An integrated stereoscopic viscosity varying acid system and a preparation method thereof

Abstract

The present application relates to the technical field of oil and gas field acid liquid, in particular to an integrated three-dimensional variable viscosity acid system and a preparation method thereof, the temperature-resistant and salt-resistant polyacrylamide copolymer prepared by the present application can form a three-dimensional network structure by introducing strong polar groups such as sulfonic acid groups and amide groups, the structure can maintain high viscosity under high temperature and high salt environment through molecular chain stretching, and the viscosity is reduced at low temperature to realize the characteristics of three-dimensional variable viscosity; secondly, the sulfonic acid group of 2-acrylamide-2-methylpropanesulfonic acid has strong salt resistance, the cyclic structure of acryloyl morpholine can enhance the rigidity and thermal stability of the molecular chain, and polyvinyl alcohol fiber can be used as a physical crosslinking point to improve the shear resistance of the system through hydrogen bonding, and the synergistic effect of the three can make the prepared integrated three-dimensional variable viscosity acid system have a more stable molecular structure.

Description

Technical Field

[0001] This invention relates to the field of acid technology in oil and gas fields, specifically to an integrated three-dimensional variable viscosity acid system and its preparation method. Background Technology

[0002] In the field of acid fracturing in oil and gas fields, traditional acid systems face many technical challenges. For example, they have insufficient viscosity control capabilities. Conventional acids are prone to a sudden drop in viscosity under high temperature or high salinity conditions, resulting in an excessively fast acid-rock reaction rate and insufficient penetration depth, making it impossible to achieve three-dimensional reservoir stimulation of distant fractures. Secondly, they have low flowback efficiency. Residual acid has strong adhesion to the rock surface, making flowback difficult. Furthermore, it is impossible to adjust the viscosity of the acid system, resulting in insufficient construction flexibility, significant reservoir damage, and extended preparation cycle.

[0003] While existing technologies attempt to improve these properties by adding polyacrylamide polymers, surfactants, or corrosion inhibitors, they often suffer from problems such as single components, insufficient functionality, and poor synergy. For example, simply increasing the polymer concentration can increase viscosity, but it easily leads to high-temperature shear degradation; a single corrosion inhibitor can suppress corrosion, but it cannot solve the problem of iron ion precipitation; surfactants can reduce interfacial tension, but they are difficult to form an effective synergy with polymers, and polymer thickeners in the system cannot achieve viscosity adjustment, resulting in limited improvement in the overall performance of the acid system. To address these technical bottlenecks, this invention proposes an integrated three-dimensional variable viscosity acid system, aiming to achieve performance breakthroughs through multi-component synergistic design. Summary of the Invention

[0004] Technical problems to be solved To address the aforementioned shortcomings of existing technologies, this invention provides an integrated three-dimensional viscosity-modifying acid system and its preparation method, which can effectively solve the problems of insufficient viscosity control capability and low backflow efficiency of traditional acid systems in existing technologies.

[0005] Technical solution To achieve the above objectives, the present invention provides the following technical solution: An integrated three-dimensional viscosity-modifying acid system, the integrated three-dimensional viscosity-modifying acid system being composed of the following raw materials: hydrochloric acid solution, temperature-resistant and salt-resistant polyacrylamide copolymer, oleamide propyl betaine, polydimethyldiallyl ammonium chloride, corrosion inhibitor, iron ion stabilizer, clay stabilizer, drainage aid, and deionized water. The temperature-resistant and salt-resistant polyacrylamide copolymer is prepared by copolymerization reaction using acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acryloylmorpholine and polyvinyl alcohol fiber as raw materials. The oleic acid amyl betaine was prepared from oleic acid and N,N-dimethylaminopropylamine. The polydimethyldiallyl ammonium chloride is prepared by polymerization of dimethyldiallyl ammonium chloride.

