A method for preparing an acid liquid system

Abstract

The present application provides a preparation method of an acid liquid system, comprising the following steps: adding 20-50 parts by mass of emulsified gelling acid into 50-80 parts by mass of gelling acid to obtain the acid liquid system; preferably adding 25-45 parts by mass of emulsified gelling acid into 55-75 parts by mass of gelling acid to obtain the acid liquid system.

Description

Technical Field

[0001] This invention provides a method for preparing an acidic liquid system. Background Technology

[0002] Existing acid solutions either suffer from short acid-etched fractures, limiting the range of reservoir penetration and resulting in poor acid fracturing effects; or they exhibit poor temperature resistance and high friction, failing to meet the goal of deep penetration under acid fracturing in high-temperature deep wells. With the continuous deepening of exploration and development of high-temperature carbonate reservoirs, higher requirements are being placed on the performance of high-temperature acid systems in terms of slow speed and low friction. Summary of the Invention

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

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

[0005] In one specific embodiment, the emulsified gelling acid is added dropwise to the gelling acid being stirred at a first stirring speed at a first dropping rate. After the addition is complete, the mixture is stirred at a second stirring speed to obtain the acid system.

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

[0007] 1) Add the first corrosion inhibitor, the first acid thickener and the first iron ion stabilizer to the first acid solution, stir evenly at the third stirring speed and let stand to obtain the acid phase;

[0008] 2) Dissolve the water-in-oil emulsifier in the oil to obtain the oil phase;

[0009] 3) The acid phase is added dropwise to the oil phase being stirred at a fourth stirring speed at a second dropping rate. After the addition is complete, the mixture is stirred at a fifth stirring speed to obtain the emulsified gel acid.

[0010] In one specific embodiment, in step 2) of preparing the emulsified gelling 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 one specific embodiment, based on 100 parts by volume of 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 one specific embodiment, based on 100 parts by volume of emulsified gelling acid, the acid phase comprises 65 to 70 parts by mass, and the oil phase comprises 30 to 35 parts by volume.

[0013] In one specific embodiment, based on 100 parts by mass of the acid phase, the first acid solution comprises 95.2 to 97.7 parts by mass, the first corrosion inhibitor comprises 1.5 to 3 parts by mass, the first acid thickener comprises 0.1 to 0.6 parts by mass, and the first iron ion stabilizer comprises 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 one 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 one specific embodiment, based on 100 parts by weight of the oil phase, the oil comprises 96 to 98 parts by weight, and the water-in-oil emulsifier comprises 2 to 4 parts by weight.

[0016] In one specific embodiment, based on 100 parts by weight of the oil phase, the oil comprises 96.5 to 97.5 parts by weight, and the water-in-oil emulsifier comprises 2.5 to 3.5 parts by weight.

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

[0018] I) Add a thickener for the second acid to the second acid solution being stirred at the seventh stirring speed. After adding the thickener for the second acid, stir at the eighth stirring speed to obtain a thickened acid solution.

[0019] II) Add a second iron ion stabilizer and a second corrosion inhibitor to the thickened acid solution, stir evenly at the ninth stirring speed, and let stand to obtain the gelled acid.

[0020] In one specific embodiment, based on 100 parts by mass of the gelling acid, the second acid solution comprises 94.2 to 97.4 parts by mass, the second acid thickener comprises 0.3 to 1 part 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 one specific embodiment, based on 100 parts by mass of the gelling 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 one 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 one specific embodiment, the first iron ion stabilizer and the second iron ion stabilizer are independently organic acids.

[0024] Preferably, in one 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 one 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, ketaldehyde amine condensates, and Mannich bases.

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

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

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

[0029] In one 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 one specific embodiment, the first polyacrylamide copolymer has a relative molecular weight of 8 million to 10 million.

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

[0032] In one specific embodiment, the first polyacrylamide copolymer is a copolymer prepared by reacting acrylamide with 2-acrylamide-2-methylpropanesulfonic acid monomer 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) Dissolve acrylamide, acid-resistant monomer, water-soluble monomer containing dimethylamine group and quaternary ammonium salt polymerizable surfactant in water to obtain the first solution;

[0035] B) Add a cosolvent, chain transfer agent, complexing agent, activator, and water-soluble anionic surfactant to the first solution, mix well, and obtain a second solution;

[0036] C) Adjust the pH of the second solution to 9 or 10 to obtain a third solution; then add the third solution to the polymerization apparatus and introduce nitrogen gas.

[0037] D) Add water-soluble azo initiator, reducing agent, and oxidizing agent to the polymerization apparatus to obtain a fourth solution, and then continue to purge with nitrogen gas;

[0038] E) After the temperature of the fourth solution rises, it is kept at that temperature to obtain a polymeric gel.

[0039] F) The polymeric gel is granulated, dried, pulverized, and sieved to obtain the second polyacrylamide copolymer in dry powder form.

[0040] In one 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 one 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 one specific embodiment, during the preparation of the second polyacrylamide copolymer, the quaternary ammonium salt 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-acrylamidopropyl) ammonium chloride.

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

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

[0045] In one 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 dimethylamine, and the quaternary ammonium salt polymerizable surfactant accounts for 25 wt% to 29 wt% of the total mass of the first solution.

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

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

[0048] In one 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 one 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 one specific embodiment, during the preparation of the second polyacrylamide copolymer, the complexing agent is selected from at least one of ethylenediaminetetraacetic acid disodium salt, ethylenediaminetetraacetic acid tetrasodium salt, and triethylenetetraaminepentaacetic acid salt. For example, the salt can 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 one 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 one 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 one 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 ferrous ammonium sulfate.

[0054] In one specific embodiment, during the preparation of the second polyacrylamide copolymer, the water-soluble azo initiator is selected from azobisisobutyramidine hydrochloride and / or azobisisobutyrazoline hydrochloride. For example, the salt can be a sodium salt or a potassium salt. For example, the water-soluble azo initiator is selected from sodium azobisisobutyramidine hydrochloride and / or sodium azobisisobutyrazoline hydrochloride.

