A high-temperature resistant acid system, its preparation method and its application

Abstract

This invention discloses an ultra-high temperature resistant acid system, its preparation method, and its application, belonging to the field of oilfield chemistry. The ultra-high temperature resistant acid system of this invention comprises the following raw materials in weight percentages: thickener 0.4%-0.6%, complexing agent 0.05%-0.1%, corrosion inhibitor 4%-6%, surfactant 0.1%-0.3%, stabilizer 0.1%-0.3%, and the balance being hydrochloric acid. The ultra-high temperature resistant acid system of this invention exhibits stable performance under ultra-high temperature conditions, effectively exerting a slowing effect, enabling the acid to penetrate further into the formation under ultra-high temperature conditions, increasing the stimulation volume; furthermore, the corrosion inhibitor in the ultra-high temperature resistant acid system has strong metal-metal interaction capabilities, effectively protecting the metal tubing and ensuring safe operation under ultra-high temperature conditions; the low surface tension surfactant in the ultra-high temperature resistant acid system allows residual acid to be quickly returned to the formation after operation, reducing reservoir damage caused by residual acid retention in the formation.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemistry, specifically to an ultra-high temperature resistant acid system, its preparation method, and its application. Background Technology

[0002] A significant portion of the reservoirs currently being developed in my country are ultra-high temperature reservoirs. When using conventional acidizing techniques to stimulate these reservoirs, the acid reacts violently near the wellbore, causing severe corrosion of the underground tubing. This not only leads to substantial acid consumption near the wellbore but also poses significant safety hazards to underground operations, severely impacting the effectiveness of acidizing. Therefore, for these reservoirs, a high-temperature resistant and corrosion-inhibiting acid system is required to achieve the desired acidizing results.

[0003] Currently, slow-rate acid systems are commonly used in oilfield acidizing to slow down the acid-rock reaction rate. However, existing slow-rate acid systems are no longer sufficient for acidizing ultra-high temperature reservoirs. This is because the temperature of ultra-high temperature reservoirs often exceeds 180°C. Under ultra-high temperatures, the acid-rock reaction rate of conventional acid systems becomes extremely rapid. Conventional slow-rate acids can slow down the acid-rock reaction rate by affecting different stages of the reaction. However, since the temperature of ultra-high temperature reservoirs far exceeds the tolerance limit of current slow-rate acid systems, the viscosity of the slow-rate acid decreases, preventing the formation of a complex network structure to prevent acid-rock contact or adsorption on the rock surface to form an effective barrier layer. Consequently, corrosion inhibitors cannot form a corrosion-inhibiting layer on the surface of underground tubing. Therefore, acid systems that can maintain a certain slow-rate and corrosion-inhibiting capacity under ultra-high temperatures have become a very effective means of agitating ultra-high temperature reservoirs.

[0004] Existing literature, such as Yang Ming et al.'s "Preparation and Performance Evaluation of Thickened Acid System Resistant to 180℃", describes the design and preparation of a series of polyacrylamide-based cationic thickeners resistant to high temperatures and acids, and studies their basic properties. They also screened corrosion inhibitors suitable for high-temperature acid solutions, combined with other additives to form a high-temperature resistant thickened acid, and further investigated the performance of the thickened acid. Under 180℃ high-temperature and high-pressure dynamic corrosion testing, the corrosion rate of N80 steel sheets was only 41.614 g / (m²). 2 ·h). At 180℃, 170s -1 The viscosity of the thickened acid system was maintained at 33.258 mPa·s (Science, Technology and Engineering, Vol. 23, 2024, pp. 9827-9833), but for ultra-high temperature reservoirs with higher temperatures, the overall temperature resistance of the acid solution still cannot meet the requirements.

