Preparation method of acid liquid system

Abstract

The invention provides a preparation method of an acid liquid system, which comprises the following steps: adding 20-50 parts by mass of emulsified gelled acid into 50-80 parts by mass of gelled acid to obtain the acid liquid system, preferably, 25-45 parts by mass of the emulsified gelled acid is added into 55-75 parts by mass of the gelled acid, and the acid liquid system is obtained.

Description

Technical Field

[0001] The invention provides a method for preparing an acid solution system. Background Art

[0002] The acid solutions in the prior art either have problems such as short acid fractures, limited reservoir communication range, and poor acid fracturing effect; or have problems such as poor temperature resistance and high friction resistance, which cannot meet the purpose of deep penetration under high-temperature deep well acid fracturing. With the continuous deepening of high-temperature carbonate reservoir exploration and development, higher requirements are put forward for the performance of high-temperature acid solution systems in terms of slow speed and low friction resistance. Summary of the invention

[0003] The present invention provides a method for preparing an acid solution system, which comprises the following steps: based on 100 parts by volume of the acid solution system, adding 20 to 50 parts by volume of emulsified gelled acid to 50 to 80 parts by volume of gelled acid to obtain the acid solution system.

[0004] In a specific embodiment, based on 100 parts by volume of the acid solution system, 25 to 45 parts by volume of the emulsified gelled acid are added to 55 to 75 parts by volume of the gelled acid to obtain the acid solution system.

[0005] In a specific embodiment, the emulsified gelled acid is added dropwise at a first dropping acceleration to the gelled acid stirred at a first stirring speed, and after the addition is completed, the acid solution is stirred at a second stirring speed to obtain the acid solution system.

[0006] In one embodiment, the emulsified gelled acid is prepared as follows:

[0007] 1) adding a first corrosion inhibitor, a first acid thickener and a first iron ion stabilizer to the first acid solution, stirring the mixture at a third stirring speed and then standing the mixture to obtain an acid phase;

[0008] 2) dissolving a water-in-oil emulsifier in oil to obtain an oil phase;

[0009] 3) adding the acid phase dropwise at a second dropping acceleration to the oil phase stirred at a fourth stirring speed, and after the dropping is completed, stirring is performed at a fifth stirring speed to obtain the emulsified gelled acid.

[0010] In one embodiment, in step 2) of preparing the emulsified gelled acid, the water-in-oil emulsifier is dissolved in the oil by heating to a temperature of 40 to 60° C. and stirring at a sixth stirring speed.

[0011] In a specific embodiment, based on 100 parts by volume of the emulsified gelling acid, the acid phase comprises 60 to 80 parts by volume, and the oil phase comprises 20 to 40 parts by volume.

[0012] In a specific embodiment, based on 100 parts by volume of the emulsified gelled acid, the acid phase is 65 to 70 parts by volume, and the oil phase is 30 to 35 parts by volume.

[0013] In a specific embodiment, based on 100 parts by mass of the acid phase, the first acid solution is 95.2 to 97.7 parts by mass, the first corrosion inhibitor is 1.5 to 3 parts by mass, the first acid thickener is 0.1 to 0.6 parts by mass, and the first iron ion stabilizer is 0.8 to 1.8 parts by mass; wherein the mass concentration of the acid in the first acid solution is 15% to 30%.

[0014] In a specific embodiment, based on 100 parts by mass of the acid phase, the first acid solution comprises 96 to 97 parts by mass, the first iron ion stabilizer comprises 1 to 1.5 parts by mass, and the first corrosion inhibitor comprises 2 to 2.5 parts by mass; wherein the mass concentration of the acid in the first acid solution is 15% to 20%.

[0015] In a specific embodiment, based on 100 parts by mass of the oil phase, the oil is in an amount of 96 to 98 parts by mass, and the water-in-oil emulsifier is in an amount of 2 to 4 parts by mass.

[0016] In a specific embodiment, based on 100 parts by mass of the oil phase, the oil is in an amount of 96.5 to 97.5 parts by mass, and the water-in-oil emulsifier is in an amount of 2.5 to 3.5 parts by mass.

[0017] In one embodiment, the gelling acid is prepared as follows:

[0018] 1) adding a second acid thickener to the second acid solution stirred at a seventh stirring speed, and after adding the second acid thickener, stirring at an eighth stirring speed to obtain a thickened acid solution;

[0019] II) adding a second iron ion stabilizer and a second corrosion inhibitor to the thickened acid solution, stirring at a ninth stirring speed until uniform, and then standing to obtain the gelled acid.

[0020] In a specific embodiment, based on 100 parts by mass of the gelled acid, the second acid solution comprises 94.2 to 97.4 parts by mass, the second acid thickener comprises 0.3 to 1 parts by mass, the second iron ion stabilizer comprises 0.8 to 1.8 parts by mass, and the second corrosion inhibitor comprises 1.5 to 3 parts by mass; wherein the mass concentration of the acid in the second acid solution is 15% to 30%.

[0021] In a specific embodiment, based on 100 parts by mass of the gelled acid, the second acid solution comprises 95.4 to 96.2 parts by mass, the second acid thickener comprises 0.4 to 0.8 parts by mass, the second iron ion stabilizer comprises 1 to 1.5 parts by mass, and the second corrosion inhibitor comprises 2 to 2.5 parts by mass; wherein the mass concentration of the acid in the second acid solution is 15% to 20%.

[0022] In a specific embodiment, the first acid solution and the second acid solution are independently selected from aqueous hydrochloric acid and / or aqueous hydrofluoric acid.

[0023] In a specific embodiment, the first iron ion stabilizer and the second iron ion stabilizer are independently organic acids.

[0024] Preferably, in a specific embodiment, the first iron ion stabilizer and the second iron ion stabilizer are independently selected from at least one of citric acid, acetic acid, ethylenediaminetetraacetic acid, ascorbic acid and lactic acid.

[0025] In a specific embodiment, the first corrosion inhibitor and / or the second corrosion inhibitor are independently selected from at least one of imidazoline corrosion inhibitors, quinoline quaternary ammonium salts, ketoaldehyde amine condensates and Mannich bases.

[0026] In a specific embodiment, the first corrosion inhibitor and / or the second corrosion inhibitor are independently selected from at least one of 1-aminoethyl-2-pentadecylimidazolium quaternary ammonium salt, formaldehyde-p-phenylenediamine-acetophenone (obtained by reacting formaldehyde, p-phenylenediamine and acetophenone as reaction raw materials) and 2-methylquinoline benzyl quaternary ammonium salt.

[0027] In a specific embodiment, the water-in-oil emulsifier is selected from at least one of dipolyhydroxystearate, sorbitan sesquioleate, sorbitan fatty acid ester, polyoxyethylene octylphenol ether-10, dipolyhydroxystearate and hexadecylamine.

[0028] In a specific embodiment, the oil is selected from at least one of diesel, kerosene, white oil and light crude oil.

[0029] In a specific embodiment, the first acid thickener and the second acid thickener are independently a first polyacrylamide copolymer and / or a second polyacrylamide copolymer.

[0030] In a specific embodiment, the relative molecular weight of the first polyacrylamide copolymer is 8 million to 10 million.

[0031] In a specific embodiment, the first polyacrylamide copolymer is a copolymer prepared by using acrylamide and 2-acrylamide-2-methylpropanesulfonic acid monomers in a molar ratio of 1:1 to 3:1.

[0032] In a specific embodiment, the first polyacrylamide copolymer is a copolymer prepared by using acrylamide and 2-acrylamide-2-methylpropanesulfonic acid monomers in a molar ratio of 2:1 to 2.5:1.

