A kind of self-generated acidic slippery water and its preparation method and application

Abstract

The invention discloses a self-generated acidic slick water and a preparation method and application thereof, belonging to the technical field of acidic slick water preparation. The invention firstly performs an acyl chloride reaction on sorbic acid to obtain an intermediate product I, thereby increasing the reaction activity of the carboxyl group of sorbic acid, then performs an esterification reaction on the intermediate product I and hydroxyethyl acrylate to obtain an intermediate product II, and finally performs a polymerization reaction on the intermediate product II and acrylamide to obtain a polyacrylamide drag reducer, and uniformly mixes the polyacrylamide drag reducer with a clay stabilizer, a drainage aid and an appropriate amount of water to obtain a self-generated acidic slick water; the self-generated acidic slick water generates two alkyl free radicals by breaking the carbon-carbon double bond of the polyacrylamide drag reducer under the action of an oxidant, hydrogen peroxide, so that the side chain of the polyacrylamide drag reducer becomes shorter, and the alkyl free radicals react with the oxidant to release oxalic acid, and the released oxalic acid consolidates the cracks, providing conditions for the retention of the cracks after pressure relief.

Description

Technical Field

[0001] The invention belongs to the technical field of acidic slick water preparation, and in particular relates to self-generated acidic slick water and a preparation method and application thereof. Background Art

[0002] At present, unconventional oil and gas reservoirs account for a large proportion of resource reserves and have rich resource potential. However, due to the difficulty of exploitation, a large amount of resources cannot be utilized. With the continuous expansion of oil resource demand, the exploration and development of unconventional oil and gas layers is imminent. Therefore, it is necessary to improve fracturing technology to form good fracture conductivity to achieve increased production of oil and gas fields. The application of slick water fracturing fluid began when early researchers found that its friction resistance was too high when using clean water for fracturing. Subsequently, it was rapidly developed due to its excellent application effect in shale gas development. As the core component of slick water fracturing fluid, drag reducer plays a key role in alleviating construction friction and is also a key factor in determining the success of slick water exploitation.

[0003] Polymer drag reducers are the most commonly used type at present. Among them, polyacrylamide drag reducers have more amide groups on the polymer molecular chain. The amide groups are easily hydrolyzed, have good water solubility, and the reaction conditions are controllable. Therefore, a large number of scholars have optimized the performance of drag reducers by modifying polyacrylamide. For calcareous rock reservoir types, conventional slickwater drag reducers have a significant decrease in viscosity and precipitation under high mineralization and acidic conditions. Some scholars have studied the effect of adding hydrochloric acid to the slickwater system on rock mechanics and dissolution pores, proving that adding hydrochloric acid can effectively improve the pore structure of the rock core and effectively improve the conductivity of the supported fractures. However, the addition of hydrochloric acid will react quickly with carbonates, and the action time is short, which cannot achieve the purpose of long-term fracture retention and affects the fracturing effect. Summary of the invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a self-generated acidic slickwater and a preparation method and application thereof, so as to solve the problem in the prior art that the slickwater drag reducer directly adds acid, which directly reacts with carbonates, has a short action time, and cannot keep the cracks for a long time.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention discloses a method for preparing autogenous acidic slick water, comprising the following steps:

[0007] S1, mix sorbic acid, thionyl chloride and ethanol, stir and heat to 65 o C-75 oC for heat preservation reaction to form a reaction system, cooling the reaction system to room temperature, evaporating to obtain intermediate product I; mixing intermediate product I, triethylamine and hydroxyethyl acrylate with stirring to react to obtain intermediate product II, and dissolving intermediate product II, OP-10 and sodium dodecyl sulfate in white oil to obtain an oil phase;

[0008] The structural formula of the intermediate product I is:

[0009]

[0010] The structural formula of the intermediate product II is:

[0011]

[0012] S2, mixing acrylamide and water and adding tert-butyl hydroperoxide to obtain an aqueous phase;

[0013] S3, after mixing the oil phase and the water phase to obtain a mixed system, the pH value of the mixed system is adjusted to 6-8, sodium metabisulfite is added dropwise, and the mixture is first reacted at room temperature, and then heated at 60 o C-75 o C reaction to obtain a polyacrylamide drag reducer;

[0014] S4, mixing the polyacrylamide drag reducer, the clay stabilizer and the drainage aid in water, and stirring to obtain autogenous acidic slippery water.

[0015] Preferably, in S1, the mixing mass ratio of sorbic acid to ethanol is 1:(1-3), and 50-100 mL of thionyl chloride is added for every 20 g of sorbic acid. The mixing ratio of sorbic acid, ethanol and thionyl chloride is controlled to promote the chlorination reaction of sorbic acid and thionyl chloride while ensuring that sorbic acid is fully dissolved.

