Thickened polymer as well as preparation method and application thereof

Abstract

The invention provides a thickened polymer as well as a preparation method and application thereof. The thickened polymer comprises a first monomer, a second monomer, a third monomer, a fourth monomer with a structure as shown in a formula I and amphoteric modified nano silicon dioxide, in the imgabs0 #, m is 1 to 10, R1 and R2 are independently H or alkyl with 1 to 6 carbon atoms, and R3 is alkyl with 1 to 18 carbon atoms. The thickened polymer has better temperature resistance, and can generate stable coordination with a cross-linking agent when cross-linked acid is prepared, so that the strength of an intermolecular network structure is improved, and the cross-linked acid is endowed with good high-temperature rheological property and high-temperature-resistant stability. The thickened polymer as a thickening agent has a better crosslinking effect with various conventional crosslinking agents for crosslinking acids, is wide in application range, and meets the requirements of high-temperature acidification on the thickening agent.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield chemistry, and particularly relates to a thickening polymer, a preparation method thereof, and an application thereof. Background Art

[0002] Oil is currently the most widely used and most widely applied energy source in the world, and its advantages in use and fundamental role are still irreplaceable in the next period. Carbonate formations in China are widely distributed with a large area and rich oil and gas reserves. Increasing the development of carbonate reservoirs can effectively ensure the supply of oil and gas resources. For the development of carbonate reservoirs, acid fracturing has unique advantages. Acid fracturing technology can not only connect natural fractures in the reservoir through fracturing, but also form acid-etched fractures, effectively improving reservoir heterogeneity and forming highly conductive fractures for oil and gas. Therefore, acidification technology has been widely applied in carbonate reservoirs and achieved good results. Acidification technology mainly conducts acid fracturing construction through crosslinked acid. A thickening agent and a crosslinking agent act on the acid solution of the crosslinked acid through the crosslinking agent to form a system with an intermolecular three-dimensional network structure to increase the viscosity of the acid solution system, enhance the temperature resistance, shear resistance, sand-carrying capacity, and retardation performance of the acid solution system, thereby achieving the purpose of reducing formation damage, increasing the acid etching distance, realizing deep formation acidification, and increasing oil and gas production. In a high-temperature resistant crosslinked acid system, the thickening agent is usually an acrylamide polymer, and the crosslinking agent is usually an organic metal ion compound. The high-valent metal ions in the crosslinking agent form a coordination effect with groups such as carboxyl groups and amide groups in the thickening agent to achieve crosslinking. By improving the molecular structure of the thickening agent, the performance of the crosslinked acid system can be improved.

[0003] However, based on the existing structural design, the thickening agent often has the following deficiencies: large dosage, high low-temperature viscosity, and poor injection performance; at high temperatures (such as 180 °C), the interaction between the thickening agent and the crosslinking agent is weak, and the intermolecular network structure is not shear-resistant and is damaged, resulting in a sharp drop in the viscosity of the crosslinked acid, affecting the acidification effect in a high-temperature environment. Summary of the Invention

[0004] One aspect of the present invention provides a thickening polymer, which comprises a first monomer, a second monomer, a third monomer, a fourth monomer, and amphoteric modified nano-silica; the structure of the fourth monomer is shown in Formula I:

[0005]

[0006] Wherein, m is 1-10, R1 and R2 are independently H or an alkyl group with 1-6 carbon atoms, and R3 is an alkyl group with 1-18 carbon atoms.

[0007] According to an embodiment of the present invention, in Formula I, m is 1-4, R1 and R2 are independently H or methyl, and R3 is an alkyl group with 1-5 carbon atoms.

[0008] According to an embodiment of the present invention, the mass ratio of the first monomer, the second monomer, the third monomer, and the fourth monomer is 1:(0.01 - 0.5):(0.005 - 0.2):(0.005 - 0.05); and / or

[0009] The mass ratio of the total mass of the first monomer, the second monomer, the third monomer, and the fourth monomer to the mass of the amphoteric modified nano-silica is 1:(0.001 - 0.1).

[0010] According to a preferred embodiment of the present invention, the mass ratio of the first monomer, the second monomer, the third monomer, and the fourth monomer is 1:(0.05 - 0.3):(0.01 - 0.15):(0.01 - 0.03); and / or

[0011] The mass ratio of the total mass of the first monomer, the second monomer, the third monomer, and the fourth monomer to the mass of the amphoteric modified nano-silica is 1:(0.005 - 0.1).

