Small-molecule retarder suitable for carbonate rock thermal reservoir and preparation method of small-molecule retarder

Abstract

The invention relates to a micromolecular retarder suitable for a carbonate rock thermal reservoir and a preparation method of the micromolecular retarder, and belongs to the technical field of petrochemical engineering. The micromolecular retarder is prepared from the following components in parts by mass: 0.3 to 0.7 part of polymer drag reducer, 0.8 to 1.3 parts of ionic surfactant and 0.5 to 1.5 parts of nonionic polyoxyethylene ether, the polymer drag reducer is a copolymer of dimethyl carbonate, acrylamide and diallyldimethylammonium chloride. The invention also discloses a preparation method of the micromolecular retarder. The preparation process of the micromolecular retarder is simple, raw materials are easy to obtain, substances in the reaction process belong to products, and no by-product is generated. Experiments show that the micromolecular retarder provided by the invention has good temperature resistance, acid resistance and corrosion resistance, and is sufficient to meet field requirements.

Description

Technical Field

[0001] The invention relates to an ionic surfactant and a preparation method thereof, in particular to a small molecule retarder and a preparation method thereof, especially a small molecule retarder suitable for carbonate thermal reservoirs and a preparation method thereof, belonging to the technical field of petrochemical industry. Background Art

[0002] Under the demand for energy resource security, the development of hot dry rock resources has become a key breakthrough direction for energy exploration and development at home and abroad in recent years. Carbonate hot dry rock reservoirs are rich in resources and have great development potential. The carbonate reservoir rocks have characteristics such as active chemical properties and developed natural fractures. Conventional liquid systems react quickly with them, resulting in a short acid rock action distance and difficulty in controlling the fracture height, making the effective transformation volume of acid fracturing construction small and unable to meet on-site construction conditions. Therefore, by optimizing the slow acid system to increase the acid etching action distance and increase the effective transformation volume of acid fracturing; by optimizing the acid injection process to increase the degree and length of non-uniform fracture etching, the fracture conductivity is improved.

[0003] The technical difficulties of hot dry rock reservoir acidification are: high reservoir temperature, fast acid-rock reaction speed, limited acid penetration, resulting in a short effective action distance; high reservoir temperature, serious corrosion of downhole pipes. The main reaction process of acidification includes: generating active H in the liquid phase + ; Lively H + Diffusion to the rock surface; H + Reacts with rock surfaces.

[0004] If any step of the reaction in the above process can be slowed down, the reaction rate of the acid can be effectively slowed down, the action time of the active acid can be prolonged, and the purpose of slow acid release can be achieved. The slow release mechanism of autogenous acid is to control the generation of active H + The slow release mechanism of thickened acid and encapsulated acid is to control the H + Diffusion rate; Foaming acid, active acid, and emulsified acid are obtained by controlling the active H + The reaction rate with the rock surface achieves the purpose of slow release.

[0005] In terms of technology, the pre-fluid can be injected to reduce the temperature, the displacement can be increased, alternating injection or differential acid system can be injected alternately, slow acid can be used, and the hydrogen ion mass transfer effect can be reduced. Summary of the invention

[0006] The present invention provides a small molecule retarder and a preparation method thereof to address the shortcomings of the existing retarder, such as poor heat resistance, acid resistance and corrosion resistance. The small molecule retarder suitable for carbonate hot dry rock reservoirs has a wide source of raw materials, a simple synthesis process, and low cost, and can effectively reduce the acid-rock reaction rate with a small amount.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows: A small molecule retarder suitable for carbonate thermal reservoirs, comprising, by weight, 0.3-0.7 parts (preferably 0.4-0.6 parts) of a polymer drag reducer, 0.8-1.3 parts (preferably 0.8-1.2 parts) of an ionic surfactant and 0.5-1.5 parts (preferably 0.8-1.2 parts) of a nonionic polyoxyethylene ether, wherein the polymer drag reducer is a copolymer of dimethyl carbonate (DMC), acrylamide (AM) and diallyldimethylammonium chloride (DMDAAC).

[0008] Furthermore, the small molecule retarder suitable for carbonate thermal reservoirs is composed of 0.5 parts of polymer drag reducer, 1 part of ionic surfactant and 1 part of non-ionic polyoxyethylene ether in terms of mass fractions.

