Online blending-free variable-viscosity high-resistance-reduction retarded acid

Abstract

The invention discloses an on-line blending-free variable-viscosity high-resistance-reduction retarded acid, and according to an on-line blending-free variable-viscosity high-resistance-reduction retarded acid system provided by the invention, the performance of an acid solution can be changed by changing the dosage of a medicament, and the preparation in advance is not needed. The film coating agent can form an adsorption film on the surface of the rock, and the existence of the adsorption film blocks the contact between H < + > and the rock, so that the acid-rock reaction rate is slowed down. In addition, the retarding agent also has multiple composite retarding performance, the characteristics of foam retarding acid and gelling retarding acid are combined, and the rate of acid-rock reaction is greatly reduced under the double retarding action of tackifying retarding of the multi-effect agent and blocking retarding of the film coating agent. In addition to a good tackifying effect, the tackifying agent also has excellent resistance reducing performance and is multipurpose, and the dosage and types of additives are reduced. Meanwhile, the resistance reduction rate of the system reaches 85% or above and is far better than 70% of that of a traditional system.

Description

Technical Field

[0001] The invention relates to the technical field of reservoir transformation in oil production, and more particularly to an online non-mixing variable viscosity high drag reduction retarding acid. Background Art

[0002] Carbonate reservoirs account for about 70% of the world's oil and gas production, and carbonate oil and gas reservoirs are widely distributed. The Tarim Basin, Sichuan Basin, Ordos, Bohai Bay and other regions contain abundant carbonate reservoirs. Most carbonate reservoirs have the characteristics of deep burial, high temperature and developed fractures.

[0003] Conventional acid systems used for acidizing carbonate reservoirs are mostly hydrochloric acid systems, which have achieved certain results in the early stage. However, with the intensification of 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 too fast reaction rate and severe filtration, which causes excessive consumption of acid near the wellbore, making it difficult to form acid wormholes in the reservoir and unable to communicate oil and gas channels deep in the formation.

[0004] Therefore, controlling the acid-rock reaction rate is the main focus of carbonate reservoir acidizing technology and fluid research. The existing slow-rate acid system delays the time for H+ to be transferred to the rock surface through high viscosity and oil-in-acid, thereby reducing the H+ mass transfer coefficient and achieving the purpose of slowing down.

[0005] The existing retarding acid system has the following defects: (1) The high molecular weight thickened acid has high viscosity and large molecular weight, which makes it difficult to prepare the liquid, and the friction resistance during construction is high, making it difficult to pump. The formation is not completely debonded, which will cause a large amount of clogging of the formation and cause serious damage to the pore throat; (2) Emulsified acid and foamed acid have poor stability and poor temperature resistance, and are complex to construct and have average retarding effect; (3) The shell (capsule) of the solid acid encapsulating the active acid has poor solubility, making it difficult to flow back and causing serious damage to the formation. At the same time, the supporting construction process is relatively complicated.

[0006] In summary, the existing retarded acid system cannot meet the requirements of high-temperature carbonate reservoir development. It is necessary to develop a retarded acid system with simple process, outstanding resistance reduction performance, little damage to the reservoir, and excellent high-temperature retarding performance to improve the transformation effect and efficiently develop carbonate reservoirs. Summary of the invention

[0007] In view of this, the present invention provides an online mixing-free variable viscosity high drag reduction retarding acid.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] An online non-mixing variable viscosity high drag reduction retarding acid, comprising the following components by mass percentage:

[0010] The iron ion stabilizer is 0.5-2.5wt%, the acidifying drainage aid is 1.0-2.5wt%, the corrosion inhibitor is 0.5-4wt%, the coating agent is 1.0-4.5wt%, the multi-effect agent is 0.1-3wt%, and the balance is 20% by weight of hydrochloric acid.

[0011] Preferably, the iron ion stabilizer is a mixture of one or more of sodium citrate, sodium ethylenediaminetetraethyl, sodium formate, aminotri(methylenephosphonic acid), and ethylenediaminetetra(methylenephosphonic acid).