[0033] In one specific embodiment, the second polyacrylamide copolymer is prepared as follows:

[0034] A) dissolving acrylamide, an acid-resistant monomer, a water-soluble monomer containing a dimethylamine group and a quaternary ammonium salt type polymerizable surfactant in water to obtain a first solution;

[0035] B) adding a cosolvent, a chain transfer agent, a complexing agent, an activator, and a water-soluble anionic surfactant to the first solution, and mixing them uniformly to obtain a second solution;

[0036] C) adjusting the pH value of the second solution to 9 to 10 to obtain a third solution; then adding the third solution to a polymerization device and introducing nitrogen;

[0037] D) adding a water-soluble azo initiator, a reducing agent, and an oxidizing agent into the polymerization device to obtain a fourth solution, and then continuing to introduce nitrogen;

[0038] E) after the temperature of the fourth solution rises, maintaining the temperature, thereby obtaining a polymerized jelly;

[0039] F) granulating, drying, crushing and sieving the polymer colloid to obtain the thickener in dry powder form.

[0040] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the acid-resistant monomer is selected from at least one of 2-acrylamide-2-methylpropanesulfonic acid, acryloyloxyethyltrimethylammonium chloride and methacryloyloxyethyltrimethylammonium chloride.

[0041] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the water-soluble monomer containing a dimethylamine group is selected from methacryloyloxyethyl dimethylamine and / or N,N-dimethylacrylamide.

[0042] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the quaternary ammonium salt type polymerizable surfactant is selected from at least one of tetradecyl dimethyl allyl ammonium chloride, hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, methacryloyloxyethyl dimethyl hexadecyl ammonium bromide and dimethyl octadecyl (2-hydroxy-3-acrylamide propyl) ammonium chloride.

[0043] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the acrylamide has 30 to 50 parts by mass, the acid-resistant monomer has 50 to 70 parts by mass, the water-soluble monomer containing a dimethylamine group has 1.4 to 1.7 parts by mass, and the quaternary ammonium salt type polymerizable surfactant has 0.2 to 1 part by mass.

[0044] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the acrylamide has 30 to 45 parts by mass, the acid-resistant monomer has 50 to 64 parts by mass, the water-soluble monomer containing a dimethylamine group has 1.4 to 1.7 parts by mass, and the quaternary ammonium salt type polymerizable surfactant has 0.2 to 0.6 parts by mass.

[0045] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the total mass of the acrylamide, the acid-resistant monomer, the water-soluble monomer containing a dimethylamine group and the quaternary ammonium salt type polymerizable surfactant accounts for 25 wt % to 29 wt % of the total mass of the first solution.

[0046] In a specific embodiment, in the process of preparing the second polyacrylamide copolymer, based on the total mass of the acrylamide, the acid-resistant monomer, the water-soluble monomer containing a dimethylamine group and the quaternary ammonium salt type polymerizable surfactant as 100% (that is, the aqueous solution of these four monomers is not taken as 100%), the amount of the cosolvent is 1wt% to 3wt%, the amount of the chain transfer agent is 0.05wt% to 0.1wt%, the amount of the complexing agent is 0.03wt% to 0.08wt%, the amount of the activator is 0.05wt% to 0.1wt%, the amount of the oxidant is 0.01wt% to 0.06wt%, the amount of the reducing agent is 0.005wt% to 0.03wt%, the amount of the water-soluble azo initiator is 0.02wt% to 0.06wt%, and the amount of the water-soluble anionic surfactant is 3wt% to 5wt%.

[0047] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the acrylamide has 35 to 45 parts by mass, the acid-resistant monomer has 53 to 64 parts by mass, the water-soluble monomer containing a dimethylamine group has 1.5 to 1.7 parts by mass, and the quaternary ammonium salt type polymerizable surfactant has 0.3 to 0.6 parts by mass.

[0048] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the co-solvent is selected from at least one of urea, thiourea and triethanolamine.

[0049] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the chain transfer agent is selected from at least one of sodium formate, potassium formate and isopropanol.

[0050] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the complexing agent is selected from at least one of ethylenediaminetetraacetic acid disalt, ethylenediaminetetraacetic acid tetrasalt and triethylenetetraaminepentaacetic acid salt. For example, the salt may be a sodium salt or a potassium salt. For example, the complexing agent is selected from at least one of ethylenediaminetetraacetic acid disodium salt, ethylenediaminetetraacetic acid tetrasodium salt and triethylenetetraaminepentaacetic acid pentasodium salt.

[0051] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the activator is selected from at least one of N,N-tetramethylethylenediamine, ethylenediamine and triethanolamine.

[0052] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the oxidant is selected from at least one of ammonium persulfate, potassium persulfate, and hydrogen peroxide.

[0053] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the reducing agent is selected from at least one of sodium bisulfite, sodium sulfite and ammonium ferrous sulfate.

[0054] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the water-soluble azo initiator is selected from azobisisobutylamidine hydrochloride and / or azobisisobutylimidazoline hydrochloride. For example, the salts thereof may be sodium salts or potassium salts. For example, the water-soluble azo initiator is selected from azobisisobutylamidine hydrochloride sodium salt and / or azobisisobutylimidazoline hydrochloride sodium salt.

[0055] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, the water-soluble anionic surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate, triethanolamine dodecyl sulfate and triethanolamine dodecylbenzene sulfonate.

[0056] During the preparation of the second polyacrylamide copolymer, depending on the type of monomer, some may release heat while others may not; in order to facilitate the subsequent low-temperature polymerization, it is best to cool the second solution. In a specific embodiment, in step B), the second solution obtained by mixing uniformly is cooled to 5°C to 10°C. For example, it is placed in a water bath at 5°C to 10°C and cooled for 30 minutes.

[0057] In the process of preparing the second polyacrylamide copolymer, generally speaking, heat is released during the process of adjusting the pH value. Therefore, in order to facilitate the subsequent low-temperature polymerization, it is best to cool the third solution. In a specific embodiment, in step C), the third solution obtained after adjusting the pH value is cooled to 5°C to 10°C. For example, it is placed in a water bath at 5°C to 10°C and cooled for 30 minutes.

[0058] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, in step C) and step D, the time for introducing nitrogen is independently 20 to 30 minutes.

[0059] In the process of preparing the second polyacrylamide copolymer, in step D), before the azo initiator, the reducing agent and the oxidizing agent are added to the polymerization device, they are preferably prepared into aqueous solutions respectively, so as to be added to the polymerization device and the aqueous solution of the reaction monomer (i.e., the third solution). As for the prepared concentration, there is no special requirement, and it can be adjusted according to actual needs and use scale.

[0060] In the process of preparing the second polyacrylamide copolymer, step E) is mainly a polymerization process, during which a certain amount of heat is released. When the heat is released to a certain extent, i.e., 60° C. to 80° C., insulation is performed. Therefore, in a specific embodiment, in the process of preparing the second polyacrylamide copolymer, in step E), the insulation temperature is 60° C. to 80° C.

[0061] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, in step E), the insulation time is 4 to 5 hours.

[0062] In one specific embodiment, during the preparation of the second polyacrylamide copolymer, in step F), the size of the granulated particles is 0.3 to 0.5 cm.

[0063] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, in step F), the drying temperature is 60°C to 80°C.

[0064] In one embodiment, during the preparation of the second polyacrylamide copolymer, in step F), the moisture content of the dried product is less than 10 wt %, for example, the moisture content of the dried product is less than 5 wt %, or the moisture content of the dried product is less than 3 wt %.

[0065] In a specific embodiment, during the preparation of the second polyacrylamide copolymer, in step F), the mesh size of the sieve is 20 to 40 meshes.

[0066] In a specific embodiment, the first dripping speed and the second dripping speed are independently 60 to 120 drops / minute.