[0016] Preferably, in S1, the mass ratio of intermediate product I, triethylamine and hydroxyethyl acrylate is 1:(0.2-0.5):(0.2-0.5); by controlling the amount of intermediate product I, triethylamine and hydroxyethyl acrylate, the esterification reaction can be carried out.

[0017] Preferably, in S1, the mass ratio of the intermediate product II and the white oil is (1-1.5):15; the mass ratio of the OP-10 and the sodium dodecyl sulfate is (1-1.2):3, and the total mass of OP-10 and the sodium dodecyl sulfate is 1%-2% of the total mass of the intermediate product II and the white oil; by limiting the amount of each substance, it is ensured that the intermediate product II can be dissolved in the white oil under the action of dodecylphenol polyoxyethylene ether (OP-10) and sodium dodecyl sulfate to obtain an oil phase.

[0018] Preferably, in S2, the mixing mass ratio of acrylamide to water is 1:(15-20); the amount of tert-butyl hydroperoxide added is 0.5%-1% of the total mass of acrylamide and water. Acrylamide is dissolved in water, tert-butyl hydroperoxide is added thereto, and the mixture is mixed to form a water phase, in preparation for the next step of reaction with the oil phase.

[0019] Preferably, in S3, the mixing mass ratio of the oil phase to the water phase is 1:(1.5-3), and the amount of sodium metabisulfite added is 1%-2% of the mass of the water phase. The amount of the oil phase and the water phase is limited to ensure that the polymerization reaction can generate the target product.

[0020] Preferably, in S3, the reaction time at room temperature is 2h-4h, and the heating reaction temperature is 60 o C-75 o C, and the heating time is 6h-8h. By limiting the reaction temperature and reaction time of the polyacrylamide drag reducer, it is ensured that the oil phase and the water phase can fully react to form the polyacrylamide drag reducer.

[0021] The invention discloses an autogenous acidic slick water prepared by any one of the preparation methods mentioned above, comprising, by mass percentage, 0.2%-2.0% of polyacrylamide drag reducer, 0.4%-0.8% of clay stabilizer and 0.2%-0.5% of drainage aid, and the balance is water.

[0022] An application of the above-mentioned self-generated acidic slick water, when the self-generated acidic slick water is used, it is added to the formation together with hydrogen peroxide. When the temperature is above 80°C, the polyacrylamide drag reducer in the self-generated acidic slick water reacts with the hydrogen peroxide to release oxalic acid.

[0023] Preferably, when the self-generated acidic slippery water is used, the amount of hydrogen peroxide added is 0.5%-1% of the mass of the polyacrylamide drag reducer. When the self-generated acidic slippery water is used, controlling the amount of hydrogen peroxide added can ensure that at a certain reaction temperature, the hydrogen peroxide and the polyacrylamide drag reducer react to release oxalic acid.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The invention discloses a method for preparing authigenic acidic slick water, firstly, sorbic acid is subjected to chlorination reaction to obtain intermediate product I, the reaction activity of sorbic acid carboxyl group is increased, then esterification reaction is carried out with hydroxyethyl acrylate to obtain intermediate product II, finally intermediate product II is subjected to polymerization reaction with acrylamide to obtain a polyacrylamide drag reducer, and polyacrylamide drag reducer, clay stabilizer, drainage aid and appropriate amount of water are uniformly mixed to obtain authigenic acidic slick water. Conventional acidic slick water directly adds hydrochloric acid to polyacrylamide solution, and the obtained acidic slick water causes hydrochloric acid to react with carbonate rapidly, and cannot exist in rock formation for a long time, and the action time is short; however, when the authigenic acidic slick water is used, it is mixed with hydrogen peroxide, and the acid is released by the acid carried by the polyacrylamide drag reducer. In the initial stage of operation, the polyacrylamide drag reducer acts as a polymer in slippery water to thicken and reduce drag. In the process of flowing into the formation, as the temperature of the formation rises, under the action of the oxidant hydrogen peroxide, the carbon-carbon double bond of the polyacrylamide drag reducer breaks to generate two alkyl free radicals, which shortens the side chain of the polymer. The alkyl free radicals react with the oxidant to produce oxalic acid. The released oxalic acid consolidates the cracks. The acid of the present invention comes from the polymer itself, which ensures the depth of action, can consolidate the cracks, and provide conditions for retaining the cracks after pressure relief.