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

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

[0014] Preferably, the coating agent is a mixture of one or more of sodium polyacrylate, sodium palmitate, sodium humate, and aminotri(methylenephosphonic acid).

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

[0016] (1) Preparation of aqueous phase: dissolving AM, DMC and EDTA in deionized water, and then adjusting the pH of the solution with aqueous ammonia;

[0017] (2) Preparation of oil phase: Add liquid paraffin, Span 80 and Tween 80 into a beaker and heat slightly at 40°C until completely dissolved;

[0018] (3) Preparation of multi-effect agent: add the oil phase into the container, then add the water phase into the oil phase, stir vigorously and emulsify for 30 minutes, after emulsification, add 2,2'-di(2-methylpropionamido) dichloride into the prepolymerization system, stir vigorously at 60°C, carry out copolymerization reaction in a warm water bath at 60°C for 6 hours, cool at room temperature, and then precipitate in a mixed solution of acetone and methanol, extract with a Soxhlet extractor for 24 hours, completely remove the homopolymer, and form a multi-effect agent;

[0019] The synthetic route is as follows:

[0020]

[0021] The beneficial effect of adopting the above preferred scheme is that the multi-effect agent of the present invention is different from the conventional gelling agent. The multi-effect agent is a cationic emulsion, which has good solubility and thermal stability in the hydrochloric acid environment and is extremely suitable for high temperature and strong acid environment. The multi-effect agent has dual functions. First, the multi-effect agent molecules can be intertwined with each other under non-bonding action to form a network structure, which increases the viscosity of the acid solution. The increase in the viscosity of the acid solution is conducive to slowing down the H+ mass transfer rate, thereby slowing down the acid-rock reaction rate. Through the viscosity increase and slowing down of the multi-effect agent and the barrier and slowing down of the coating agent, the rate of the acid-rock reaction is greatly reduced under the dual slowing effect of the two; second, the multi-effect agent can also inhibit the generation of turbulence in the acid solution during pumping, thereby significantly reducing the friction resistance of the acid solution (the resistance reduction rate is more than 85%), and has excellent adaptability in deep wells and ultra-deep wells.

[0022] Preferably, the pH of the 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] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

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

[0026] 2) The drainage aids selected in the present invention are all non-ionic surfactants, which have excellent solubility, good acid and salt resistance, and will not lose the effect of reducing surface tension due to strong acid environment; and non-ionic surfactants will not be affected by calcium and magnesium ions in the reservoir. In addition, the drainage aids will not interact with rocks due to static electricity, which greatly improves the drainage efficiency.

[0027] 3) The online non-mixing variable viscosity high drag reduction slow acid system provided by the present invention can change the performance of the acid solution by changing the amount of the agent added, without the need for advance configuration. In traditional methods, the acid solution is usually prepared in advance on the ground, which may lead to problems of over- or under-preparation. Online mixing can prepare the required acid solution immediately as needed, reducing material waste. At the same time, since there is no need to prepare a large amount of acid solution for storage in advance, the equipment and site required on site can also be reduced, thereby further reducing costs. In addition, the present invention can also adjust the concentration and formula of the acid solution according to real-time conditions, so that it can better adapt to changes in the formation and the needs of different stages, and provide better construction effects.

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

[0029] 5) The multifunctional agent molecules provided by the present invention can be interwoven with each other to form a network structure under non-bonding action, thereby increasing the viscosity of the acid solution. The increased viscosity of the acid solution is conducive to slowing 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 surface of the rock. 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 mixing-free variable viscosity high drag-reducing retarding acid, which has multiple composite retarding properties and combines the characteristics of foam retarding acid and gelling retarding acid. Through the viscosity-increasing retarding effect of the multi-effect agent and the barrier retarding effect of the coating agent, the rate of the acid-rock reaction is greatly reduced under the dual retarding effect of the two.

[0032] 8) In addition to having a good viscosity-increasing effect, the multi-effect agent provided by the present invention also has excellent drag-reducing performance, and one agent has multiple uses, reducing the amount and type of additives used. At the same time, the drag-reducing rate of the system reaches more than 85%, which is far better than the traditional system (70%).