[0012] According to a preferred embodiment of the present invention, the mass ratio of the first monomer, the second monomer, the third monomer, and the fourth monomer is 1:(0.2 - 0.3):(0.06 - 0.1):(0.012 - 0.028); and / or

[0013] The mass ratio of the total mass of the first monomer, the second monomer, the third monomer, and the fourth monomer to the mass of the amphoteric modified nano-silica is 1:(0.014 - 0.016).

[0014] According to an embodiment of the present invention, the molecular weight of the thickening polymer is 2 million - 25 million.

[0015] According to an embodiment of the present invention, the first monomer includes acrylamide monomers and / or monomers having the structure shown in Formula II, where n is 1 or 2;

[0016]

[0017] and / or

[0018] The second monomer includes acrylamidoalkyl sulfonate monomers and / or alkenyl sulfonate monomers; and / or

[0019] The third monomer includes acrylic acid monomers and / or unsaturated dibasic acid monomers.

[0020] According to an embodiment of the present invention, the first monomer includes at least one of acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, vinylpyrrolidone, and vinylcaprolactam;

[0021] and / or

[0022] The second monomer includes at least one of 2-acrylamido-2-methylpropanesulfonate, styrenesulfonate, and vinylsulfonate; and / or

[0023] The third monomer includes at least one of acrylic acid, methacrylic acid, maleic acid, itaconic acid, and fumaric acid.

[0024] According to an embodiment of the present invention, the amphoteric modified nano-silica is amino / carboxyl modified nano-silica;

[0025] Preferably, the particle size of the amphoteric modified nano-silica is 1-300 nm;

[0026] Preferably, the particle size of the amphoteric modified nano-silica is 1-100 nm;

[0027] Preferably, the average particle size of the amphoteric modified nano-silica is 15-60 nm.

[0028] According to an embodiment of the present invention, the amphoteric modified nano-silica is prepared by the following method:

[0029] 1) Aminating and modifying hydrophilic nano-silica with a silicon-containing modifier and an amine compound in a first solvent to obtain aminated modified nano-silica;

[0030] 2) Carboxylating and modifying the aminated modified nano-silica with an acid anhydride compound in a second solvent to obtain the amphoteric modified nano-silica.

[0031] According to a specific embodiment of the present invention, in step 1), the mass ratio of the hydrophilic nano-silica, the silicon-containing modifier, and the amine compound is 1:(0.01-1):(0.01-0.5); and / or

[0032] The mass ratio of the total mass of the hydrophilic nano-silica, the silicon-containing modifier, and the amine compound to the mass of the first solvent is 1:(2-200); and / or

[0033] The first solvent includes water and C1-C4 alcohols (such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol);

[0034] Preferably, in the first solvent, the mass ratio of the C1-C4 alcohol to water is 1:(0.01-0.35).

[0035] According to a preferred embodiment of the present invention, in step 1), the mass ratio of the hydrophilic nano-silica, the silicon-containing modifier, and the amine compound is 1:(0.06 - 1):(0.01 - 0.2); and / or

[0036] the mass ratio of the total mass of the hydrophilic nano-silica, the silicon-containing modifier, and the amine compound to the mass of the first solvent is 1:(5 - 100); and / or

[0037] in the first solvent, the mass ratio of the C1 - C4 alcohol to water is 1:(0.05 - 0.25).

[0038] According to a preferred embodiment of the present invention, in step 1), the mass ratio of the hydrophilic nano-silica, the silicon-containing modifier, and the amine compound is 1:(0.4 - 0.65):(0.05 - 0.1); and / or

[0039] the mass ratio of the total mass of the hydrophilic nano-silica, the silicon-containing modifier, and the amine compound to the mass of the first solvent is 1:(19.4 - 26.2); and / or

[0040] the first solvent is a mixture of water and a C1 - C3 alcohol (such as methanol, ethanol, isopropanol);

[0041] in the first solvent, the mass ratio of the C1 - C3 alcohol to water is 1:(0.08 - 0.17).

[0042] According to an embodiment of the present invention, in step 2), the mass ratio of the amino-modified nano-silica and the acid anhydride compound is 1:(0.01 - 0.8); and / or

[0043] the mass ratio of the total mass of the amino-modified nano-silica and the acid anhydride compound to the mass of the second solvent is 1:(4 - 200);

[0044] Preferably, the second solvent is at least one of acetone, tetrahydrofuran, carbon tetrachloride, methyl ethyl ketone, toluene, and xylene;

[0045] Preferably, the second solvent is at least one of acetone, tetrahydrofuran, and methyl ethyl ketone.