[0006] Furthermore, the preparation method of the temperature-resistant and salt-resistant polyacrylamide copolymer is as follows: S2.1 Weigh 10-15g of Span-80 and 5-8g of Tween-60 and pour them into a beaker containing 300-450g of white oil. Stir and mix evenly. The resulting mixture is recorded as the oil phase component. S2.2 Weigh 220-350g of acrylamide, 50-70g of 2-acrylamide-2-methylpropanesulfonic acid, 20-30g of acryloylmorpholine, 20-30g of polyvinyl alcohol fiber and 2-3g of ammonium persulfate solution and pour them into 300-450mL of deionized water. Stir to dissolve and then add sodium hydroxide solution to adjust the pH value to 7. The result is recorded as the aqueous phase component. S2.3. Under stirring conditions, pour the aqueous phase component into the oil phase component, stir thoroughly, and then purge with nitrogen for 45 minutes. Next, add 2-3g of sodium bisulfite solution, heat to 40℃ under a nitrogen atmosphere, and react at a constant temperature for 4-5 hours. After adding 60-80g of Tween-80, stir and disperse at a temperature of 40-45℃. The resulting product is a temperature-resistant and salt-resistant polyacrylamide copolymer.

[0007] Furthermore, the method for uniform mixing in S2.1 is to stir at a stirring speed of 300-500 r / min for 10 min, the mass fraction of ammonium persulfate solution in S2.2 is 2%, the stirring and dissolving in S2.2 is to stir at a stirring speed of 400-600 r / min for 20 min, and the mass fraction of sodium hydroxide solution in S2.2 is 10%.

[0008] Furthermore, the stirring speed in S2.3 is 800-1000 r / min, the method for thorough stirring in S2.3 is to continue stirring at the original stirring speed for 30 min, the mass fraction of sodium bisulfite solution in S2.3 is 1%, and the method for dispersion in S2.3 is to stir at a stirring speed of 500-600 r / min for 30-60 min.

[0009] Furthermore, the preparation method of the oleamidopropyl betaine is as follows: S5.1 Weigh 280-285g of oleic acid and 110-115g of N,N-dimethylaminopropylamine into a flask, add 2g of potassium hydroxide, stir and reflux at 170-180℃, react for 6-7h, then remove excess N,N-dimethylaminopropylamine by vacuuming under reduced pressure, cool to room temperature and stand for 12h, the result is recorded as intermediate product; S5.2 Weigh 350-360g of the intermediate product and pour it into a flask. Add 120-130mL of sodium chloroacetate solution in 3-5 portions. Reflux the mixture at 80-90℃ for 7-8 hours to obtain oleamidopropyl betaine.

[0010] Furthermore, the sodium chloroacetate solution in S5.2 has a mass fraction of 30%.

[0011] Furthermore, the preparation method of the polydimethyldiallylammonium chloride is as follows: Weigh 500g of a 65% dimethyl diallyl ammonium chloride aqueous solution and pour it into a reaction vessel. Add 0.05g of sodium ethylenediaminetetraacetate and then add glacial acetic acid to adjust the pH to 7. After stirring and mixing, heat the mixture to 70℃. Under constant temperature conditions, add 120-130mL of ammonium persulfate initiator solution dropwise over 3 hours. After the addition is complete, keep the mixture at the temperature for 2 hours. After the reaction is complete, cool it to room temperature. The resulting product is polydimethyl diallyl ammonium chloride.

[0012] Furthermore, in the preparation method of polydimethyldiallylammonium chloride, the stirring and mixing method is to stir at a stirring speed of 400-500 r / min for 30 min, and the mass fraction of the ammonium persulfate initiator solution is 5%.

[0013] A method for preparing an integrated stereoviscosity-modifying acid system, wherein the preparation method comprises: Step 1: Add 110-120 parts by weight of 30% hydrochloric acid solution to a reactor containing 100 parts by weight of deionized water. After stirring and mixing evenly, add 1-2 parts by weight of corrosion inhibitor, 1 part by weight of iron ion stabilizer, 1 part by weight of clay stabilizer and 0.5-0.6 parts by weight of drainage aid in sequence. Stir at the original stirring speed for 3-5 minutes after each addition. The result is recorded as the acid solution component. Step 2: Under high-speed stirring, add 1.2-1.5 parts by weight of heat-resistant and salt-resistant polyacrylamide copolymer to the acid solution within 30 minutes. Then, under low-speed stirring, add 5-6 parts by weight of oleamidopropyl betaine and 0.8-0.9 parts by weight of polydimethyldiallyl ammonium chloride. Continue stirring for 30 minutes and let stand for 1-2 hours for maturation. The result is the integrated three-dimensional viscosity-modifying acid system.