[0067] In a specific embodiment, in step 1) of the process for preparing the emulsified gelled acid, the first iron ion stabilizer and the first corrosion inhibitor are added at 60 to 120 drops / min.

[0068] In one embodiment, in step I) of the gelled acid preparation process, the first acid thickener is added at 60 to 120 drops / minute.

[0069] In a specific embodiment, the first stirring speed, the second stirring speed, the third stirring speed, the sixth stirring speed, the seventh stirring speed, the eighth stirring speed and the ninth stirring speed are independently 300 to 1500 r / min.

[0070] In a specific embodiment, the first stirring speed, the second stirring speed, the third stirring speed, the sixth stirring speed, the seventh stirring speed, the eighth stirring speed and the ninth stirring speed are independently 500 to 1000 r / min.

[0071] In a specific embodiment, the fourth stirring speed and the fifth stirring speed are independently 1000 to 3000 r / min.

[0072] In a specific embodiment, the fourth stirring speed and the fifth stirring speed are independently 1500 to 2500 r / min.

[0073] In a specific embodiment, the stirring time at the second stirring speed is 3 to 10 minutes.

[0074] In one embodiment, the standing time after stirring uniformly at the third stirring speed is 0.5 to 2 hours. In one embodiment, the stirring time at the fifth stirring speed is 10 to 20 minutes.

[0075] In a specific embodiment, the stirring time at the fifth stirring speed is preferably 15 to 20 minutes.

[0076] In a specific embodiment, the stirring time at the eighth stirring speed is 30 to 50 minutes.

[0077] In a specific embodiment, the standing time after stirring uniformly at the ninth stirring speed is 4 to 6 hours.

[0078] (1) The acid solution system of the present invention can reduce the overall reaction rate, and at the same time, the emulsified gelled acid can achieve secondary acidification, thereby increasing the acid-pressure channel distance; in addition, it is more important that the friction of the acid solution system is significantly reduced;

[0079] (2) When the second polyacrylamide copolymer is used, the temperature resistance can reach 160°C. In addition, the second polyacrylamide copolymer used has good acid resistance and solubility, and can improve the elasticity and shear recovery performance of the acid liquid, thereby improving the slow speed and shear resistance of the acid liquid; and the gelled acid prepared using the second thickener is placed at room temperature (25±5°C) for more than 10 days without increasing viscosity and having stable performance, which solves a major problem in on-site construction. DETAILED DESCRIPTION

[0080] The present invention will be further described below in conjunction with examples, but the examples of the present invention are only exemplary descriptions, and the implementation methods do not constitute limitations of the present invention under any circumstances.

[0081] Acid Thickener Preparation:

[0082] Thickener for acid 1

[0083] Weigh a certain amount of distilled water, add AM and AMPS in a molar ratio of 3:1 to make the total mass content of the monomers 25wt%, adjust the pH to about 7.0 with sodium hydroxide, cool to room temperature (25°C), pass nitrogen for 30 minutes, add 0.04wt% ammonium persulfate and 0.02wt% sodium bisulfite to initiate polymerization, and react in a closed container at room temperature for 12 hours. Granulate the reacted rubber block, dry at 60°C, and crush to obtain a 40-mesh polymer powder sample.

[0084] Thickener for acid 2

[0085] Weigh a certain amount of distilled water, add AM and AMPS in a molar ratio of 2.5:1 to make the total mass content of the monomers 30wt%, adjust the pH to about 7.0 with sodium hydroxide, cool to room temperature (25°C), pass nitrogen for 30 minutes, add 0.04wt% ammonium persulfate and 0.02wt% sodium bisulfite to initiate polymerization, and react in a closed chamber at room temperature for 12 hours. Granulate the reacted rubber block, dry at 60°C, and crush to obtain a 40-mesh polymer powder sample.

[0086] Thickener for acid 3

[0087] Weigh a certain amount of distilled water, add AM and AMPS in a 2:1 molar ratio to make the total monomer content 25wt%, adjust the pH to about 7.0 with sodium hydroxide, cool to room temperature (25°C), pass nitrogen for 30 minutes, add 0.04wt% ammonium persulfate and 0.02wt% sodium bisulfite to initiate polymerization, and react in a closed chamber at room temperature for 12 hours. Granulate the reacted rubber block, dry at 60°C, and crush to obtain a 40-mesh polymer powder sample.

[0088] Thickener for acid 4

[0089] Weigh a certain amount of distilled water, add AM and AMPS in a molar ratio of 1.5:1 to make the total mass content of the monomers 25wt%, adjust the pH to about 7.0 with sodium hydroxide, cool to room temperature (25°C), pass nitrogen for 30 minutes, add 0.04wt% ammonium persulfate and 0.02wt% sodium bisulfite to initiate polymerization, and react in a closed chamber at room temperature for 12 hours. Granulate the reacted rubber block, dry at 60°C, and crush to obtain a 40-mesh polymer powder sample.

[0090] Thickener for acid 5

[0091] Weigh a certain amount of distilled water, add AM and AMPS in a 1:1 molar ratio to make the total monomer content 27wt%, adjust the pH to about 7.0 with sodium hydroxide, cool to room temperature (25°C), pass nitrogen for 30 minutes, add 0.04wt% ammonium persulfate and 0.02wt% sodium bisulfite to initiate polymerization, and react in a closed chamber at room temperature for 12 hours. Granulate the reacted rubber block, dry at 60°C, and crush to obtain a 40-mesh polymer powder sample.

[0092] Other drugs are commercially available.

[0093] Thickener for acid 6

[0094] 1) preparing a polymerization monomer aqueous solution, by weight, adding 35 parts of acrylamide, 64 parts of 2-acrylamide-2-methylpropanesulfonic acid monomer (AMPS), 1.4 parts of N,N-dimethylacrylamide, and 0.3 parts of hexadecyldimethylallylammonium chloride monomer into a beaker, and adding distilled water to dissolve, so that the total mass content of the four types of monomers is 25wt%;

[0095] 2) Add 1.0% urea, 0.05% sodium formate, 0.03% tetrasodium ethylenediaminetetraacetate, 3.0% sodium dodecyl sulfate, and 0.05% ethylenediamine to the above monomer aqueous solution (based on the total mass of the four monomers as 100%), stir and dissolve evenly, and cool in a 5°C water bath for 30 minutes to cool the temperature to 5°C;

[0096] 3) Add a certain amount of sodium carbonate to the above solution to adjust the pH value of the solution to 9, continue cooling for 30 minutes, put it in a 5°C water bath to cool the temperature to 5°C, introduce the liquid into an adiabatic polymerization device, and pass nitrogen for 20 minutes;

[0097] 4) Add 0.02% azobisisobutylamidine hydrochloride, 0.005% sodium bisulfite and 0.01% ammonium persulfate aqueous solution to the mother liquor in sequence, continue to flow nitrogen for 20 minutes until it becomes viscous, and then stop flowing nitrogen;

[0098] 5) Observe the temperature change of the system, and keep it warm for 5 hours when the system temperature rises to 70°C;

[0099] 6) The rubber block obtained by polymerization is taken out and granulated, dried at 70° C. to a moisture content of 10 wt %, crushed, and passed through a 30-mesh sieve to obtain a dry powder of the acid thickener 6.