[0046] According to a preferred embodiment of the present invention, in step 2), the mass ratio of the amino-modified nano-silica and the acid anhydride compound is 1:(0.01 - 0.5); and / or

[0047] the mass ratio of the total mass of the amino-modified nano-silica and the acid anhydride compound to the mass of the second solvent is 1:(8 - 100).

[0048] According to a preferred embodiment of the present invention, in step 2), the mass ratio of the aminated modified nano-silica and the anhydride compound is 1:(0.2 - 0.45); and / or

[0049] The mass ratio of the total mass of the aminated modified nano-silica and the anhydride compound to the mass of the second solvent is 1:(34.4 - 66.7).

[0050] According to an embodiment of the present invention, the silicon-containing modifier includes at least one of 3-aminopropyltriethoxysilane, 3-aminopropylethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane; and / or

[0051] The amine compound is selected from at least one of triethylamine, tri-n-propylamine, and tri-n-butylamine; and / or

[0052] The anhydride compound is selected from at least one of succinic anhydride, glutaric anhydride, adipic anhydride, phthalic anhydride, and diglycolic anhydride;

[0053] The particle size of the hydrophilic nano-silica is 1 - 300 nm;

[0054] Preferably, the particle size of the hydrophilic nano-silica is 1 - 100 nm;

[0055] Preferably, the particle size of the hydrophilic nano-silica is 15 - 60 nm.

[0056] According to a preferred embodiment of the present invention, the silicon-containing modifier is 3-aminopropyltriethoxysilane and / or 3-(2-aminoethylamino)propyltrimethoxysilane; and / or

[0057] The amine compound is triethylamine and / or tri-n-propylamine; and / or

[0058] The anhydride compound is at least one of succinic anhydride, adipic anhydride, and phthalic anhydride.

[0059] According to a specific embodiment of the present invention, in step 1), the product obtained by amination modification is purified, and then step 2) is carried out; and / or

[0060] In step 2), the product obtained by carboxylation modification is purified to obtain the purified amphoteric modified nano-silica;

[0061] Preferably, the purification in step 1) and step 2) is to filter the product, collect the filter residue, and then wash it with ethanol and dry it;

[0062] Preferably, the number of times of ethanol washing is not less than 3 times.

[0063] According to an embodiment of the present invention, in step 1), the conditions for amination modification are at 50-90°C for 1-6 h; and / or

[0064] In step 2), the conditions for carboxylation modification are to react at 30-65°C for 5-10 h.

[0065] According to a preferred embodiment of the present invention, in step 1), the conditions for amination modification are at 70°C for 5 h; and / or

[0066] In step 2), the conditions for carboxylation modification are to react at 65°C for 8 h.

[0067] The second aspect of the present invention provides a method for preparing the thickening polymer as described in the first aspect of the present invention, which includes the following steps:

[0068] React the first monomer, the second monomer, the third monomer, the fourth monomer and the amphoteric modified nano-silica under the action of an initiator to obtain the thickening polymer.

[0069] According to an embodiment of the present invention, first mix the first monomer, the second monomer, the third monomer, the fourth monomer, the amphoteric modified nano-silica and water, adjust the pH, and then carry out the reaction under the action of the initiator;

[0070] Preferably, the pH is adjusted to 6-11;

[0071] Preferably, the pH is adjusted to 6-9;

[0072] Preferably, the initiator is a mixture of persulfate (such as ammonium persulfate), sulfite (such as sodium sulfite), 2,2'-azobis(2-methylpropionamidine) dihydrochloride, peroxide (such as hydrogen peroxide);

[0073] Preferably, the mass ratio of ammonium persulfate, sodium sulfite, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, hydrogen peroxide is (0.00005-0.005):(0.0001-0.006):(0.0001-0.005):(0.00001-0.0003);

[0074] Preferably, the mass ratio of ammonium persulfate, sodium sulfite, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, hydrogen peroxide is (0.00015-0.002):(0.0002-0.003):(0.00025-0.0035):(0.00005-0.0002);

[0075] Preferably, the mass ratio of ammonium persulfate, sodium sulfite, azodiisobutyramidine hydrochloride, and hydrogen peroxide is (0.0005 - 0.0008):(0.0004 - 0.00085):(0.0006 - 0.0008):(0.00007 - 0.00016).