[0026] The present invention also discloses a kind of self-generated acidic slick water and its application. During the application process, the carbon-carbon double bond of the polyacrylamide drag reducer in the slick water can be broken to generate two alkyl free radicals, so that the side chain of the polyacrylamide drag reducer becomes shorter, and the alkyl free radicals react with the oxidant to release oxalic acid. The released oxalic acid consolidates the cracks and provides conditions for the retention of the cracks after the pressure is released. The polyacrylamide drag reducer releases oxalic acid under the action of the oxidant, which better plays the role of further maintaining the cracks through corrosion when the cracks are not completely closed during the fracturing process. Since the polyacrylamide drag reducer will start to decompose oxalic acid at above 80°C when the formation is deep, the slick water can ensure the depth of action and achieve the purpose of acid slow release. Secondly, oxalic acid is a medium-strong acid and has a strong rock formation corrosion effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the nuclear magnetic hydrogen spectrum of the polyacrylamide drag reducer prepared in Example 4 of the present invention;

[0028] Figure 2 This is a graph showing the pH value change of the polyacrylamide drag reducer prepared in various embodiments of the present invention after reacting with hydrogen peroxide for 10 minutes;

[0029] Figure 3 This is a time-pH diagram of the self-generated acidic slick water prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0031] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0032] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0033] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0034] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0035] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0036] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0037] The present invention discloses a method for preparing autogenous acidic slick water, which specifically comprises the following steps:

[0038] (1) Sorbic acid and thionyl chloride (SOCl 2 ) and ethanol are added to a three-necked flask, ultrasonicated for 1 hour, then nitrogen is introduced into the three-necked flask, and the temperature is raised from room temperature to 65°C-75°C under stirring, and kept warm for 24 hours; after the entire reaction system is cooled to room temperature, rotary evaporation is performed for 2 hours to obtain intermediate product I; then intermediate product I, triethylamine and hydroxyethyl acrylate are added to the three-necked flask, stirred on a magnetic stirrer at room temperature for 8h-12h, left overnight and then filtered, the filter residue is washed 3 times with ethanol, and dried to obtain intermediate product II, and intermediate product II is dissolved in white oil under the action of dodecylphenol polyoxyethylene ether (OP-10) and sodium dodecyl sulfate to obtain an oil phase.

[0039] The mass ratio of sorbic acid to ethanol is 1:(1-3); 50m-100mL of thionyl chloride is added for every 20g of sorbic acid; the mass ratio of the intermediate product I, triethylamine and hydroxyethyl acrylate is 1:(0.2-0.5):(0.2-0.5); the mass ratio of the intermediate product II and white oil is (1-1.5):15; the mass ratio of OP-10 and sodium dodecyl sulfate is (1-1.2):3, and the sum of the mass of OP-10 and sodium dodecyl sulfate is 1%-2% of the total mass of the intermediate product II and the white oil.

[0040] In this step, the reaction process is as follows:

[0041] In the above process, sorbic acid is first subjected to chlorination reaction to obtain intermediate product I, thereby increasing the reactivity of the carboxyl group of sorbic acid; intermediate product I is subjected to esterification reaction with hydroxyethyl acrylate to obtain intermediate product II. The specific reaction process is as follows:

[0042]

[0043] (2) Mix acrylamide and water at 60 o C, and stir thoroughly and evenly, add tert-butyl hydroperoxide to obtain an aqueous phase;

[0044] The mass ratio of acrylamide to water is 1:(15-20), and the amount of tert-butyl hydroperoxide used is 0.5%-1% of the total mass of acrylamide and water.

[0045] (3) Mix the above oil phase and water phase, adjust the pH value to 6-8, add sodium metabisulfite dropwise, keep the reaction at room temperature for 2h-4h, and then raise the temperature to 60 o C-75 oC is reacted for 6h-8h to obtain a polyacrylamide drag reducer; in this process, the intermediate product II undergoes a polymerization reaction with acrylamide to generate a polyacrylamide drag reducer.

[0046] In this process, the mass ratio of the oil phase to the water phase is 1:(1.5-3); the amount of sodium metabisulfite added is 1%-2% of the mass of the water phase.

[0047] The reaction process of this step is:

[0048]

[0049] Among them, m and n are the degree of polymerization, the value range of m is 50-100, and the value range of n is 500-2500.

[0050] (4) Add polyacrylamide drag reducer, clay stabilizer and drainage aid into a proper amount of water in sequence according to the set mass content, and stir and mix them thoroughly to obtain a self-generated acidic slippery water.

[0051] In the present invention, the room temperature is 20°C-30°C.

[0052] The autogenous acidic slippery water includes, by mass percentage, 0.2%-2.0% of polyacrylamide drag reducer, 0.4%-0.8% of clay stabilizer, 0.2%-0.5% of drainage aid, and the balance is water.

[0053] The clay stabilizer is one or more of ammonium chloride, potassium chloride and hexadecyltrimethylammonium chloride; the drainage aid is one or more of fluorocarbon, OP-10 and dodecylbenzene sulfonic acid.