[0009] Furthermore, the ionic surfactant can be selected from a variety of options, such as erucic acid amide propyl alkyl sulfonyl betaine, erucic acid acyl propyl dimethyl betaine, quaternary ammonium salt gemini surfactant N , N '- Dihexadecyldimethyl-1,4-p-phenylenedimethylammonium chloride and quaternary ammonium salt Gemini surfactant N , N '- One or more of bis-erucic acid amide propyl dimethyl-1,4-diphenyl dimethyl ammonium chloride salt, etc. Taking erucic acid amide propyl alkyl sulfonyl betaine as an example, it is composed of epichlorohydrin, sodium bisulfite, erucic acid and N,N - It is prepared from dimethyl-1,3-propylenediamine.

[0010] Furthermore, the nonionic polyoxyethylene ether is emulsifier OP-10.

[0011] Furthermore, the small molecule retarder suitable for carbonate thermal reservoirs is a solution dissolved in a 15wt.% to 25wt.% HCl solution, wherein the mass percentage of the polymer drag reducer is 0.3% to 0.7%, the mass percentage of the ionic surfactant is 0.8% to 1.3%, preferably 0.8% to 1.2%, and the mass percentage of the nonionic polyoxyethylene ether is 0.5% to 1.5%, preferably 0.8% to 1.2%.

[0012] Furthermore, the small molecule retarder suitable for carbonate thermal reservoirs is a solution dissolved in a 20wt.% HCl solution, wherein the mass percentage of the polymer drag reducer is 0.5%, the mass percentage of the ionic surfactant is 1%, and the mass percentage of the non-ionic polyoxyethylene ether is 1%.

[0013] A method for preparing a small molecule retarder suitable for carbonate thermal reservoirs comprises the following steps: preparing a 15wt.% to 25wt.% HCl solution, dissolving 0.3wt.% to 0.7wt.%, preferably 0.4wt.% to 0.6wt.%, a polymer drag reducer, 0.8% to 1.3%, preferably 0.8wt.% to 1.2wt.%, an ionic surfactant, and 0.5% to 1.5%, preferably 0.8wt.% to 1.2wt.%, a nonionic polyoxyethylene ether into the HCl solution.

[0014] An application of a small molecule retarder suitable for carbonate thermal reservoirs comprises the following steps: (1) For a regular rectangular marble, the surface area of ​​the marble is: the volume of hydrochloric acid = 1 cm 2 :4cm 3 Prepare a 15wt.% to 25wt.% HCl solution, dissolve 0.3wt.% to 0.7wt.%, preferably 0.4wt.% to 0.6wt.% of a polymer drag reducer, 0.8wt.% to 1.3%, preferably 0.8wt.% to 1.2wt.% of an ionic surfactant, and 0.5% to 1.5%, preferably 0.8wt.% to 1.2wt.% of a nonionic polyoxyethylene ether (op-10) in the 15wt.% to 25wt.% HCl solution prepared above; (2) Heat the solution in a water bath at 80°C to 100°C for half an hour and then add the marble. Take out the marble every 5 minutes and measure its weight and surface area until the 30th to 60th minute. Draw the acid-rock reaction rate change graph and slow rate change graph based on the data.

[0015] A preparation method of a polymer drag reducer comprises the following steps: adding water to prepare an aqueous solution of DMC, AM and DMDAAC in a mass ratio of (5-7): (2.5-3.5): (0.6-1.4), adjusting the pH value of the solution to 5-6, adding an azoamidine initiator, sealing the solution and introducing nitrogen, sealing the solution again and placing the solution in a constant temperature water bath until the solution is polymerized into a gel block, thereby obtaining a copolymer of DMC (dimethyl carbonate), AM (acrylamide) and DMDAAC (diallyldimethylammonium chloride).

[0016] Furthermore, the azo amidine initiator is V50 initiator (azobisisobutylamidine hydrochloride), and the added amount of the initiator is 0.8wt.%~1.2wt.%.

[0017] Furthermore, the solid content of the DMC, AM and DMDAAC aqueous solutions is 45 wt.%~55 wt.%, the pH value of the solution is adjusted to 5~6 using NaOH and acrylic acid, the solution is sealed, nitrogen is introduced for 20~40 minutes, and then sealed again and placed in a constant temperature water bath at 40℃~50℃ for 4~12 hours.