[0076] According to an embodiment of the present invention, the mass ratio of the first monomer, the second monomer, the third monomer, and the fourth monomer is 1:(0.01 - 0.5):(0.005 - 0.2):(0.005 - 0.05); and / or

[0077] The ratio of the total mass of the first monomer, the second monomer, the third monomer, and the fourth monomer, the mass of the amphoteric modified nano-silica, and the mass of the water is 1:(0.001 - 0.1):(1 - 10); and / or

[0078] The mass ratio of the total mass of the first monomer, the second monomer, the third monomer, and the fourth monomer and the mass of the initiator is 1:(0.00026 - 0.0123).

[0079] According to a preferred embodiment of the present invention, the mass ratio of the first monomer, the second monomer, the third monomer, and the fourth monomer is 1:(0.05 - 0.3):(0.01 - 0.15):(0.01 - 0.03); and / or

[0080] The ratio of the total mass of the first monomer, the second monomer, the third monomer, and the fourth monomer, the mass of the amphoteric modified nano-silica, and the mass of the water is 1:(0.005 - 0.1):(1 - 6); and / or

[0081] The mass ratio of the total mass of the first monomer, the second monomer, the third monomer, and the fourth monomer and the mass of the initiator is 1:(0.00065 - 0.0087).

[0082] According to a preferred embodiment of the present invention, the mass ratio of the first monomer, the second monomer, the third monomer, and the fourth monomer is 1:(0.2 - 0.3):(0.06 - 0.1):(0.012 - 0.028); and / or

[0083] The ratio of the total mass of the first monomer, the second monomer, the third monomer, and the fourth monomer, the mass of the amphoteric modified nano-silica, and the mass of the water is 1:(0.014 - 0.16):(2.1 - 3.5); and / or

[0084] The mass ratio of the total mass of the first monomer, the second monomer, the third monomer, and the fourth monomer and the mass of the initiator is 1:(0.0017 - 0.0024).

[0085] According to an embodiment of the present invention, the conditions of the reaction are as follows: first react at 0-40°C for 1-12 h, and then raise the temperature to 80°C and react for 1 h;

[0086] Preferably, the conditions of the reaction are as follows: first react at 0-10°C for 1-8 h, and then raise the temperature to 80°C and react for 1 h;

[0087] Preferably, the conditions of the reaction are as follows: first react at 5-10°C for 4-6 h, and then raise the temperature to 80°C and react for 1 h;

[0088] Preferably, the reaction is carried out under anaerobic conditions.

[0089] Application of the thickening polymer according to one of the present inventions or the thickening polymer prepared by the method according to the second of the present inventions as a thickening agent, especially as a thickening agent for crosslinked acid.

[0090] Advantages of the present invention:

[0091] Aiming at the problem that the interaction between the thickening agent in the prior art and the crosslinking agent is weak at high temperature and the intermolecular network structure formed is not shear-resistant, the present invention provides a thickening polymer, a preparation method and an application thereof. The thickening polymer includes a first monomer, a second monomer, a third monomer, a fourth monomer with a structure shown in formula I and amphoteric modified nano-silica. The inventor designed an inorganic / organic structure in which the polymerization product of nano-silica and four specific monomers is compounded, which enhances the temperature resistance of the thickening polymer. At the same time, when formulating crosslinked acid, the thickening polymer can form a more stable coordination with the crosslinking agent, which is beneficial to improving the strength of the intermolecular network structure and endowing the crosslinked acid with good high-temperature rheology and high-temperature stability. The crosslinked acid further formulated with the thickening polymer provided by the present invention as a thickening agent can maintain the apparent viscosity at a relatively high level at 140 to 180°C. Specifically, under the high temperature and shear action at 180°C, the apparent viscosity of the crosslinked acid can reach 84 mPa·s. The thickening polymer provided by the present invention as a thickening agent has good crosslinking effects with various conventional crosslinking agents for crosslinked acid, has a wide application range, and meets the requirements of high-temperature acidification for thickening agents. Specific embodiments

[0092] The following further illustrates the present invention with reference to embodiments, but the embodiments of the present invention are only exemplary descriptions, and this embodiment does not constitute a limitation to the present invention under any circumstances.

[0093] The experimental methods used in the following experimental evaluations are all conventional methods unless otherwise specified.

[0094] The crosslinked acid agents used in the following experimental evaluations, including crosslinking agent (PCA-1), corrosion inhibitor (PHT-2), corrosion inhibitor synergist (PHTA-2), high-temperature stabilizer (PTR), and iron ion stabilizer (PFAA), were all purchased from Puyang Lutong Petrochemical Co., Ltd. Other materials, reagents, etc., can be obtained from commercial sources without special instructions.

