Online mixing-free high-viscosity high-drag-reducing retarded acid

Abstract

The application discloses an online mixing-free variable-viscosity high-resistance-slowing acid, and provides an online mixing-free variable-viscosity high-resistance-slowing acid system, wherein the performance of acid liquid can be changed by changing the adding amount of the agent, and the acid liquid does not need to be prepared in advance. The film-forming agent can form an adsorption film on the surface of rock, and the adsorption film blocks the contact between H+ and rock, thereby slowing the acid-rock reaction rate. The application also has multiple composite slow-down performances, and combines the characteristics of foam slow-down acid and gelling slow-down acid. Through the thickening and slowing down of the multiple-effect agent and the blocking and slowing down of the film-forming agent, the acid-rock reaction rate is greatly reduced under the double slow-down effect of the two. In addition to the good thickening effect, the application also has excellent resistance-reducing performance, and one agent is used for multiple purposes to reduce the adding amount and type of the additive. Meanwhile, the resistance-reducing rate of the system reaches more than 85%, which is much higher than the 70% of the traditional system.

Description

Technical Field

[0001] This invention relates to the field of reservoir stimulation technology in oil extraction, and more specifically to an online, non-mixing, high-viscosity, high-drag-reducing, slow-release acid. Background Technology

[0002] Carbonate reservoirs account for approximately 70% of the world's oil and gas production, and these reservoirs are widely distributed. The Tarim Basin, Sichuan Basin, Ordos Basin, and Bohai Bay regions contain abundant carbonate reservoirs. Carbonate reservoirs are generally characterized by deep burial, high temperatures, and well-developed fractures.

[0003] Conventional acid systems used for acidizing carbonate reservoirs are mostly hydrochloric acid systems, which achieved some success in the early stages. However, with the increased exploration and development of carbonate reservoirs, a large number of high-temperature and high-pressure deep wells have emerged. Conventional acid systems are prone to problems such as excessively fast reaction rates and severe filtration loss, resulting in excessive consumption of acid near the wellbore, making it difficult to form acid wormholes in the reservoir and connect oil and gas channels in the deeper formations.

[0004] Therefore, controlling the acid-rock reaction rate is a major focus of acidizing processes and fluid research in carbonate reservoirs. Existing slow-reaction acid systems delay the time it takes for H+ to be transferred to the rock surface through high viscosity and oil-in-acid methods, thereby reducing the H+ mass transfer coefficient and achieving the goal of slowing down the reaction.

[0005] The existing slow-release acid system has the following defects: (1) High-molecular-weight thickened acid has high viscosity and large molecular weight, making it difficult to prepare the solution, resulting in high construction friction, difficult pumping, incomplete formation breaking, and large-scale blockage of the formation, causing significant damage to pore throats; (2) Emulsified acid and foam acid have poor stability and poor temperature resistance, making construction complex and the slow-release effect is generally poor; (3) Solid acid encapsulates active acid in poor solubility, making it difficult to return to the source, causing significant damage to the formation, and the supporting construction process is relatively complex.

[0006] In summary, existing slow-rate acid systems cannot meet the requirements for developing high-temperature carbonate reservoirs. There is a need to develop slow-rate acid systems that are simple to manufacture, have excellent drag reduction performance, cause minimal damage to the reservoir, and have superior high-temperature slow-rate performance in order to improve the stimulation effect and efficiently develop carbonate reservoirs. Summary of the Invention

[0007] In view of this, the present invention provides an online, non-mixing, high-viscosity, high-resistance, slow-release acid.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A non-mixing, viscosity-reducing, high-drag-reducing slow-release acid, comprising the following components by mass percentage:

[0010] Iron ion stabilizer 0.5-2.5wt%, acidification and drainage aid 1.0-2.5wt%, corrosion inhibitor 0.5-4wt%, coating agent 1.0-4.5wt%, multi-effect agent 0.1-3wt%, and the balance is hydrochloric acid with a weight fraction of 20%.

[0011] Preferably, the iron ion stabilizer is one or a mixture of sodium citrate, sodium ethylenediaminetetraethyl sodium, sodium formate, aminotrimethylphosphonic acid, and ethylenediaminetetramethylphosphonic acid.