[0054] A self-generated acidic slippery water prepared by the above preparation method, the self-generated acidic slippery water comprises a polyacrylamide drag reducer, a clay stabilizer, a drainage aid and water. The structural formula of the polyacrylamide drag reducer is:

[0055]

[0056] Among them, m and n are the degree of polymerization, the value range of m is 50-100, and the value range of n is 500-2500.

[0057] The components and mass proportions of the self-generated acidic slick water are as follows: 0.2%-2.0% of polyacrylamide drag reducer, 0.4%-0.8% of clay stabilizer, 0.2%-0.5% of drainage aid, and the balance of water.

[0058] The self-generated acidic slick water is used in the field of oilfield fracturing. During the application process, it is added to the formation together with hydrogen peroxide. The amount of hydrogen peroxide added is 0.5%-1% of the mass of the polyacrylamide drag reducer in the self-generated acidic slick water. In the formation, as the temperature rises to above 80°C, hydrogen peroxide and polyacrylamide drag reducer react to release oxalic acid. The reaction process is as follows:

[0059]

[0060] The following is a further analysis and description in conjunction with specific embodiments.

[0061] Example 1

[0062] (1) 20 g of sorbic acid, 50 mL of thionyl chloride and 20 g of ethanol were added to a three-necked flask, ultrasonicated for 1 h, then nitrogen was introduced into the flask, and the temperature was raised from room temperature to 65 °C under stirring, and kept warm for 24 h; after cooling to room temperature, the intermediate product I was obtained by rotary evaporation for 2 h; 12.5 g of the intermediate product I was then taken into the three-necked flask, and 2.5 g of triethylamine and 2.5 g of hydroxyethyl acrylate were slowly added dropwise at room temperature in a mass ratio of 1:0.2:0.2, and stirred on a magnetic stirrer for 8 h. h, and then filtered, washed, and dried to obtain intermediate product II after standing overnight; 6.25 g of intermediate product II was dissolved in 93.75 g of white oil under the action of 0.25 g of OP-10 and 0.75 g of sodium dodecyl sulfate, and mixed evenly to obtain an oil phase; wherein the mass ratio of intermediate product II to white oil was 1:15, the mass ratio of OP-10 to sodium dodecyl sulfate was 1:3, and the total mass of OP-10 and sodium dodecyl sulfate was 1% of the total mass of intermediate product I and white oil.

[0063] (2) Mix 12.5 g acrylamide and 187.5 g water at 60 o C, stir evenly, add 1g of tert-butyl hydroperoxide, stir evenly, and obtain an aqueous phase; wherein the mass ratio of acrylamide to water is 1:15, and the amount of tert-butyl hydroperoxide is 0.5% of the total mass of acrylamide and water.

[0064] (3) Mix the above 66.67 g of oil phase and 133.34 g of water phase, adjust the pH value to 6, add 1.3334 g of sodium metabisulfite dropwise, keep the reaction at room temperature for 2 h, and then raise the temperature to 60 o C for 6 hours to obtain a polyacrylamide drag reducer; wherein the usage ratio of the oil phase to the water phase is 1:2; and the usage of the sodium metabisulfite is 1% of the total mass of the water phase.

[0065] (4) By mass fraction, 0.2% polyacrylamide drag reducer, 0.4% hexadecyltrimethylammonium chloride and 0.2% fluorocarbon were added to an appropriate amount of water in sequence, and the mixture was stirred thoroughly to obtain a self-generated acidic slippery water.

[0066] In order to prove that the above-mentioned polyacrylamide drag reducer and hydrogen peroxide can react to generate the corresponding acid, 30g polyacrylamide drag reducer and 0.15g hydrogen peroxide were added to a three-necked flask filled with 100mL DMF in the laboratory. The amount of hydrogen peroxide added was 0.5% of the polyacrylamide drag reducer. The temperature was raised to 80 o C, react for 10 minutes, measure the pH value, and the pH value is about 6.

[0067] Example 2

[0068] (1) 20 g of sorbic acid, 100 mL of thionyl chloride and 60 g of ethanol were added to a three-necked flask, ultrasonicated for 1 h, then nitrogen was introduced into the flask, and the temperature was raised from room temperature to 75 °C under stirring, and kept warm for 24 h; after cooling to room temperature, the intermediate product I was obtained by rotary evaporation for 2 h; 12.5 g of the intermediate product I was then taken into the three-necked flask, and 6.25 g of triethylamine and 6.25 g of hydroxyethyl acrylate were slowly added dropwise in sequence at room temperature, with the mass ratio of the three being 1:0.5:0.5, and stirred on a magnetic stirrer for 12 h. h, and then filtered, washed, and dried to obtain an intermediate product II after standing overnight; 9.09 g of the intermediate product II was dissolved in 90.75 g of white oil under the action of 0.4992 g of OP-10 and 1.4976 g of sodium dodecyl sulfate, and mixed evenly to obtain an oil phase; wherein the mass ratio of the intermediate product II to the white oil was 1.5:15, the mass ratio of OP-10 to sodium dodecyl sulfate was 1:3, and the total mass of OP-10 and sodium dodecyl sulfate was 2% of the total mass of the intermediate product I and the white oil.