[0095] The hydrophilic nano-silica used in the following examples was purchased from Shandong Jiquan Biotechnology Co., Ltd., and the fourth monomer was purchased from Jiangsu Runfeng Synthetic Technology Co., Ltd. Other materials, reagents, etc., can be obtained from commercial sources without special instructions.

[0096] Preparation of amphoteric modified nano-silica

[0097] Example 1

[0098] 1) Add 10 g of hydrophilic nano-SiO2 (average particle size of 15 nm), 4 g of 3-aminopropyltriethoxysilane, 0.5 g of triethylamine, and 330 g of the first solvent (specifically 300 g of ethanol and 30 g of water) into a round-bottom flask equipped with a stirrer, spherical condenser, and thermometer. After stirring and mixing evenly, control the temperature at 70 °C and react for 5 h to carry out amino modification on the hydrophilic nano-SiO2. Subsequently, filter the product, wash it three times with ethanol, and dry it to obtain amino-modified nano-SiO2;

[0099] 2) Add 10 g of the amino-modified nano-SiO2 prepared in step 1) and 500 g of the second solvent tetrahydrofuran into a round-bottom flask equipped with a stirrer, spherical condenser, and thermometer. After ultrasonic dispersion, add 2 g of succinic anhydride, stir and mix evenly, control the temperature at 65 °C, and react for 8 h to carry out carboxylation modification on the amino-modified nano-SiO2. Subsequently, filter the product, wash it three times with ethanol, and dry it to obtain amino / carboxyl-modified nano-SiO2, that is, amphoteric modified nano-silica, with an average particle size of 15 nm.

[0100] Example 2

[0101] Adjust the average particle size of the hydrophilic nano-SiO2 in step 1) of Example 1 to 60 nm, and the others are the same as in Example 1 to obtain amino / carboxyl-modified nano-SiO2, that is, amphoteric modified nano-silica, with an average particle size of 60 nm.

[0102] Example 3

[0103] Replace 4 g of 3-aminopropyltriethoxysilane in step 1) of Example 1 with 6.5 g of 3-(2-aminoethylamino)propyltrimethoxysilane, and the others are the same as in Example 1 to obtain amino / carboxyl-modified nano-SiO2, that is, amphoteric modified nano-silica, with an average particle size of 15 nm.

[0104] Example 4

[0105] Replace 0.5 g of triethylamine in step 1) of Example 1 with a mixture of 0.5 g of triethylamine and 0.5 g of tri-n-propylamine, and keep the others the same as in Example 1 to obtain amino / carboxyl modified nano-SiO2, that is, amphoteric modified nano-silica, with an average particle size of 15 nm.

[0106] Example 5

[0107] Replace 300 g of ethanol in the first solvent in step 1) of Example 1 with a mixture of 200 g of methanol and 150 g of isopropanol, and keep the others the same as in Example 1 to obtain amino / carboxyl modified nano-SiO2, that is, amphoteric modified nano-silica, with an average particle size of 15 nm.

[0108] Example 6

[0109] Adjust the amount of water in the first solvent in step 1) of Example 1 to 50 g, and keep the others the same as in Example 1 to obtain amino / carboxyl modified nano-SiO2, that is, amphoteric modified nano-silica, with an average particle size of 15 nm.

[0110] Example 7

[0111] Replace 500 g of the second solvent tetrahydrofuran in step 2) of Example 1 with a mixture of 300 g of acetone and 500 g of butanone, and keep the others the same as in Example 1 to obtain amino / carboxyl modified nano-SiO2, that is, amphoteric modified nano-silica, with an average particle size of 15 nm.

[0112] Example 8

[0113] Replace 2 g of succinic anhydride in step 2) of Example 1 with 1 g of adipic anhydride, and keep the others the same as in Example 1 to obtain amino / carboxyl modified nano-SiO2, that is, amphoteric modified nano-silica, with an average particle size of 15 nm.

[0114] Example 9

[0115] Replace 2 g of succinic anhydride in step 2) of Example 1 with 3.5 g of phthalic anhydride, and keep the others the same as in Example 1 to obtain amino / carboxyl modified nano-SiO2, that is, amphoteric modified nano-silica, with an average particle size of 15 nm.