[0005] High-temperature resistance is a key focus of acid system research. In existing acid systems, thickeners with high-temperature resistant groups on their molecular chains have weak high-temperature resistance, and their thickening ability is almost completely lost under shear stress, resulting in a severe lack of acid systems resistant to ultra-high temperatures. Corrosion inhibitors can slow down the corrosion of underground casings, pipelines, and other metal materials by acid, but current retarders cannot guarantee the corrosion resistance of underground pipes under ultra-high temperatures. The poor ultra-high temperature resistance of existing acid systems necessitates extensive preliminary work to mitigate the impact of ultra-high temperatures on the formation, increasing the complexity of on-site construction. For ultra-high temperature reservoirs, existing acid systems are unsuitable. Summary of the Invention

[0006] The purpose of this invention is to provide an ultra-high temperature resistant acid system, its preparation method, and its application, in order to solve the technical problem that existing acid systems have poor high temperature resistance.

[0007] To achieve the above objectives, one embodiment of the present invention provides an ultra-high temperature resistant acid system, comprising the following raw materials in weight percentage: thickener 0.4%-0.6%, complexing agent 0.05%-0.1%, corrosion inhibitor 4%-6%, surfactant 0.1%-0.3%, stabilizer 0.1%-0.3%, and the balance being hydrochloric acid;

[0008] The thickener is a copolymer of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide.

[0009] The corrosion inhibitor comprises the following raw materials in the following weight percentages: 1,4-bis((butyryloxy)-3-methylimidazoline)butene 15%-30%, small molecule alcohol 20%-30%, propynyl alcohol 2%-6%, formic acid 5%-10%, alkyl polyoxyethylene ether 0.5%-2%, and the balance being water.

[0010] In one preferred embodiment of the present invention, the mass percentage of acrylamide: 2-acrylamido-2-methylpropanesulfonic acid: acrylic acid: dimethyldodecyl(2-acrylamidoethyl)ammonium bromide is 3-4:0.5:0.5:3.

[0011] In one preferred embodiment of the present invention, the complexing agent is an aqueous solution of chromium trichloride, the surfactant is an aqueous solution of perfluorodecyl polyoxyethylene ether, and the stabilizer is a mixture of sodium isosorbide and citric acid.

[0012] In one preferred embodiment of the present invention, the small molecule alcohol is a mixture of methanol and ethylene glycol, wherein the mass ratio of methanol to ethylene glycol is 2-5:1.

[0013] In one preferred embodiment of the present invention, the alkyl group of the alkyl polyoxyethylene ether is any one of octyl alkyl or decanyl alkyl.

[0014] The present invention also discloses a method for preparing an ultra-high temperature resistant acid system, comprising: adding a thickener, a corrosion inhibitor, a stabilizer and a surfactant to hydrochloric acid respectively, mixing and stirring evenly, and adding a complexing agent when injecting into the formation to obtain an ultra-high temperature resistant acid system;

[0015] The preparation method of the thickener includes: adding 2-acrylamido-2-methylpropanesulfonic acid to water, adjusting the pH, and then sequentially adding acrylamide, acrylic acid and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide, mixing and stirring to obtain the thickener;

[0016] The method for preparing the corrosion inhibitor includes: sequentially adding a small molecule alcohol, propynyl alcohol, formic acid, 1,4-bis((butyryloxy)-3-methylimidazoline)butene and alkyl polyoxyethylene ether and stirring to obtain the corrosion inhibitor.

[0017] One preferred embodiment of the present invention is a method for preparing a thickener, comprising: adding 2-acrylamido-2-methylpropanesulfonic acid to water, adjusting the pH, sequentially adding acrylamide, acrylic acid and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide and stirring, and after stirring, adding sodium sulfite and sodium thiosulfate to react and obtain a thickener.

[0018] In one preferred embodiment of the present invention, the mass percentage of acrylamide: 2-acrylamido-2-methylpropanesulfonic acid: acrylic acid: dimethyldodecyl(2-acrylamidoethyl)ammonium bromide is 3-4:0.5:0.5:3.

[0019] One preferred embodiment of the present invention is a method for preparing 1,4-bis((butyryloxy)-3-methylimidazoline)butene, comprising: reacting N-hydroxymethylimidazoline and acyl chloride in tetrahydrofuran, rotary evaporating to obtain the product, washing the product, adding n-hexane and 1,4-dibromobutene and stirring to react, and filtering to obtain 1,4-bis((butyryloxy)-3-methylimidazoline)butene.