[0033] 9) The product of the present invention has little residue after gel breaking and has very little damage to the reservoir, and is very suitable for increasing the production of low-permeability or ultra-low-permeability reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0035] Figure 1 The actual measured results of drag reduction rate of an online non-mixing variable viscosity high drag reduction slow acid provided in an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of an online non-mixing variable viscosity high drag reduction retarding acid double retarding provided by an embodiment of the present invention;

[0037] Figure 3 The retarding property test result of an online non-mixing variable viscosity high drag reduction retarding acid provided in an embodiment of the present invention;

[0038] Figure 4 This is the test result of the acid solubility of an online non-mixing variable viscosity high drag reduction slow-speed material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Example 1

[0041] This embodiment provides an online non-mixing variable viscosity high drag reduction retarding acid, comprising:

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

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

[0044] (1) Preparation of aqueous phase: Dissolve AM, DMC and EDTA in deionized water, and then adjust the pH of the solution to 7-8 with 25% ammonia water.

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

[0046] (3) Preparation of multifunctional agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, a nitrogen inlet, a thermometer and a condenser. The aqueous phase was then added to the oil phase and stirred vigorously for emulsification for 30 minutes. After emulsification, 2,2'-di(2-methylpropionamido)dichloride was added to the prepolymerization system and stirred vigorously at 60°C. The copolymerization reaction was carried out in a warm water bath at 60°C for 6 hours, cooled at 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 to form a multifunctional agent CPAM.

[0047] The key performance of the system was tested (solubility, retarding rate, drag reduction rate, and damage rate). The test method was carried out in accordance with SYT 5886-2018 "Acidizing Working Fluid Performance Evaluation Method" and SY / 5107-2016 "Fracturing Fluid Performance Evaluation Standard". It was found that the system was completely dissolved within 2 minutes, the retarding rate was 94.26%, the drag reduction rate was more than 80%, and the damage rate was 2.86%.

[0048] Example 2

[0049] This embodiment provides an online non-mixing variable viscosity high drag reduction retarding acid, comprising:

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

[0051] Among them, the iron ion stabilizer is a mixture of sodium formate, aminotri(methylenephosphonic acid) and ethylenediaminetetra(methylenephosphonic acid) in a mass ratio of 1:1:2; the acidifying agent 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 aminotri(methylenephosphonic acid) in a mass ratio of 2:1; the synthesis method of the multi-effect agent CPAM is as follows:

[0052] (1) Preparation of aqueous phase: Dissolve AM, DMC and EDTA in deionized water, and then adjust the pH of the solution to 7-8 with 25% ammonia water.

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

[0054] (3) Preparation of multifunctional agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, a nitrogen inlet, a thermometer and a condenser. The aqueous phase was then added to the oil phase and stirred vigorously for emulsification for 30 minutes. After emulsification, 2,2'-di(2-methylpropionamido)dichloride was added to the prepolymerization system and stirred vigorously at 60°C. The copolymerization reaction was carried out in a warm water bath at 60°C for 6 hours, cooled at 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 to form a multifunctional agent CPAM.

[0055] The key performance of the system was tested (solubility, retarding rate, drag reduction rate, and damage rate) in accordance with SYT 5886-2018 "Acidizing Working Fluid Performance Evaluation Method" and SY / 5107-2016 "Fracturing Fluid Performance Evaluation Standard". It was found that the system was completely dissolved within 3 minutes, the retarding rate was 93.15%, the drag reduction rate was over 82%, and the damage rate was 3.55%.

[0056] Figure 2 It is a schematic diagram of the double retardation of the line-free mixing variable viscosity high drag reduction retarding acid. The multi-effect agent is dispersed in the solution to effectively increase the viscosity of the solution, which reduces the mass transfer rate of H+, thereby delaying the acid-rock reaction rate; in addition, the coating agent is adsorbed on the rock surface to form an adsorption layer, which can effectively block the contact between H+ and the rock surface, thereby reducing the acid-rock reaction rate; under the combined action of these two retardation methods, the acid-rock reaction rate is further reduced.