[0012] Preferably, the acidifying and drainage aid is one or more of n-decyl glucoside, isooctyl glucoside, fatty alcohol polyoxyethylene ether, etc.

[0013] Preferably, the corrosion inhibitor is one or a mixture of hydroxyethylidene diphosphonic acid, benzotriazole, polyethoxyethanol, and diethanolamine.

[0014] Preferably, the coating agent is one or a mixture of sodium polyacrylate, sodium palmitate, sodium humate, and aminotrimethylphosphonic acid.

[0015] Preferably, the pleiotropic agent is prepared by the following method:

[0016] (1) Aqueous phase preparation: AM, DMC and EDTA were dissolved in deionized water, and then the pH of the solution was adjusted with ammonia.

[0017] (2) Preparation of oil phase: Liquid paraffin, Span 80 and Tween 80 were added to a beaker and heated at 40°C until completely dissolved;

[0018] (3) Preparation of multi-effect agent: The oil phase is added to the container, and then the aqueous phase is added to the oil phase. The mixture is stirred vigorously and emulsified for 30 minutes. After emulsification, 2,2'-bis(2-methylpropionamido)dichloride is added to the prepolymerization system. The mixture is stirred vigorously at 60°C and copolymerized in a 60°C water bath for 6 hours. The mixture is cooled at room temperature and then precipitated in a mixed solution of acetone and methanol. The homopolymer is extracted for 24 hours using a Soxhlet extractor to completely remove the homopolymer and form a multi-effect agent.

[0019] The synthesis route is as follows:

[0020]

[0021] The beneficial effects of adopting the above-mentioned preferred solution are as follows: The multi-effect agent of the present invention differs from conventional gelling agents. It is a cationic emulsion with good solubility and thermal stability in hydrochloric acid environments, making it extremely suitable for high-temperature, strongly acidic environments. The multi-effect agent has a dual function: First, the multi-effect agent molecules can intertwine to form a network structure under non-bonded interaction, increasing the viscosity of the acid solution. Increased viscosity helps slow down the H+ mass transfer rate, thereby slowing down the acid-rock reaction rate. Through the viscosity-increasing and slowing effects of the multi-effect agent and the barrier-reducing effects of the coating agent, the acid-rock reaction rate is significantly reduced under the dual slowing effect. Second, the multi-effect agent can also inhibit the generation of turbulence in the acid solution during pumping, thereby significantly reducing the friction of the acid solution (drag reduction rate of over 85%), exhibiting excellent adaptability in deep and ultra-deep wells.

[0022] Preferably, the pH of the adjusted solution is adjusted to 7-8.

[0023] Preferably, the container is a four-necked round-bottom flask equipped with a mechanical stirrer, a nitrogen inlet, a thermometer, and a condenser.

[0024] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The raw materials provided by this invention are all liquids, and on-site preparation is simple, requiring only simple mixing and stirring, which effectively reduces the difficulty and cost of preparation.

[0026] 2) The drainage aids selected in this invention are all nonionic surfactants, which not only have excellent solubility but also good acid and salt resistance, and will not lose their surface tension reduction effect in strong acid environments; moreover, nonionic surfactants are not affected by calcium and magnesium ions in the reservoir. In addition, the drainage aids do not interact with rocks due to electrostatic effects, greatly improving drainage efficiency.

[0027] 3) The online, no-mixing, variable-viscosity, high-drag-reducing, slow-release acid system provided by this invention allows for modification of acid performance simply by changing the dosage of the reagent, eliminating the need for pre-mixing. In traditional methods, the acid is typically pre-mixed on the ground, which can lead to over- or under-mixing. Online mixing allows for the immediate preparation of the required acid, reducing material waste. Simultaneously, since large quantities of acid need not be stored in advance, the required on-site equipment and space can be reduced, further lowering costs. Furthermore, this invention allows for adjustment of the acid concentration and formulation based on real-time conditions, better adapting to changes in geological formations and the needs of different stages, resulting in better construction outcomes.

[0028] 4) The multi-effect agent provided by the present invention is a cationic emulsion, which has good solubility and thermal stability in hydrochloric acid environment and is extremely suitable for high temperature and strong acid environment.