[0020] In one preferred embodiment of the present invention, the acyl chloride is either butyryl chloride or hexanoyl chloride.

[0021] In one preferred embodiment of the present invention, the alkyl group of the alkyl polyoxyethylene ether is any one of octyl or decanyl, and the small molecule alcohol is a mixture of methanol and ethylene glycol, wherein the mass ratio of methanol to ethylene glycol is 2-5:1.

[0022] In one preferred embodiment of the present invention, the complexing agent is an aqueous solution of chromium trichloride, the surfactant is an aqueous solution of perfluorodecyl polyoxyethylene ether, and the stabilizer is a mixture of sodium isosorbide and citric acid.

[0023] This invention also discloses the application of an ultra-high temperature resistant acid solution system for use in the acidizing modification of ultra-high temperature reservoirs.

[0024] In summary, the beneficial effects of the present invention are as follows:

[0025] 1. The ultra-high temperature resistant acid system of the present invention exhibits stable performance under ultra-high temperature conditions and can effectively exert a slowing effect, enabling the acid to penetrate into more distant formations under ultra-high temperature conditions, thereby increasing the volume of the modified formation. Furthermore, the corrosion inhibitor in the ultra-high temperature resistant acid system has strong metal-metal interaction capabilities, effectively protecting the metal tubing and ensuring the safety of construction under ultra-high temperature conditions. The low surface tension surfactant in the ultra-high temperature resistant acid system allows residual acid to be quickly returned to the formation after construction, reducing reservoir damage caused by residual acid remaining in the formation.

[0026] 2. The thickener in the ultra-high temperature acid system of this invention has a high viscosity after cross-linking, which can effectively slow down the transfer rate of acid and reduce the reaction rate between acid and rock; and the cross-linked acid system has a high cross-linking density and strong shear resistance, which can effectively cover the metal surface and avoid contact between acid and metal.

[0027] 3. The ultra-high temperature corrosion inhibitor contained in the ultra-high temperature acid-resistant system of the present invention contacts the metal through coordination bonds via double bonds and ring structures to form a complex structure, which isolates the acid from the metal and prevents the metal from being corroded by the acid at high temperatures.

[0028] 4. The surfactant in the ultra-high temperature acid solution system of this invention can be effectively adsorbed on the rock surface under ultra-high temperature conditions, reducing the surface tension between water and rock, and promoting the return of the reacted acid solution to the formation.

[0029] 5. The ultra-high temperature acid system of the present invention can meet the requirements of smooth construction under ultra-high temperature conditions and ensure the construction effect.

[0030] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be appreciated by way of the effects described in the description. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the content of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0033] This invention discloses an ultra-high temperature resistant acid system, comprising the following raw materials in weight percentage: thickener 0.4%-0.6%, complexing agent 0.05%-0.1%, corrosion inhibitor 4%-6%, surfactant 0.1%-0.3%, stabilizer 0.1%-0.3%, and the balance being hydrochloric acid.

[0034] The copolymer of thickener acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide, wherein the mass percentage of acrylamide:2-acrylamide-2-methylpropanesulfonic acid:acrylic acid:dimethyldodecyl(2-acrylamidoethyl)ammonium bromide is 3-4:0.5:0.5:3;

[0035] The complexing agent is an aqueous solution of chromium trichloride with a mass percentage of 18%;

[0036] The surfactant is a 1%-4% aqueous solution of perfluorodecyl polyoxyethylene ether;

[0037] The stabilizer is an iron ion stabilizer, specifically a mixture of sodium isosorbate and citric acid, preferably in a mass ratio of sodium isosorbate to citric acid of 1:3;

[0038] The corrosion inhibitor comprises the following raw materials in the following weight percentages: 1,4-bis((butyryloxy)-3-methylimidazoline)butene 15%-30%, small molecule alcohol 20%-30%, propynyl alcohol 2%-6%, formic acid 5%-10%, alkyl polyoxyethylene ether 0.5%-2%, and the balance being water;