[0069] (2) Mix 9.52 g acrylamide and 190.4 g water at 60 o C, stir evenly, add 1.9992g of tert-butyl hydroperoxide, stir evenly, and obtain an aqueous phase; wherein the mass ratio of acrylamide to water is 1:20, and the amount of tert-butyl hydroperoxide is 1% of the total mass of acrylamide and water.

[0070] (3) Mix the above 50 g oil phase and 150 g water phase, adjust the pH value to 8, add 3 g sodium metabisulfite dropwise, keep the reaction at room temperature for 4 h, and then raise the temperature to 75 o C for 8 hours to obtain a polyacrylamide drag reducer; wherein the usage ratio of the oil phase to the water phase is 1:3; and the usage of the sodium metabisulfite is 2% of the total mass of the water phase.

[0071] (4) By mass fraction, 2% of the above-mentioned polyacrylamide drag reducer, 0.8% of ammonium chloride and 0.5% of dodecylbenzene sulfonic acid were added to an appropriate amount of water in sequence, and the mixture was stirred thoroughly to obtain a self-generated acidic slippery water.

[0072] In order to prove that the above-mentioned polyacrylamide drag reducer and hydrogen peroxide can react to generate the corresponding acid, 30g polyacrylamide drag reducer and 0.3g hydrogen peroxide were added to a three-necked flask containing 100 mL DMF in the laboratory. The amount of hydrogen peroxide added was 1% of the polyacrylamide drag reducer. The temperature was raised to 120 o C, react for 10 minutes, measure the pH value, and the pH value is about 5.

[0073] Example 3

[0074] (1) 20 g of sorbic acid, 80 mL of thionyl chloride and 40 g of ethanol were added to a three-necked flask, and ultrasonicated for 1 h. Then, nitrogen was introduced into the flask, and the temperature was raised from room temperature to 70 °C under stirring, and kept warm for 24 h. After cooling to room temperature, the intermediate product I was obtained by rotary evaporation for 2 h. Then, 12.5 g of the intermediate product I was added to the three-necked flask, and 3.75 g of triethylamine and 3.75 g of hydroxyethyl acrylate were slowly added dropwise at room temperature in a mass ratio of 1:0.3:0.3. The mixture was stirred on a magnetic stirrer for 12 h. h, and then filtered, washed, and dried to obtain an intermediate product II after standing overnight; 7.4 g of the intermediate product II was dissolved in 92.5 g of white oil under the action of 0.34 g of OP-10 and 0.85 g of sodium dodecyl sulfate, and mixed evenly to obtain an oil phase; wherein the mass ratio of the intermediate product II to the white oil was 1.2:15, the mass ratio of OP-10 to sodium dodecyl sulfate was 1.2:3, and the total mass of OP-10 and sodium dodecyl sulfate was 1.19% of the total mass of the intermediate product I and the white oil.

[0075] (2) 11.11 g acrylamide and 188.87 g water were mixed at 60 o C, stir evenly, add 1.59 g of tert-butyl hydroperoxide, stir evenly, and obtain an aqueous phase; wherein the mass ratio of acrylamide to water is 1:17, and the amount of tert-butyl hydroperoxide is 0.8% of the total mass of acrylamide and water.

[0076] (3) Mix the above 80 g oil phase and 120 g water phase, adjust the pH value to 7, add 1.8 g sodium metabisulfite dropwise, keep the reaction at room temperature for 3 h, and then raise the temperature to 70 o C for 7 hours to obtain a polyacrylamide drag reducer; wherein the usage ratio of the oil phase to the water phase is 1:1.5; and the usage of the sodium metabisulfite is 1.5% of the total mass of the water phase.

[0077] (4) By mass fraction, 0.5% of the above-mentioned polyacrylamide drag reducer, 0.6% of potassium chloride and 0.4% of OP-10 were added to an appropriate amount of water in sequence, and the mixture was stirred and mixed thoroughly to obtain a self-generated acidic slippery water.