[0029] 5) The multi-effect agent molecules provided by this invention can intertwine with each other to form a network structure under non-bonded interaction, which increases the viscosity of the acid solution. The increased viscosity of the acid solution helps to slow down the H+ mass transfer rate, thereby slowing down the acid-rock reaction rate.

[0030] 6) The coating agent provided by the present invention can form an adsorption film on the rock surface. The presence of the adsorption film blocks the contact between H+ and the rock, thereby slowing down the acid-rock reaction rate.

[0031] 7) The present invention provides an online, non-mixing, high-viscosity, high-resistance, slow-reducing acid with multiple composite slow-reducing properties. It combines the characteristics of foam slow-reducing acid and gel slow-reducing acid. Through the thickening and slowing effect of the multi-effect agent and the barrier slowing effect of the coating agent, the acid-rock reaction rate is greatly reduced under the dual slowing effect of the two.

[0032] 8) In addition to its excellent thickening effect, the multi-effect agent provided by this invention also has superior drag-reducing properties, allowing for multiple uses with a single agent and reducing the amount and type of additives required. At the same time, the drag reduction rate of this system reaches over 85%, far exceeding that of traditional systems (70%).

[0033] 9) The product of this invention leaves little residue after debonding and causes very little damage to the reservoir, making it very suitable for production enhancement and transformation of low-permeability or ultra-low-permeability reservoirs. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0035] Figure 1 This invention provides measured results of the drag reduction rate of an online, non-mixing, variable viscosity, high drag-reducing, slow-release acid.

[0036] Figure 2 This is a schematic diagram of an online, non-mixing, high-viscosity, high-resistance, slow-release acid with dual slow-release mechanism provided in an embodiment of the present invention.

[0037] Figure 3 This invention provides the results of an online, non-mixing, variable viscosity, high drag reduction, and slow-reducing acid retardation test.

[0038] Figure 4 The present invention provides an online, non-mixing, variable viscosity, high drag reduction, and slow-release acid solubility test result. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] This embodiment provides an online, non-mixing, high-viscosity, high-drag-reducing, slow-release acid, comprising:

[0042] Weigh out 0.5 wt% iron ion stabilizer, 1.0 wt% acidification and drainage aid, 0.5 wt% corrosion inhibitor, 1.0 wt% coating agent, 0.1 wt% multi-effect agent, and the balance is 20% hydrochloric acid by weight;

[0043] The iron ion stabilizer is a mixture of sodium citrate and ethylenediaminetetraethyl sodium in a mass ratio of 1:1; the acidification and drainage aid is n-decyl glucoside; the corrosion inhibitor is a mixture of benzotriazole and diethanolamine in a mass ratio of 2:1; the coating agent is a mixture of sodium palmitate and sodium polyacrylate in a mass ratio of 1:1; and the multi-effect agent CPAM is synthesized as follows:

[0044] (1) Aqueous phase preparation: AM, DMC and EDTA were dissolved in deionized water, and then the pH of the solution was adjusted to 7-8 with 25% ammonia water.

[0045] (2) Preparation of oil phase: Add liquid paraffin, Span 80 and Tween 80 to a beaker and heat at 40°C until completely dissolved.

[0046] (3) Preparation of the multi-effect agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer, and condenser. Then, the aqueous phase was added to the oil phase, and the mixture was vigorously stirred and emulsified for 30 minutes. After emulsification, 2,2'-bis(2-methylpropionamido)dichloride was added to the prepolymerization system, and the mixture was vigorously stirred at 60°C. The copolymerization reaction was carried out in a 60°C water bath for 6 hours, cooled to room temperature, and then precipitated in a mixed solution of acetone and methanol. The homopolymer was completely removed by extraction with a Soxhlet extractor for 24 hours, forming the multi-effect agent CPAM.

[0047] The key performance characteristics of the system were tested (solubility, slowing rate, drag reduction rate, and damage rate). The test methods were carried out in accordance with SYT 5886-2018 "Performance Evaluation Method for Acidizing Working Fluids" and SY / 5107-2016 "Performance Evaluation Standard for Fracturing Fluids". The results showed that the system completely dissolved within 2 minutes, the slowing rate was 94.26%, the drag reduction rate reached more than 80%, and the damage rate was 2.86%.