[0018] An ionic surfactant, specifically a method for preparing erucic acid amide propyl alkyl sulfobetaine, has a specific structural formula as follows:

[0019] The specific preparation process of the ionic surfactant is as follows: (1) Synthesis reaction of intermediate 3-chloro-2-alkylpropyl sodium sulfonate:

[0020] (2) Synthesis reaction of erucic acid amide propyl dimethylamine:

[0021] The specific preparation method of the ionic surfactant comprises the following steps: (1) Add sodium bisulfite to a three-necked flask equipped with a condenser and a stirrer, dissolve it with an appropriate amount of water, heat it, and slowly drop epichlorohydrin at a molar ratio of n(sodium bisulfite):n(epichlorohydrin)=(0.5~1.5):(0.5~1.5). After the reaction, let it stand until white crystals of sodium 3-chloro-2-hydroxypropanesulfonate precipitate. Filter it with suction, dry it, and set it aside; (2) Add erucic acid and N,N-dimethyl-1,3-propylenediamine in a certain proportion to a four-necked flask equipped with a condenser, a stirrer and a temperature measuring device, use boric acid as a catalyst, introduce nitrogen, and react at high temperature; evaporate the excess N,N-dimethyl-1,3-propylenediamine under reduced pressure, and the crude product is a brown solid, which is recrystallized from ethanol to obtain relatively pure erucic acid amide propyl dimethylamine; (3) The erucamidopropyl dimethylamine obtained in step (2) and the sodium 3-chloro-2-hydroxypropanesulfonate obtained in step (1) are stirred in a mixed solvent of ethanol and water, and reacted at a certain temperature. When the solution becomes viscous, additional solvent is added to maintain the pH at an alkaline level. The reaction is terminated when the pH remains unchanged. An appropriate amount of sample is dissolved in isopropanol, and titrated with a calibrated hydrochloric acid-isopropanol solution using bromophenol blue as an indicator. When the solution changes from blue to yellow, it is the end point, and the amount of unreacted tertiary amine can be calculated, and then the yield of betaine can be calculated. The mixture is dried in vacuum, the solvent is evaporated, and recrystallized repeatedly with ethanol to obtain erucamidopropyl hydroxysulfobetaine.

[0022] In step (1), sodium bisulfite is dissolved in water at a concentration of 35wt.% to 45wt.%; the heating temperature is 40°C to 50°C; the reaction time is 3 to 5 hours, and the standing time is 2 to 3 hours.

[0023] In step (2), the molar ratio of erucic acid to N,N-dimethyl-1,3-propylenediamine is (0.5-1.5):(0.5-1.5); the amount of boric acid catalyst added is 5wt.%-10wt.%. The temperature of the high temperature reaction is 140-180°C, and the reaction time is 6-10h.

[0024] In step (3), the molar ratio of erucic acid amide propyl dimethylamine to sodium 3-chloro-2-hydroxypropane sulfonate is (0.5-1.5):(0.5-1.5); the volume ratio of ethanol to water in the mixed solvent is (0.5-1.5):(1.5-2.5); the reaction is carried out at 60-90° C. for 4-8 hours; and the number of recrystallizations is 2-4 times.

[0025] The present invention has the following beneficial effects: (1) The preparation process of the small molecule retarder of the present invention is simple, the raw materials are easy to obtain, and the substances in the reaction process are all products without any by-products; (2) The small molecule retarder of the present invention has good heat resistance, acid resistance and corrosion resistance, and its retarding capacity meets the on-site requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a graph showing the reaction rate test results of polymer drag reducer + erucic acid amide propyl hydroxysulfobetaine + OP-10 in Example 1; FIG2 is a graph showing the test results of the slowing rate of polymer drag reducer + erucic acid amide propyl hydroxysulfobetaine + OP-10 in Example 1; FIG3 is a graph showing the reaction rate test results of Example 2 polymer drag reducer + erucic acid acylopropyl dimethyl betaine + OP-10; FIG4 is a graph showing the test results of the slowing rate of polymer drag reducer + erucic acid acylopropyl dimethyl betaine + OP-10 in Example 2; 5 is a graph showing the reaction rate test results of Example 3 of polymer drag reducer + quaternary ammonium salt Gemini surfactant N,N'-dihexadecyl dimethyl-1,4-p-phenylenedimethyl ammonium chloride salt + OP-10; Figure 6 This is a graph showing the test results of the slowing rate of the polymer drag reducer + quaternary ammonium salt Gemini surfactant N,N'-dihexadecyl dimethyl-1,4-p-phenylenedimethyl ammonium chloride salt + OP-10 of Example 3; 7 is a graph showing the reaction rate test results of Example 4 of polymer drag reducer + quaternary ammonium salt Gemini surfactant N,N'-biserucic acid amide propyl dimethyl-1,4-p-phenylenedimethyl ammonium chloride salt + OP-10; Figure 8 This is a graph showing the test results of the drag reduction rate of the polymer drag reducer of Example 4 + quaternary ammonium salt Gemini surfactant N,N'-biserucic acid amide propyl dimethyl-1,4-p-phenylenedimethyl ammonium chloride salt + OP-10. DETAILED DESCRIPTION