[0014] Furthermore, in Step 1, the method for mixing evenly is to stir at a stirring speed of 300-500 r / min for 10-30 min; in Step 2, the stirring speed under high-speed conditions is 800-1000 r / min; and in Step 2, the stirring speed under low-speed conditions is 400-500 r / min.

[0015] Beneficial effects This invention provides an integrated stereoviscosity-modifying acid system and its preparation method. Compared with the prior art, this invention has the following advantages: 1. The temperature-resistant and salt-resistant polyacrylamide copolymer prepared by this invention can form a three-dimensional network structure by introducing strong polar groups such as sulfonic acid groups and amide groups. This structure can maintain high viscosity through molecular chain extension in high-temperature and high-salt environments, and reduce viscosity by molecular chain contraction at low temperatures, thus achieving the characteristic of stereo viscosity. Secondly, the sulfonic acid groups of 2-acrylamido-2-methylpropanesulfonic acid have strong salt resistance, the cyclic structure of acryloylmorpholine can enhance the rigidity and thermal stability of the molecular chain, and polyvinyl alcohol fiber, as a physical crosslinking point, can improve the shear resistance of the system through hydrogen bonding. The synergistic effect of the three can make the prepared integrated stereo viscosity acid system have a more stable molecular structure.

[0016] 2. The polydimethyldiallyl ammonium chloride in this invention can generate strong interactions with oleamidopropyl betaine through electrostatic interactions and hydrophobic association. At high temperatures, it can stabilize the micelle structure, thereby forming a stable three-dimensional network structure, significantly increasing the overall viscosity, and weakening the electrostatic shielding effect of opposite charges on polymer molecules in the solution, thus improving the salt resistance of the acid system. The synergistic effect of polydimethyldiallyl ammonium chloride and the temperature- and salt-resistant polyacrylamide copolymer can enhance the system stability through charge neutralization and bridging. Furthermore, oleamidopropyl betaine can reduce surface tension, thereby promoting the penetration of acid into the micropores of rock strata and expanding the radius of action. Secondly, the high viscosity of oleamidopropyl betaine combined with the temperature- and salt-resistant polyacrylamide copolymer in this invention ensures both the penetration depth of the acid at high temperatures and the efficient return of residual acid. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] The present invention will be further described below with reference to embodiments.

[0019] The sources of some components in the examples and comparative examples are as follows: Siban-80, Langfang Qianyao Technology Co., Ltd.; Twain-60, Langfang Qianyao Technology Co., Ltd.; White oil, Shandong Taichang Petrochemical Technology Co., Ltd.; Acrylamide, Tianjin Kewei Reagent Company; 2-Acrylamide-2-methylpropanesulfonic acid, Chengdu Kelong Chemical Reagent Factory; Acryloylmorpholine, Chengdu Kelong Chemical Reagent Factory; Polyvinyl alcohol fiber, water-soluble polyvinyl alcohol fiber, specification 1.25dtex, length 4mm; Ammonium persulfate, Langfang Qianyao Technology Co., Ltd.; Sodium hydroxide, Shandong Longhui Chemical Co., Ltd.; Sodium bisulfite, Beijing Chemical Plant; Twain-80, Langfang Qianyao Technology Co., Ltd.; Oleic acid, Jinan Jinyu Chemical Co., Ltd.; N,N-Dimethylaminopropylamine, Condis Chemical (Hubei) Co., Ltd.; Potassium hydroxide, Shandong Longhui Chemical Co., Ltd.; Sodium chloroacetate, McLean Ltd. Dimethyl diallyl ammonium chloride, Tianjin Xingmark Reagent Company; Sodium ethylenediaminetetraacetate, Maclean's Ltd. Glacial acetic acid, Suzhou Jiujia Chemical Co., Ltd.; Corrosion inhibitor, quaternary ammonium salt BH-HS, Bohai Drilling Engineering Co., Ltd.; Iron ion stabilizer, Panjin Haoyuan Science & Industry Trade Co., Ltd.; Drainage aid, surfactant BH-PZ, Bohai Drilling Engineering Co., Ltd. Demulsifier, Zhengzhou Jingfan Environmental Protection Technology Co., Ltd.