[0078] In order to prove that the above-mentioned polyacrylamide drag reducer and hydrogen peroxide can react to generate the corresponding acid, 30g polyacrylamide drag reducer and 0.18g hydrogen peroxide were added to a three-necked flask containing 100mL DMF in the laboratory. The amount of hydrogen peroxide added was 0.6% of the polyacrylamide drag reducer. The temperature was raised to 120 o C, react for 10 minutes, measure the pH value, and the pH value is about 5.3.

[0079] Example 4

[0080] (1) 20 g of sorbic acid, 90 mL of thionyl chloride and 60 g of ethanol were added to a three-necked flask, and ultrasonicated for 1 h. Then, nitrogen was introduced into the flask, and the temperature was raised from room temperature to 75 °C under stirring, and kept warm for 24 h. After cooling to room temperature, the intermediate product I was obtained by rotary evaporation for 2 h. Then, 12.5 g of the intermediate product I was added to the three-necked flask, and 3.75 g of triethylamine and 3.75 g of hydroxyethyl acrylate were slowly added dropwise at room temperature in a mass ratio of 1:0.3:0.3. The mixture was stirred on a magnetic stirrer for 12 h. h, and then filtered, washed, and dried to obtain an intermediate product II after standing overnight; 7.4 g of the intermediate product II was dissolved in 92.5 g of white oil under the action of 0.34 g of OP-10 and 0.9 g of sodium dodecyl sulfate, and mixed evenly to obtain an oil phase; wherein the mass ratio of the intermediate product II to the white oil was 1.2:15, the mass ratio of OP-10 to sodium dodecyl sulfate was 1.13:3, and the total mass of OP-10 and sodium dodecyl sulfate was 1% of the total mass of the intermediate product I and the white oil.

[0081] (2) 11.11 g acrylamide and 188.87 g water were mixed at 60 o C, stir evenly, add 1.59 g of tert-butyl hydroperoxide, stir evenly, and obtain an aqueous phase; wherein the mass ratio of acrylamide to water is 1:17, and the amount of tert-butyl hydroperoxide is 0.8% of the total mass of acrylamide and water.

[0082] (3) Mix the above 66.67 g of oil phase and 133.34 g of water phase, adjust the pH value to 6, add 1.3334 g of sodium metabisulfite dropwise, keep the reaction at room temperature for 2 h, and then raise the temperature to 60 o C for 6 hours to obtain a polyacrylamide drag reducer; wherein the usage ratio of the oil phase to the water phase is 1:2; and the usage of the sodium metabisulfite is 1% of the total mass of the water phase.

[0083] (4) By mass fraction, 0.3% of the above-mentioned polyacrylamide drag reducer, 0.5% of hexadecyltrimethylammonium chloride and 0.3% of fluorocarbon are added to an appropriate amount of water in sequence, and the mixture is stirred and mixed thoroughly to obtain a self-generated acidic slippery water.

[0084] In order to characterize the structural characteristics of the product of this example, a nuclear magnetic resonance spectroscopy test was performed on it, and the test results are as follows Figure 1 As shown, Figure 1 The horizontal axis in which fp stands for fluorescence intensity (Fluorescence Intensity), NMR stands for nuclear magnetic resonance (NMR), from Figure 1 It can be seen that:

[0085] 1 H NMR (300 MHz, CCl 3 D): δ = 8.09ppm, 7.41ppm, 6.12ppm, 4.48ppm, 3.71ppm, 2.70ppm, 1.12ppm. Among them, 8.09ppm is -NH 2 The chemical shift of the conjugated -CH is at 7.41ppm; the double bond -CH=CH is at 6.12ppm 2 Chemical shift; 4.48 ppm is for the methoxy group (-O-CH 2 -) chemical shift; 3.71ppm is -CH 2 -Chemical shift; 2.70ppm is -CH 3 Chemical shift; 1.12ppm is -CH 3 The chemical shift.

[0086] In order to prove that the above-mentioned polyacrylamide drag reducer and hydrogen peroxide can react to generate the corresponding acid, 30g polyacrylamide drag reducer and 0.15g hydrogen peroxide were added to a three-necked flask containing 100 mL DMF in the laboratory. The amount of hydrogen peroxide added was 0.5% of the polyacrylamide drag reducer. The temperature was raised to 110 o C, react for 10 minutes, measure the pH value, and the pH value is about 5.5.

