Workover fluid suitable for high-temperature well section and preparation method of workover fluid

Abstract

The invention belongs to the technical field of oil and gas well workover, and particularly relates to a modified phenolic resin-based solid-free workover fluid suitable for a high-temperature well section and a preparation method of the modified phenolic resin-based solid-free workover fluid. The modified phenolic resin-based solid-free workover fluid comprises the following raw materials in parts by weight: 150 parts of phenol, 205-258 parts of a formaldehyde aqueous solution, 3-4.5 parts of ammonia water, 3-7 parts of phosphoric acid, 142-426 parts of 1, 4-butanediol and 0-5 parts of a 30% sodium hydroxide solution. According to the invention, 1, 4-butanediol is introduced as a modifier, and reaction conditions are controlled, so that high-temperature delayed curing of the workover fluid is realized, the viscosity of the workover fluid is regulated and controlled, the dual requirements of workover operation on the setting time and the viscosity under a high-temperature condition can be fully met, and the applicable working conditions of the workover fluid are widened.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas well workover, and particularly relates to a workover fluid suitable for high-temperature well sections and a preparation method thereof. BACKGROUND

[0002] Cement sheath sealing integrity is crucial for safe operation of the wellbore, and micro-cracks in the cement sheath induced by external factors are the main factor leading to annular pressure buildup in oil and gas wells. At present, the treatment of annular pressure buildup wells in engineering mostly adopts methods such as periodic detection and pressure release, cement sheath micro-crack self-repairing technology and cement squeezing technology. However, long-term detection and pressure release of oil and gas wells will consume huge costs and cannot fundamentally solve the problem, and there are certain safety hazards. Although the cement self-repairing technology has remarkable effects, it has not been widely applied. The cement squeezing technology is the most common, but ordinary G-grade cement is difficult to be injected into micro-cracks below 500 μm due to its large solid phase particles. Although the particle size of ultra-fine cement is improved, it is still difficult to enter micro-cracks below 300 μm, and the repair effect is still poor. Compared with epoxy resin, phenolic resin has excellent water solubility, fluidity, adhesion and high temperature resistance, and is more in line with the concept of modern oilfield green and low-cost operation. However, with the development of oil and gas exploitation to deep and ultra-deep layers, the conventional phenolic resin workover fluid cannot meet the needs of workover operations under high-temperature working conditions due to its rapid solidification and high viscosity.

[0003] Etherification modification of phenolic resin is a key means to improve its solidification rate, but the traditional n-butanol etherified phenolic resin has the following defects: (1) poor water solubility, which is easy to cause damage to equipment; (2) high viscosity, which needs to be reduced by diluent, and the diluent will negatively affect the mechanical properties of the resin, resulting in poor plugging effect; (3) the n-butanol modified phenolic resin has a strong odor and is toxic, which is easy to threaten the environment and the health of construction personnel. SUMMARY

[0004] In view of the problems in the prior art, the application discloses a workover fluid suitable for high-temperature well sections and a preparation method thereof. The workover fluid obtained by the application has good water solubility, low viscosity, high-temperature delayed solidification and excellent mechanical properties.

[0005] The workover fluid suitable for high-temperature well sections comprises the following raw materials in parts by weight: phenol 150 parts, formaldehyde aqueous solution 205-258 parts, ammonia water 3-4.5 parts, phosphoric acid 3-7 parts, 1,4-butanediol 142-426 parts and 30% sodium hydroxide aqueous solution 0-5 parts.

[0006] The specific preparation steps are as follows: (1) weigh the molten phenol and the formaldehyde aqueous solution, mix and heat to stir and react to obtain a reaction solution I; (2) adding ammonia water to the reaction liquid I, heating, stirring to obtain reaction liquid II; (3) adding formaldehyde aqueous solution to the reaction liquid II again, heating and stirring to obtain reaction liquid III; (4) adding 1, 4-butanediol to the reaction liquid III after cooling, stirring uniformly, adding phosphoric acid to adjust pH value, heating, stirring to obtain reaction liquid IV; (5) cooling the reaction liquid IV, adding 30% sodium hydroxide aqueous solution to adjust pH value to obtain the workover fluid.