[0020] Example 1 This embodiment presents an integrated three-dimensional viscosity-modifying acid system, which is composed of the following raw materials: hydrochloric acid solution, temperature-resistant and salt-resistant polyacrylamide copolymer, oleamide propyl betaine, polydimethyldiallyl ammonium chloride, corrosion inhibitor, iron ion stabilizer, clay stabilizer, drainage aid, and deionized water. The temperature- and salt-resistant polyacrylamide copolymer is prepared by copolymerization reaction using acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acryloylmorpholine and polyvinyl alcohol fiber as raw materials. The preparation method of the temperature-resistant and salt-resistant polyacrylamide copolymer is as follows: S2.1 Weigh 10g of Span-80 and 5g of Tween-60 and pour them into a beaker containing 300g of white oil. Stir at 300r / min for 10min and record the result as the oil phase component. S2.2 Weigh 220g acrylamide, 50g 2-acrylamide-2-methylpropanesulfonic acid, 20g acryloylmorpholine, 20g polyvinyl alcohol fiber and 2g ammonium persulfate solution (2% by mass) and pour them into 300mL of deionized water. Stir at 400r / min for 20min and then add 10% sodium hydroxide solution (10% by mass) to adjust the pH to 7. The result is recorded as the aqueous phase component. S2.3. Under stirring conditions of 800 r / min, the aqueous phase component is poured into the oil phase component, and stirring is continued at the original stirring speed for 30 min. Nitrogen gas is then introduced for 45 min. Next, 2 g of 1% sodium bisulfite solution is added, and the mixture is heated to 40℃ under a nitrogen atmosphere and reacted at a constant temperature for 4 h. After adding 60 g of Tween-80, the mixture is placed at 40℃ and stirred at a stirring speed of 500 r / min for 30 min. The resulting product is a temperature-resistant and salt-resistant polyacrylamide copolymer.

[0021] Oleamidopropyl betaine is prepared from oleic acid and N,N-dimethylaminopropylamine. The preparation method of oleamidopropyl betaine is as follows: S5.1 Weigh 280g of oleic acid and 110g of N,N-dimethylaminopropylamine into a flask, add 2g of potassium hydroxide, stir and reflux at 170℃, react for 6h, remove excess N,N-dimethylaminopropylamine under reduced pressure and vacuum, cool to room temperature and stand for 12h, the result is recorded as intermediate product. S5.2 Weigh 350g of the intermediate product and pour it into a flask. Add 120mL of 30% sodium chloroacetate solution in three portions. Reflux the mixture at 80℃ for 7 hours to obtain oleamidopropyl betaine.

[0022] Polydimethyl diallyl ammonium chloride is prepared by polymerization of dimethyl diallyl ammonium chloride. The preparation method of polydimethyldiallylammonium chloride is as follows: Weigh 500g of a 65% dimethyl diallyl ammonium chloride aqueous solution and pour it into a reaction vessel. Add 0.05g of sodium ethylenediaminetetraacetate and then add glacial acetic acid dropwise to adjust the pH to 7. Stir at 400r / min for 30min and then heat to 70℃. Under constant temperature conditions, add 120mL of a 5% ammonium persulfate initiator solution dropwise over 3h. After the addition is complete, keep the reaction at the temperature for 2h. After the reaction is complete, cool to room temperature. The result is polydimethyl diallyl ammonium chloride.

[0023] A method for preparing an integrated stereoviscosity-modifying acid system, the preparation method being as follows: Step 1: Add 110 parts by weight of 30% hydrochloric acid solution to a reactor containing 100 parts by weight of deionized water. Stir at 300 r / min for 10 min. Then add 1 part by weight of corrosion inhibitor, 1 part by weight of iron ion stabilizer, 1 part by weight of clay stabilizer and 0.5 parts by weight of drainage aid in sequence. Stir at the original stirring speed for 3 min after each addition. The result is recorded as the acid solution component. Step 2: Under high-speed stirring at 800 r / min, add 1.2 parts by weight of heat-resistant and salt-resistant polyacrylamide copolymer to the acid solution within 30 min. Then, under low-speed stirring at 400 r / min, add 5 parts by weight of oleamidopropyl betaine and 0.8 parts by weight of polydimethyldiallyl ammonium chloride. Continue stirring for 30 min and let stand for 1 h for maturation. The result is the integrated stereotactic viscosity-modifying acid system.