[0039] The structural formula of 1,4-bis((butyryloxy)-3-methylimidazoline)butene is as follows:

[0040] ;

[0041] The preparation method of 1,4-bis((butyryloxy)-3-methylimidazoline)butene is as follows: 40-50% N-hydroxymethylimidazoline and 50-60% acyl chloride are reacted in tetrahydrofuran at a molar ratio of 200-300% N-hydroxymethylimidazoline mass, with 5-10% N-hydroxymethylimidazoline mass of triethylamine as a catalyst. The mixture is refluxed at 60-70℃ for 2-3 hours, followed by rotary evaporation to obtain a brown solid. The solid is then treated with 300-400% N-hydroxymethyl... The product was washed three times with methanol containing the mass of imidazoline. The resulting product was placed in a flask, and 200-300% hexane (by mass of N-hydroxymethylimidazoline) was added. Then, 10-20% 1,4-dibromobutene (by mass of N-hydroxymethylimidazoline) was added. The mixture was stirred at room temperature for 10-12 hours, filtered, and the precipitate was obtained as 1,4-bis((butyryloxy)-3-methylimidazoline)butene, wherein the precipitate is any one of butyryl chloride and hexanoyl chloride.

[0042] Small molecule alcohols are mixtures of methanol and ethylene glycol, with a mass ratio of methanol to ethylene glycol of 2-5:1.

[0043] The alkyl group in alkyl polyoxyethylene ether is either octyl alkyl or decanyl alkyl;

[0044] The concentration of hydrochloric acid is 12%-20%.

[0045] This invention also discloses a method for preparing an ultra-high temperature resistant acid system, comprising: adding a thickener, a corrosion inhibitor, a stabilizer, and a surfactant to hydrochloric acid, mixing and stirring until homogeneous, and adding a complexing agent when injecting into the formation to obtain an ultra-high temperature resistant acid system; specifically, adding hydrochloric acid to a reactor, and using a suction pump to draw the thickener into the reactor under stirring, with the suction rate controlled to be completed in 10-15 minutes, adding the corrosion inhibitor, stabilizer, and surfactant under stirring using a liquid addition pump, mixing until homogeneous, and using a proportioning pump to complex the agent when injecting into the formation.

[0046] The complexing agent is an aqueous solution of chromium trichloride with a mass percentage of 18%, the surfactant is an aqueous solution of perfluorodecyl polyoxyethylene ether with a concentration of 1%-4%, and the stabilizer is an iron ion stabilizer, specifically a mixture of sodium isosorbate and citric acid. Preferably, the mass ratio of sodium isosorbate to citric acid is 1:3.

[0047] The preparation method of the thickener includes: adding 2-acrylamido-2-methylpropanesulfonic acid to water, adjusting the pH, then sequentially adding acrylamide, acrylic acid, and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide and stirring. After stirring, sodium sulfite and sodium thiosulfate are added to react and obtain the thickener. Specifically, the method includes: in a reaction vessel with good heat preservation performance, adding water at a mass of 1.5-2 times the mass of the above monomers (the monomer mass refers to the total mass of the four monomers 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, acrylic acid, and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide), controlling the temperature at 10-15℃, and adding 2-acrylamido-2-methylpropanesulfonic acid. 2-Methylpropanesulfonic acid is added, and sodium hydroxide is added to adjust the pH to 7. Then acrylamide, acrylic acid, and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide are added. The mixture is stirred at 100-300 rpm for 10-20 minutes, maintaining a nitrogen atmosphere during stirring. 0.1-0.3% sodium sulfite and 0.2-0.4% sodium thiosulfate are added, and the water bath temperature is raised to 30-35°C and maintained for 2-3 hours to obtain a thickener. The mass percentage of acrylamide:2-acrylamido-2-methylpropanesulfonic acid:acrylic acid:dimethyldodecyl(2-acrylamidoethyl)ammonium bromide is 3-4:0.5:0.5:3.