[0057] Example 3

[0058] This embodiment provides an online non-mixing variable viscosity high drag reduction retarding acid, comprising:

[0059] Weigh 1wt% of iron ion stabilizer, 1wt% of acidifying drainage agent, 1wt% of corrosion inhibitor, 2.5wt% of coating agent, 0.5wt% of multi-effect agent, and the balance is 20wt% of hydrochloric acid;

[0060] Among them, the iron ion stabilizer is sodium formate; the acidification and drainage agent is fatty alcohol polyoxyethylene ether; the corrosion inhibitor is diethanolamine; the coating agent is a mixture of sodium humate and aminotri(methylenephosphonic acid) with a mixing mass ratio of 2:1; the multi-effect agent is CPAM, and the synthesis method is as follows:

[0061] (1) Preparation of aqueous phase: Dissolve AM, DMC and EDTA in deionized water, and then adjust the pH of the solution to 7-8 with 25% ammonia water.

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

[0063] (3) Preparation of multifunctional agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, a nitrogen inlet, a thermometer and a condenser. The aqueous phase was then added to the oil phase and stirred vigorously for emulsification for 30 minutes. After emulsification, 2,2'-di(2-methylpropionamido)dichloride was added to the prepolymerization system and stirred vigorously at 60°C. The copolymerization reaction was carried out in a warm water bath at 60°C for 6 hours, cooled at 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 to form a multifunctional agent CPAM.

[0064] The key performance of the system was tested (solubility, retarding rate, drag reduction rate, and damage rate) in accordance with SYT 5886-2018 "Acidizing Working Fluid Performance Evaluation Method" and SY / 5107-2016 "Fracturing Fluid Performance Evaluation Standard". It was found that the system was completely dissolved within 3 minutes, the retarding rate was 96%, the drag reduction rate was over 82.5%, and the damage rate was 4.56%.

[0065] Example 4

[0066] This embodiment provides an online non-mixing variable viscosity high drag reduction retarding acid, comprising:

[0067] Weigh 1wt% of iron ion stabilizer, 1wt% of acidifying drainage agent, 1wt% of corrosion inhibitor, 2.5wt% of coating agent, 1wt% of multi-effect agent, and the balance is 20wt% hydrochloric acid;

[0068] Among them, the iron ion stabilizer is ethylenediaminetetramethylenephosphonic acid; the acidification and drainage agent is a mixture of fatty alcohol polyoxyethylene ether and isooctyl glucoside, and the mixing mass ratio is 3:2; the corrosion inhibitor is diethanolamine; the coating agent is a mixture of sodium humate and aminotrimethylenephosphonic acid, and the mixing mass ratio is 2:1; the multi-effect agent is CPAM, and the synthesis method is as follows:

[0069] (1) Preparation of aqueous phase: Dissolve AM, DMC and EDTA in deionized water, and then adjust the pH of the solution to 7-8 with 25% ammonia water.

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

[0071] (3) Preparation of multifunctional agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, a nitrogen inlet, a thermometer and a condenser. The aqueous phase was then added to the oil phase and stirred vigorously for emulsification for 30 minutes. After emulsification, 2,2'-di(2-methylpropionamido)dichloride was added to the prepolymerization system and stirred vigorously at 60°C. The copolymerization reaction was carried out in a warm water bath at 60°C for 6 hours, cooled at 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 to form a multifunctional agent CPAM.

[0072] The key performance of the system was tested (solubility, retarding rate, drag reduction rate, and damage rate) in accordance with SYT 5886-2018 "Acidizing Working Fluid Performance Evaluation Method" and SY / 5107-2016 "Fracturing Fluid Performance Evaluation Standard". It was found that the system was completely dissolved within 3 minutes, the retarding rate was 98%, the drag reduction rate was over 85%, and the damage rate was 5.02%.