[0100] Thickener for acid 7

[0101] 1) preparing a polymerization monomer aqueous solution, by weight, adding 45 parts of acrylamide, 53 parts of acryloyloxyethyl trimethyl ammonium chloride (DAC), 1.7 parts of methacryloyloxyethyl dimethyl amine, and 0.6 parts of methacryloyloxyethyl dimethyl hexadecyl ammonium bromide monomers into a beaker, and adding distilled water to dissolve, so that the total mass content of the four types of monomers is 29wt%;

[0102] 2) Add 3.0% thiourea, 0.08% potassium formate, 0.05% disodium ethylenediaminetetracarboxylate, 5.0% sodium dodecylsulfonate, and 0.1% N,N-tetramethylethylenediamine to the above monomer aqueous solution (based on the total mass of the four monomers as 100%), stir and dissolve evenly, and cool in a 10°C water bath for 30 minutes to cool the temperature to 10°C;

[0103] 3) Add a certain amount of sodium carbonate to the above solution to adjust the pH value of the solution to 9.5, continue cooling for 30 minutes, put it in a 10°C water bath to cool the temperature to 10°C, introduce the liquid into an adiabatic polymerization device, and pass nitrogen for 20 minutes;

[0104] 4) Add 0.06% azobisisobutylimidazoline hydrochloride, 0.03% sodium sulfite and 0.06% potassium persulfate aqueous solution to the mother liquor in sequence, continue to flow nitrogen for 20 minutes until it becomes viscous, and then stop flowing nitrogen;

[0105] 5) Observe the temperature change of the system, and keep it warm for 5 hours when the system temperature rises to 70°C;

[0106] 6) The rubber block obtained by polymerization is taken out and granulated, dried at 70° C. to a moisture content of 5 wt %, crushed, and passed through a 30-mesh sieve to obtain a dry powder of the acid thickener 7.

[0107] Thickener for acid 8

[0108] 1) Prepare a polymerization monomer aqueous solution, by adding 30 parts of acrylamide, 50 parts of DMC, 1.5 parts of methacryloyloxyethyl dimethylamine, and 0.2 parts of dimethyloctadecyl (2-hydroxy-3-acrylamide propyl) ammonium chloride monomers into a beaker, and add distilled water to dissolve, so that the total mass content of the four monomers is 25wt%;

[0109] 2) Add 1wt% thiourea, 0.05% potassium formate, 0.03% pentasodium triethylenetetraamine pentaacetate, 3% sodium dodecylbenzenesulfonate triethanolamine, and 0.05% N,N-tetramethylethylenediamine to the above monomer aqueous solution (based on the total mass of the four monomers as 100%), stir and dissolve evenly, put into a 10°C water bath and cool for 30 minutes to cool the temperature to 10°C;

[0110] 3) Add a certain amount of sodium carbonate to the above solution to adjust the pH value of the solution to 10, continue cooling for 30 minutes, put it in a 10°C water bath to cool the temperature to 10°C, introduce the liquid into an adiabatic polymerization device, and pass nitrogen for 20 minutes;

[0111] 4) adding 0.02 wt % of azobisisobutylimidazoline hydrochloride, 0.005 wt % of ammonium ferrous sulfate and 0.01 wt % of hydrogen peroxide aqueous solution to the mother liquor in sequence, continuing to pass nitrogen for 20 min until the mixture becomes viscous, and then stopping passing nitrogen;

[0112] 5) Observe the temperature change of the system, and keep it warm for 4 hours when the system temperature rises to 60°C;

[0113] 6) The rubber block obtained by polymerization is taken out and granulated, dried at 60° C. to a moisture content of 3 wt %, crushed, and passed through a 20-mesh sieve to obtain a dry powder of the acid thickener 8.

[0114] Example 1

[0115] 1) Preparation of emulsified gelled acid phase: 97.0 parts by mass of 15 wt% hydrochloric acid aqueous solution were added at a stirring speed of 500 r / min, 1.0 parts by mass of ethylenediaminetetraacetic acid (Tianjin Guangfu Chemical Reagent Factory) as an iron ion stabilizer and 2.0 parts by mass of 1-aminoethyl-2-pentadecylimidazoline quaternary ammonium salt corrosion inhibitor were added at a rate of 80 drops / min, 0.1 parts by mass of acid thickener 1 was added at a stirring speed of 500 r / min, and the mixture was stirred for another hour;

[0116] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by mass of dipolyhydroxystearate and 0.5 parts by mass of hexadecylamine were heated to 50° C. and dissolved in 97.5 parts by mass of diesel, stirred at a stirring speed of 500 r / min, and cooled to natural ambient temperature;

[0117] 3) Preparation of emulsified gelled acid: The volume ratio of the acid phase to the oil phase is 75:25. Under the condition of stirring speed of 1500 r / min, the acid phase is slowly added to the oil phase at a rate of 80 drops / min. After the addition, stirring is continued at a stirring speed of 1500 r / min for 20 minutes to obtain emulsified gelled acid.

[0118] 4) Preparation of gelled acid: 94.2 parts by weight of 15 wt% hydrochloric acid solution was taken, 1 part by weight of acid thickener 1 was slowly added at a rate of 80 drops / minute at a stirring speed of 500 r / min, and stirred at a stirring speed of 500 r / min for half an hour to form a uniform thickened acid solution, and then 1.8 parts by weight of iron ion stabilizer ethylenediaminetetraacetic acid (Tianjin Guangfu Chemical Reagent Factory) and 3 parts by weight of 1-aminoethyl-2-pentadecylimidazoline quaternary ammonium salt (commercially available) were added, stirred uniformly at a stirring speed of 500 r / min, and sealed and left to stand at natural ambient temperature for 4 hours;

[0119] 5) Preparation of acid solution system: The volume ratio of emulsified gelled acid to gelled acid is 50:50. Under the condition of stirring speed of 500 r / min, the emulsified gelled acid is slowly added to the gelled acid at a rate of 80 drops / min. After the addition, stirring is continued at a stirring speed of 500 r / min for 3 minutes to obtain a low-friction step-by-step reaction acid solution system.

[0120] Example 2

[0121] 1) Preparation of emulsified gelled acid phase: 96.5 parts by mass of 15 wt% hydrochloric acid aqueous solution were added at a stirring speed of 1500 r / min, 1.2 parts by mass of citric acid (commercially available), an iron ion stabilizer, and 2.3 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) were added at a rate of 60 drops / min, and 0.2 parts by mass of acid thickener 3 was added at a stirring speed of 1500 r / min, and stirred for 0.5 hours;

[0122] 2) Preparation of emulsified gelled acid oil phase: 1.5 parts by weight of sorbitan sesquioleate and 0.5 parts by weight of polyoxyethylene octylphenol ether-10 were heated to 40° C. and dissolved in 98 parts by weight of white oil, stirred at a stirring speed of 1500 r / min, and cooled to natural ambient temperature;

[0123] 3) Preparation of emulsified gelled acid: The volume ratio of the acid phase to the oil phase is 65:35. Under the condition of stirring at a speed of 2000 r / min, the acid phase is slowly added dropwise to the oil phase at a speed of 60 drops / min. After the addition, stirring is continued at a stirring speed of 2000 r / min for 15 minutes to obtain emulsified acid.

[0124] 4) Preparation of gelled acid: 97.4 parts by weight of a 20 wt% hydrochloric acid solution was taken, 0.3 parts by weight of an acid thickener 2 was slowly added at a rate of 60 drops / minute at a stirring speed of 1500 r / min, and the mixture was stirred at a stirring speed of 1500 r / min for half an hour to form a uniform thickened acid solution, and then 0.8 parts by weight of an iron ion stabilizer citric acid (commercially available) and 1.5 parts by weight of 1-aminoethyl-2-pentadecylimidazoline quaternary ammonium salt (commercially available) were added, and the mixture was stirred uniformly at a stirring speed of 1500 r / min, and the mixture was sealed and left to stand at natural ambient temperature for 6 hours;

[0125] 5) Preparation of acid solution system: The volume ratio of emulsified gelled acid to gelled acid is 40:60. Under the condition of stirring speed of 1500r / min, the emulsified gelled acid is slowly added to the gelled acid at a rate of 60 drops / min. After the addition, stirring is continued at a stirring speed of 1500r / min for 4 minutes to obtain a low-friction step-by-step reaction acid solution system.