[0027] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0028] A small molecule retarder, a new type of small molecule retarder composed of a polymer drag reducer (DMC, AM, DMDAAC copolymer), an ionic surfactant and a nonionic polyoxyethylene ether (emulsifier OP-10). There are many options for the ionic surfactant in the preparation of the small molecule retarder, such as erucic acid amide propyl alkyl sulfonyl betaine, erucic acid acyl propyl dimethyl betaine, quaternary ammonium salt gemini surfactant N , N '- Dihexadecyl dimethyl-1,4-p-phenylenedimethyl ammonium chloride, quaternary ammonium salt Gemini surfactant N , N '- Bis-erucic acid amide propyl dimethyl-1,4-diphenyl dimethyl ammonium chloride, etc. Taking erucic acid amide propyl alkyl sulfobetaine as an example, it is composed of epichlorohydrin, sodium bisulfite, erucic acid and N,N - It is prepared from dimethyl-1,3-propylenediamine.

[0029] A method for synthesizing a small molecule retarder comprises the following steps: (1) DMC, AM, and DDAAC were added to an aqueous solution at a mass ratio of 6:3:1 and a solid content of 50%. The pH of the solution was adjusted to 5-6 using NaOH and acrylic acid. 1% V50 initiator was added. The solution was sealed and nitrogen was introduced for half an hour. After being sealed again, it was placed in a constant temperature water bath for 4-12 hours until it was polymerized into a gel block to obtain a polymer drag reducer. (2) Add sodium bisulfite to a three-necked flask equipped with a condenser and a stirrer, and dissolve it with an appropriate amount of water. When the temperature rises to 50°C, slowly add an appropriate amount of epichlorohydrin according to the ratio of n (sodium bisulfite): n (epichlorohydrin) = 1:1, react for 3-5 hours, let stand for 2-3 hours, and white crystals will precipitate. Filter, dry and set aside; (3) Add a certain amount of erucic acid and N,N-dimethyl-1,3-propylenediamine in a certain proportion to a four-necked flask equipped with a condenser, a stirrer and a temperature measuring device, use boric acid as a catalyst, introduce nitrogen, and react at 140-180°C for 6-10 hours; evaporate the excess N,N-dimethyl-1,3-propylenediamine under reduced pressure, and the crude product is a brown solid, which is recrystallized from ethanol to obtain relatively pure erucic acid amide propyl dimethylamine; (4) Stir erucic acid amidopropyl dimethylamine and sodium 3-chloro-2-hydroxypropanesulfonate in a mixed solvent of ethanol and water in a volume ratio of 1:2, and react at 60-90°C for 4-8 hours. When the solution becomes viscous, add solvent to keep the pH alkaline. The reaction ends when the pH remains unchanged. Take an appropriate amount of sample and dissolve it in isopropanol. Use bromophenol blue as an indicator and titrate with a calibrated hydrochloric acid-isopropanol solution. When the solution changes from blue to yellow, it is the end point. The amount of unreacted tertiary amine can be calculated, and then the yield of betaine can be calculated. Vacuum dry, evaporate the solvent, and repeatedly recrystallize with ethanol for 3 times to obtain erucic acid amidopropyl hydroxysulfobetaine. (5) Prepare a regular rectangular marble. The surface area of ​​the marble is: the volume of hydrochloric acid = 1 cm 2 : 4cm 3 Prepare a 20% HCl solution, dissolve 0.5% polymer drag reducer, 1% ionic surfactant (erucic acid amide propyl hydroxysulfobetaine), and 1% non-ionic polyoxyethylene ether (OP-10) in the previously prepared 20% HCl solution; heat the solution in a 90℃ water bath for half an hour and then put the marble in, then take out the rock every 5 minutes and measure its weight and surface area until the 30th minute; draw the acid-rock reaction rate change graph and the slow rate change graph based on the data.