[0007] The reaction temperature in step (1) is 50-55℃, and the reaction time is 30-40 min.

[0008] After heating in step (2), the temperature is 60-65℃, and the stirring time is 10-30 min; the ammonia water can provide the necessary alkaline environment for the synthesis of thermosetting phenolic resin, and the catalytic effect is more moderate, so that the synthesis reaction can be easily controlled, which is conducive to the extension of the curing time of the resin, and also avoids the high viscosity of the workover fluid.

[0009] After heating in step (3), the temperature is 70-80℃, and the stirring time is 40-60 min.

[0010] In step (4), the reaction liquid III needs to be cooled to 30-35℃ within 5-10 min, so as to prevent the subsequent 1, 4-butanediol from volatilizing, and also to prevent the residual temperature from causing the synthesis reaction to continue during the pH value adjustment; after adjusting the pH value by phosphoric acid, the pH value is in the range of 3-7.

[0011] After heating in step (4), the temperature is 100-120℃, and the stirring time is 1-3 h.

[0012] After cooling in step (5), the temperature is 30℃, and the pH value is 7.

[0013] The mass ratio of the formaldehyde aqueous solution in step (1) to the formaldehyde aqueous solution in step (3) is 2:1.

[0014] In the present application, 1, 4-butanediol is selected as the modifier, which has two hydroxyl groups in the molecule and has stronger hydrogen bonding ability with water molecules, so it has excellent water solubility, which lays a foundation for synthesizing modified phenolic resin with better water solubility. In terms of environmental protection and safety, 1, 4-butanediol is non-toxic and odorless, which can significantly improve the working environment, reduce the health risk and the safety hidden danger in production. In terms of high-temperature retarding, 1, 4-butanediol can react with the hydroxymethyl in the phenolic resin to introduce ether bond to occupy the crosslinking site, thereby reducing the reactivity of the resin and meeting the demand of high-temperature retarding. In addition, the double hydroxyl property of 1, 4-butanediol may make it act as a crosslinking site in the resin molecular chain, which has a positive effect on the toughness and mechanical properties of the network after curing.

[0015] Compared with the prior art, the present application has the following beneficial effects: (1) The present application uses ammonia as a catalyst in the synthesis process of the resin, which is conducive to prolonging the curing time of the resin, and avoids the problem of excessive viscosity of the workover fluid, so that it can fully meet the dual requirements of the workover operation under high temperature conditions for the setting time and the viscosity.

[0016] (2) In the present application, the reaction solution III is directly used for subsequent modification without any treatment, which avoids the problem of excessive viscosity of the workover fluid.

[0017] (3) In the synthesis process of the present application, a modifier for etherification reaction with methylol is introduced, which effectively reduces the chemical reactivity and meets the stringent requirement of the workover fluid for the setting time under high temperature and deep well operation.

[0018] (4) The present application introduces a modifier with multiple hydroxyl groups, which is non-toxic and odorless, has low viscosity and good water solubility, significantly improves the water solubility of the etherified modified phenolic resin, and does not cause false viscosity rise due to poor water solubility, and greatly reduces the harm to the human body, equipment and environment. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The sealing effect diagram of the workover fluid of the present application on 100 μm cement micro-cracks. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application are clearly and completely described in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0021] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as familiar to those skilled in the art. In addition, any method and material similar or equivalent to those described herein can be applied to the present application. The preferred implementation methods and materials described herein are only used for demonstration, but cannot limit the content of the present application.

[0022] Example 1 A workover fluid suitable for high temperature well sections, comprising the following raw materials by weight: phenol 150 g, formaldehyde aqueous solution 207 g, ammonia 3.75 g, phosphoric acid 5 g, 1,4-butanediol 284 g, 30% sodium hydroxide solution 3 g; The specific preparation steps are as follows: (1) take the molten phenol and 138 g formaldehyde aqueous solution, mix and then put into a three-necked flask, stir under the condition of water bath 50℃ for 30 min, to obtain solution I; (2) add ammonia water to solution I, stir under the condition of warming to 60℃ for 10 min, to obtain solution II; (3) add 69 g formaldehyde aqueous solution to solution II, stir under the condition of warming to 80℃ for 40 min, to obtain solution III; (4) cool solution III to 30℃ within 5 min, add 1, 4-butanediol and stir uniformly, add phosphoric acid to adjust pH = 3, stir under the condition of oil bath 110℃ for 2 h, to obtain solution IV; (5) cool solution IV to 30℃, add 30% sodium hydroxide solution to adjust pH = 7, to obtain the workover fluid.