[0048] Example 2

[0049] This embodiment provides an online, non-mixing, high-viscosity, high-drag-reducing, slow-release acid, comprising:

[0050] Weigh out 1 wt% iron ion stabilizer, 1.0 wt% acidification and drainage aid, 1 wt% corrosion inhibitor, 2.5 wt% coating agent, 0.2 wt% multi-effect agent, and the balance is 20% hydrochloric acid by weight;

[0051] The iron ion stabilizer is a mixture of sodium formate, aminotrimethylphosphonic acid, and ethylenediaminetetramethylphosphonic acid in a mass ratio of 1:1:2; the acidification and drainage aid is isooctyl glucoside; the corrosion inhibitor is a mixture of hydroxyethylidene diphosphonic acid and polyethoxyethanol in a mass ratio of 1:2; the coating agent is a mixture of sodium humate and aminotrimethylphosphonic acid in a mass ratio of 2:1; and the multi-effect agent CPAM is synthesized as follows:

[0052] (1) Aqueous phase preparation: AM, DMC and EDTA were dissolved in deionized water, and then the pH of the solution was adjusted to 7-8 with 25% ammonia water.

[0053] (2) Preparation of oil phase: Add liquid paraffin, Span 80 and Tween 80 to a beaker and heat at 40°C until completely dissolved.

[0054] (3) Preparation of the multi-effect agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer, and condenser. Then, the aqueous phase was added to the oil phase, and the mixture was vigorously stirred and emulsified for 30 minutes. After emulsification, 2,2'-bis(2-methylpropionamido)dichloride was added to the prepolymerization system, and the mixture was vigorously stirred at 60°C. The copolymerization reaction was carried out in a 60°C water bath for 6 hours, cooled to room temperature, and then precipitated in a mixed solution of acetone and methanol. The homopolymer was completely removed by extraction with a Soxhlet extractor for 24 hours, forming the multi-effect agent CPAM.

[0055] The key performance characteristics of the system were tested (solubility, slowing rate, drag reduction rate, and damage rate). The test methods were carried out in accordance with SYT 5886-2018 "Performance Evaluation Method for Acidizing Working Fluids" and SY / 5107-2016 "Performance Evaluation Standard for Fracturing Fluids". The results showed that the system completely dissolved within 3 minutes, the slowing rate was 93.15%, the drag reduction rate reached more than 82%, and the damage rate was 3.55%.

[0056] Figure 2 This diagram illustrates a dual-retardant process for acid-rock reaction, characterized by non-mixing, high viscosity, and drag reduction. The multi-effect agent disperses effectively in the solution, increasing its viscosity and reducing the mass transfer rate of H+, thus slowing the acid-rock reaction rate. Furthermore, the coating agent adsorbs onto the rock surface, forming an adsorption layer that effectively blocks H+ from contacting the rock surface, further reducing the acid-rock reaction rate. Under the combined effect of these two retardant mechanisms, the acid-rock reaction rate is further reduced.

[0057] Example 3

[0058] This embodiment provides an online, non-mixing, high-viscosity, high-drag-reducing, slow-release acid, comprising:

[0059] Weigh out 1 wt% iron ion stabilizer, 1 wt% acidification aid, 1 wt% corrosion inhibitor, 2.5 wt% coating agent, 0.5 wt% multi-effect agent, and the balance is 20% hydrochloric acid by weight;

[0060] The iron ion stabilizer is sodium formate; the acidification and drainage aid is fatty alcohol polyoxyethylene ether; the corrosion inhibitor is diethanolamine; the coating agent is a mixture of sodium humate and aminotrimethylphosphonic acid in a mass ratio of 2:1; and the multi-effect agent is CPAM, synthesized as follows:

[0061] (1) Aqueous phase preparation: AM, DMC and EDTA were dissolved in deionized water, and then the pH of the solution was adjusted to 7-8 with 25% ammonia water.

[0062] (2) Preparation of oil phase: Add liquid paraffin, Span 80 and Tween 80 to a beaker and heat at 40°C until completely dissolved.