[0087] Example 5

[0088] (1) 20 g of sorbic acid, 70 mL of thionyl chloride and 30 g of ethanol were added to a three-necked flask, and ultrasonicated for 1 h. Then, nitrogen was introduced into the flask, and the temperature was raised from room temperature to 75 °C under stirring, and kept warm for 24 h. After cooling to room temperature, the intermediate product I was obtained by rotary evaporation for 2 h. Then, 12.5 g of the intermediate product I was taken into the three-necked flask, and 6.25 g of triethylamine and 6.25 g of hydroxyethyl acrylate were slowly added dropwise in sequence at room temperature, with the mass ratio of the three being 1:0.5:0.5, and stirred on a magnetic stirrer for 12 hours. h, and then filtered, washed, and dried to obtain an intermediate product II after standing overnight; 9.09 g of the intermediate product II was dissolved in 90.75 g of white oil under the action of 0.4992 g of OP-10 and 1.4976 g of sodium dodecyl sulfate, and mixed evenly to obtain an oil phase; wherein the mass ratio of the intermediate product II to the white oil was 1.5:15, the mass ratio of OP-10 to sodium dodecyl sulfate was 1:3, and the total mass of OP-10 and sodium dodecyl sulfate was 2% of the total mass of the intermediate product I and the white oil.

[0089] (2) Mix 9.52 g acrylamide and 190.4 g water at 60 o C, stir evenly, add 1.9992g of tert-butyl hydroperoxide, stir evenly, and obtain an aqueous phase; wherein the mass ratio of acrylamide to water is 1:20, and the amount of tert-butyl hydroperoxide is 1% of the total mass of acrylamide and water.

[0090] (3) Mix the above 80 g oil phase and 120 g water phase, adjust the pH value to 7, add 1.8 g sodium metabisulfite dropwise, keep the reaction at room temperature for 3 h, and then raise the temperature to 70 o C for 7 hours to obtain a polyacrylamide drag reducer; wherein the usage ratio of the oil phase to the water phase is 1:1.5; and the usage of the sodium metabisulfite is 1.5% of the total mass of the water phase.

[0091] (4) By mass fraction, 1% of the above-mentioned polyacrylamide drag reducer, 0.5% of potassium chloride and 0.5% of OP-10 were added to an appropriate amount of water in sequence, and the mixture was stirred and mixed thoroughly to obtain a self-generated acidic slippery water.

[0092] In order to prove that the above-mentioned polyacrylamide drag reducer and hydrogen peroxide can react to generate the corresponding acid, 30g polyacrylamide drag reducer and 0.18g hydrogen peroxide were added to a three-necked flask containing 100mL DMF in the laboratory. The amount of hydrogen peroxide added was 0.6% of the polyacrylamide drag reducer. The temperature was raised to 100 o C, react for 10 minutes, measure the pH value, and the pH value is about 5.5.

[0093] Example 6

[0094] (1) 20 g of sorbic acid, 80 mL of thionyl chloride and 50 g of ethanol were added to a three-necked flask, and ultrasonicated for 1 h. Then, nitrogen was introduced into the flask, and the temperature was raised from room temperature to 75 °C under stirring, and kept warm for 24 h. After cooling to room temperature, the intermediate product I was obtained by rotary evaporation for 2 h. Then, 12.5 g of the intermediate product I was taken into the three-necked flask, and 2.5 g of triethylamine and 2.5 g of hydroxyethyl acrylate were slowly added dropwise at room temperature in a mass ratio of 1:0.2:0.2. The mixture was stirred on a magnetic stirrer for 8 h. h, and then filtered, washed, and dried to obtain intermediate product II after standing overnight; 6.25 g of intermediate product II was dissolved in 93.75 g of white oil under the action of 0.25 g of OP-10 and 0.75 g of sodium dodecyl sulfate, and mixed evenly to obtain an oil phase; wherein the mass ratio of intermediate product II to white oil was 1:15, the mass ratio of OP-10 to sodium dodecyl sulfate was 1:3, and the total mass of OP-10 and sodium dodecyl sulfate was 1% of the total mass of intermediate product I and white oil.

[0095] (2) Mix 9.52 g acrylamide and 190.4 g water at 60 o C, stir evenly, add 1.9992g of tert-butyl hydroperoxide, stir evenly, and obtain an aqueous phase; wherein the mass ratio of acrylamide to water is 1:20, and the amount of tert-butyl hydroperoxide is 1% of the total mass of acrylamide and water.

[0096] (3) Mix the above 66.67 g of oil phase and 133.34 g of water phase, adjust the pH value to 6, add 1.3334 g of sodium metabisulfite dropwise, keep the reaction at room temperature for 2 h, and then raise the temperature to 60 o C for 6 hours to obtain a polyacrylamide drag reducer; wherein the usage ratio of the oil phase to the water phase is 1:2; and the usage of the sodium metabisulfite is 1% of the total mass of the water phase.

[0097] (4) By mass fraction, 0.4% of the above-mentioned polyacrylamide drag reducer, 0.8% of ammonium chloride and 0.4% of dodecylbenzene sulfonic acid are added to an appropriate amount of water in sequence, and the mixture is stirred and mixed thoroughly to obtain a self-generated acidic slippery water.