[0023] Example 2 A workover fluid suitable for high temperature well section, comprising the following raw materials by weight: phenol 150 g, formaldehyde aqueous solution 207 g, ammonia water 4.5 g, phosphoric acid 6 g, 1, 4-butanediol 426 g, 30% sodium hydroxide solution 3.5 g; The specific preparation steps are as follows: (1) take the molten phenol and 138 g formaldehyde aqueous solution, mix and then put into a three-necked flask, stir under the condition of water bath 50℃ for 30 min, to obtain solution I; (2) add ammonia water to solution I, stir under the condition of warming to 60℃ for 10 min, to obtain solution II; (3) add 69 g formaldehyde aqueous solution to solution II, stir under the condition of warming to 80℃ for 40 min, to obtain solution III; (4) cool solution III to 30℃ within 10 min, add 1, 4-butanediol and stir uniformly, add phosphoric acid to adjust pH = 3, stir under the condition of oil bath 120℃ for 3 h, to obtain solution IV; (5) cool solution IV to 30℃, add 30% sodium hydroxide solution to adjust pH = 7, to obtain the workover fluid.

[0024] Example 3 A workover fluid suitable for high temperature well section, comprising the following raw materials by weight: phenol 150 g, formaldehyde aqueous solution 207 g, ammonia water 3 g, phosphoric acid 3 g, 1, 4-butanediol 142 g, 30% sodium hydroxide solution 1 g; The specific preparation steps are as follows: (1) take the molten phenol and 138 g formaldehyde aqueous solution, mix and then put into a three-necked flask, stir under the condition of water bath 50℃ for 30 min, to obtain solution I; (2) To solution I, add ammonia water, and stir at 60°C for 10 min to obtain solution II; (3) To solution II, add 69 g of formaldehyde aqueous solution, and stir at 80°C for 40 min to obtain solution III; (4) Reduce solution III to 30°C within 5 min, add 1, 4-butanediol, and stir to be uniform, add phosphoric acid to adjust pH = 5, and stir at 110°C for 3 h in an oil bath to obtain solution IV; (5) Reduce solution IV to 30°C, add 30% sodium hydroxide solution to adjust pH = 7 to obtain the workover fluid.

[0025] Example 4 A workover fluid suitable for high-temperature well sections includes the following raw materials by weight: phenol 150 g, formaldehyde aqueous solution 231 g, ammonia water 3.75 g, phosphoric acid 3.5 g, 1, 4-butanediol 426 g, 30% sodium hydroxide solution 1.5 g; The specific preparation steps are as follows: (1) Take molten phenol and 154 g of formaldehyde aqueous solution, mix, and then put into a three-necked flask, and stir at 55°C in a water bath for 40 min to obtain solution I; (2) To solution I, add ammonia water, and stir at 60°C for 10 min to obtain solution II; (3) To solution II, add 77 g of formaldehyde aqueous solution, and stir at 70°C for 60 min to obtain solution III; (4) Reduce solution III to 30°C within 5 min, add 1, 4-butanediol, and stir to be uniform, add phosphoric acid to adjust pH = 5, and stir at 100°C for 2 h in an oil bath to obtain solution IV; (5) Reduce solution IV to 30°C, add 30% sodium hydroxide solution to adjust pH = 7 to obtain the workover fluid.

[0026] Example 5 A workover fluid suitable for high-temperature well sections includes the following raw materials by weight: phenol 150 g, formaldehyde aqueous solution 258 g, ammonia water 3.75 g, phosphoric acid 3 g, 1, 4-butanediol 142 g; The specific preparation steps are as follows: (1) Take molten phenol and 172 g of formaldehyde aqueous solution, mix, and then put into a three-necked flask, and stir at 50°C in a water bath for 30 min to obtain solution I; (2) To solution I, add ammonia water, and stir at 65°C for 10 min to obtain solution II; (3) To solution II, add 86 g of formaldehyde aqueous solution, and stir at 80°C for 40 min to obtain solution III; (4) Solution III was cooled to 30°C in 5 min, 1,4-butanediol was added and stirred uniformly, phosphoric acid was added to adjust pH=7, and oil bath was stirred at 120°C for 2 h to obtain solution IV; (5) Solution IV was cooled to 30°C to obtain the well repair fluid.