[0063] (3) Preparation of the multi-effect agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer, and condenser. Then, the aqueous phase was added to the oil phase, and the mixture was vigorously stirred and emulsified for 30 minutes. After emulsification, 2,2'-bis(2-methylpropionamido)dichloride was added to the prepolymerization system, and the mixture was vigorously stirred at 60°C. The copolymerization reaction was carried out in a 60°C water bath for 6 hours, cooled to room temperature, and then precipitated in a mixed solution of acetone and methanol. The homopolymer was completely removed by extraction with a Soxhlet extractor for 24 hours, forming the multi-effect agent CPAM.

[0064] The key performance characteristics of the system were tested (solubility, slowing rate, drag reduction rate, and damage rate). The test methods were carried out in accordance with SYT 5886-2018 "Performance Evaluation Method for Acidizing Working Fluids" and SY / 5107-2016 "Performance Evaluation Standard for Fracturing Fluids". The results showed that the system completely dissolved within 3 minutes, the slowing rate was 96%, the drag reduction rate reached more than 82.5%, and the damage rate was 4.56%.

[0065] Example 4

[0066] This embodiment provides an online, non-mixing, high-viscosity, high-drag-reducing, slow-release acid, comprising:

[0067] Weigh out 1 wt% iron ion stabilizer, 1 wt% acidification aid, 1 wt% corrosion inhibitor, 2.5 wt% coating agent, 1 wt% multi-effect agent, and the balance is 20% hydrochloric acid by weight;

[0068] The iron ion stabilizer is ethylenediaminetetramethylphosphonic acid; the acidification and drainage aid is a mixture of fatty alcohol polyoxyethylene ether and isooctyl glucoside in a mass ratio of 3:2; the corrosion inhibitor is diethanolamine; the coating agent is a mixture of sodium humate and aminotrimethylphosphonic acid in a mass ratio of 2:1; and the pleiotropic agent is CPAM. The synthesis method is shown below:

[0069] (1) Aqueous phase preparation: AM, DMC and EDTA were dissolved in deionized water, and then the pH of the solution was adjusted to 7-8 with 25% ammonia water.

[0070] (2) Preparation of oil phase: Add liquid paraffin, Span 80 and Tween 80 to a beaker and heat at 40°C until completely dissolved.

[0071] (3) Preparation of the multi-effect agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer, and condenser. Then, the aqueous phase was added to the oil phase, and the mixture was vigorously stirred and emulsified for 30 minutes. After emulsification, 2,2'-bis(2-methylpropionamido)dichloride was added to the prepolymerization system, and the mixture was vigorously stirred at 60°C. The copolymerization reaction was carried out in a 60°C water bath for 6 hours, cooled to room temperature, and then precipitated in a mixed solution of acetone and methanol. The homopolymer was completely removed by extraction with a Soxhlet extractor for 24 hours, forming the multi-effect agent CPAM.

[0072] The key performance characteristics of the system were tested (solubility, slowing rate, drag reduction rate, and damage rate). The test methods were carried out in accordance with SYT 5886-2018 "Performance Evaluation Method for Acidizing Working Fluids" and SY / 5107-2016 "Performance Evaluation Standard for Fracturing Fluids". The results showed that the system completely dissolved within 3 minutes, the slowing rate was 98%, the drag reduction rate reached more than 85%, and the damage rate was 5.02%.

[0073] Example 5

[0074] This embodiment provides an online, non-mixing, high-viscosity, high-drag-reducing, slow-release acid, comprising:

[0075] Weigh out 1 wt% iron ion stabilizer, 1 wt% acidification aid, 1 wt% corrosion inhibitor, 2.5 wt% coating agent, 1.5 wt% multi-effect agent, and the balance is 20% hydrochloric acid by weight;

[0076] The iron ion stabilizer is a mixture of ethylenediaminetetramethylenephosphonic acid and sodium formate in a mass ratio of 1:2; the acidification aid is a mixture of fatty alcohol polyoxyethylene ether and n-decyl glucoside in a mass ratio of 1:1; the corrosion inhibitor is diethanolamine; the coating agent is a mixture of sodium humate and aminotrimethylenephosphonic acid in a mass ratio of 2:1; and the multi-effect agent is CPAM. The synthesis method is shown below:

[0077] (1) Aqueous phase preparation: AM, DMC and EDTA were dissolved in deionized water, and then the pH of the solution was adjusted to 7-8 with 25% ammonia water.