[0055] In one 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 monomers are exothermic while others are not; to facilitate subsequent low-temperature polymerization, it is best to cool the second solution. In one specific embodiment, in step B), the second solution obtained by uniform mixing is cooled to 5°C to 10°C. For example, it is cooled in a water bath at 5°C to 10°C for 30 minutes.

[0057] In the preparation of the second polyacrylamide copolymer, exothermic reactions generally occur during pH adjustment. Therefore, to facilitate subsequent low-temperature polymerization, it is preferable to cool the third solution. In one specific embodiment, in step C), the third solution obtained after pH adjustment is cooled to 5°C to 10°C. For example, it is cooled in a water bath at 5°C to 10°C for 30 minutes.

[0058] In one specific embodiment, during the preparation of the second polyacrylamide copolymer, in steps C) and D, the nitrogen gas is introduced for 20 to 30 minutes independently.

[0059] In the preparation of the second polyacrylamide copolymer, in step D), before the azo initiator, reducing agent, and oxidizing agent are added to the polymerization apparatus, it is best to prepare them as aqueous solutions separately so that they can be added to the polymerization apparatus and the aqueous solution of the reactant monomer (i.e., the third solution). There are no particular requirements regarding the concentration of the solutions; they can be adjusted according to actual needs and the scale of use.

[0060] In the preparation of the second polyacrylamide copolymer, step E) is mainly a polymerization process. During polymerization, a certain amount of heat is released. When the heat release reaches a certain level, namely 60°C to 80°C, a heat preservation temperature is applied. Therefore, in one specific embodiment, in the preparation of the second polyacrylamide copolymer, the heat preservation temperature in step E) is 60°C to 80°C.

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

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

[0063] In one 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 specific 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 one specific embodiment, during the preparation of the second polyacrylamide copolymer, in step F), the sieve mesh size is 20 to 40 mesh.

[0066] In one specific embodiment, the first drop acceleration and the second drop acceleration are independently 60 to 120 drops / minute.

[0067] In one specific embodiment, in step 1) of the preparation process of the emulsified gelling acid, a first iron ion stabilizer and a first corrosion inhibitor are added at a rate of 60 to 120 drops / minute.

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

[0069] In one 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 one 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 one specific embodiment, the fourth stirring speed and the fifth stirring speed are independently between 1000 and 3000 r / min.

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

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

[0074] In one specific embodiment, the settling time after uniform mixing at the third mixing speed is 0.5 to 2 hours. In another specific embodiment, the mixing time at the fifth mixing speed is 10 to 20 minutes.

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

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

[0077] In one specific embodiment, the settling time after uniform mixing at the ninth stirring speed is 4 to 6 hours.

[0078] The beneficial effects of this invention are:

[0079] (1) The acid system of the present invention can reduce the overall reaction rate and enable the emulsified gel acid to achieve secondary acidification, thereby increasing the acid pressure communication distance; in addition, an important point is that the friction of the acid system is significantly reduced.

[0080] (2) When using the second polyacrylamide copolymer, the temperature resistance can reach 160℃. In addition, the second polyacrylamide copolymer used has good acid resistance and solubility, and can improve the elasticity and shear recovery performance of acid, thereby improving the slowing and shear resistance of acid; and the gel acid prepared using the second thickener does not increase in viscosity and has stable performance after being placed at room temperature (25±5℃) for more than 10 days, which solves a major problem in on-site construction. Detailed Implementation

[0081] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0082] Acid prepared using a thickener:

[0083] Acid thickener 1

[0084] A certain amount of distilled water was weighed and added to AM and AMPS in a 3:1 molar ratio to make the total monomer content 25wt%. The pH was adjusted to about 7.0 with sodium hydroxide, cooled to room temperature (25℃), and nitrogen gas was purged for 30 min. Then, 0.04wt% ammonium persulfate and 0.02wt% sodium bisulfite were added to initiate the polymerization reaction, and the reaction was carried out in a sealed environment at room temperature for 12 h. The resulting gel was granulated, dried at 60℃, and pulverized to obtain a 40-mesh polymer powder sample.

[0085] Acid thickener 2

[0086] A certain amount of distilled water was weighed and added to AM and AMPS at a molar ratio of 2.5:1 to make the total monomer content 30wt%. The pH was adjusted to about 7.0 with sodium hydroxide, cooled to room temperature (25℃), and nitrogen gas was purged for 30 min. Then, 0.04wt% ammonium persulfate and 0.02wt% sodium bisulfite were added to initiate the polymerization reaction, and the reaction was carried out in a sealed environment at room temperature for 12 h. The resulting gel was granulated, dried at 60℃, and pulverized to obtain a 40-mesh polymer powder sample.

[0087] Acid thickener 3

[0088] A certain amount of distilled water was weighed and added to AM and AMPS in a 2:1 molar ratio to make the total monomer content 25wt%. The pH was adjusted to about 7.0 with sodium hydroxide, cooled to room temperature (25℃), and nitrogen gas was purged for 30 min. Then, 0.04wt% ammonium persulfate and 0.02wt% sodium bisulfite were added to initiate the polymerization reaction, and the reaction was carried out in a sealed environment at room temperature for 12 h. The resulting gel was granulated, dried at 60℃, and pulverized to obtain a 40-mesh polymer powder sample.

[0089] Acid thickener 4

[0090] A certain amount of distilled water was weighed and added to AM and AMPS in a 1.5:1 molar ratio to make the total monomer content 25wt%. The pH was adjusted to about 7.0 with sodium hydroxide, cooled to room temperature (25℃), and nitrogen gas was purged for 30 min. Then, 0.04wt% ammonium persulfate and 0.02wt% sodium bisulfite were added to initiate the polymerization reaction, and the reaction was carried out in a sealed environment at room temperature for 12 h. The resulting gel was granulated, dried at 60℃, and pulverized to obtain a 40-mesh polymer powder sample.