[0116] Preparation of thickening polymer

[0117] Example 10

[0118] Add 100 g of acrylamide, 20 g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 8 g of acrylic acid, 1.5 g of the fourth monomer (m = 1, R1 = H, R2 = CH3, R3 = CH3), 2 g of the amphoteric modified nano-SiO2 prepared in Example 1, and 300 g of deionized water into a four-necked glass bottle equipped with a stirrer, a nitrogen inlet tube, a spherical condenser and a thermometer. Stir until all the raw materials are dissolved, then adjust the pH of the solution to 7.6 with NaOH, introduce nitrogen for 30 min, control the temperature at 5 °C, then add 0.08 g of ammonium persulfate, 0.06 g of sodium sulfite, 0.1 g of azodiisobutyramidine hydrochloride, and 0.01 g of hydrogen peroxide. React for 6 h, then raise the temperature to 80 °C and react for 1 h. Dry and crush the product to obtain the thickening polymer with a molecular weight of 2 million - 25 million, which is a thickening agent for high-temperature resistant crosslinked acid.

[0119] Example 11

[0120] Replace the amphoteric modified nano-SiO2 in Example 10 with the amphoteric modified nano-SiO2 prepared in Example 2 with the same mass, and the others are the same as Example 10, then the thickening polymer can be obtained. The molecular weight is 2 million - 25 million, which is a thickening agent for high-temperature resistant crosslinked acid.

[0121] Example 12

[0122] Replace the amphoteric modified nano-SiO2 in Example 10 with the amphoteric modified nano-SiO2 prepared in Example 3 with the same mass, and the others are the same as Example 10, then the thickening polymer can be obtained. The molecular weight is 2 million - 25 million, which is a thickening agent for high-temperature resistant crosslinked acid.

[0123] Example 13

[0124] Replace the amphoteric modified nano-SiO2 in Example 10 with the amphoteric modified nano-SiO2 prepared in Example 4 with the same mass, and the others are the same as Example 10, then the thickening polymer can be obtained. The molecular weight is 2 million - 25 million, which is a thickening agent for high-temperature resistant crosslinked acid.

[0125] Example 14

[0126] Replace the amphoteric modified nano-SiO2 in Example 10 with the amphoteric modified nano-SiO2 prepared in Example 5 with the same mass, and the others are the same as Example 10, then the thickening polymer can be obtained. The molecular weight is 2 million - 25 million, which is a thickening agent for high-temperature resistant crosslinked acid.

[0127] Example 15

[0128] Replace the amphoteric modified nano-SiO₂ in Example 10 with an equal mass of amphoteric modified nano-SiO₂ prepared in Example 6. Keep the others the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0129] Example 16

[0130] Replace the amphoteric modified nano-SiO₂ in Example 10 with an equal mass of amphoteric modified nano-SiO₂ prepared in Example 7. Keep the others the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0131] Example 17

[0132] Replace the amphoteric modified nano-SiO₂ in Example 10 with an equal mass of amphoteric modified nano-SiO₂ prepared in Example 8. Keep the others the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0133] Example 18

[0134] Replace the amphoteric modified nano-SiO₂ in Example 10 with an equal mass of amphoteric modified nano-SiO₂ prepared in Example 9. Keep the others the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0135] Example 19

[0136] Replace 100 g of acrylamide in Example 10 with a mixture of 80 g of acrylamide and 20 g of N,N-dimethylacrylamide. Keep the others the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0137] Example 20

[0138] Adjust the dosage of 2-acrylamido-2-methylpropanesulfonic acid sodium in Example 10 to 30 g. Keep the others the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0139] Example 21

[0140] Replace 8 g of acrylic acid in Example 10 with 6 g of maleic acid. Keep the others the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0141] Example 22

[0142] Replace 8 g of acrylic acid in Example 10 with a mixture of 7 g of acrylic acid and 3 g of itaconic acid, and keep other conditions the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0143] Example 23

[0144] Adjust the dosage of the fourth monomer (m = 1, R1 = H, R2 = CH3, R3 = CH3) in Example 10 to 2.8 g, and keep other conditions the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0145] Example 24

[0146] Adjust 1.5 g of the fourth monomer (m = 1, R1 = H, R2 = CH3, R3 = CH3) in Example 10 to 1.2 g of the fourth monomer (m = 4, R1 = H, R2 = H, R3 = CH2CH2CH3), and keep other conditions the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0147] Example 25

[0148] Adjust 1.5 g of the fourth monomer (m = 1, R1 = H, R2 = CH3, R3 = CH3) in Example 10 to 1.6 g of the fourth monomer (m = 4, R1 = H, R2 = H, R3 = CH2CH2CH2CH2CH3), and keep other conditions the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0149] Example 26