[0078] (2) Preparation of oil phase: Add liquid paraffin, Span 80 and Tween 80 to a beaker and heat at 40°C until completely dissolved.

[0079] (3) Preparation of the multi-effect agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer, and condenser. Then, the aqueous phase was added to the oil phase, and the mixture was vigorously stirred and emulsified for 30 minutes. After emulsification, 2,2'-bis(2-methylpropionamido)dichloride was added to the prepolymerization system, and the mixture was vigorously stirred at 60°C. The copolymerization reaction was carried out in a 60°C water bath for 6 hours, cooled to room temperature, and then precipitated in a mixed solution of acetone and methanol. The homopolymer was completely removed by extraction with a Soxhlet extractor for 24 hours, forming the multi-effect agent CPAM.

[0080] The key performance characteristics of the system were tested (solubility, slowing rate, drag reduction rate, and damage rate). The test methods were carried out in accordance with SYT 5886-2018 "Performance Evaluation Method for Acidizing Working Fluids" and SY / 5107-2016 "Performance Evaluation Standard for Fracturing Fluids". The results showed that the system completely dissolved within 3 minutes, the slowing rate was 98.65%, the drag reduction rate reached more than 85%, and the damage rate was 5.46%.

[0081] Example 6

[0082] This embodiment provides an online, non-mixing, high-viscosity, high-drag-reducing, slow-release acid, comprising:

[0083] Weigh out 1 wt% iron ion stabilizer, 1 wt% acidification aid, 1 wt% corrosion inhibitor, 2.5 wt% coating agent, 2.0 wt% multi-effect agent, and the balance is 20% hydrochloric acid by weight;

[0084] The iron ion stabilizer is a mixture of ethyl citric acid and sodium formate in a mass ratio of 1:3; the acidification and drainage aid is a mixture of fatty alcohol polyoxyethylene ether and n-decyl glucoside in a mass ratio of 2:1; the corrosion inhibitor is a mixture of benzotriazole and polyethoxyethanol in a mass ratio of 3:2; the coating agent is a mixture of sodium humate and aminotrimethylphosphonic acid in a mass ratio of 1:1; and the multi-effect agent is CPAM, synthesized as follows:

[0085] (1) Aqueous phase preparation: AM, DMC and EDTA were dissolved in deionized water, and then the pH of the solution was adjusted to 7-8 with 25% ammonia water.

[0086] (2) Preparation of oil phase: Add liquid paraffin, Span 80 and Tween 80 to a beaker and heat at 40°C until completely dissolved.

[0087] (3) Preparation of the multi-effect agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer, and condenser. Then, the aqueous phase was added to the oil phase, and the mixture was vigorously stirred and emulsified for 30 minutes. After emulsification, 2,2'-bis(2-methylpropionamido)dichloride was added to the prepolymerization system, and the mixture was vigorously stirred at 60°C. The copolymerization reaction was carried out in a 60°C water bath for 6 hours, cooled to room temperature, and then precipitated in a mixed solution of acetone and methanol. The homopolymer was completely removed by extraction with a Soxhlet extractor for 24 hours, forming the multi-effect agent CPAM.

[0088] The key performance characteristics of the system were tested (solubility, slowing rate, drag reduction rate, and damage rate). The test methods were carried out in accordance with SYT 5886-2018 "Performance Evaluation Method for Acidizing Working Fluids" and SY / 5107-2016 "Performance Evaluation Standard for Fracturing Fluids". The results showed that the system completely dissolved within 3 minutes, the slowing rate was 99.28%, the drag reduction rate reached more than 85.5%, and the damage rate was 6.45%.

[0089] Example 7

[0090] This embodiment provides an online, non-mixing, high-viscosity, high-drag-reducing, slow-release acid, comprising:

[0091] Weigh out 2.5 wt% iron ion stabilizer, 2.5 wt% acidification aid, 4 wt% corrosion inhibitor, 4.5 wt% coating agent, 3.0 wt% multi-effect agent, and the balance is 20% hydrochloric acid by weight.