[0091] Acid thickener 5

[0092] A certain amount of distilled water was weighed and added to AM and AMPS in a 1:1 molar ratio to make the total monomer content 27wt%. The pH was adjusted to about 7.0 with sodium hydroxide, cooled to room temperature (25℃), and nitrogen gas was purged for 30 min. Then, 0.04wt% ammonium persulfate and 0.02wt% sodium bisulfite were added to initiate the polymerization reaction, and the reaction was carried out in a sealed environment at room temperature for 12 h. The resulting gel was granulated, dried at 60℃, and pulverized to obtain a 40-mesh polymer powder sample.

[0093] All other medicines are commercially available.

[0094] Acid thickener 6

[0095] 1) Prepare an aqueous solution of the monomers: By weight, add 35 parts acrylamide, 64 parts 2-acrylamido-2-methylpropanesulfonic acid monomer (AMPS), 1.4 parts N,N-dimethylacrylamide, and 0.3 parts hexadecyl dimethyl allyl ammonium chloride monomer to a beaker, add distilled water to dissolve, so that the total mass content of the four monomers is 25 wt%.

[0096] 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 to dissolve evenly, and place in a 5°C water bath to cool for 30 minutes to cool the temperature to 5°C.

[0097] 3) Add a certain amount of sodium carbonate to the above solution to adjust the pH value to 9, continue to cool for 30 minutes, put it in a 5°C water bath to cool the temperature to 5°C, introduce the liquid into the adiabatic polymerization device, and purge with nitrogen for 20 minutes.

[0098] 4) Add 0.02% azobisisobutyramidine hydrochloride, 0.005% sodium bisulfite and 0.01% ammonium persulfate aqueous solution to the above mother liquor in sequence, continue to purge with nitrogen for 20 min until it becomes viscous, and then stop purging with nitrogen;

[0099] 5) Observe the temperature change of the system. When the system temperature rises to 70℃, keep it at that temperature for 5 hours.

[0100] 6) Take out the polymerized granules, dry them at 70°C to a moisture content of 10wt%, crush them, and pass them through a 30-mesh sieve to obtain dry powder of acid thickener 6.

[0101] Acid thickener 7

[0102] 1) Prepare an aqueous solution of the monomers: Add 45 parts by weight of acrylamide, 53 parts by weight of acryloyloxyethyltrimethylammonium chloride (DAC), 1.7 parts by weight of methacryloyloxyethyldimethylamine, and 0.6 parts by weight of methacryloyloxyethyldimethylhexadecylammonium bromide monomers to a beaker, add distilled water to dissolve, so that the total mass content of the four monomers is 29 wt%.

[0103] 2) Add 3.0% thiourea, 0.08% potassium formate, 0.05% disodium ethylenediaminetetraformate, 5.0% sodium dodecyl sulfonate, and 0.1% N,N-tetramethylethylenediamine to the above monomer aqueous solution (based on the total mass of the four monomers as 100%), stir to dissolve evenly, and place in a 10°C water bath to cool for 30 minutes to allow the temperature to cool to 10°C;

[0104] 3) Add a certain amount of sodium carbonate to the above solution to adjust the pH value to 9.5, continue to cool for 30 minutes, put it in a 10℃ water bath to cool the temperature to 10℃, introduce the liquid into the adiabatic polymerization device, and purge with nitrogen for 20 minutes.

[0105] 4) Add 0.06% azobisisobutyrazoline hydrochloride, 0.03% sodium sulfite and 0.06% potassium persulfate aqueous solution to the above mother liquor in sequence, continue to purge with nitrogen for 20 min until it becomes viscous, and then stop purging with nitrogen;

[0106] 5) Observe the temperature change of the system. When the system temperature rises to 70℃, keep it at that temperature for 5 hours.

[0107] 6) Take out the polymerized granules, dry them at 70°C to a moisture content of 5wt%, crush them, and pass them through a 30-mesh sieve to obtain dry powder of acid thickener 7.

[0108] Acid thickener 8

[0109] 1) Prepare an aqueous solution of the monomers: Add 30 parts by weight of acrylamide, 50 parts by weight of DMC, 1.5 parts by weight of methacryloyloxyethyl dimethylamine, and 0.2 parts by weight of dimethyloctadecyl (2-hydroxy-3-acrylamidopropyl) ammonium chloride monomer to a beaker, and dissolve in distilled water to make the total mass content of the four monomers 25 wt%.

[0110] 2) Add 1 wt% thiourea, 0.05% potassium formate, 0.03% triethylenetetraminepentaacetic acid pentasodium, 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 to dissolve evenly, and place in a 10°C water bath to cool for 30 minutes to cool the temperature to 10°C;

[0111] 3) Add a certain amount of sodium carbonate to the above solution to adjust the pH value to 10, continue to cool for 30 minutes, put it in a 10℃ water bath to cool the temperature to 10℃, introduce the liquid into the adiabatic polymerization device, and purge with nitrogen for 20 minutes.

[0112] 4) Add 0.02wt% azobisisobutyrazoline hydrochloride, 0.005wt% ferrous ammonium sulfate and 0.01wt% hydrogen peroxide aqueous solution to the above mother liquor in sequence, continue to purge with nitrogen for 20 min until it becomes viscous, and then stop purging with nitrogen.

[0113] 5) Observe the temperature change of the system. When the system temperature rises to 60℃, keep it at that temperature for 4 hours.

[0114] 6) Take out the polymerized granules, dry them at 60°C to a moisture content of 3wt%, crush them, and pass them through a 20-mesh sieve to obtain dry powder of acid thickener 8.