[0150] Adjust 1.5 g of the fourth monomer (m = 1, R1 = H, R2 = CH3, R3 = CH3) in Example 10 to 1.8 g of the fourth monomer (m = 1, R1 = CH3, R2 = CH3, R3 = CH3), and keep other conditions the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0151] Example 27

[0152] Adjust the dosage of deionized water in Example 10 to 450 g, and keep other conditions the same as in Example 10, then a thickening polymer can be obtained. The molecular weight is 2 million - 25 million, and it is a thickening agent for high-temperature resistant crosslinked acid.

[0153] Example 28

[0154] Adjust the addition amount of ammonium persulfate in Example 10 to 0.1 g, the addition amount of sodium sulfite to 0.11 g, the addition amount of azobisisobutyramidine hydrochloride to 0.08 g, and the addition amount of hydrogen peroxide to 0.02 g. Keep other conditions the same as in Example 10, then a thickening polymer can be obtained. The molecular weight of the polymer is 2 million - 25 million, and it is a thickening agent for high-temperature crosslinked acid.

[0155] Example 29

[0156] Adjust "pH adjusted to 7.6, temperature controlled at 5 °C, reaction for 6 h" in Example 10 to "pH adjusted to 8.3, temperature controlled at 10 °C, reaction for 4 h". Keep other conditions the same as in Example 10, then a thickening polymer can be obtained. The molecular weight of the polymer is 2 million - 25 million, and it is a thickening agent for high-temperature crosslinked acid.

[0157] Comparative Example 1

[0158] Add 100 g of acrylamide, 20 g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 8 g of acrylic acid, and 300 g of deionized water into a four-necked glass bottle equipped with a stirrer, a nitrogen inlet tube, a spherical condenser, and a thermometer. Stir until all raw materials are dissolved, then adjust the pH of the solution to 7.6 with NaOH, introduce nitrogen for 30 min, control the temperature at 5 °C, and then add 0.08 g of ammonium persulfate, 0.06 g of sodium sulfite, 0.1 g of azobisisobutyramidine hydrochloride, and 0.01 g of hydrogen peroxide. React for 6 h, then raise the temperature to 80 °C and react for 1 h. Dry and crush the product to obtain the thickening polymer.

[0159] Comparative Example 2

[0160] Beijing Hongyi Enze Energy Technology Co., Ltd., thickening agent PCH-2.

[0161] Performance evaluation of fracturing fluid

[0162] 1. Evaluation of high-temperature rheological properties of crosslinked acid prepared with thickening polymer

[0163] (1) Preparation of crosslinked acid:

[0164] Prepare crosslinked acid for standby according to the following crosslinked acid system formula. The crosslinked acid includes 400 g of hydrochloric acid (20%), 3.2 g of thickening agent, 8 g of crosslinking agent PCA-1, 8 g of corrosion inhibitor PHT-2, 4 g of corrosion inhibitor synergist PHTA-2, 10 g of high-temperature stabilizer PTR, and 6 g of iron ion stabilizer PFAA. Among them, the thickening agent is the thickening polymer prepared in any one of Examples 10 to 29, Comparative Example 1, or the thickening agent provided in Comparative Example 2;

[0165] (2) According to SY / T 5107-2016 "Evaluation Method for Performance of Water-Based Fracturing Fluids", at 140 °C, 160 °C, and 180 °C, at 170 s-1 The apparent viscosity of the crosslinked acid was measured after shearing at a speed for 90 min, and the results are shown in Table 1.

[0166] Table 1. Evaluation results of high-temperature rheological properties and heavy oil viscosity reduction properties of fracturing fluids

[0167]

[0168] It can be seen from the experimental results in Table 1 that the crosslinked acid prepared with the thickening polymer provided by the present invention has an apparent viscosity of 96 to 150 mPa·s at 140 °C, an apparent viscosity of 81 to 129 mPa·s at 160 °C, and an apparent viscosity of 51 to 84 mPa·s at 180 °C. It has good high-temperature rheology and good high-temperature stability, and can meet the requirements of acidizing construction not higher than 180 °C. The thickening polymer prepared in Comparative Example 1 lacks the fourth monomer. Although at 140 °C, the apparent viscosity of the crosslinked acid prepared with it is relatively high, reaching 135 mPa·s, but as the temperature increases, the decline rate of the apparent viscosity of the crosslinked acid increases. When the temperature rises to 180 °C, the apparent viscosity of the crosslinked acid drops to 39 mPa·s, and its high-temperature rheology and high-temperature stability are poor. Comparative Example 2 provides a generally commercially available thickening agent. The crosslinked acid prepared with it can have an apparent viscosity of more than 120 mPa·s at 140 °C, but similar to Comparative Example 1, during the process of continuous temperature rise, the apparent viscosity drops rapidly, and the apparent viscosity at 180 °C is only 21 mPa·s, and its high-temperature rheology and high-temperature stability are relatively poor.