[0030] Embodiment 1: The preparation method of the small molecule retarder of this embodiment comprises: Preparation of polymer drag reducer: DMC, AM, and DMDAAC were added to an aqueous solution at a mass ratio of 6:3:1 and a solid content of 50 wt.%, and the pH of the solution was adjusted to 5.31 using NaOH and acrylic acid. 1 wt.% of V50 initiator was added, and the solution was sealed and nitrogen was introduced for half an hour. After being sealed again, it was placed in a constant temperature water bath at 40°C for 8 hours, and polymerized into a gel block and taken out.

[0031] Add sodium bisulfite to a three-necked flask equipped with a condenser and a stirrer, dissolve it with appropriate amount of water, and when the temperature rises to 50°C, slowly add epichlorohydrin dropwise at a molar ratio of n (sodium bisulfite): n (epichlorohydrin) = 1:1, react for 4 hours, let stand for 2 hours, white crystals will precipitate, filter, dry and set aside.

[0032] Add erucic acid and N,N-dimethyl-1,3-propylenediamine in a molar ratio of 1:1 to a four-necked flask equipped with a condenser, a stirrer and a temperature measuring device, use 5wt.% boric acid as a catalyst, introduce nitrogen, and react at 160°C for 8h. Distill off the excess N,N-dimethyl-1,3-propylenediamine under reduced pressure, and the crude product is a brown solid, which is recrystallized from ethanol to obtain relatively pure erucic acid amide propyl dimethylamine.

[0033] The molar ratio of 1:1 erucic acid amidopropyl dimethylamine and sodium 3-chloro-2-hydroxypropanesulfonate was stirred back in a mixed solvent of ethanol and water in a volume ratio of 1:2, and reacted at 70°C for 6 hours. When the solution became viscous, additional solvent was added to keep the pH alkaline. The reaction was terminated when the pH remained unchanged. Take an appropriate amount of sample and dissolve it in isopropanol. Use bromophenol blue as an indicator and titrate with a calibrated hydrochloric acid-isopropanol solution. When the solution changes from blue to yellow, it is the end point. The amount of unreacted tertiary amine can be calculated, and then the yield of betaine can be calculated. Vacuum drying, evaporate the solvent, and repeatedly recrystallize with ethanol for 3 times to obtain erucic acid amidopropyl hydroxysulfobetaine.

[0034] Prepare a regular rectangular marble and measure its surface area to be 31.96 mm 2 , prepare 127.84 ml of 20 wt.% HCl solution, dissolve 0.5 wt.% polymer drag reducer, 1 wt.% ionic surfactant (erucic acid amide propyl hydroxysulfonyl betaine), and 1 wt.% non-ionic polyoxyethylene ether (op-10) in the previously prepared 20 wt.% HCl solution. Heat the solution in a 90°C water bath for half an hour and then put the marble in. After that, take out the rock every 5 minutes and measure its weight and surface area until the 30th minute. Draw the acid-rock reaction rate change graph and slow rate change graph based on the data, as shown in the figure. Figure 1-2 As shown, the reaction rate at the fifth minute was 2.06 g / (m 2 · s), the slowdown rate is 92.22%.

[0035] Embodiment 2: The preparation method of the small molecule retarder of this embodiment comprises: DMC, AM, and DMDAAC were added to the aqueous solution at a mass ratio of 6:3:1 and a solid content of 50 wt.%, and the pH of the solution was adjusted to 5.48 using NaOH and acrylic acid. 1 wt.% of V50 initiator was added, and the solution was sealed and nitrogen was passed through for half an hour. After being sealed again, it was placed in a constant temperature water bath at 45°C for 10 hours and polymerized into a gel block and taken out.

[0036] Add erucic acid and N,N-dimethyl-1,3-propanediamine in a molar ratio of 0.5:1 to a four-necked flask equipped with a condenser, a stirrer and a temperature measuring device, use boric acid (5wt.%) as a catalyst, introduce nitrogen, and react at 160°C for 8h. Distill off the excess N,N-dimethyl-1,3-propanediamine under reduced pressure, and the crude product is a brown solid, which is recrystallized from ethanol to obtain relatively pure erucic acid amide propyl dimethylamine.