[0115] Example 1

[0116] 1) Preparation of emulsified gel acid phase: Take 97.0 parts by weight of 15wt% hydrochloric acid aqueous solution, add 1.0 parts by weight of ferric ion stabilizer ethylenediaminetetraacetic acid (Tianjin Guangfu Chemical Reagent Factory) and 2.0 parts by weight of 1-aminoethyl-2-pentadecylimidazoline quaternary ammonium salt corrosion inhibitor at a stirring speed of 500 r / min at a rate of 80 drops / min, add 0.1 parts by weight of acid thickener 1 at a stirring speed of 500 r / min, and stir for another hour;

[0117] 2) Preparation of emulsified gelling acid oil phase: 2.0 parts by weight of dipolyhydroxy stearate and 0.5 parts by weight of hexadecylamine were heated to 50°C and dissolved in 97.5 parts by weight of diesel oil. The mixture was stirred evenly at a stirring speed of 500 r / min and then cooled to ambient temperature.

[0118] 3) Preparation of emulsified gelling acid: The volume ratio of acid phase to 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 is complete, stirring is continued at a stirring speed of 1500 r / min for 20 min to obtain emulsified gelling acid.

[0119] 4) Preparation of gelling acid: Take 94.2 parts by mass of 15wt% hydrochloric acid solution, and slowly add 1 part by mass of acid thickener 1 at a rate of 80 drops / min while stirring at 500r / min. Stir at 500r / min for half an hour to form a uniform thickened acid solution. Then add 1.8 parts by mass of ethylenediaminetetraacetic acid (Tianjin Guangfu Chemical Reagent Factory) as iron ion stabilizer and 3 parts by mass of 1-aminoethyl-2-pentadecylimidazoline quaternary ammonium salt (commercially available). Stir at 500r / min until uniform, seal and let stand at ambient temperature for 4 hours.

[0120] 5) Preparation of acid system: The volume ratio of emulsified gelling acid and gelling acid is 50:50. Under the condition of stirring speed of 500 r / min, the emulsified gelling acid is slowly added to the gelling acid at a rate of 80 drops / min. After the addition is complete, stirring is continued at a stirring speed of 500 r / min for 3 min to obtain an acid system with low friction and stepwise reaction.

[0121] Example 2

[0122] 1) Preparation of emulsified gel acid phase: Take 96.5 parts by mass of 15wt% hydrochloric acid aqueous solution, add 1.2 parts by mass of citric acid (commercially available) as iron ion stabilizer and 2.3 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) at a stirring speed of 1500 r / min at a rate of 60 drops / min, add 0.2 parts by mass of acid thickener 3 at a stirring speed of 1500 r / min, and stir for another 0.5 hours;

[0123] 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. The mixture was stirred evenly at a stirring speed of 1500 r / min and cooled to ambient temperature.

[0124] 3) Preparation of emulsified gelling acid: The volume ratio of acid phase to oil phase is 65:35. Under the condition of stirring speed of 2000 r / min, the acid phase is slowly added to the oil phase at a rate of 60 drops / min. After the addition is complete, stirring is continued at a stirring speed of 2000 r / min for 15 min to obtain emulsified acid.

[0125] 4) Preparation of gelling acid: Take 97.4 parts by mass of 20wt% hydrochloric acid solution, and slowly add 0.3 parts by mass of acid thickener 2 at a rate of 60 drops / min while stirring at 1500r / min. Stir at 1500r / min for half an hour to form a uniform thickened acid solution. Then add 0.8 parts by mass of citric acid (commercially available) as an iron ion stabilizer and 1.5 parts by mass of 1-aminoethyl-2-pentadecylimidazoline quaternary ammonium salt (commercially available). Stir at 1500r / min until uniform, seal and let stand at ambient temperature for 6 hours.

[0126] 5) Preparation of acid system: The volume ratio of emulsified gelling acid and gelling acid is 40:60. Under the condition of stirring speed of 1500 r / min, the emulsified gelling acid is slowly added to the gelling acid at a rate of 60 drops / min. After the addition is complete, stirring is continued at a stirring speed of 1500 r / min for 4 min to obtain an acid system with low friction and stepwise reaction.

[0127] Example 3

[0128] 1) Preparation of the emulsified gel acid phase: Take 96.0 parts by weight of 20wt% hydrochloric acid aqueous solution, add 1.5 parts by weight of iron ion stabilizer (a mixture of acetic acid and citric acid in a 1:1 mass ratio) and 2.5 parts by weight of formaldehyde-p-phenylenediamine-acetophenone corrosion inhibitor (commercially available) at a stirring speed of 1000r / min and a stirring speed of 120 drops / min. Add 0.3 parts by weight of acid thickener 2 at a stirring speed of 1000r / min and stir for another 2 hours.

[0129] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by weight of dehydrated sorbitol 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. The mixture was stirred evenly at a stirring speed of 1000 r / min and cooled to ambient temperature.

[0130] 3) Preparation of emulsified gelling acid: The volume ratio of acid phase to oil phase is 60:40. Under the condition of stirring speed of 2500 r / min, the acid phase is slowly added to the oil phase at a rate of 120 drops / min. After the addition is complete, stirring is continued at a stirring speed of 2500 r / min for 10 min to obtain emulsified gelling acid.

[0131] 4) Preparation of gelling acid solution: Take 95.6 parts by mass of 25wt% hydrochloric acid solution, and slowly add 0.4 parts by mass of acid thickener 3 at a rate of 120 drops / min while stirring at 1000r / min. Stir at 1000r / min for half an hour to form a uniform thickened acid solution. Then add 1.5 parts by mass of acetic acid (commercially available) as an iron ion stabilizer and 3.5 parts by mass of formaldehyde-p-phenylenediamine-acetophenone corrosion inhibitor (commercially available). Stir at 1000r / min until uniform, seal and let stand at ambient temperature for 5 hours.

[0132] 5) Preparation of acid system: The volume ratio of emulsified gelling acid to gelling acid is 25:75. Under the condition of stirring speed of 1000 r / min, the emulsified gelling acid is slowly added to the gelling acid at a rate of 120 drops / min. After the addition is complete, stirring is continued at a stirring speed of 1000 r / min for 5 min to obtain an acid system with low friction and stepwise reaction.