[0126] Example 3

[0127] 1) Preparation of emulsified gelled acid phase: 96.0 parts by mass of a 20 wt% hydrochloric acid aqueous solution was added at a rate of 120 drops / min at a stirring speed of 1000 r / min to 1.5 parts by mass of an iron ion stabilizer (a mixture of acetic acid and citric acid in a mass ratio of 1:1) and 2.5 parts by mass of a formaldehyde-p-phenylenediamine-acetophenone corrosion inhibitor (commercially available), and 0.3 parts by mass of an acid thickener 2 was added at a stirring speed of 1000 r / min, and stirred for another 2 hours;

[0128] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by weight of sorbitan fatty acid ester and 2 parts by weight of polyoxyethylene octylphenol ether-10 were heated to 60° C. and dissolved in 96 parts by weight of light crude oil, stirred at a stirring speed of 1000 r / min, and cooled to natural ambient temperature;

[0129] 3) Preparation of emulsified gelled acid: The volume ratio of the acid phase to the oil phase is 60:40. Under the condition of stirring at a speed of 2500 r / min, the acid phase is slowly added to the oil phase at a speed of 120 drops / min. After the addition, stirring is continued at a stirring speed of 2500 r / min for 10 minutes to obtain emulsified gelled acid.

[0130] 4) Preparation of gelled acid solution: 95.6 parts by mass of 25 wt% hydrochloric acid solution was taken, 0.4 parts by mass of acid thickener 3 was slowly added at a rate of 120 drops / minute at a stirring speed of 1000 r / min, and stirred at a stirring speed of 1000 r / min for half an hour to form a uniform thickened acid solution, and then 1.5 parts by mass of acetic acid (commercially available), an iron ion stabilizer, and 3.5 parts by mass of formaldehyde-p-phenylenediamine-acetophenone corrosion inhibitor (commercially available) were added, stirred uniformly at a stirring speed of 1000 r / min, and sealed and left to stand at natural ambient temperature for 5 hours;

[0131] 5) Preparation of acid solution system: The volume ratio of emulsified gelled acid to gelled acid is 25:75. Under the condition of stirring speed of 1000 r / min, the emulsified gelled acid is slowly added to the gelled acid at a rate of 120 drops / min. After the addition, stirring is continued at a stirring speed of 1000 r / min for 5 minutes to obtain a low-friction step-by-step reaction acid solution system.

[0132] Example 4

[0133] 1) Preparation of emulsified gelled acid phase: 96.0 parts by mass of a 20 wt % hydrochloric acid aqueous solution was added at a stirring speed of 300 r / min, 1.0 parts by mass of an iron ion stabilizer (a mixture of acetic acid and citric acid in a mass ratio of 1:1) and 2.5 parts by mass of formaldehyde-p-phenylenediamine-acetophenone (commercially available) were added at a rate of 85 drops / min, and 0.4 parts by mass of an acid thickener 6 was added at a stirring speed of 300 r / min, and the mixture was stirred for another hour;

[0134] 2) Preparation of emulsified gelled acid oil phase: 2.5 parts by weight of sorbitan fatty acid ester and 1 part by weight of tetradecylamine were heated to 50° C. and dissolved in 96.5 parts by weight of kerosene, stirred at a stirring speed of 300 r / min, and cooled to natural ambient temperature;

[0135] 3) Preparation of emulsified gelled acid: The volume ratio of the acid phase to the oil phase is 80:20. Under the condition of stirring speed of 2500 r / min, the acid phase is slowly added to the oil phase at a rate of 80 drops / min. After the addition, stirring is continued at a stirring speed of 2500 r / min for 15 minutes to obtain emulsified gelled acid.

[0136] 4) Preparation of gelled acid: 96.2 parts by weight of a 20 wt% hydrochloric acid solution was taken, 0.8 parts by weight of an acid thickener 4 was slowly added at a rate of 70 drops / minute at a stirring speed of 300 r / min, and the mixture was stirred at a stirring speed of 300 r / min for half an hour to form a uniform thickened acid solution, and then 1 part by weight of an iron ion stabilizer acetic acid (commercially available) and 2 parts by weight of a 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) were added, and the mixture was stirred uniformly at a stirring speed of 300 r / min, and the mixture was sealed and left to stand at natural ambient temperature for 5 hours;

[0137] 5) Preparation of acid solution system: The volume ratio of emulsified gelled acid to gelled acid is 45:55. Under the condition of stirring speed of 300 r / min, the emulsified gelled acid is slowly added to the gelled acid at a rate of 100 drops / min. After the addition, stirring is continued at a stirring speed of 300 r / min for 10 minutes to obtain an acid solution system with low friction and step-by-step reaction.

[0138] Example 5

[0139] 1) Preparation of emulsified gelled acid phase: 96.0 parts by mass of 20 wt% hydrochloric acid aqueous solution were added at a rate of 90 drops / min at a stirring speed of 1000 r / min to 1.5 parts by mass of iron ion stabilizer (a mixture of acetic acid and citric acid in a mass ratio of 1:1) and 2.5 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available), and 0.5 parts by mass of acid thickener 4 was added at a stirring speed of 1000 r / min, and stirred for another hour;

[0140] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by weight of sorbitan fatty acid ester and 0.5 parts by weight of polyoxyethylene octylphenol ether-10 were heated to 60° C. and dissolved in 97.5 parts by weight of light crude oil, stirred at a stirring speed of 1000 r / min, and cooled to natural ambient temperature;

[0141] 3) Preparation of emulsified gelled acid: The volume ratio of the acid phase to the oil phase is 60:40. Under the condition of stirring at a speed of 2500 r / min, the acid phase is slowly added to the oil phase at a rate of 90 drops / min. After the addition, stirring is continued at a stirring speed of 2500 r / min for 10 minutes to obtain emulsified gelled acid.

[0142] 4) Preparation of gelled acid solution: 95.4 parts by weight of 25 wt% hydrochloric acid solution was taken, 0.6 parts by weight of acid thickener 5 was slowly added at a rate of 80 drops / minute at a stirring speed of 1000 r / min, and stirred at a stirring speed of 1000 r / min for half an hour to form a uniform thickened acid solution, and then 1.5 parts by weight of acetic acid (commercially available), an iron ion stabilizer, and 2.5 parts by weight of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) were added, stirred uniformly at a stirring speed of 1000 r / min, and sealed and left to stand at natural ambient temperature for 5 hours;

[0143] 5) Preparation of acid solution system: The volume ratio of emulsified gelled acid to gelled acid is 45:55. Under the condition of stirring speed of 1000 r / min, the emulsified gelled acid is slowly added to the gelled acid at a rate of 80 drops / min. After the addition, stirring is continued at a stirring speed of 1000 r / min for 5 minutes to obtain a low-friction step-by-step reaction acid solution system.