[0024] Example 2 This embodiment presents an integrated three-dimensional viscosity-modifying acid system, which is composed of the following raw materials: hydrochloric acid solution, temperature-resistant and salt-resistant polyacrylamide copolymer, oleamide propyl betaine, polydimethyldiallyl ammonium chloride, corrosion inhibitor, iron ion stabilizer, clay stabilizer, drainage aid, and deionized water. The temperature- and salt-resistant polyacrylamide copolymer is prepared by copolymerization reaction using acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acryloylmorpholine and polyvinyl alcohol fiber as raw materials. The preparation method of the temperature-resistant and salt-resistant polyacrylamide copolymer is as follows: S2.1 Weigh 15g of Span-80 and 8g of Tween-60 and pour them into a beaker containing 450g of white oil. Stir at 500r / min for 10min and record the result as the oil phase component. S2.2 Weigh 350g acrylamide, 70g 2-acrylamide-2-methylpropanesulfonic acid, 30g acryloylmorpholine, 30g polyvinyl alcohol fiber and 3g ammonium persulfate solution (2% by mass) and pour them into 450mL of deionized water. Stir at 600r / min for 20min and then add 10% sodium hydroxide solution (10% by mass) to adjust the pH to 7. The result is recorded as the aqueous phase component. S2.3. Under the stirring condition of 1000 r / min, the aqueous phase component is poured into the oil phase component, and the stirring is continued at the original stirring speed for 30 min. Nitrogen gas is then introduced for 45 min. Next, 3 g of sodium bisulfite solution with a mass fraction of 1% is added. The mixture is heated to 40℃ under a nitrogen atmosphere and reacted at a constant temperature for 5 h. After adding 80 g of Tween-80, the mixture is placed at a temperature of 45℃ and stirred at a stirring speed of 600 r / min for 60 min. The resulting product is a temperature-resistant and salt-resistant polyacrylamide copolymer.

[0025] Oleamidopropyl betaine is prepared from oleic acid and N,N-dimethylaminopropylamine. The preparation method of oleamidopropyl betaine is as follows: S5.1 Weigh 285g of oleic acid and 115g of N,N-dimethylaminopropylamine and pour them into a flask. Add 2g of potassium hydroxide and stir and reflux at 180℃. After reacting for 7h, remove excess N,N-dimethylaminopropylamine by vacuuming under reduced pressure. After cooling to room temperature, let stand for 12h. The result is recorded as the intermediate product. S5.2 Weigh 360g of the intermediate product and pour it into a flask. Add 130mL of 30% sodium chloroacetate solution in 5 portions. Reflux the mixture at 90℃ for 8 hours to obtain oleamidopropyl betaine.

[0026] Polydimethyl diallyl ammonium chloride is prepared by polymerization of dimethyl diallyl ammonium chloride. The preparation method of polydimethyldiallylammonium chloride is as follows: Weigh 500g of a 65% dimethyl diallyl ammonium chloride aqueous solution and pour it into a reaction vessel. Add 0.05g of sodium ethylenediaminetetraacetate and then add glacial acetic acid dropwise to adjust the pH to 7. Stir at 500r / min for 30min and then heat to 70℃. Under constant temperature conditions, add 130mL of a 5% ammonium persulfate initiator solution dropwise over 3h. After the addition is complete, keep the reaction at the temperature for 2h. After the reaction is complete, cool to room temperature. The result is polydimethyl diallyl ammonium chloride.

[0027] A method for preparing an integrated stereoviscosity-modifying acid system, the preparation method being as follows: Step 1: Add 120 parts by weight of 30% hydrochloric acid solution to a reactor containing 100 parts by weight of deionized water. Stir at 500 r / min for 30 min. Then add 2 parts by weight of corrosion inhibitor, 1 part by weight of iron ion stabilizer, 1 part by weight of clay stabilizer and 0.6 parts by weight of drainage aid in sequence. Stir at the original stirring speed for 5 min after each addition. The result is recorded as the acid solution component. Step 2: Under high-speed stirring at 1000 r / min, add 1.5 parts by weight of heat-resistant and salt-resistant polyacrylamide copolymer to the acid solution within 30 min. Then, under low-speed stirring at 500 r / min, add 6 parts by weight of oleamidopropyl betaine and 0.9 parts by weight of polydimethyldiallyl ammonium chloride. Continue stirring for 30 min and let stand for 2 h for maturation. The result is the integrated stereotactic viscosity-modifying acid system.