[0133] Example 4

[0134] 1) Preparation of the acid phase of the emulsified gel: Take 96.0 parts by weight of 20wt% hydrochloric acid aqueous solution, add 1.0 parts by weight of iron ion stabilizer (a mixture of acetic acid and citric acid in a 1:1 mass ratio) and 2.5 parts by weight of formaldehyde-p-phenylenediamine-acetophenone (commercially available) at a stirring speed of 300r / min at a rate of 85 drops / min, add 0.4 parts by weight of acid thickener 6 at a stirring speed of 300r / min, and stir for another hour;

[0135] 2) Preparation of emulsified gelled acid oil phase: 2.5 parts by weight of dehydrated sorbitol 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. The mixture was stirred evenly at a stirring speed of 300 r / min and cooled to ambient temperature.

[0136] 3) Preparation of emulsified gelling acid: The volume ratio of acid phase to 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 is complete, stirring is continued at a stirring speed of 2500 r / min for 15 min to obtain emulsified gelling acid.

[0137] 4) Preparation of gelling acid: Take 96.2 parts by mass of 20wt% hydrochloric acid solution, and slowly add 0.8 parts by mass of acid thickener 4 at a rate of 70 drops / min while stirring at 300r / min. Stir at 300r / min for half an hour to form a uniform thickened acid solution. Then add 1 part by mass of acetic acid (commercially available) as an iron ion stabilizer and 2 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available). Stir at 300r / min until uniform, seal and let stand at ambient temperature for 5 hours.

[0138] 5) Preparation of acid system: The volume ratio of emulsified gelling acid and gelling acid is 45:55. Under the condition of stirring speed of 300 r / min, the emulsified gelling acid is slowly added to the gelling acid at a rate of 100 drops / min. After the addition is complete, stirring is continued at 300 r / min for 10 min to obtain a low frictional stepwise reaction acid system.

[0139] Example 5

[0140] 1) Preparation of emulsified gel acid phase: Take 96.0 parts by weight of 20wt% hydrochloric acid aqueous solution, add 1.5 parts by weight of iron ion stabilizer (a mixture of acetic acid and citric acid in a 1:1 mass ratio) and 2.5 parts by weight of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) at a stirring speed of 1000 r / min at a rate of 90 drops / min, add 0.5 parts by weight of acid thickener 4 at a stirring speed of 1000 r / min, and stir for another hour;

[0141] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by weight of dehydrated sorbitol 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. The mixture was stirred evenly at a stirring speed of 1000 r / min and cooled to ambient temperature.

[0142] 3) Preparation of emulsified gelling acid: The volume ratio of acid phase to oil phase is 60:40. Under the condition of stirring 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 is complete, stirring is continued at a stirring speed of 2500 r / min for 10 min to obtain emulsified gelling acid.

[0143] 4) Preparation of gelling acid solution: Take 95.4 parts by mass of 25wt% hydrochloric acid solution, and slowly add 0.6 parts by mass of acid thickener 5 at a rate of 80 drops / min while stirring at 1000r / min. Stir at 1000r / min for half an hour to form a uniform thickened acid solution. Then add 1.5 parts by mass of acetic acid (commercially available) as an iron ion stabilizer and 2.5 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available). Stir at 1000r / min until uniform, seal and let stand at ambient temperature for 5 hours.

[0144] 5) Preparation of acid system: The volume ratio of emulsified gelling acid and gelling acid is 45:55. Under the condition of stirring speed of 1000 r / min, the emulsified gelling acid is slowly added to the gelling acid at a rate of 80 drops / min. After the addition is complete, the stirring is continued at a stirring speed of 1000 r / min for 5 min to obtain an acid system with low friction and stepwise reaction.

[0145] Example 6

[0146] 1) Preparation of emulsified gel acid phase: Take 96.0 parts by weight of 20wt% hydrochloric acid aqueous solution, add 1.5 parts by weight of iron ion stabilizer (a mixture of acetic acid and citric acid in a 1:1 mass ratio) and 2.5 parts by weight of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) at a stirring speed of 1000 r / min at a rate of 90 drops / min, add 0.6 parts by weight of acid thickener 5 at a stirring speed of 1000 r / min, and stir for another hour;

[0147] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by weight of dehydrated sorbitol 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. The mixture was stirred evenly at a stirring speed of 1000 r / min and cooled to ambient temperature.

[0148] 3) Preparation of emulsified gelling acid: The volume ratio of acid phase to oil phase is 60:40. Under the condition of stirring 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 is complete, stirring is continued at a stirring speed of 2500 r / min for 10 min to obtain emulsified gelling acid.

[0149] 4) Preparation of gelling acid solution: Take 95.4 parts by mass of 25wt% hydrochloric acid solution, and slowly add 0.6 parts by mass of acid thickener 6 at a rate of 80 drops / min while stirring at 1000r / min. Stir at 1000r / min for half an hour to form a uniform thickened acid solution. Then add 1.5 parts by mass of acetic acid (commercially available) as an iron ion stabilizer and 2.5 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available). Stir at 1000r / min until uniform, seal and let stand at ambient temperature for 5 hours.

[0150] 5) Preparation of acid system: The volume ratio of emulsified gelling acid and gelling acid is 45:55. Under the condition of stirring speed of 1000 r / min, the emulsified gelling acid is slowly added to the gelling acid at a rate of 80 drops / min. After the addition is complete, the stirring is continued at a stirring speed of 1000 r / min for 5 min to obtain an acid system with low friction and stepwise reaction.