[0048] The method for preparing the corrosion inhibitor includes: sequentially adding a small molecule alcohol, propynyl alcohol, formic acid, 1,4-bis((butyryloxy)-3-methylimidazoline)butene and alkyl polyoxyethylene ether and stirring to obtain the corrosion inhibitor; wherein, the alkyl group of the alkyl polyoxyethylene ether is any one of octyl or decanyl, and the small molecule alcohol is a mixture of methanol and ethylene glycol, with a mass ratio of methanol to ethylene glycol of 2-5:1; specifically, the small molecule alcohol, propynyl alcohol, formic acid, 1,4-bis((butyryloxy)-3-methylimidazoline)butene and alkyl polyoxyethylene ether are sequentially added to an enamel-lined reactor, and stirred at 3000 r / min for 1-3 h at room temperature to obtain the corrosion inhibitor;

[0049] The preparation method of 1,4-bis((butyryloxy)-3-methylimidazoline)butene includes: reacting N-hydroxymethylimidazoline and acyl chloride in tetrahydrofuran, rotary evaporating to obtain the product, washing the product, adding n-hexane and 1,4-dibromobutene, stirring and reacting, filtering to obtain 1,4-bis((butyryloxy)-3-methylimidazoline)butene; specifically, the molar ratio is 40-50% N-hydroxymethylimidazoline and 50-60% acyl chloride, reacting in tetrahydrofuran at 200-300% N-hydroxymethylimidazoline mass, with 5-10% N-hydroxymethylimidazoline mass... Using triethylamine as a catalyst, the mixture was refluxed at 60-70℃ for 2-3 hours, followed by rotary evaporation to obtain a brown solid. This solid was washed three times with 300-400% N-hydroxymethylimidazoline-based methanol. The resulting product was placed in a flask, and 200-300% N-hydroxymethylimidazoline-based n-hexane was added, along with 10-20% N-hydroxymethylimidazoline-based 1,4-dibromobutene. The mixture was stirred at room temperature for 10-12 hours, filtered, and the precipitate was obtained as 1,4-bis((butyryloxy)-3-methylimidazoline)butene; any one of butyryl chloride and hexanoyl chloride.

[0050] The key to acidification is reducing the reaction rate between acid and rock and metal tubing. Temperature has an exponential effect on the acid-rock reaction rate, and the reaction rate is extremely rapid under ultra-high temperature conditions. The thickener in the ultra-high temperature resistant acid system of this invention has a high viscosity after cross-linking, effectively slowing down the acid transfer rate and reducing the reaction rate between acid and rock. Furthermore, the cross-linked acid system has a high cross-linking density and strong shear resistance, effectively covering the metal surface and preventing contact between acid and metal. Simultaneously, the ultra-high temperature corrosion inhibitor in the system of this invention, through its double bonds and ring structures, contacts the metal via coordination bonds, forming a complex structure that isolates the acid from the metal, preventing corrosion of the metal at high temperatures. Furthermore, the surfactant in the system effectively adsorbs onto the rock surface under ultra-high temperature conditions, reducing the surface tension between water and rock and promoting the return of reacted acid to the formation.

[0051] The ultra-high temperature resistant acid system of this invention exhibits stable performance under ultra-high temperature conditions and can effectively exert a slowing effect, enabling the acid to penetrate deeper into the formation under ultra-high temperature conditions, thereby increasing the volume of the modified formation. Furthermore, the corrosion inhibitor in the ultra-high temperature resistant acid system has strong metal-reactive properties, effectively protecting the metal tubing and ensuring the safety of construction under ultra-high temperature conditions. The low surface tension surfactant in the ultra-high temperature resistant acid system allows residual acid to be quickly returned to the formation after construction, reducing reservoir damage caused by residual acid remaining in the formation.

[0052] This invention also discloses the application of an ultra-high temperature resistant acid solution system for use in the acidizing modification of ultra-high temperature reservoirs.