[0092] The iron ion stabilizer is a mixture of ethyl citric acid and sodium formate in a mass ratio of 1:3; the acidification and drainage aid is a mixture of fatty alcohol polyoxyethylene ether and n-decyl glucoside in a mass ratio of 2:1; the corrosion inhibitor is a mixture of benzotriazole and polyethoxyethanol in a mass ratio of 3:2; the coating agent is a mixture of sodium humate and aminotrimethylphosphonic acid in a mass ratio of 1:1; and the multi-effect agent is CPAM, synthesized as follows:

[0093] (1) Aqueous phase preparation: AM, DMC and EDTA were dissolved in deionized water, and then the pH of the solution was adjusted to 7-8 with 25% ammonia water.

[0094] (2) Preparation of oil phase: Add liquid paraffin, Span 80 and Tween 80 to a beaker and heat at 40°C until completely dissolved.

[0095] (3) Preparation of the multi-effect agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer, and condenser. Then, the aqueous phase was added to the oil phase, and the mixture was vigorously stirred and emulsified for 30 minutes. After emulsification, 2,2'-bis(2-methylpropionamido)dichloride was added to the prepolymerization system, and the mixture was vigorously stirred at 60°C. The copolymerization reaction was carried out in a 60°C water bath for 6 hours, cooled to room temperature, and then precipitated in a mixed solution of acetone and methanol. The homopolymer was completely removed by extraction with a Soxhlet extractor for 24 hours, forming the multi-effect agent CPAM.

[0096] The key performance characteristics of the system were tested (solubility, slowing rate, drag reduction rate, and damage rate). The test methods were carried out in accordance with SYT 5886-2018 "Performance Evaluation Method for Acidizing Working Fluids" and SY / 5107-2016 "Performance Evaluation Standard for Fracturing Fluids". The results showed that the system completely dissolved within 5 minutes, the slowing rate was 99.68%, the drag reduction rate reached more than 85%, and the damage rate was 8.11%.

[0097] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0098] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An online, non-mixing, high-viscosity, high-drag-reducing, slow-release acid, characterized in that... Listed by weight percentage, it includes the following ingredients: Iron ion stabilizer 0.5-2.5wt%, acidification aid 1.0-2.5wt%, corrosion inhibitor 0.5-4wt%, coating agent 1.0-4.5wt%, multi-effect agent 0.1-3wt%, balance is hydrochloric acid with a weight fraction of 20%; The coating agent is a mixture of sodium humate and aminotrimethylphosphonic acid; The pleiotropic agent is prepared by the following method: (1) Aqueous phase preparation: Acrylamide AM, methacryloyloxyethyltrimethylammonium chloride DMC and disodium ethylenediaminetetraacetate (EDTA) were dissolved in deionized water, and then the pH of the solution was adjusted to 7-8 with 25% ammonia water. (2) Preparation of oil phase: Add liquid paraffin, Span 80 and Tween 80 to a beaker and heat gently at 40°C until completely dissolved; (3) Preparation of multi-effect agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer and condenser. Then the aqueous phase was added to the oil phase and the mixture was stirred vigorously for 30 minutes for emulsification. After emulsification, 2,2'-azobisisobutylamidine hydrochloride was added to the prepolymerization system. Under nitrogen protection, the mixture was stirred vigorously in a 60°C water bath for 6 hours for copolymerization. The mixture was cooled at room temperature and then precipitated in a mixed solution of acetone and methanol. The homopolymer was extracted for 24 hours using a Soxhlet extractor to completely remove the homopolymer and form the multi-effect agent.

2. The online, non-mixing, high-viscosity, high-resistance, slow-release acid according to claim 1, characterized in that, The iron ion stabilizer is one or a mixture of sodium citrate, sodium ethylenediaminetetrasodium formate, aminotrimethylphosphonic acid, and ethylenediaminetetramethylphosphonic acid.

3. The online, non-mixing, high-viscosity, high-resistance, slow-release acid according to claim 1, characterized in that, The acidification aid is one or more of n-decyl glucoside, isooctyl glucoside, and fatty alcohol polyoxyethylene ether.

4. The online, non-mixing, high-viscosity, high-drag-reducing, slow-release acid according to claim 1, characterized in that, The corrosion inhibitor is one or a mixture of hydroxyethylidene diphosphonic acid, benzotriazole, polyethoxyethanol, and diethanolamine.

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