[0151] Example 7

[0152] 1) Preparation of emulsified gel acid phase: Take 96.0 parts by weight of 20wt% hydrochloric acid aqueous solution, add 1.5 parts by weight of iron ion stabilizer (a mixture of acetic acid and citric acid in a 1:1 mass ratio) and 2.5 parts by weight of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) at a stirring speed of 1000 r / min at a rate of 90 drops / min, add 0.3 parts by weight of acid thickener 7 at a stirring speed of 1000 r / min, and stir for another hour;

[0153] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by weight of dehydrated sorbitol 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. The mixture was stirred evenly at a stirring speed of 1000 r / min and cooled to ambient temperature.

[0154] 3) Preparation of emulsified gelling acid: The volume ratio of acid phase to oil phase is 60:40. Under the condition of stirring 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 is complete, stirring is continued at a stirring speed of 2500 r / min for 10 min to obtain emulsified gelling acid.

[0155] 4) Preparation of gelling acid solution: Take 95.4 parts by mass of 25wt% hydrochloric acid solution, and slowly add 0.6 parts by mass of acid thickener 7 at a rate of 80 drops / min while stirring at 1000r / min. Stir at 1000r / min for half an hour to form a uniform thickened acid solution. Then add 1.5 parts by mass of acetic acid (commercially available) as an iron ion stabilizer and 2.5 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available). Stir at 1000r / min until uniform, seal and let stand at ambient temperature for 5 hours.

[0156] 5) Preparation of acid system: The volume ratio of emulsified gelling acid and gelling acid is 45:55. Under the condition of stirring speed of 1000 r / min, the emulsified gelling acid is slowly added to the gelling acid at a rate of 80 drops / min. After the addition is complete, the stirring is continued at a stirring speed of 1000 r / min for 5 min to obtain an acid system with low friction and stepwise reaction.

[0157] Example 8

[0158] 1) Preparation of emulsified gel acid phase: Take 96.0 parts by weight of 20wt% hydrochloric acid aqueous solution, add 1.5 parts by weight of iron ion stabilizer (a mixture of acetic acid and citric acid in a 1:1 mass ratio) and 2.5 parts by weight of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available) at a stirring speed of 1000 r / min at a rate of 90 drops / min, add 0.3 parts by weight of acid thickener 8 at a stirring speed of 1000 r / min, and stir for another hour;

[0159] 2) Preparation of emulsified gelled acid oil phase: 2.0 parts by weight of dehydrated sorbitol 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. The mixture was stirred evenly at a stirring speed of 1000 r / min and cooled to ambient temperature.

[0160] 3) Preparation of emulsified gelling acid: The volume ratio of acid phase to oil phase is 60:40. Under the condition of stirring 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 is complete, stirring is continued at a stirring speed of 2500 r / min for 10 min to obtain emulsified gelling acid.

[0161] 4) Preparation of gelling acid solution: Take 95.4 parts by mass of 25wt% hydrochloric acid solution, and slowly add 0.6 parts by mass of acid thickener 8 at a rate of 80 drops / min while stirring at 1000r / min. Stir at 1000r / min for half an hour to form a uniform thickened acid solution. Then add 1.5 parts by mass of acetic acid (commercially available) as an iron ion stabilizer and 2.5 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available). Stir at 1000r / min until uniform, seal and let stand at ambient temperature for 5 hours.

[0162] 5) Preparation of acid system: The volume ratio of emulsified gelling acid and gelling acid is 45:55. Under the condition of stirring speed of 1000 r / min, the emulsified gelling acid is slowly added to the gelling acid at a rate of 80 drops / min. After the addition is complete, the stirring is continued at a stirring speed of 1000 r / min for 5 min to obtain an acid system with low friction and stepwise reaction.

[0163] Comparative Example 1

[0164] The preparation process of emulsified gelling acid in Example 4:

[0165] 1) Preparation of emulsified gel acid phase: Take 96.0 parts by weight of 20wt% hydrochloric acid aqueous solution, add 1.0 parts by weight of iron ion stabilizer (a mixture of acetic acid and citric acid in a 1:1 mass ratio) and 2.5 parts by weight of formaldehyde-p-phenylenediamine-acetophenone (commercially available) at a stirring speed of 300 r / min at a rate of 85 drops / min, and add 0.4 parts by weight of acid thickener 6 at a stirring speed of 300 r / min, and stir for another hour;

[0166] 2) Preparation of emulsified acid oil phase: 2.5 parts by weight of dehydrated sorbitol 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. The mixture was stirred evenly at a stirring speed of 300 r / min and cooled to ambient temperature.

[0167] 3) Preparation of emulsified gelling acid: The volume ratio of acid phase to 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 is complete, stirring is continued at a stirring speed of 2500 r / min for 15 min to obtain emulsified gelling acid.

[0168] Comparative Example 2

[0169] Preparation process of gelling acid in Example 4:

[0170] Take 96.2 parts by mass of a 20wt% hydrochloric acid solution, and slowly add 0.8 parts by mass of acid thickener 4 at a rate of 70 drops / minute while stirring at 300 rpm. Stir at 300 rpm for half an hour to form a uniform thickened acid solution. Then add 1 part by mass of acetic acid (commercially available) as an iron ion stabilizer and 2.5 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available). Stir at 300 rpm until uniform, seal and let stand at ambient temperature for 5 hours.

[0171] Comparative Example 3

[0172] The difference from Example 4 is that no acid thickener was added in step 1). Specifically:

[0173] 1) Preparation of emulsified acid phase: Take 96.0 parts by weight of 20wt% hydrochloric acid aqueous solution, add 1.0 parts by weight of iron ion stabilizer (a mixture of acetic acid and citric acid in a 1:1 mass ratio) and 2.5 parts by weight of formaldehyde-p-phenylenediamine-acetophenone (commercially available) at a stirring speed of 300 r / min at a rate of 85 drops / min, and then stir at a stirring speed of 300 r / min for 1 hour;

[0174] 2) Preparation of emulsified acid oil phase: 2.5 parts by weight of dehydrated sorbitol 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. The mixture was stirred evenly at a stirring speed of 300 r / min and cooled to ambient temperature.