[0053] Preparation Example 1

[0054] A method for preparing a thickener in an ultra-high temperature acid system includes: adding 525L of water to a reaction vessel with good heat preservation performance, controlling the temperature at 10℃, adding 25kg of 2-acrylamido-2-methylpropanesulfonic acid, adding sodium hydroxide to adjust the pH to 7, then adding 150kg of acrylamide, 25kg of acrylic acid and 150kg of dimethyldodecyl(2-acrylamidoethyl)ammonium bromide, stirring at 100r / min for 10min, maintaining a nitrogen atmosphere during stirring, adding 0.25kg of sodium sulfite and 0.5kg of sodium thiosulfate, raising the water bath temperature to 30℃ and maintaining it for 2h to obtain the thickener.

[0055] Preparation Example 2

[0056] A method for preparing a thickener for an ultra-high temperature acid system includes: adding 400L of water to a reaction vessel with good heat preservation performance, controlling the temperature at 15℃, adding 12.5kg of 2-acrylamido-2-methylpropanesulfonic acid, adding sodium hydroxide to adjust the pH to 7, then adding 100kg of acrylamide, 12.5kg of acrylic acid and 75kg of dimethyldodecyl(2-acrylamidoethyl)ammonium bromide, stirring at 300r / min for 20min while maintaining a nitrogen atmosphere during stirring, adding 0.2kg of sodium sulfite and 0.5kg of sodium thiosulfate, raising the water bath temperature to 35℃ and maintaining it for 3h to obtain the thickener.

[0057] Preparation Example 3

[0058] A method for preparing a thickener for an ultra-high temperature acid system includes: adding 400L of water to a reaction vessel with good heat preservation performance, controlling the temperature at 13℃, adding 12.5kg of 2-acrylamido-2-methylpropanesulfonic acid, adding sodium hydroxide to adjust the pH to 7, then adding 87.5kg of acrylamide, 12.5kg of acrylic acid and 75kg of dimethyldodecyl(2-acrylamidoethyl)ammonium bromide, stirring at 250r / min for 15min, maintaining a nitrogen atmosphere during stirring, adding 0.3kg of sodium sulfite and 0.6kg of sodium thiosulfate, raising the water bath temperature to 33℃ and maintaining it for 2.5h to obtain the thickener.

[0059] Preparation Example 4

[0060] A method for preparing a corrosion inhibitor for ultra-high temperature acid systems includes: sequentially adding 115L of water, 40kg of small molecule alcohol (methanol: ethylene glycol = 2:1), 4kg of propargyl alcohol, 10kg of formic acid, 30kg of 1,4-bis((butyryloxy)-3-methylimidazoline)butene, and 1kg of alkyl polyoxyethylene ether to an enamel-lined reactor, and stirring at 3000r / min for 3h at room temperature to obtain the corrosion inhibitor.

[0061] Preparation Example 5

[0062] A method for preparing a corrosion inhibitor for ultra-high temperature acid systems includes: sequentially adding 44L of water, 60kg of small molecule alcohol (methanol: ethylene glycol = 2:1), 12kg of propargyl alcohol, 20kg of formic acid, 60kg of 1,4-bis((butyryloxy)-3-methylimidazoline)butene, and 4kg of alkyl polyoxyethylene ether to an enamel-lined reactor, and stirring at 3000r / min for 1h at room temperature to obtain the corrosion inhibitor.

[0063] A high-temperature resistant acid system was prepared based on the thickener and corrosion inhibitor synthesized in Examples 1-5.

[0064] Example 1

[0065] A method for preparing an ultra-high temperature resistant acid system includes: adding 95.35 kg of 12% hydrochloric acid to a reactor; using a suction pump to draw 0.4 kg of thickener from Example 1 into the reactor while stirring, controlling the suction rate to complete within 10 minutes; adding 4 kg of corrosion inhibitor, 0.1 kg of iron ion stabilizer, and 0.1 kg of 1% perfluorodecyl polyoxyethylene ether from Example 5 using a liquid addition pump while stirring, and mixing evenly; and adding 0.05 kg of complexing agent using a proportioning pump when injecting into the formation.