[0037] Add erucamidopropyl dimethylamine in a molar ratio of 0.8:0.6 and an appropriate amount of isopropanol into a three-necked flask, stir and heat, add a 30 wt.% sodium chloroacetate buffer solution in portions, so that the molar ratio of erucamidopropyl dimethylamine and sodium chloroacetate solution is 1:1.05, reflux reaction, and after completion, a high-purity erucamidopropyl dimethyl betaine surfactant is obtained.

[0038] Prepare a regular rectangular marble with a surface area of ​​31.45mm 2 , prepare 125.8 ml of 20 wt.% HCl solution, dissolve 0.5 wt.% polymer drag reducer, 1 wt.% ionic surfactant (erucic acid amide propyl dimethyl betaine), and 1 wt.% non-ionic polyoxyethylene ether (op-10) in the previously prepared 20 wt.% HCl solution. Heat the solution in a 90°C water bath for half an hour and then put the marble in. After that, take out the rock every 5 minutes and measure its weight and surface area until the 30th minute. Draw the acid-rock reaction rate change graph and slow rate change graph based on the data, as shown in the figure. Figure 3-4 As shown, the reaction rate at the fifth minute was 3.01 g / (m 2 · s), the slowdown rate is 88.35%.

[0039] Embodiment 3: The preparation method of the small molecule retarder of this embodiment comprises: DMC, AM, and DMDAAC were added to the aqueous solution at a mass ratio of 6:3:1 and a solid content of 50 wt.%, and the pH of the solution was adjusted to 5.33 using NaOH and acrylic acid. 1 wt.% of V50 initiator was added, and the solution was sealed and nitrogen was passed through for half an hour. After being sealed again, it was placed in a constant temperature water bath at 50°C for 11 hours and polymerized into a gel block and taken out.

[0040] 1,4-dichlorobenzyl and hexadecyl dimethyl tertiary amine were placed in a round-bottom flask at a molar ratio of 1:2, and ethanol solvent was added to make the solid content 50 wt.%, and a rotor was placed. The flask was placed in an oil bath, a condenser was connected, and a certain speed was adjusted, and the temperature was set to 80°C, and it was kept for 8 hours before being taken out. Rotary evaporation was performed for another 2 hours. When the liquid could not be evaporated by rotary evaporation, an appropriate amount of acetone was added to dissolve for 6 hours, the acetone was poured out, and rotary evaporation was continued to obtain the quaternary ammonium gemini surfactant N,N'-dihexadecyl dimethyl-1,4-diphenyl dimethyl ammonium chloride salt.

[0041] Prepare a regular rectangular marble with a surface area of ​​31.11mm 2 , prepare 124.44 ml of 20 wt.% HCl solution, dissolve 0.5 wt.% polymer drag reducer, 1 wt.% ionic surfactant (quaternary ammonium gemini surfactant N,N'-bis-hexadecyl dimethyl-1,4-p-phenylenedimethyl ammonium chloride salt), and 1 wt.% non-ionic polyoxyethylene ether (op-10) in the previously prepared 20 wt.% HCl solution. Heat the solution in a 90°C water bath for half an hour and then put the marble in. After that, take out the rock every 5 minutes and measure its weight and surface area until the 30th minute. Draw the acid-rock reaction rate change graph and slow rate change graph based on the data, as shown in the figure. Figure 5-6 As shown, the reaction rate at the fifth minute was 4.52 g / (m 2 · s), the slowdown rate is 84.11%.

[0042] Embodiment 4: The preparation method of the small molecule retarder of this embodiment comprises: DMC, AM, and DMDAAC were added to the aqueous solution at a mass ratio of 6:3:1 and a solid content of 50 wt.%, and the pH of the solution was adjusted to 5.23 using NaOH and acrylic acid. 1 wt.% of V50 initiator was added, and the solution was sealed and nitrogen was passed through for half an hour. After being sealed again, it was placed in a constant temperature water bath at 48°C for 12 hours and polymerized into a gel block and taken out.

[0043] 1,4-dichlorobenzyl and erucic acid amide propyl dimethyl tertiary amine were placed in a round-bottom flask at a molar ratio of 1:2, and ethanol solvent was added to make the solid content 50 wt.%, and a rotor was placed. The flask was placed in an oil bath, a condenser was connected, and a certain speed was adjusted, and the temperature was set to 80°C, and it was kept for 8 hours before being taken out. Rotary evaporation was performed for another 2 hours. When the liquid could not be evaporated by rotary evaporation, an appropriate amount of acetone was added to dissolve for 6 hours, the acetone was poured out, and rotary evaporation was continued to obtain the quaternary ammonium gemini surfactant N,N'-biserucic acid amide propyl dimethyl-1,4-p-phenylenedimethyl ammonium chloride salt.

