were measured using a DSA100 contact angle meter. The specific test results are shown in Table 2.

[0051] Table 2 Contact Angle with Specimen

[0052] Serial Number Type of immersion solution for specimens Contact angle θ / ° 1 Pretreatment fluid A1 115.8 2 Pretreatment fluid A2 128.1 3 Pretreatment fluid A3 161.5 4 Pretreatment fluid A4 83.0 5 Pretreatment fluid A5 53.7 6 distilled water 22.8 7 Unsoaked 20.2

[0053] As can be seen from Tables 1 and 2, the contact angles of the cement blocks and specimens after soaking in pretreatment solutions A1-A6 changed, indicating a change in wettability. Among them, the cement blocks and specimens treated with pretreatment solutions A1-A3 prepared in Examples 1-3 of this invention changed from hydrophilic to oleophilic, with pretreatment solution A3 showing the best oleophilic effect. The contact angles of the cement blocks and specimens treated with pretreatment solutions A4 and A5 prepared in Comparative Examples 1-2 changed, but they still exhibited hydrophilicity. This is mainly because no corresponding catalyst was added during the emulsification process of pretreatment solutions A4 and A5 prepared in Comparative Examples 1-2, resulting in poor wetting reversal ability of the synthesized treatment solutions.

[0054] (2) Corrosion resistance

[0055] Commonly used J-55 type casing material was processed into test pieces (30mm in length, 30mm in width, and 2mm in height). After grinding and removing rust, the test pieces were cleaned with ethanol and dried in a 60℃ oven for 24 hours. The weighed test pieces were then immersed in the pretreatment solutions A1-A5 prepared in Examples 1-3 and Comparative Examples 1-2, as well as distilled water, for 24 hours. After removal, the test pieces were placed in a 10% hydrochloric acid environment for 30 days of corrosion. The samples were then removed to remove the loose corrosion products on the surface, rinsed with distilled water, and dried in a 60℃ oven for 24 hours. The corrosion resistance efficiency was calculated according to the petroleum and natural gas standard SY / T5273-2000, thus characterizing the corrosion resistance of the pretreatment solutions A1-A5 prepared in Examples 1-3 and Comparative Examples 1-2. The specific test results are shown in Table 3.

[0056] Table 3 Corrosion Resistance

[0057] Serial Number Type of immersion solution for specimens Corrosion resistance efficiency / % 1 Pretreatment fluid A1 95.83 2 Pretreatment fluid A2 96.92 3 Pretreatment fluid A3 98.71 4 Pretreatment fluid A4 66.16 5 Pretreatment fluid A5 59.52 6 distilled water 42.38 7 Unsoaked 38.95

[0058] As shown in Table 3, the corrosion resistance of the specimens treated with pretreatment solutions A1-A5 prepared in Examples 1-3 and Comparative Examples 1-2 was significantly improved. Among them, the specimens treated with pretreatment solution A3 had the strongest corrosion resistance, indicating that the protective film structure formed by pretreatment solution A3 on the surface of the specimen is strong and dense, which can prevent the fluid from contacting the specimen and avoid corrosion damage to the specimen.

[0059] In summary, the pretreatment fluid of this invention can indirectly improve the repair effect of casing and cement sheath gaps. It can not only clean the surface of the casing cement sheath gaps, change the surface wettability, and improve the repair effect of the gap surface, but also form a protective film by adsorbing on the inner surface of the well casing, thereby improving the corrosion resistance of the inner surface of the casing and preventing the fluids used in subsequent well operations from causing corrosion damage.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. The application of a pretreatment fluid in the pretreatment for repairing cement sheaths in wellbore integrity casing, characterized in that, The pretreatment solution is prepared by emulsification of bisphenol A type epoxy resin, catalyst A, catalyst B, solvent, alkoxylating agent and pH adjuster; The catalyst A is one or more of tetrabutylammonium chloride, triethanolamine, sodium hydroxide, magnesium hydroxide, and boron trifluoride diethyl ether; The catalyst B is one or more of sodium acetate, ammonium chloride, boron trifluoride, and tin tetrachloride; In the pretreatment solution, the weight ratio of the bisphenol A type epoxy resin, catalyst A, solvent, catalyst B, and alkoxylation reagent is 1:0.001~0.005:1~3:0.0008~0.009:0.5~1.5; The pH adjuster adjusts the pH of the pretreatment solution to 6-7; The solvent is one or more of stearic acid, isostearic acid, lauric acid, and palmitic acid; The alkoxylating agent is one or more of ethylene oxide, propylene oxide, and butane oxide. The pH adjuster is one or more of hydrochloric acid, sulfuric acid, propionic acid, and dodecylbenzenesulfonic acid; The preparation method of the pretreatment solution includes the following steps: 1) Stir and mix the bisphenol A type epoxy resin and the catalyst A, heat the mixture to a temperature of 140~160℃, add the solvent to carry out the reaction, test the epoxy value of the system, and stop the reaction when the epoxy value no longer changes. 2) Add the catalyst B to the reaction system in step 1), heat to 170~190°C under vacuum, and then continuously add the alkoxylation reagent. Continue the reaction until the system pressure is negative and no longer changes, then stop the reaction. 3) Cool the reaction system in step 2) to 50~70℃, add the pH adjuster to adjust the pH of the system to 6~7, and the pretreatment solution is obtained.

2. The application according to claim 1, characterized in that, The viscosity of the pretreatment solution is 42-50 cP.