[0066] Example 2

[0067] A method for preparing an ultra-high temperature resistant acid system includes: adding 93.3 kg of 15% hydrochloric acid to a reactor; using a suction pump to draw 0.6 kg of thickener from Example 3 into the reactor while stirring, controlling the suction rate to complete the suction within 12 minutes; adding 5 kg of corrosion inhibitor, 0.2 kg of iron ion stabilizer, and 0.2 kg of 4% perfluorodecyl polyoxyethylene ether from Example 4 using a liquid addition pump while stirring, and mixing evenly; and adding 0.07 kg of complexing agent using a proportioning pump when injecting into the formation.

[0068] Example 3

[0069] A method for preparing an ultra-high temperature resistant acid system includes: adding 93.91 kg of 17% hydrochloric acid to a reaction vessel; using a suction pump to draw 0.5 kg of thickener from Example 2 into the vessel while stirring, controlling the suction rate to complete the suction within 14 minutes; adding 5 kg of corrosion inhibitor, 0.25 kg of iron ion stabilizer, and 0.25 kg of 3% perfluorodecyl polyoxyethylene ether from Example 5 using a liquid addition pump while stirring; mixing thoroughly; and adding 0.09 kg of complexing agent using a proportioning pump when injecting into the formation.

[0070] Example 4

[0071] A method for preparing an ultra-high temperature resistant acid system includes: adding 92.7 kg of 20% hydrochloric acid to a reactor; using a suction pump to draw 0.6 kg of thickener from Example 3 into the reactor while stirring, controlling the suction rate to complete the suction within 15 minutes; adding 6 kg of ultra-high temperature corrosion inhibitor, 0.3 kg of iron ion stabilizer, and 0.3 kg of 4% perfluorodecyl polyoxyethylene ether from Example 4 using a liquid addition pump while stirring; mixing thoroughly; and adding 0.1 kg of complexing agent using a proportioning pump when injecting into the formation.

[0072] Testing and Inspection

[0073] The corrosion rate inhibition and corrosion inhibition properties of the ultra-high temperature resistant acid systems prepared in Examples 1-4 of this invention were tested at an ultra-high temperature of 220℃ according to the standard SY-T 5886-2012 "Evaluation Method for Performance of Resistant Acids" and SYT 5405-2019 "Test Method and Evaluation Index for Performance of Corrosion Inhibitors for Acidification". The test results are shown in Table 1.

[0074] Table 1: Performance test results of the ultra-high temperature resistant acid liquid systems prepared in Examples 1-4

[0075]

[0076] As can be seen from Table 1, the surface tension, slowing rate and corrosion rate of the ultra-high temperature acid-resistant systems prepared in Examples 1-4 of this invention can all meet industry standards, and they have slowing and corrosion-inhibiting properties under ultra-high temperature conditions of 220℃.

[0077] In summary, the ultra-high temperature resistant acid system of the present invention exhibits stable performance under ultra-high temperature conditions, effectively exerts a slowing effect, enables the acid to penetrate deeper into the formation under ultra-high temperature conditions, increases the modification volume, and ensures smooth construction under ultra-high temperature conditions, guaranteeing the construction effect.

[0078] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A high-temperature resistant acid solution system, characterized in that, It includes the following raw materials in weight percentage: thickener 0.4%-0.6%, complexing agent 0.05%-0.1%, corrosion inhibitor 4%-6%, surfactant 0.1%-0.3%, stabilizer 0.1%-0.3%, and the balance is hydrochloric acid; The thickener is a copolymer of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide; the mass ratio of acrylamide:2-acrylamido-2-methylpropanesulfonic acid:acrylic acid:dimethyldodecyl(2-acrylamidoethyl)ammonium bromide is 3-4:0.5:0.5:

3. The corrosion inhibitor comprises the following raw materials in the following weight percentages: 15%-30% 1,4-bis((butyryloxy)-3-methylimidazoline)butene, 20%-30% small molecule alcohol, 2%-6% propargyl alcohol, 5%-10% formic acid, 0.5%-2% alkyl polyoxyethylene ether, and the balance being water; wherein the small molecule alcohol is a mixture of methanol and ethylene glycol, and the mass ratio of methanol to ethylene glycol is 2-5:

1.