[0044] Prepare a regular rectangular marble with a surface area of ​​33.19 mm2 , prepare 132.76 ml of 20 wt.% HCl solution, dissolve 0.5 wt.% polymer drag reducer, 1 wt.% ionic surfactant (quaternary ammonium gemini surfactant), and 1 wt.% non-ionic polyoxyethylene ether (op-10) in the previously prepared 20 wt.% HCl. Heat the solution in a 90°C water bath for half an hour and then add marble. After that, take out the rock every 5 minutes and measure its weight and surface area until the 30th minute. Draw the acid-rock reaction rate change graph and slow rate change graph based on the data, as shown in the figure. Figure 7-8 As shown, the reaction rate at the fifth minute is 3.68 g / (m 2 · s), the slowdown rate is 87.21%.

[0045] The small molecule retarder of the present invention is a novel small molecule retarder composed of a polymer drag reducer (DMC, AM, DMDAAC copolymer), an ionic surfactant and a nonionic polyoxyethylene ether (emulsifier OP-10). There are many choices of ionic surfactants in the preparation of small molecule retarder, such as erucic acid amide propyl alkyl sulfonyl betaine, erucic acid acyl propyl dimethyl betaine, quaternary ammonium salt gemini surfactant N, N'-bis-hexadecyl dimethyl-1,4-p-phenylenedimethyl ammonium chloride salt, quaternary ammonium salt gemini surfactant N, N'-bis-erucic acid amide propyl dimethyl-1,4-p-phenylenedimethyl ammonium chloride salt, etc. Experiments show that the small molecule retarder provided by the present invention has good temperature resistance, acid resistance and corrosion resistance, which is sufficient to meet the needs of the site.

Claims

1. A small molecule retarder suitable for carbonate thermal reservoirs, characterized in that: According to the weight percentage, it is composed of 0.3-0.7 parts of polymer drag reducer, 0.8-1.3 parts of ionic surfactant and 0.5-1.5 parts of non-ionic polyoxyethylene ether; the polymer drag reducer is a copolymer of dimethyl carbonate, acrylamide and diallyldimethylammonium chloride.

2. The small molecule retarder suitable for carbonate thermal reservoir according to claim 1, characterized in that: The ionic surfactants are erucic acid amide propyl alkyl sulfonyl betaine, erucic acid acyl propyl dimethyl betaine, quaternary ammonium salt gemini surfactant N , N '- Dihexadecyldimethyl-1,4-p-phenylenedimethylammonium chloride and quaternary ammonium salt Gemini surfactant N , N '- One or more of biserucic acid amide propyl dimethyl-1,4-p-phenylenedimethyl ammonium chloride salt; the non-ionic polyoxyethylene ether is emulsifier OP-10.

3. The small molecule retarder suitable for carbonate thermal reservoir according to claim 1, characterized in that: The small molecule retarder is a solution dissolved in a 15wt.% to 25wt.% HCl solution, the mass percentage of the polymer drag reducer is 0.3% to 0.7%, the mass percentage of the ionic surfactant is 0.8% to 1.3%, and the mass percentage of the nonionic polyoxyethylene ether is 0.5% to 1.5%.

4. The method for preparing a small molecule retarder suitable for carbonate thermal reservoir according to claim 1 or 2, comprising the following steps: A 15wt.% to 25wt.% HCl solution is prepared, and 0.3wt.% to 0.7wt.% of a polymer drag reducer, 0.8wt.% to 1.3wt.% of an ionic surfactant, and 0.5wt.% to 1.5wt.% of a nonionic polyoxyethylene ether are dissolved in the HCl solution.