[0028] Example 3 This embodiment presents an integrated three-dimensional viscosity-modifying acid system, which is composed of the following raw materials: hydrochloric acid solution, temperature-resistant and salt-resistant polyacrylamide copolymer, oleamide propyl betaine, polydimethyldiallyl ammonium chloride, corrosion inhibitor, iron ion stabilizer, clay stabilizer, drainage aid, and deionized water. The temperature- and salt-resistant polyacrylamide copolymer is prepared by copolymerization reaction using acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acryloylmorpholine and polyvinyl alcohol fiber as raw materials. The preparation method of the temperature-resistant and salt-resistant polyacrylamide copolymer is as follows: S2.1 Weigh 13g of Span-80 and 7g of Tween-60 and pour them into a beaker containing 380g of white oil. Stir at 400r / min for 10min and record the result as the oil phase component. S2.2 Weigh 280g acrylamide, 60g 2-acrylamide-2-methylpropanesulfonic acid, 25g acryloylmorpholine, 25g polyvinyl alcohol fiber and 3g ammonium persulfate solution (2% by mass) and pour them into 380mL of deionized water. Stir at 500r / min for 20min and then add 10% sodium hydroxide solution (10% by mass) to adjust the pH to 7. The result is recorded as the aqueous phase component. S2.3. Under stirring conditions of 900 r / min, the aqueous phase component is poured into the oil phase component, and stirring is continued at the original stirring speed for 30 min. Nitrogen gas is then introduced for 45 min. Next, 3 g of 1% sodium bisulfite solution is added, and the mixture is heated to 40℃ under a nitrogen atmosphere and reacted at a constant temperature for 5 h. After adding 70 g of Tween-80, the mixture is placed at a temperature of 43℃ and stirred at a stirring speed of 600 r / min for 45 min. The resulting product is a temperature-resistant and salt-resistant polyacrylamide copolymer.

[0029] Oleamidopropyl betaine is prepared from oleic acid and N,N-dimethylaminopropylamine. The preparation method of oleamidopropyl betaine is as follows: S5.1 Weigh 283g of oleic acid and 112g of N,N-dimethylaminopropylamine into a flask, add 2g of potassium hydroxide, stir and reflux at 175℃, react for 7h, remove excess N,N-dimethylaminopropylamine under reduced pressure and vacuum, cool to room temperature and stand for 12h, the result is recorded as intermediate product. S5.2 Weigh 355g of the intermediate product and pour it into a flask. Add 125mL of 30% sodium chloroacetate solution in four portions. Reflux the mixture at 85℃ for 8 hours to obtain oleamidopropyl betaine.

[0030] Polydimethyl diallyl ammonium chloride is prepared by polymerization of dimethyl diallyl ammonium chloride. The preparation method of polydimethyldiallylammonium chloride is as follows: Weigh 500g of a 65% dimethyl diallyl ammonium chloride aqueous solution and pour it into a reaction vessel. Add 0.05g of sodium ethylenediaminetetraacetate and then add glacial acetic acid dropwise to adjust the pH to 7. Stir at 500r / min for 30min and then heat to 70℃. Under constant temperature conditions, add 125mL of a 5% ammonium persulfate initiator solution dropwise over 3h. After the addition is complete, keep the reaction at the temperature for 2h. After the reaction is complete, cool to room temperature. The result is polydimethyl diallyl ammonium chloride.

[0031] A method for preparing an integrated stereoviscosity-modifying acid system, the preparation method being as follows: Step 1: Add 115 parts by weight of 30% hydrochloric acid solution to a reactor containing 100 parts by weight of deionized water. Stir at 400 r / min for 20 min. Then add 2 parts by weight of corrosion inhibitor, 1 part by weight of iron ion stabilizer, 1 part by weight of clay stabilizer and 0.5 parts by weight of drainage aid in sequence. Stir at the original stirring speed for 4 min after each addition. The result is recorded as the acid solution component. Step 2: Under high-speed stirring at 900 r / min, add 1.3 parts by weight of heat-resistant and salt-resistant polyacrylamide copolymer to the acid solution within 30 min. Then, under low-speed stirring at 500 r / min, add 6 parts by weight of oleamidopropyl betaine and 0.9 parts by weight of polydimethyldiallyl ammonium chloride. Continue stirring for 30 min and let stand for 2 h for maturation. The result is the integrated stereotactic viscosity-modifying acid system.