[0175] 3) Preparation of emulsified acid: The volume ratio of acid phase to 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 is complete, stirring is continued at a stirring speed of 2500 r / min for 15 min to obtain emulsified acid.

[0176] 4) Preparation of gelling acid: Take 96.2 parts by mass of 20wt% hydrochloric acid solution, and slowly add 0.8 parts by mass of acid thickener 4 at a rate of 70 drops / min while stirring at 300r / min. Stir at 300r / min for half an hour to form a uniform thickened acid solution. Then add 1 part by mass of acetic acid (commercially available) as an iron ion stabilizer and 2 parts by mass of 2-methylquinoline benzyl quaternary ammonium salt corrosion inhibitor (commercially available). Stir at 300r / min until uniform, seal and let stand at ambient temperature for 5 hours.

[0177] 5) Preparation of acid system: The volume ratio of emulsified acid and gelling acid is 45:55. Under the condition of stirring speed of 300 r / min, the emulsified acid is slowly added to the gelling acid at a rate of 100 drops / min. After the addition is complete, stirring is continued at a stirring speed of 300 r / min for 10 min to obtain an acid system with low friction and stepwise reaction.

[0178] Performance testing

[0179] (1) The apparent viscosity (measured using a six-speed viscometer) of the acid systems prepared in Examples 1 to 8, the emulsified gel acid prepared in Comparative Example 1, and the acid system prepared in Comparative Example 3 at room temperature of 25°C and 120°C, as well as the demulsification rate observed by the naked eye at 120°C, were measured. The results are shown in Table 1.

[0180] As shown in Table 1, the acid system prepared in Example 4 has a lower viscosity at room temperature compared to Comparative Example 1, thus exhibiting lower on-site friction and easier pumping. Compared to Comparative Example 3, Example 4 has a higher viscosity at 120°C, thus exhibiting a better retardation effect. Furthermore, other embodiments of the present invention also exhibit lower viscosity at room temperature and higher viscosity at 120°C, demonstrating excellent low friction and retardation effects.

[0181] Table 1

[0182]

[0183] (2) The acid-rock reaction rate of the multi-emulsified gelling acid prepared in Examples 1 to 8 and the gelling acid prepared in Comparative Example 2 was tested at 120℃ (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 with those of gelling acid. The results are shown in Table 2.

[0184] As shown in Table 2, the acid system prepared in Example 4 exhibited a lower reaction rate at 5 min and 10 min compared to Comparative Examples 2 and 3. Particularly at 10 min, the acid-rock reaction rate of the acid system in Example 4 decreased by approximately 10 times. Compared to Comparative Example 3, Example 4 showed higher viscosity at high temperatures, thus exhibiting a better retarding effect. Furthermore, other embodiments of the present invention also exhibited similar reaction characteristics to Example 4, indicating that the acid system of the present invention has superior retarding and stepwise acidification characteristics at high temperatures.

[0185] Table 2

[0186]

[0187] As can be seen from the above comparison of the two properties, the low-friction stepwise reaction emulsified gelling acid of the present invention has the advantages of low apparent viscosity, low friction, good temperature stability and good retardation effect, which meets the requirements of high-temperature reservoir acid fracturing application, and the preparation method is simple and worth promoting and applying.

[0188] While this application has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made without departing from the true spirit and scope of this application. Furthermore, various modifications can be made to the subject, spirit, and scope of this application to suit specific situations, materials, material compositions, and methods. All such modifications are included within the scope of the claims of this application.

Claims

1. A method for preparing an acid system, comprising the following steps: adding 20 to 50 parts by volume of emulsified gelling acid to 50 to 80 parts by volume of gelling acid, based on 100 parts by volume of the acid system, to obtain the acid system; in, The emulsified gelling acid is prepared as follows: 1) Add the first corrosion inhibitor, the first acid thickener and the first iron ion stabilizer to the first acid solution, stir evenly at the third stirring speed and let stand to obtain the acid phase; 2) Dissolve the water-in-oil emulsifier in the oil to obtain the oil phase; 3) The acid phase is added dropwise to the oil phase being stirred at a fourth stirring speed at a second dropping rate. After the addition is complete, the mixture is stirred at a fifth stirring speed to obtain the emulsified gel acid. Based on 100 parts by mass of the acid phase, the first acid solution comprises 95.2 to 97.7 parts by mass, the first corrosion inhibitor comprises 1.5 to 3 parts by mass, the first acid thickener comprises 0.1 to 0.6 parts by mass, and the first iron ion stabilizer comprises 0.8 to 1.8 parts by mass; wherein the mass concentration of the acid in the first acid solution is 15% to 30%. The gelling acid is prepared as follows: I) Add a thickener for the second acid to the second acid solution being stirred at the seventh stirring speed. After adding the thickener for the second acid, stir at the eighth stirring speed to obtain a thickened acid solution. II) Add a second iron ion stabilizer and a second corrosion inhibitor to the thickened acid solution, stir evenly at the ninth stirring speed, and let stand to obtain the gelled acid; Wherein, the first acid solution and the second acid solution are independently selected from aqueous hydrochloric acid solution and / or aqueous hydrofluoric acid solution; The first iron ion stabilizer and the second iron ion stabilizer are independently organic acids; 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, ketaldehyde amine condensates and Mannich bases; The water-in-oil emulsifier is selected from at least one of dihydroxystearate, sorbitan sesquioleate, dehydrated sorbitan fatty acid ester, polyoxyethylene octylphenol ether-10, dihydroxystearate and hexadecylamine; The oil is selected from at least one of diesel, kerosene, white oil and light crude oil; The first acid thickener and the second acid thickener are independently a first polyacrylamide copolymer and / or a second polyacrylamide copolymer; The first polyacrylamide copolymer is a copolymer prepared by reacting acrylamide with 2-acrylamide-2-methylpropanesulfonic acid monomer in a molar ratio of 1:1 to 3:1; The second polyacrylamide copolymer was prepared as follows: A) Dissolve acrylamide, acid-resistant monomer, water-soluble monomer containing dimethylamine group and quaternary ammonium salt polymerizable surfactant in water to obtain the first solution; B) Add a cosolvent, chain transfer agent, complexing agent, activator, and water-soluble anionic surfactant to the first solution, mix well, and obtain a second solution; C) Adjust the pH of the second solution to 9 or 10 to obtain a third solution; then add the third solution to the polymerization apparatus and introduce nitrogen gas. D) Add water-soluble azo initiator, reducing agent, and oxidizing agent to the polymerization apparatus to obtain a fourth solution, and then continue to purge with nitrogen gas; E) After the temperature of the fourth solution rises, it is kept at that temperature to obtain a polymeric gel. F) The polymeric gel is granulated, dried, pulverized, and sieved to obtain the second polyacrylamide copolymer in dry powder form; In the preparation of the second polyacrylamide copolymer, the acid-resistant monomer is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, acryloyloxyethyltrimethylammonium chloride, and methacryloyloxyethyltrimethylammonium chloride; the water-soluble monomer containing a dimethylamine group is selected from methacryloyloxyethyldimethylamine and / or N,N-dimethylacrylamide; and the quaternary ammonium salt polymerizable surfactant is selected from at least one of tetradecyldimethylallylammonium chloride, hexadecyldimethylallylammonium chloride, octadecyldimethylallylammonium chloride, methacryloyloxyethyldimethylhexadecylammonium bromide, and dimethyloctadecyl(2-hydroxy-3-acrylamidopropyl)ammonium chloride.