[0144] Example 6

[0145] 1) Preparation of emulsified gelled acid phase: 96.0 parts by mass of a 20 wt % hydrochloric acid aqueous solution was added at a rate of 90 drops / min at a stirring speed of 1000 r / min to 1.5 parts by mass of an iron ion stabilizer (a mixture of acetic acid and citric acid in a mass ratio of 1:1) and 2.5 parts by mass of a 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available), and 0.6 parts by mass of an acid thickener 5 was added at a stirring speed of 1000 r / min, and stirred for another hour;

[0146] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by weight of sorbitan fatty acid ester and 0.5 parts by weight of polyoxyethylene octylphenol ether-10 were heated to 60° C. and dissolved in 97.5 parts by weight of light crude oil, stirred at a stirring speed of 1000 r / min, and cooled to natural ambient temperature;

[0147] 3) Preparation of emulsified gelled acid: The volume ratio of the acid phase to the oil phase is 60:40. Under the condition of stirring at a speed of 2500 r / min, the acid phase is slowly added to the oil phase at a rate of 90 drops / min. After the addition, stirring is continued at a stirring speed of 2500 r / min for 10 minutes to obtain emulsified gelled acid.

[0148] 4) Preparation of gelled acid solution: 95.4 parts by mass of 25 wt% hydrochloric acid solution was taken, 0.6 parts by mass of acid thickener 6 was slowly added at a rate of 80 drops / minute at a stirring speed of 1000 r / min, and stirred at a stirring speed of 1000 r / min for half an hour to form a uniform thickened acid solution, and then 1.5 parts by mass of acetic acid (commercially available), an iron ion stabilizer, and 2.5 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) were added, stirred uniformly at a stirring speed of 1000 r / min, and sealed and left to stand at natural ambient temperature for 5 hours;

[0149] 5) Preparation of acid solution system: The volume ratio of emulsified gelled acid to gelled acid is 45:55. Under the condition of stirring speed of 1000 r / min, the emulsified gelled acid is slowly added to the gelled acid at a rate of 80 drops / min. After the addition, stirring is continued at a stirring speed of 1000 r / min for 5 minutes to obtain a low-friction step-by-step reaction acid solution system.

[0150] Example 7

[0151] 1) Preparation of emulsified gelled acid phase: 96.0 parts by mass of a 20 wt % hydrochloric acid aqueous solution was added at a rate of 90 drops / min at a stirring speed of 1000 r / min to 1.5 parts by mass of an iron ion stabilizer (a mixture of acetic acid and citric acid in a mass ratio of 1:1) and 2.5 parts by mass of a 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available), and 0.3 parts by mass of an acid thickener 7 was added at a stirring speed of 1000 r / min, and the mixture was stirred for another hour;

[0152] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by weight of sorbitan fatty acid ester and 0.5 parts by weight of polyoxyethylene octylphenol ether-10 were heated to 60° C. and dissolved in 97.5 parts by weight of light crude oil, stirred at a stirring speed of 1000 r / min, and cooled to natural ambient temperature;

[0153] 3) Preparation of emulsified gelled acid: The volume ratio of the acid phase to the oil phase is 60:40. Under the condition of stirring at a speed of 2500 r / min, the acid phase is slowly added to the oil phase at a rate of 90 drops / min. After the addition, stirring is continued at a stirring speed of 2500 r / min for 10 minutes to obtain emulsified gelled acid.

[0154] 4) Preparation of gelled acid solution: 95.4 parts by weight of 25 wt% hydrochloric acid solution was taken, 0.6 parts by weight of acid thickener 7 was slowly added at a rate of 80 drops / minute at a stirring speed of 1000 r / min, and stirred at a stirring speed of 1000 r / min for half an hour to form a uniform thickened acid solution, and then 1.5 parts by weight of acetic acid (commercially available), an iron ion stabilizer, and 2.5 parts by weight of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) were added, stirred uniformly at a stirring speed of 1000 r / min, and sealed and left to stand at natural ambient temperature for 5 hours;

[0155] 5) Preparation of acid solution system: The volume ratio of emulsified gelled acid to gelled acid is 45:55. Under the condition of stirring speed of 1000 r / min, the emulsified gelled acid is slowly added to the gelled acid at a rate of 80 drops / min. After the addition, stirring is continued at a stirring speed of 1000 r / min for 5 minutes to obtain a low-friction step-by-step reaction acid solution system.

[0156] Example 8

[0157] 1) Preparation of emulsified gelled acid phase: 96.0 parts by mass of a 20 wt % hydrochloric acid aqueous solution was added at a rate of 90 drops / min at a stirring speed of 1000 r / min to 1.5 parts by mass of an iron ion stabilizer (a mixture of acetic acid and citric acid in a mass ratio of 1:1) and 2.5 parts by mass of a 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available), and 0.3 parts by mass of an acid thickener 8 was added at a stirring speed of 1000 r / min, and the mixture was stirred for another hour;

[0158] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by weight of sorbitan fatty acid ester and 0.5 parts by weight of polyoxyethylene octylphenol ether-10 were heated to 60° C. and dissolved in 97.5 parts by weight of light crude oil, stirred at a stirring speed of 1000 r / min, and cooled to natural ambient temperature;

[0159] 3) Preparation of emulsified gelled acid: The volume ratio of the acid phase to the oil phase is 60:40. Under the condition of stirring at a speed of 2500 r / min, the acid phase is slowly added to the oil phase at a rate of 90 drops / min. After the addition, stirring is continued at a stirring speed of 2500 r / min for 10 minutes to obtain emulsified gelled acid.

[0160] 4) Preparation of gelled acid solution: 95.4 parts by weight of 25 wt% hydrochloric acid solution was taken, 0.6 parts by weight of acid thickener 8 was slowly added at a rate of 80 drops / minute at a stirring speed of 1000 r / min, and stirred at a stirring speed of 1000 r / min for half an hour to form a uniform thickened acid solution, and then 1.5 parts by weight of acetic acid (commercially available), an iron ion stabilizer, and 2.5 parts by weight of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) were added, stirred uniformly at a stirring speed of 1000 r / min, and sealed and left to stand at natural ambient temperature for 5 hours;

[0161] 5) Preparation of acid solution system: The volume ratio of emulsified gelled acid to gelled acid is 45:55. Under the condition of stirring speed of 1000 r / min, the emulsified gelled acid is slowly added to the gelled acid at a rate of 80 drops / min. After the addition, stirring is continued at a stirring speed of 1000 r / min for 5 minutes to obtain a low-friction step-by-step reaction acid solution system.

[0162] Comparative Example 1

[0163] The preparation process of emulsified gelled acid in Example 4:

[0164] 1) Preparation of emulsified gelled acid phase: 96.0 parts by mass of 20 wt% hydrochloric acid aqueous solution were added at a stirring speed of 300 r / min, 1.0 parts by mass of iron ion stabilizer (a mixture of acetic acid and citric acid in a mass ratio of 1:1) and 2.5 parts by mass of formaldehyde-p-phenylenediamine-acetophenone (commercially available) were added at a rate of 85 drops / min, and 0.4 parts by mass of acid thickener 6 was added at a stirring speed of 300 r / min, and stirred for another hour;

[0165] 2) Preparation of emulsified acid oil phase: 2.5 parts by weight of sorbitan fatty acid ester and 1.0 parts by weight of tetradecylamine were heated to 50° C. and dissolved in 96.5 parts by weight of light crude oil, stirred at a stirring speed of 300 r / min, and cooled to natural ambient temperature;

[0166] 3) Preparation of emulsified gelled acid: The volume ratio of the acid phase to the oil phase is 80:20. Under the condition of stirring speed of 2500 r / min, the acid phase is slowly added to the oil phase at a rate of 80 drops / min. After the addition, stirring is continued at a stirring speed of 2500 r / min for 15 minutes to obtain emulsified gelled acid.

[0167] Comparative Example 2

[0168] Preparation process of gelled acid in Example 4:

[0169] Take 96.2 parts by mass of 20wt% hydrochloric acid solution, slowly add 0.8 parts by mass of acid thickener 4 at a rate of 70 drops / minute at a stirring speed of 300 r / min, stir at a stirring speed of 300 r / min for half an hour to form a uniform thickened acid solution, then add 1 part by mass of iron ion stabilizer acetic acid (commercially available), 2.5 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) at a stirring speed of 300 r / min, stir evenly, and seal and place at natural ambient temperature for 5 hours.