[0032] Comparative Example 1 The integrated stereovisual acid system and its preparation method provided in this comparative example are largely the same as those in Example 1. The main difference is that polyvinyl alcohol fiber was not added during the preparation of the temperature-resistant and salt-resistant polyacrylamide copolymer in this comparative example.

[0033] Comparative Example 2 The integrated stereoviscosity acid system and its preparation method provided in this comparative example are largely the same as those in Example 1. The main difference is that in this comparative example, oleamidopropyl betaine in Example 1 is replaced with polydimethyldiallyl ammonium chloride.

[0034] Comparative Example 3 The integrated stereoviscosity acid system and its preparation method provided in this comparative example are largely the same as those in Example 1. The main difference is that the polydimethyldiallylammonium chloride in Example 1 is replaced with oleamidopropyl betaine in this comparative example.

[0035] Performance testing The integrated stereo viscosity-modifying acid systems prepared in Examples 1-3 and Comparative Examples 1-3 were labeled as Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. The acid viscosity of Examples 1-3 and Comparative Examples 1-3 at different operating times was detected, and the data obtained are recorded in Table 1. Table 1 Performance Test Data As shown in Table 1, the integrated three-dimensional variable viscosity acid system prepared in Examples 1-3 has a low viscosity at the initial operation. As time increases, the viscosity of the acid gradually increases, thus achieving the requirements of "low friction" in the wellbore and "high slow speed" in the formation, making it more suitable for use in oilfield acid fracturing operations. Compared with Comparative Examples 1-3, the integrated three-dimensional variable viscosity acid system prepared in Examples 1-3 has a higher viscosity, indicating that the integrated three-dimensional variable viscosity acid system prepared from the raw materials in this example has better viscosity-changing performance.

[0036] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between such entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only such elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitations, an element qualified as "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprise said element.

[0037] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An integrated three-dimensional viscosity-modifying acid system, characterized in that, The integrated three-dimensional viscosity-modifying acid system is composed of the following raw materials: hydrochloric acid solution, temperature-resistant and salt-resistant polyacrylamide copolymer, oleamide propyl betaine, polydimethyldiallyl ammonium chloride, corrosion inhibitor, iron ion stabilizer, clay stabilizer, drainage aid, and deionized water. The temperature-resistant and salt-resistant polyacrylamide copolymer is prepared by copolymerization reaction using acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acryloylmorpholine and polyvinyl alcohol fiber as raw materials. The oleic acid amyl betaine was prepared from oleic acid and N,N-dimethylaminopropylamine. The polydimethyldiallyl ammonium chloride is prepared by polymerization of dimethyldiallyl ammonium chloride.

2. The integrated three-dimensional viscosity-modifying acid system according to claim 1, characterized in that, The preparation method of the temperature-resistant and salt-resistant polyacrylamide copolymer is as follows: S2.1 Weigh 10-15g of Span-80 and 5-8g of Tween-60 and pour them into a beaker containing 300-450g of white oil. Stir and mix evenly. The resulting mixture is called the oil phase component. S2.2 Weigh 220-350g of acrylamide, 50-70g of 2-acrylamide-2-methylpropanesulfonic acid, 20-30g of acryloylmorpholine, 20-30g of polyvinyl alcohol fiber and 2-3g of ammonium persulfate solution and pour them into 300-450mL of deionized water. Stir to dissolve and then add sodium hydroxide solution to adjust the pH value to 7. The result is recorded as the aqueous phase component. S2.

3. Under stirring conditions, pour the aqueous phase component into the oil phase component, stir thoroughly, and then purge with nitrogen for 45 minutes. Next, add 2-3g of sodium bisulfite solution, heat to 40℃ under a nitrogen atmosphere, and react at a constant temperature for 4-5 hours. After adding 60-80g of Tween-80, stir and disperse at a temperature of 40-45℃. The resulting product is a temperature-resistant and salt-resistant polyacrylamide copolymer.