[0169] Although the present invention has been described with reference to specific embodiments, those skilled in the art should understand that various changes can be made without departing from the true spirit and scope of the present invention. In addition, various changes can be made to the main body, spirit and scope of the present invention to adapt to specific situations, materials, material compositions and methods. All such changes are included within the scope of the claims of the present invention.

Claims

1. A thickening polymer, which comprises a first monomer, a second monomer, a third monomer, a fourth monomer and amphoteric modified nano-silica; the structure of the fourth monomer is shown in Formula I: Among them, m is 1 - 10, R1 and R2 are independently H or an alkyl group with 1 - 6 carbon atoms, and R3 is an alkyl group with 1 - 18 carbon atoms.

2. The thickened polymer according to claim 1, wherein The mass ratio of the first monomer, the second monomer, the third monomer and the fourth monomer is 1:(0.01 - 0.5):(0.005 - 0.2):(0.005 - 0.05); and / or The mass ratio of the total mass of the first monomer, the second monomer, the third monomer and the fourth monomer and the mass of the amphoteric modified nano-silica is 1:(0.001 - 0.1).

3. The thickened polymer according to claim 1 or 2, characterized in that, The molecular weight of the thickening polymer is 2 million - 25 million.

4. The thickening polymer according to any one of claims 1 to 3, characterized in that, The first monomer includes acrylamide monomers and / or monomers with the structure shown in Formula II, where n is 1 or 2; and / or The second monomer includes acrylamidoalkylsulfonate monomers and / or vinylsulfonate monomers; and / or The third monomer includes acrylic acid monomers and / or unsaturated dibasic acid monomers.

5. The thickened polymer according to claim 4, characterized in that, The first monomer includes at least one of acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, vinylpyrrolidone, vinylcaprolactam; and / or The second monomer includes at least one of 2-acrylamido-2-methylpropanesulfonate, styrenesulfonate, vinylsulfonate; and / or The third monomer includes at least one of acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid.

6. The thickened polymer according to any one of claims 1 to 5, characterized in that, The amphoteric modified nano-silica is amino / carboxyl modified nano-silica; Preferably, the particle size of the amphoteric modified nano-silica is 1 - 300 nm.

7. A method for preparing the thickening polymer according to any one of claims 1 to 6, which comprises the following steps: React the first monomer, the second monomer, the third monomer, the fourth monomer and the amphoteric modified nano-silica under the action of an initiator to obtain the thickening polymer.

8. The method according to claim 7, characterized in that First mix the first monomer, the second monomer, the third monomer, the fourth monomer, the amphoteric modified nano-silica and water, adjust the pH, and then carry out the reaction under the action of the initiator; Preferably, the pH is adjusted to 6 - 11; Preferably, the initiator is a mixture of persulfate, sulfite, azodiisobutyramidine hydrochloride and peroxide.

9. The method according to claim 8, wherein The mass ratio of the first monomer, the second monomer, the third monomer and the fourth monomer is 1:(0.01 - 0.5):(0.005 - 0.2):(0.005 - 0.05); and / or The mass ratio of the total mass of the first monomer, the second monomer, the third monomer and the fourth monomer, the mass of the amphoteric modified nano-silica, and the mass of water is 1:(0.001 - 0.1):(1 - 10); and / or The mass ratio of the total mass of the first monomer, the second monomer, the third monomer and the fourth monomer and the mass of the initiator is 1:(0.00026 - 0.0123).

10. The method according to any one of claims 7 to 9, characterized in that, The reaction conditions are to react at 0 - 40 °C for 1 - 12 h first, and then raise the temperature to 80 °C and react for 1 h; Preferably, the reaction is carried out under anaerobic conditions.

11. Use of the thickened polymer according to any one of claims 1 to 6 or the thickened polymer prepared by the method according to any one of claims 7 to 10 as a thickening agent, in particular as a thickening agent for crosslinked acid.

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