[0098] In order to prove that the above-mentioned polyacrylamide drag reducer and hydrogen peroxide can react to generate the corresponding acid, 30g polyacrylamide drag reducer and 0.15g hydrogen peroxide were added to a three-necked flask filled with 100mL DMF in the laboratory. The amount of hydrogen peroxide added was 0.6% of the polyacrylamide drag reducer. The temperature was raised to 80 o C, react for 10 minutes, measure the pH value, and the pH value is about 5.8.

[0099] In order to characterize whether the self-generated acidic slippery water prepared in each example releases oxalic acid, the pH value of the self-generated acidic slippery water after mixing with hydrogen peroxide for 10 minutes was tested using a pH meter. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that the pH values ​​of the acidic slippery water prepared in the six examples are between 5 and 6, which means that at a temperature above 80° C., the two start to react when in contact, gradually releasing oxalic acid, and the pH value of the entire system begins to decrease.

[0100] For Example 4, heating was continued for 30 minutes, and the pH value was measured every 5 minutes. Figure 3 It can be seen that as time goes by, oxalic acid is continuously released and the pH value gradually decreases. When the time is 30 minutes, the pH value can reach about 3.6.

[0101] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing autogenous acidic slick water, characterized in that: The following steps are involved: S1, mix sorbic acid, thionyl chloride and ethanol, stir and heat to 65 o C-75 o C for heat preservation reaction to form a reaction system, cooling the reaction system to room temperature, evaporating to obtain intermediate product I; mixing intermediate product I, triethylamine and hydroxyethyl acrylate with stirring to react to obtain intermediate product II, and dissolving intermediate product II, OP-10 and sodium dodecyl sulfate in white oil to obtain an oil phase; The structural formula of the intermediate product I is: The structural formula of the intermediate product II is: S2, mixing acrylamide and water and adding tert-butyl hydroperoxide to obtain an aqueous phase; S3, after mixing the oil phase and the water phase to obtain a mixed system, the pH value of the mixed system is adjusted to 6-8, sodium metabisulfite is added dropwise, and the mixture is first reacted at room temperature, and then heated at 60 o C-75 o C reaction to obtain a polyacrylamide drag reducer; S4, mixing the polyacrylamide drag reducer, the clay stabilizer and the drainage aid in water, and stirring to obtain autogenous acidic slippery water.

2. The method for preparing authigenic acidic slick water according to claim 1, characterized in that: In S1, the mixing mass ratio of sorbic acid to ethanol is 1:(1-3), and 50mL-100mL of thionyl chloride is added for every 20g of sorbic acid.

3. The method for preparing authigenic acidic slick water according to claim 1, characterized in that: In S1, the mass ratio of intermediate product I, triethylamine and hydroxyethyl acrylate is 1:(0.2-0.5):(0.2-0.5).

4. The method for preparing authigenic acidic slick water according to claim 1, characterized in that: In S1, the mass ratio of the intermediate product II and the white oil is (1-1.5):15; the mass ratio of the OP-10 and sodium dodecyl sulfate is (1-1.2):3, and the total mass of OP-10 and sodium dodecyl sulfate is 1%-2% of the total mass of the intermediate product II and the white oil.

5. The method for preparing authigenic acidic slick water according to claim 1, characterized in that: In S2, the mixing mass ratio of acrylamide and water is 1:(15-20); the added amount of tert-butyl hydroperoxide is 0.5%-1% of the total mass of acrylamide and water.

6. The method for preparing authigenic acidic slick water according to claim 1, characterized in that: In S3, the mixing mass ratio of the oil phase to the water phase is 1:(1.5-3), and the amount of sodium metabisulfite added is 1%-2% of the mass of the water phase.

7. The method for preparing authigenic acidic slick water according to claim 1, characterized in that: In S3, the reaction time at room temperature is 2h-4h, and the reaction time under heating is 6h-8h.

8. An autogenous acidic slick water prepared by the preparation method according to any one of claims 1 to 7, characterized in that: Calculated by mass percentage, it includes 0.2%-2.0% of polyacrylamide drag reducer, 0.4%-0.8% of clay stabilizer and 0.2%-0.5% of drainage aid, and the balance is water.

9. An application of the self-generated acidic slippery water according to claim 8, characterized in that: When the self-generated acidic slick water is used, it is added to the formation together with hydrogen peroxide. When the temperature is above 80° C., the polyacrylamide drag reducer in the self-generated acidic slick water reacts with the hydrogen peroxide to release oxalic acid.

10. The use of the self-generated acidic slick water according to claim 9, characterized in that: When the self-generated acidic slick water is used, the amount of hydrogen peroxide added is 0.5%-1% of the mass of the polyacrylamide drag reducer.

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