[0073] Example 5

[0074] This embodiment provides an online non-mixing variable viscosity high drag reduction retarding acid, comprising:

[0075] Weigh 1wt% of iron ion stabilizer, 1wt% of acidifying drainage agent, 1wt% of corrosion inhibitor, 2.5wt% of coating agent, 1.5wt% of multi-effect agent, and the balance is 20wt% hydrochloric acid;

[0076] Among them, the iron ion stabilizer is a mixture of ethylenediaminetetramethylenephosphonic acid and sodium formate, with a mixing mass ratio of 1:2; the acidification drainage agent is a mixture of fatty alcohol polyoxyethylene ether and n-decyl glucoside, with a mixing mass ratio of 1:1; the corrosion inhibitor is diethanolamine; the coating agent is a mixture of sodium humate and aminotrimethylenephosphonic acid, with a mixing mass ratio of 2:1; the multi-effect agent is CPAM, and the synthesis method is as follows:

[0077] (1) Preparation of aqueous phase: Dissolve AM, DMC and EDTA in deionized water, and then adjust the pH of the solution to 7-8 with 25% ammonia water.

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

[0079] (3) Preparation of multifunctional agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, a nitrogen inlet, a thermometer and a condenser. The aqueous phase was then added to the oil phase and stirred vigorously for emulsification for 30 minutes. After emulsification, 2,2'-di(2-methylpropionamido)dichloride was added to the prepolymerization system and stirred vigorously at 60°C. The copolymerization reaction was carried out in a warm water bath at 60°C for 6 hours, cooled at 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 to form a multifunctional agent CPAM.

[0080] The key performance of the system was tested (solubility, retarding rate, drag reduction rate, and damage rate) in accordance with SYT 5886-2018 "Acidizing Working Fluid Performance Evaluation Method" and SY / 5107-2016 "Fracturing Fluid Performance Evaluation Standard". It was found that the system was completely dissolved within 3 minutes, the retarding rate was 98.65%, the drag reduction rate was over 85%, and the damage rate was 5.46%.

[0081] Example 6

[0082] This embodiment provides an online non-mixing variable viscosity high drag reduction retarding acid, comprising:

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

[0084] Among them, the iron ion stabilizer is a mixture of acetic acid and sodium formate, with a mixing mass ratio of 1:3; the acidification aid is a mixture of fatty alcohol polyoxyethylene ether and n-decyl glucoside, with a mixing mass ratio of 2:1; the corrosion inhibitor is a mixture of benzotriazole and polyethoxyethanol, with a mixing mass ratio of 3:2; the coating agent is a mixture of sodium humate and aminotri(methylenephosphonic) acid, with a mixing mass ratio of 1:1; the multi-effect agent is CPAM, and the synthesis method is as follows:

[0085] (1) Preparation of aqueous phase: Dissolve AM, DMC and EDTA in deionized water, and then adjust the pH of the solution to 7-8 with 25% ammonia water.

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

[0087] (3) Preparation of multifunctional agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, a nitrogen inlet, a thermometer and a condenser. The aqueous phase was then added to the oil phase and stirred vigorously for emulsification for 30 minutes. After emulsification, 2,2'-di(2-methylpropionamido)dichloride was added to the prepolymerization system and stirred vigorously at 60°C. The copolymerization reaction was carried out in a warm water bath at 60°C for 6 hours, cooled at 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 to form a multifunctional agent CPAM.

[0088] The key performance of the system was tested (solubility, retarding rate, drag reduction rate, and damage rate). The test method was carried out in accordance with SYT 5886-2018 "Acidizing Working Fluid Performance Evaluation Method" and SY / 5107-2016 "Fracturing Fluid Performance Evaluation Standard". It was found that the system was completely dissolved within 3 minutes, the retarding 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 variable viscosity high drag reduction retarding acid, comprising:

[0091] Weigh 2.5wt% of iron ion stabilizer, 2.5wt% of acidifying drainage agent, 4wt% of corrosion inhibitor, 4.5wt% of coating agent, 3.0wt% of multi-effect agent, and the balance is 20wt% of hydrochloric acid;

[0092] Among them, the iron ion stabilizer is a mixture of acetic acid and sodium formate, with a mixing mass ratio of 1:3; the acidification aid is a mixture of fatty alcohol polyoxyethylene ether and n-decyl glucoside, with a mixing mass ratio of 2:1; the corrosion inhibitor is a mixture of benzotriazole and polyethoxyethanol, with a mixing mass ratio of 3:2; the coating agent is a mixture of sodium humate and aminotri(methylenephosphonic) acid, with a mixing mass ratio of 1:1; the multi-effect agent is CPAM, and the synthesis method is as follows:

[0093] (1) Preparation of aqueous phase: Dissolve AM, DMC and EDTA in deionized water, and then adjust the pH of the solution to 7-8 with 25% ammonia water.