5. The use of the small molecule retarder suitable for carbonate thermal reservoir according to claim 1 or 2, comprising the following steps: (1) For a regular rectangular marble, the surface area of ​​the marble is: the volume of hydrochloric acid = 1 cm 2 :4cm 3 Prepare a 15wt.% to 25wt.% HCl solution, dissolve 0.3wt.% to 0.7wt.% of a polymer drag reducer, 0.8wt.% to 1.3wt.% of an ionic surfactant, and 0.5wt.% to 1.5wt.% of a nonionic polyoxyethylene ether in the HCl solution; (2) Heat the solution in a water bath at 80°C to 100°C for half an hour and then add the marble. Take out the marble every 5 minutes and measure its weight and surface area until the 30th to 60th minute. Draw the acid-rock reaction rate change graph and slow rate change graph based on the data.

6. A method for preparing a polymer drag reducer, comprising the following steps: Dimethyl carbonate, acrylamide and diallyldimethylammonium chloride are added with water in a mass ratio of 5-7:2.5-3.5:0.6-1.4 to prepare an aqueous solution, the pH value of the solution is adjusted to 5-6, an azoamidine initiator is added, nitrogen is introduced into the solution after sealing, and the solution is sealed again and placed in a constant temperature water bath until polymerized into a gel block; a copolymer of dimethyl carbonate, acrylamide and diallyldimethylammonium chloride is obtained.

7. The method for preparing a polymer drag reducer according to claim 6, characterized in that: The azo amidine initiator is V50 initiator, and the added amount of the initiator is 0.8wt.%~1.2wt.%; the solid content of the aqueous solution of dimethyl carbonate, acrylamide and diallyldimethylammonium chloride is 45wt.%~55wt.%, and the pH value of the solution is adjusted to 5~6 by using NaOH and acrylic acid. After the solution is sealed, nitrogen is introduced for 20~40 minutes, and after being sealed again, it is placed in a constant temperature water bath at 40℃~50℃ for 4~12 hours.

8. A method for preparing an ionic surfactant, comprising the following steps: (1) Add sodium bisulfite to a three-necked flask equipped with a condenser and a stirrer, dissolve it with an appropriate amount of water, heat it, and slowly drop epichlorohydrin at a molar ratio of sodium bisulfite:epichlorohydrin = 0.5~1.5:0.5~1.

5. After the reaction, let it stand until white crystals of sodium 3-chloro-2-hydroxypropanesulfonate precipitate. Filter it with suction, dry it, and set it aside; (2) Add erucic acid and N,N-dimethyl-1,3-propylenediamine in a certain proportion to a four-necked flask equipped with a condenser, a stirrer and a temperature measuring device, use boric acid as a catalyst, introduce nitrogen, and react at high temperature; evaporate the excess N,N-dimethyl-1,3-propylenediamine under reduced pressure, and the crude product is a brown solid, which is recrystallized from ethanol to obtain relatively pure erucic acid amide propyl dimethylamine; (3) The erucamidopropyl dimethylamine obtained in step (2) and the sodium 3-chloro-2-hydroxypropanesulfonate obtained in step (1) are stirred in a mixed solvent of ethanol and water, and reacted at a certain temperature. When the solution becomes viscous, additional solvent is added to maintain the pH at an alkaline level. The reaction is terminated when the pH remains unchanged. An appropriate amount of sample is dissolved in isopropanol, and titrated with a calibrated hydrochloric acid-isopropanol solution using bromophenol blue as an indicator. When the solution changes from blue to yellow, it is the end point, and the amount of unreacted tertiary amine can be calculated, and then the yield of betaine can be calculated. The mixture is dried in vacuum, the solvent is evaporated, and recrystallized repeatedly with ethanol to obtain erucamidopropyl hydroxysulfobetaine.

9. The method for preparing the ionic surfactant according to claim 8, characterized in that: Sodium bisulfite is dissolved in water with a concentration of 35wt.%~45wt.%; the heating temperature is 40℃~50℃; the reaction time is 3~5h, and the standing time is 2~3h; the molar ratio of erucic acid to N,N-dimethyl-1,3-propylenediamine is 0.5~1.5:0.5~1.5; the amount of catalyst boric acid added is 5wt.%~10wt.%; the temperature of the high-temperature reaction is 140~180℃, and the reaction time is 6~10h.

10. The method for preparing an ionic surfactant according to claim 8, characterized in that: The molar ratio of erucic acid amide propyl dimethylamine to sodium 3-chloro-2-hydroxypropane sulfonate is 0.5-1.5:0.5-1.5; in the mixed solvent, the volume ratio of ethanol to water is 0.5-1.5:1.5-2.5; the reaction is carried out at 60-90° C. for 4-8 hours; and the number of recrystallizations is 2-4 times.

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