3. The integrated three-dimensional viscosity-modifying acid system according to claim 2, characterized in that, The method for uniform mixing in S2.1 is to stir at a stirring speed of 300-500 r / min for 10 min. The mass fraction of ammonium persulfate solution in S2.2 is 2%. The method for dissolving in S2.2 is to stir at a stirring speed of 400-600 r / min for 20 min. The mass fraction of sodium hydroxide solution in S2.2 is 10%.

4. The integrated three-dimensional viscosity-modifying acid system according to claim 2, characterized in that, The stirring speed in S2.3 is 800-1000 r / min. The method for thorough stirring in S2.3 is to continue stirring at the original stirring speed for 30 min. The mass fraction of sodium bisulfite solution in S2.3 is 1%. The method for dispersion in S2.3 is to stir at a stirring speed of 500-600 r / min for 30-60 min.

5. The integrated three-dimensional viscosity-modifying acid system according to claim 1, characterized in that, The preparation method of the oleamidopropyl betaine is as follows: S5.1 Weigh 280-285g of oleic acid and 110-115g of N,N-dimethylaminopropylamine into a flask, add 2g of potassium hydroxide, stir and reflux at 170-180℃, react for 6-7h, then remove excess N,N-dimethylaminopropylamine by vacuuming under reduced pressure, cool to room temperature and stand for 12h, the result is recorded as intermediate product; S5.2 Weigh 350-360g of the intermediate product and pour it into a flask. Add 120-130mL of sodium chloroacetate solution in 3-5 portions. Reflux the mixture at 80-90℃ for 7-8 hours to obtain oleamidopropyl betaine.

6. The integrated three-dimensional viscosity-modifying acid system according to claim 5, characterized in that, The mass fraction of sodium chloroacetate solution in S5.2 is 30%.

7. The integrated three-dimensional viscosity-modifying acid system according to claim 1, characterized in that, The preparation method of the polydimethyldiallylammonium chloride is as follows: Weigh 500g of a 65% dimethyl diallyl ammonium chloride aqueous solution and pour it into a reaction vessel. Add 0.05g of sodium ethylenediaminetetraacetate and then add glacial acetic acid to adjust the pH to 7. After stirring and mixing, heat the mixture to 70℃. Under constant temperature conditions, add 120-130mL of ammonium persulfate solution as an initiator over 3 hours. After the addition is complete, keep the mixture at the temperature for 2 hours. After the reaction is complete, cool it to room temperature. The resulting product is polydimethyl diallyl ammonium chloride.

8. The integrated three-dimensional viscosity-modifying acid system according to claim 7, characterized in that, In the preparation method of polydimethyldiallyl ammonium chloride, the stirring and mixing method is to stir at a stirring speed of 400-500 r / min for 30 min, and the mass fraction of ammonium persulfate initiator solution is 5%.

9. A method for preparing an integrated stereosensitive viscosity-modifying acid system according to any one of claims 1-8, characterized in that, The preparation method is as follows: Step 1: Add 110-120 parts by weight of 30% hydrochloric acid solution to a reactor containing 100 parts by weight of deionized water. After stirring and mixing evenly, add 1-2 parts by weight of corrosion inhibitor, 1 part by weight of iron ion stabilizer, 1 part by weight of clay stabilizer and 0.5-0.6 parts by weight of drainage aid in sequence. Stir at the original stirring speed for 3-5 minutes after each addition. The result is recorded as the acid solution component. Step 2: Under high-speed stirring, add 1.2-1.5 parts by weight of heat-resistant and salt-resistant polyacrylamide copolymer to the acid solution within 30 minutes. Then, under low-speed stirring, add 5-6 parts by weight of oleamidopropyl betaine and 0.8-0.9 parts by weight of polydimethyldiallyl ammonium chloride. Continue stirring for 30 minutes and let stand for 1-2 hours for maturation. The result is the integrated three-dimensional viscosity-modifying acid system.

10. The method for preparing an integrated stereosensitive viscosity-modifying acid system according to claim 9, characterized in that, In Step 1, the method for mixing evenly is to stir at a stirring speed of 300-500 r / min for 10-30 minutes. In Step 2, the stirring speed under high-speed conditions is 800-1000 r / min, and the stirring speed under low-speed conditions is 400-500 r / min.

Images