2. The preparation method according to claim 1, characterized in that, Based on 100 parts by volume of the acid system, 25 to 45 parts by volume of the emulsified gelling acid are added to 55 to 75 parts by volume of the gelling acid to obtain the acid system.

3. The preparation method according to claim 1, characterized in that, The emulsified gelling acid is added dropwise to the gelling acid being stirred at a first stirring speed at a first dropping rate. After the addition is complete, the mixture is stirred at a second stirring speed to obtain the acid solution system.

4. The preparation method according to claim 3, characterized in that, In step 2) of the preparation of the emulsified gelling 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 1, characterized in that, Based on 100 parts by volume of emulsified gelling acid, the acid phase comprises 60 to 80 parts by volume, and the oil phase comprises 20 to 40 parts by volume. Based on 100 parts by weight of the oil phase, the oil comprises 96 to 98 parts by weight, and the water-in-oil emulsifier comprises 2 to 4 parts by weight.

6. The preparation method according to claim 5, characterized in that, Based on 100 parts by volume of emulsified gelling acid, the acid phase comprises 65 to 70 parts by volume, and the oil phase comprises 30 to 35 parts by volume. 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%. Based on 100 parts by weight of the oil phase, the oil comprises 96.5 to 97.5 parts by weight, and the water-in-oil emulsifier comprises 2.5 to 3.5 parts by weight.

7. The preparation method according to any one of claims 1 to 6, characterized in that, Based on 100 parts by mass of the gelling acid, the second acid solution comprises 94.2 to 97.4 parts by mass, the second acid thickener comprises 0.3 to 1 part 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%.

8. The preparation method according to claim 7, characterized in that, Based on 100 parts by mass of the gelling 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%.

9. The preparation method according to any one of claims 1 to 6, characterized in that, 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; The first corrosion inhibitor and / or the second corrosion inhibitor are independently selected from at least one of 1-aminoethyl-2-pentadecanylimidazoline quaternary ammonium salt, formaldehyde-p-phenylenediamine-acetophenone, and 2-methylquinoline benzyl quaternary ammonium salt; The relative molecular weight of the first polyacrylamide copolymer is 8 million to 10 million; In the preparation of the second polyacrylamide copolymer, the acrylamide comprises 30 to 50 parts by weight, the acid-resistant monomer comprises 50 to 70 parts by weight, the water-soluble monomer containing dimethylamine groups comprises 1.4 to 1.7 parts by weight, and the quaternary ammonium salt polymerizable surfactant comprises 0.2 to 1 part by weight. In the preparation of the second polyacrylamide copolymer, the total mass of the acrylamide, the acid-resistant monomer, the water-soluble monomer containing dimethylamine, and the quaternary ammonium salt polymerizable surfactant accounts for 25 wt% to 29 wt% of the total mass of the first solution; In the preparation of the second polyacrylamide copolymer, based on the total mass of the acrylamide, the acid-resistant monomer, the water-soluble monomer containing dimethylamine groups, and the quaternary ammonium salt polymerizable surfactant as 100%, the amount of the cosolvent is 1 wt% to 3 wt%, the amount of the chain transfer agent is 0.05 wt% to 0.1 wt%, the amount of the complexing agent is 0.03 wt% to 0.08 wt%, the amount of the activator is 0.05 wt% to 0.1 wt%, the amount of the oxidant is 0.01 wt% to 0.06 wt%, the amount of the reducing agent is 0.005 wt% to 0.03 wt%, the amount of the water-soluble azo initiator is 0.02 wt% to 0.06 wt%, and the amount of the water-soluble anionic surfactant is 3 wt% to 5 wt%.

10. The preparation method according to claim 4, characterized in that, The first drop acceleration and the second drop acceleration are independently between 60 and 120 drops / minute; 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; The fourth and fifth stirring speeds are independently between 1000 and 3000 r / min.

11. The preparation method according to claim 10, characterized in that, 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; The fourth and fifth stirring speeds are independently between 1500 and 2500 r / min.

12. The preparation method according to claim 3, characterized in that, The mixing time at the second mixing speed is 3 to 10 minutes; The standing time after uniform mixing at the third stirring speed is 0.5 to 2 hours; The stirring time at the fifth stirring speed is 10 to 20 minutes; The stirring time at the eighth stirring speed is 30 to 50 minutes; After being stirred evenly at the ninth stirring speed, the settling time is 4 to 6 hours.

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