[0027] Comparative Example 1 The unmodified well repair fluid comprises the following raw materials by weight: phenol 150 g, formaldehyde aqueous solution 207 g, ammonia water 3.75 g; The specific preparation steps are as follows: (1) Melted phenol and 138 g of formaldehyde aqueous solution were weighed, mixed, and then placed in a three-necked flask, and stirred at 50°C in water bath for 30 min to obtain solution I; (2) Ammonia water was added to solution I, and stirred at 60°C for 10 min to obtain solution II; (3) Formaldehyde aqueous solution was added to solution II, and stirred at 80°C for 40 min to obtain solution III; (4) Solution III was cooled to 30°C to obtain the unmodified well repair fluid.

[0028] Comparative Example 2 A well repair fluid comprises the following raw materials by weight: phenol 150 g, formaldehyde aqueous solution 207 g, sodium carbonate 3.75 g, phosphoric acid 5 g, 1,4-butanediol 284 g, and 30% sodium hydroxide solution 3 g; The specific preparation steps are as follows: (1) Melted phenol and 138 g of formaldehyde aqueous solution were weighed, mixed, and then placed in a three-necked flask, and stirred at 50°C in water bath for 30 min to obtain solution I; (2) Sodium carbonate was added to solution I, and stirred at 60°C for 10 min to obtain solution II; (3) 69 g of formaldehyde aqueous solution was added to solution II, and stirred at 80°C for 40 min to obtain solution III; (4) Solution III was cooled to 30°C in 5 min, 1,4-butanediol was added and stirred uniformly, phosphoric acid was added to adjust pH=3, and oil bath was stirred at 110°C for 2 h to obtain solution IV; (5) Solution IV was cooled to 30°C, 30% sodium hydroxide solution 3 g was added to adjust pH=7 to obtain the well repair fluid.

[0029] Test Example 1 The well repair fluids obtained in Examples 1-5 and Comparative Example 1 were subjected to basic performance evaluation: (1) The viscosity of the modified phenolic resin-based solid-free well repair fluid was measured using NDJ-5S digital viscometer; (2) The setting time of the modified phenolic resin-based solid-free workover fluid was tested according to GB / T 33315-2016; (3) The workover fluid was poured into a mold with a diameter of 25 mm and a height of 50 mm, and after curing at 100°C, 120°C and 150°C, it was cured for 24 hours. The curing strength of the cured workover fluid was tested using a WEW-300B universal testing machine. The test results are shown in Table 1.

[0030] Table 1 Basic properties of the workover fluid described in Examples 1-5 .

[0031] As can be seen from Table 1, the curing time of the modified resin is prolonged, and the curing time and viscosity can be controlled by changing the synthesis conditions. The viscosity of Examples 1-5 is less than 100 mPa·s, which is very suitable for pumping.

[0032] Test Example 2 The sealing performance of the workover fluid in Examples 1-5 was evaluated: (1) A plastic sheet with a thickness of 100 μm was cut into a rectangle of 15 mm x 80 mm and inserted into a rubber plug to fix it; (2) A mold with a diameter of 25 mm and a height of 70 mm was placed on the rubber plug and moved to the center of the plastic sheet; (3) The prepared high-temperature resistant cement slurry was poured into the mold, and the sample was placed in a 90°C constant temperature water bath for 24 hours. During this period, the plastic sheet was removed when the cement slurry reached the initial setting; (4) After 24 hours of curing, the sample was removed, demolded, cut and polished to obtain a cement column with a length of 5 cm and a microcrack; (5) The workover fluid was injected into the cement column with a microcrack using a squeeze device, and after 24 hours of curing at 150°C, it was removed; (6) The cured sample was placed in the gripper of the displacement device in reverse, and an initial confining pressure of 3 MPa was applied. Then the pump was set to "constant flow" mode, and the flow rate was set to 0.2 mL / min to start the displacement experiment. The change of pressure with time was derived by computer.