2. The ultra-high temperature resistant acid system as described in claim 1, characterized in that: The complexing agent is an aqueous solution of chromium trichloride, the surfactant is an aqueous solution of perfluorodecyl polyoxyethylene ether, and the stabilizer is a mixture of sodium isosorbide and citric acid.

3. The ultra-high temperature resistant acid system as described in claim 1, characterized in that: The alkyl group of the alkyl polyoxyethylene ether is either octyl or decyl.

4. A method for preparing an ultra-high temperature resistant acid solution system, characterized in that, include: Thickener, corrosion inhibitor, stabilizer and surfactant were added to hydrochloric acid respectively, mixed and stirred evenly, and a complexing agent was added when injecting into the formation to obtain an ultra-high temperature resistant acid system. The ultra-high temperature resistant acid solution system comprises the following raw materials in the following weight percentages: thickener 0.4%-0.6%, complexing agent 0.05%-0.1%, corrosion inhibitor 4%-6%, surfactant 0.1%-0.3%, stabilizer 0.1%-0.3%, and the balance being hydrochloric acid; The preparation method of the thickener includes: adding 2-acrylamido-2-methylpropanesulfonic acid to water, adjusting the pH, and then sequentially adding acrylamide, acrylic acid, and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide, mixing and stirring to obtain the thickener; wherein the mass ratio of acrylamide:2-acrylamido-2-methylpropanesulfonic acid:acrylic acid:dimethyldodecyl(2-acrylamidoethyl)ammonium bromide is 3-4:0.5:0.5:3; The method for preparing the corrosion inhibitor includes: sequentially adding a small molecule alcohol, propynyl alcohol, formic acid, 1,4-bis((butyryloxy)-3-methylimidazoline)butene and alkyl polyoxyethylene ether and stirring to obtain the corrosion inhibitor; The corrosion inhibitor comprises the following raw materials in the following weight percentages: 15%-30% 1,4-bis((butyryloxy)-3-methylimidazoline)butene, 20%-30% small molecule alcohol, 2%-6% propargyl alcohol, 5%-10% formic acid, 0.5%-2% alkyl polyoxyethylene ether, and the balance being water; wherein the small molecule alcohol is a mixture of methanol and ethylene glycol, and the mass ratio of methanol to ethylene glycol is 2-5:

1.

5. The method for preparing an ultra-high temperature resistant acid system as described in claim 4, characterized in that: The preparation method of the thickener includes: adding 2-acrylamido-2-methylpropanesulfonic acid to water, adjusting the pH, then sequentially adding acrylamide, acrylic acid and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide and stirring, and after stirring, adding sodium sulfite and sodium thiosulfate to react and obtain the thickener.

6. The method for preparing an ultra-high temperature resistant acid system as described in claim 4, characterized in that: The method for preparing 1,4-bis((butyryloxy)-3-methylimidazoline)butene includes: reacting N-hydroxymethylimidazoline and acyl chloride in tetrahydrofuran, rotary evaporating to obtain the product, washing the product, adding n-hexane and 1,4-dibromobutene and stirring to react, filtering to obtain 1,4-bis((butyryloxy)-3-methylimidazoline)butene; wherein, the acyl chloride is either butyryl chloride or hexanoyl chloride.

7. The method for preparing an ultra-high temperature resistant acid system as described in claim 4, characterized in that: The alkyl group of the alkyl polyoxyethylene ether is either octyl or decyl.

8. The method for preparing an ultra-high temperature resistant acid system as described in claim 4, characterized in that: The complexing agent is an aqueous solution of chromium trichloride, the surfactant is an aqueous solution of perfluorodecyl polyoxyethylene ether, and the stabilizer is a mixture of sodium isosorbide and citric acid.

9. An application of the ultra-high temperature resistant acid system according to any one of claims 1-3, characterized in that: It was used for acidizing and modifying ultra-high temperature reservoirs.

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