[0170] Comparative Example 3

[0171] The difference from Example 4 is that no acid thickener is added in step 1). The details are as follows:

[0172] 1) Preparation of emulsified acid phase: 96.0 parts by mass of a 20 wt% hydrochloric acid aqueous solution was added at a rate of 85 drops / min at a stirring speed of 300 r / min to 1.0 parts by mass of an iron ion stabilizer (a mixture of acetic acid and citric acid in a mass ratio of 1:1) and 2.5 parts by mass of formaldehyde-p-phenylenediamine-acetophenone (commercially available), and then stirred at a stirring speed of 300 r / min for 1 hour;

[0173] 2) Preparation of emulsified acid oil phase: 2.5 parts by weight of sorbitan fatty acid ester and 1 part by weight of tetradecylamine were heated to 50° C. and dissolved in 96.5 parts by weight of kerosene, stirred at a stirring speed of 300 r / min, and cooled to natural ambient temperature;

[0174] 3) Preparation of emulsified acid: The volume ratio of the acid phase to the oil phase is 80:20. Under the condition of stirring at a speed of 2500 r / min, the acid phase is slowly added dropwise to the oil phase at a speed of 80 drops / min. After the addition, stirring is continued at a stirring speed of 2500 r / min for 15 minutes to obtain emulsified acid.

[0175] 4) Preparation of gelled acid: 96.2 parts by weight of a 20 wt% hydrochloric acid solution was taken, 0.8 parts by weight of an acid thickener 4 was slowly added at a rate of 70 drops / minute at a stirring speed of 300 r / min, and the mixture was stirred at a stirring speed of 300 r / min for half an hour to form a uniform thickened acid solution, and then 1 part by weight of an iron ion stabilizer acetic acid (commercially available) and 2 parts by weight of a 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) were added, and the mixture was stirred uniformly at a stirring speed of 300 r / min, and the mixture was sealed and left to stand at natural ambient temperature for 5 hours;

[0176] 5) Preparation of acid solution system: The volume ratio of emulsified acid to gelled acid is 45:55. Under the condition of stirring speed of 300 r / min, the emulsified acid is slowly added to the gelled acid at a rate of 100 drops / min. After the addition, stirring is continued at 300 r / min for 10 minutes to obtain an acid solution system with low friction and step-by-step reaction.

[0177] Performance Testing

[0178] (1) The apparent viscosity (measured by a six-speed viscometer) at room temperature 25°C and 120°C of the acid solution systems prepared in Examples 1 to 8, the emulsified gelled acid prepared in Comparative Example 1, and the acid solution system prepared in Comparative Example 3, as well as the demulsification rate observed by the naked eye at 120°C were measured. The results are shown in Table 1.

[0179] According to the results in Table 1, the acid solution system prepared in Example 4 has a lower viscosity at room temperature than that in Comparative Example 1, thus showing lower friction resistance on site and easier pumping; compared with Comparative Example 3, Example 4 has a higher viscosity at a high temperature of 120°C, thus showing a better retarding effect. In addition, other embodiments of the present invention also show the characteristics of lower viscosity at room temperature and higher viscosity at a high temperature of 120°C, that is, showing very good low friction resistance and retarding effects.

[0180] Table 1

[0181]

[0182] (2) The acid-rock reaction rates of the multiple emulsion gelled acids prepared in Examples 1 to 8 and the gelled acid prepared in Comparative Example 2 were tested at 120°C (SY / T 6526-2019 Determination of dynamic reaction rate of hydrochloric acid and carbonate rock). The acid-rock reaction rates measured at 5 min and 10 min were compared, respectively, and compared with the gelled acid. The results are shown in Table 2.

[0183] According to the results in Table 2, the acid solution system prepared in Example 4 exhibits lower reaction rates at 5 min and 10 min compared with Comparative Examples 2 and 3, especially at 10 min, the acid-rock reaction rate of the acid solution system in Example 4 decreases by about 10 times; compared with Comparative Example 3, Example 4 has a higher viscosity at high temperature, thus exhibiting a better retarding effect. In addition, other embodiments of the present invention also exhibit similar reaction characteristics to Example 4, indicating that the acid solution system of the present invention has better retarding and step-by-step reaction acidification characteristics at high temperatures.

[0184] Table 2

[0185]

[0186] From the comparison of the above two properties, it can be seen that the low-friction step-by-step reaction emulsified gelled acid of the present invention has the advantages of low apparent viscosity, low friction, good temperature stability, good retarding effect, etc., which meets the application of high-temperature reservoir acid fracturing, and the preparation method is simple, which is worthy of popularization and application.

[0187] Although the present application has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that various changes may be made without departing from the true spirit and scope of the present application. In addition, various changes may be made to the subject, spirit and scope of the present application to adapt to specific situations, materials, material combinations and methods. All of these changes are included within the scope of the claims of the present application.

Claims

1. A method for preparing an acid solution system, comprising the following steps: based on 100 parts by volume of the acid solution system, adding 20 to 50 parts by volume of an emulsified gelled acid to 50 to 80 parts by volume of a gelled acid to obtain the acid solution system; Preferably, based on 100 parts by volume of the acid solution system, 25 to 45 parts by volume of the emulsified gelled acid are added to 55 to 75 parts by volume of the gelled acid to obtain the acid solution system.

2. The preparation method according to claim 1, characterized in that: The emulsified gelled acid is added dropwise at a first dropping acceleration to the gelled acid stirred at a first stirring speed, and after the dropping is completed, the acid is stirred at a second stirring speed to obtain the acid solution system.

3. The preparation method according to claim 1 or 2, characterized in that: The emulsified gelled acid was prepared as follows: 1) adding a first corrosion inhibitor, a first acid thickener and a first iron ion stabilizer to the first acid solution, stirring the mixture at a third stirring speed and then standing the mixture to obtain an acid phase; 2) dissolving a water-in-oil emulsifier in oil to obtain an oil phase; 3) adding the acid phase dropwise at a second dropping acceleration to the oil phase stirred at a fourth stirring speed, and after the dropping is completed, stirring is performed at a fifth stirring speed to obtain the emulsified gelled acid.

4. The preparation method according to claim 3, characterized in that: In step 2) of preparing the emulsified gelled acid, the water-in-oil emulsifier is dissolved in the oil by heating to a temperature of 40 to 60° C. and stirring at a sixth stirring speed.

5. The preparation method according to claim 3 or 4, characterized in that: Based on 100 parts by volume of the emulsified gelling acid, the acid phase comprises 60 to 80 parts by volume, and the oil phase comprises 20 to 40 parts by volume; preferably, based on 100 parts by volume of the emulsified gelling acid, the acid phase comprises 65 to 70 parts by volume, and the oil phase comprises 30 to 35 parts by volume; Preferably, based on 100 parts by mass of the acid phase, the first acid solution is 95.2 to 97.7 parts by mass, the first corrosion inhibitor is 1.5 to 3 parts by mass, the first acid thickener is 0.1 to 0.6 parts by mass, and the first iron ion stabilizer is 0.8 to 1.8 parts by mass; wherein the mass concentration of the acid in the first acid solution is 15% to 30%; preferably, based on 100 parts by mass of the acid phase, the first acid solution is 96 to 97 parts by mass, the first iron ion stabilizer is 1 to 1.5 parts by mass, and the first corrosion inhibitor is 2 to 2.5 parts by mass; wherein the mass concentration of the acid in the first acid solution is 15% to 20%; Preferably, based on 100 parts by mass of the oil phase, the oil is 96 to 98 parts by mass, and the water-in-oil emulsifier is 2 to 4 parts by mass; preferably, based on 100 parts by mass of the oil phase, the oil is 96.5 to 97.5 parts by mass, and the water-in-oil emulsifier is 2.5 to 3.5 parts by mass.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The gelled acid was prepared as follows: 1) adding a second acid thickener to the second acid solution stirred at a seventh stirring speed, and after adding the second acid thickener, stirring at an eighth stirring speed to obtain a thickened acid solution; II) adding a second iron ion stabilizer and a second corrosion inhibitor to the thickened acid solution, stirring at a ninth stirring speed until uniform, and then standing to obtain the gelled acid.