[0033] The displacement experiment results of each example were derived and plotted as Figure 1 .

[0034] Figure 1 is the displacement pressure-time curve. It can be seen that the modified phenolic resin-based solid-free workover fluid obtained in Examples 1-5 has excellent sealing ability for 100 μm cement microcracks. The breakthrough pressure of each example after 24 hours of curing at 150°C is above 5 MPa, and after being broken through, it does not completely fail, but still maintains a sealing pressure of above 2 MPa.

[0035] As can be seen from the above examples, the workover fluid obtained by the application has excellent basic performance and can be applied to various complex downhole conditions.

[0036] As can be seen from the plugging performance evaluation, the workover fluid obtained by the application is suitable for 100-150℃ well section and has excellent plugging performance after solidification, and the repair ability to 100 μm cement microcrack is more prominent, and after being broken through, it can still maintain a certain plugging ability.

[0037] Obviously, the above examples are only part of the embodiments of the application, and the embodiments based on the above are also within the protection scope of the application.

[0038] Although the embodiments of the application have been shown and described, it is to be understood that for the purpose of the present application, the embodiments change, modify, replace and vary in many ways without departing from the principles and spirit of the application, and the scope of the application is defined by the appended claims and their equivalents.

[0039] The application and its embodiments have been described above, and this description is not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the application, and the actual application is not limited thereto. In summary, if a person skilled in the art is inspired by it, without departing from the purpose of the application, without creative design, similar ways and embodiments of the technical solution should belong to the protection scope of the application.

Claims

1. A workover fluid suitable for use in high temperature well sections, characterized in that, The method comprises the following raw materials by weight: phenol 150 parts, formaldehyde aqueous solution 205-258 parts, ammonia 3-4.5 parts, phosphoric acid 3-7 parts, 1,4-butanediol 142-426 parts, 30% sodium hydroxide aqueous solution 0-5 parts.

2. The method for preparing the workover fluid suitable for high temperature well section of claim 1, characterized in that, The method comprises the following steps: (1) weigh the molten phenol and formaldehyde aqueous solution, mix and heat to stir reaction to obtain reaction liquid I; (2) add ammonia water to the reaction liquid I, heat and stir to obtain reaction liquid II; (3) add formaldehyde aqueous solution to the reaction liquid II again, heat and stir to obtain reaction liquid III; (4) after cooling the reaction liquid III, add 1,4-butanediol to stir uniformly, add phosphoric acid to adjust the pH value, heat and stir to obtain reaction liquid IV; (5) after cooling the reaction liquid IV, add 30% sodium hydroxide aqueous solution to adjust the pH value to obtain the well repair fluid.

3. The method according to claim 2, wherein the well servicing fluid is prepared by adding the additive to the base fluid. In step (1), the reaction temperature is 50-55℃, and the reaction time is 30-40 min.

4. The method of claim 2, wherein the modified phenol-formaldehyde resin-based, solid- free workover fluid is prepared by the steps of: In step (2), the temperature after heating is 60-65℃, and the stirring time is 10-30 min.

5. The method of making a modified phenol-formaldehyde resin based solid-free workover fluid of claim 2, wherein, In step (3), the temperature after heating is 70-80℃, and the stirring time is 40-60 min.

6. The method of making a modified phenol-formaldehyde resin based solid-free workover fluid of claim 2, wherein, In step (4), the temperature after cooling is 30℃, and the pH value is 3-7.

7. The method of making a modified phenol-formaldehyde resin based solid-free workover fluid of claim 2, wherein, In step (4), the temperature after heating is 100-120℃, and the stirring time is 1-3 h.

8. The method of making a modified phenol-formaldehyde resin based solid-free workover fluid of claim 2, wherein, In step (5), the temperature after cooling is 30℃, and the pH value is 7.

9. The method of claim 2, wherein the workover fluid is prepared by adding the additive to the base fluid. In step (1), the mass ratio of the formaldehyde aqueous solution to the formaldehyde aqueous solution in step (3) is 2:1.

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