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

[0095] (3) Preparation of multifunctional agent: The oil phase was added to a four-necked round-bottom flask equipped with a mechanical stirrer, a nitrogen inlet, a thermometer and a condenser. The aqueous phase was then added to the oil phase and stirred vigorously for emulsification for 30 minutes. After emulsification, 2,2'-di(2-methylpropionamido)dichloride was added to the prepolymerization system and stirred vigorously at 60°C. The copolymerization reaction was carried out in a warm water bath at 60°C for 6 hours, cooled at 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 to form a multifunctional agent CPAM.

[0096] The key performance of the system was tested (solubility, retarding rate, drag reduction rate, and damage rate) in accordance with SYT 5886-2018 "Acidizing Working Fluid Performance Evaluation Method" and SY / 5107-2016 "Fracturing Fluid Performance Evaluation Standard". It was found that the system was completely dissolved within 5 minutes, the retarding rate was 99.68%, the drag reduction rate was over 85%, and the damage rate was 8.11%.

[0097] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0098] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An online non-mixing variable viscosity high drag reduction slow acid, characterized in that: In terms of mass percentage, it includes the following ingredients: The iron ion stabilizer is 0.5-2.5wt%, the acidifying drainage aid is 1.0-2.5wt%, the corrosion inhibitor is 0.5-4wt%, the coating agent is 1.0-4.5wt%, the multi-effect agent is 0.1-3wt%, and the balance is 20% by weight of hydrochloric acid.

2. The online non-mixing variable viscosity high drag reduction retarding acid according to claim 1, characterized in that: The iron ion stabilizer is a mixture of one or more of sodium citrate, sodium ethylenediaminetetraethyl, sodium formate, aminotri(methylenephosphonic acid) and ethylenediaminetetra(methylenephosphonic acid).

3. The online non-mixing variable viscosity high drag reduction retarding acid according to claim 1, characterized in that: The acidification drainage agent is a mixture of one or more of n-decyl glucoside, isooctyl glucoside, and fatty alcohol polyoxyethylene ether.

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

5. The online non-mixing variable viscosity high drag reduction retarding acid according to claim 1, characterized in that: The coating agent is a mixture of one or more of sodium polyacrylate, sodium palmitate, sodium humate and aminotri(methylenephosphonic acid).

6. The online non-mixing variable viscosity high drag reduction retarding acid according to claim 1, characterized in that: The multifunctional agent is prepared by the following method: (1) Preparation of aqueous phase: dissolving AM, DMC and EDTA in deionized water, and then adjusting the pH of the solution with aqueous ammonia; (2) Preparation of oil phase: Add liquid paraffin, Span 80 and Tween 80 into a beaker and heat slightly at 40°C until completely dissolved; (3) Preparation of multi-effect agent: Add the oil phase into the container, then add the water phase into the oil phase, stir vigorously and emulsify for 30 minutes, after emulsification, add 2,2'-bis(2-methylpropionamido) dichloride into the prepolymerization system, stir vigorously in a warm water bath at 60°C, carry out copolymerization for 6 hours, cool at room temperature, and then precipitate in a mixed solution of acetone and methanol, extract with a Soxhlet extractor for 24 hours, completely remove the homopolymer, and form a multi-effect agent; The synthetic route is as follows:

7. The online non-mixing variable viscosity high drag reduction retarding acid according to claim 6, characterized in that: The pH of the solution is adjusted to 7-8.

8. The online non-mixing variable viscosity high drag reduction retarding acid according to claim 6, characterized in that: The container was a four-necked round-bottom flask equipped with a mechanical stirrer, a nitrogen inlet, a thermometer and a condenser.

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