7. The preparation method according to claim 6, characterized in that: Based on 100 parts by mass of the gelled acid, the second acid solution comprises 94.2 to 97.4 parts by mass, the second acid thickener comprises 0.3 to 1 parts by mass, the second iron ion stabilizer comprises 0.8 to 1.8 parts by mass, and the second corrosion inhibitor comprises 1.5 to 3 parts by mass; wherein the mass concentration of the acid in the second acid solution is 15% to 30%; Preferably, based on 100 parts by mass of the gelled acid, the second acid solution comprises 95.4 to 96.2 parts by mass, the second acid thickener comprises 0.4 to 0.8 parts by mass, the second iron ion stabilizer comprises 1 to 1.5 parts by mass, and the second corrosion inhibitor comprises 2 to 2.5 parts by mass; wherein the mass concentration of the acid in the second acid solution is 15% to 20%.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The first acid solution and the second acid solution are independently selected from aqueous hydrochloric acid solution and / or aqueous hydrofluoric acid solution; Preferably, the first iron ion stabilizer and the second iron ion stabilizer are independently organic acids; preferably, the first iron ion stabilizer and the second iron ion stabilizer are independently selected from at least one of citric acid, acetic acid, ethylenediaminetetraacetic acid, ascorbic acid and lactic acid; Preferably, the first corrosion inhibitor and / or the second corrosion inhibitor are independently selected from at least one of imidazoline corrosion inhibitors, quinoline quaternary ammonium salts, ketone aldehyde amine condensates and Mannich bases; preferably, the first corrosion inhibitor and / or the second corrosion inhibitor are independently selected from at least one of 1-aminoethyl-2-pentadecylimidazoline quaternary ammonium salts, formaldehyde-p-phenylenediamine-acetophenone and 2-methylquinoline benzyl quaternary ammonium salts; Preferably, the water-in-oil emulsifier is selected from at least one of dipolyhydroxystearate, sorbitan sesquioleate, sorbitan fatty acid ester, polyoxyethylene octylphenol ether-10, dipolyhydroxystearate and hexadecylamine; Preferably, the oil is selected from at least one of diesel, kerosene, white oil and light crude oil; Preferably, the first acid thickener and the second acid thickener are independently a first polyacrylamide copolymer and / or a second polyacrylamide copolymer. Preferably, the relative molecular weight of the first polyacrylamide copolymer is 8 million to 10 million; preferably, the first polyacrylamide copolymer is a copolymer prepared by acrylamide and 2-acrylamide-2-methylpropanesulfonic acid monomers in a molar ratio of 1:1 to 3:1; Preferably, the second polyacrylamide copolymer is prepared as follows: A) dissolving acrylamide, an acid-resistant monomer, a water-soluble monomer containing a dimethylamine group and a quaternary ammonium salt type polymerizable surfactant in water to obtain a first solution; B) adding a cosolvent, a chain transfer agent, a complexing agent, an activator, and a water-soluble anionic surfactant to the first solution, and mixing them uniformly to obtain a second solution; C) adjusting the pH value of the second solution to 9 to 10 to obtain a third solution; then adding the third solution to a polymerization device and introducing nitrogen; D) adding a water-soluble azo initiator, a reducing agent, and an oxidizing agent into the polymerization device to obtain a fourth solution, and then continuing to introduce nitrogen; E) after the temperature of the fourth solution rises, maintaining the temperature, thereby obtaining a polymerized jelly; F) granulating, drying, crushing and sieving the polymer colloid to obtain the thickener in dry powder form; Preferably; in the process of preparing the second polyacrylamide copolymer, the acid-resistant monomer is selected from at least one of 2-acrylamide-2-methylpropanesulfonic acid, acryloyloxyethyl trimethylammonium chloride and methacryloyloxyethyl trimethylammonium chloride; and / or the water-soluble monomer containing a dimethylamine group is selected from methacryloyloxyethyl dimethylamine and / or N,N-dimethylacrylamide; and / or the quaternary ammonium salt type polymerizable surfactant is selected from at least one of tetradecyl dimethyl allyl ammonium chloride, hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, methacryloyloxyethyl dimethyl hexadecyl ammonium bromide and dimethyl octadecyl (2-hydroxy-3-acrylamide propyl) ammonium chloride; More preferably, in the process of preparing the second polyacrylamide copolymer, the acrylamide has 30 to 50 parts by mass, the acid-resistant monomer has 50 to 70 parts by mass, the water-soluble monomer containing a dimethylamine group has 1.4 to 1.7 parts by mass, and the quaternary ammonium salt polymerizable surfactant has 0.2 to 1 parts by mass; More preferably, during the preparation of the second polyacrylamide copolymer, the total mass of the acrylamide, the acid-resistant monomer, the water-soluble monomer containing a dimethylamine group and the quaternary ammonium salt type polymerizable surfactant accounts for 25 wt % to 29 wt % of the total mass of the first solution; More preferably, in the process of preparing the second polyacrylamide copolymer, based on the total mass of the acrylamide, the acid-resistant monomer, the water-soluble monomer containing a dimethylamine group and the quaternary ammonium salt type polymerizable surfactant as 100%, the amount of the cosolvent is 1wt% to 3wt%, the amount of the chain transfer agent is 0.05wt% to 0.1wt%, the amount of the complexing agent is 0.03wt% to 0.08wt%, the amount of the activator is 0.05wt% to 0.1wt%, the amount of the oxidant is 0.01wt% to 0.06wt%, the amount of the reducing agent is 0.005wt% to 0.03wt%, the amount of the water-soluble azo initiator is 0.02wt% to 0.06wt%, and the amount of the water-soluble anionic surfactant is 3wt% to 5wt%.

9. The preparation method according to any one of claims 2 to 8, characterized in that: The first droplet acceleration and the second droplet acceleration are independently 60 to 120 drops / minute; Preferably, the first stirring speed, the second stirring speed, the third stirring speed, the sixth stirring speed, the seventh stirring speed, the eighth stirring speed and the ninth stirring speed are independently 300 to 1500 r / min; Preferably, the first stirring speed, the second stirring speed, the third stirring speed, the sixth stirring speed, the seventh stirring speed, the eighth stirring speed and the ninth stirring speed are independently 500 to 1000 r / min; Preferably, the fourth stirring speed and the fifth stirring speed are independently 1000 to 3000 r / min; Preferably, the fourth stirring speed and the fifth stirring speed are independently 1500 to 2500 r / min.

10. The preparation method according to any one of claims 2 to 9, characterized in that: The stirring time of the second stirring speed is 3 to 10 minutes; Preferably, the standing time after stirring uniformly at the third stirring speed is 0.5 to 2 hours; Preferably, the stirring time at the fifth stirring speed is 10 to 20 minutes; Preferably, the stirring time at the fifth stirring speed is 15 to 20 minutes; Preferably, the stirring time at the eighth stirring speed is 30 to 50 minutes; Preferably, the standing time after uniform stirring at the ninth stirring speed is 4 to 6 hours.

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