A fast-dissolving hydrophobic associating polymer for reinjection water for fracturing and its preparation method

Abstract

The present invention relates to the field of oilfield chemical technology, and proposes a fast-soluble hydrophobic associating polymer for reinjection water for fracturing and a preparation method thereof. Hydrophobic functional monomers and non-ionic polarity regulators are prepared into polymerizable hydrophobic associating micelles, and the polymerizable hydrophobic associating micelle solution and conventional monomer aqueous solution are mixed. The molecular weight of the copolymer is regulated by a molecular weight regulator, and the fast-soluble hydrophobic associating polymer for reinjection water is obtained after reaction, granulation, drying and crushing. It comprehensively utilizes the synergistic effect of the multi-component supramolecular forces of the ternary hydrophobic functional monomers to achieve stability regulation of the associating micelles, and obtains a three-dimensional network structure of salt-resistant polymers with a dense associating network and a strong associating effect; introduces a polarity regulator containing a non-ionic hydrophilic structure, and utilizes self-assembly to form a hydration layer on the surface of the associating micelles, thereby weakening the water-phase aggregation effect and ion shielding effect of the hydrophobic structure, which is beneficial to the stretching of the molecular chain in the water phase, and obtaining the online mixing and fast-dissolving efficiency of the reinjection water, and having both high salt resistance and strong sand carrying performance.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemistry, in particular to a fast-soluble hydrophobic associating polymer for reinjection water for fracturing and a preparation method thereof. Background Art

[0002] With the gradual advancement of shale gas development, large-scale horizontal well fracturing technology has become the main technical means for shale gas extraction. In order to meet the huge water resource consumption, the fracturing fluid system faces the dual challenges of online mixing and rapid dissolution of high-mineralization reinjection water (TDS>10000mg / L) and the need for high salt resistance. Traditional fracturing fluid thickeners mostly use linear polyacrylamide, which suffers from a sharp drop in performance due to excessive curling of molecular chains and destruction of the solvation layer in a high-salt environment. On the one hand, the shear thinning index is significantly reduced, making it difficult for the fracturing fluid to maintain effective turbulence suppression during pipeline flow, resulting in a 30-40% reduction in drag reduction efficiency; in addition, the elastic modulus of the dynamic network structure decays sharply, resulting in insufficient proppant suspension capacity, which seriously restricts the formation of fracture conductivity.

[0003] By enhancing the hydrophobicity of the associating monomers and increasing the size of the hydrophobic microdomain structure, the salt resistance of the polymer can be greatly improved. Although the large-scale micelle system constructed with strongly hydrophobic monomers can form a high-strength fluid structure with a cross-linked network through hydrophobic association, the excessive content of hydrophobic groups in its molecular segments will significantly reduce the hydration and solubility properties of the polymer. This phenomenon is particularly prominent in salt water systems, mainly due to the synergistic effects of two aspects: (1) the salting-out effect caused by high concentrations of electrolytes exacerbates the aggregation state transformation of the hydrophobic segments, resulting in a further increase in the size of the micelles; (2) the charge shielding effect of the counterions in the solution causes the molecular chains to shrink, forming a denser core-shell structure, thereby hindering the penetration and diffusion of water molecules into the interior of the polymer particles. This dissolution kinetic hysteresis phenomenon leads to the problem that traditional hydrophobic associating polymers are difficult to dissolve quickly in the online compounding process.

[0004] The Chinese invention patent with patent number CN106190088B has developed a seawater-based salt-resistant fast-dissolving polymer, which takes 7 minutes to completely dissolve when mixed with seawater, and cannot meet the mixing requirements of large-volume fracturing. The salt-resistant and high-temperature resistant polymer proposed in the Chinese invention patent with patent number CN118496448A adopts a multi-monomer synergistic approach, introducing monomers containing salt-resistant sulfonic acid groups, high-temperature resistant two-dimensional planar structures, and strong hydrophilic groups into the macromolecular skeleton of the associative thickener, thereby simultaneously improving the high salt resistance, high temperature resistance and fast dissolution properties of the associative thickener. However, in order to meet the more appropriate sand-carrying performance, the thickener is used at a high concentration, which lacks economy in large-scale hydraulic fracturing. In some other technical routes, excessive hydrophilic groups are introduced to improve solubility. This method weakens the strength of the associative action, resulting in obvious network structure disassociation in the fracturing fluid system under high temperature and high salt conditions. In summary, based on the existing technical means, there is still a lot of room for development to obtain fracturing fluid thickeners that meet the requirements of online rapid mixing of high-mineralization reinjection water for large-scale hydraulic fracturing, while having low dosage, temperature and salt resistance, and high drag reduction and strong sand carrying capacity. Summary of the Invention

[0005] The purpose of the present invention is to provide a fast-soluble hydrophobic associating polymer for fracturing reinjection water. By designing the hydrophobic functional monomer structure and optimizing the surface hydration layer of the hydrophobic associating micelles, the polymer can be quickly dissolved in high-mineralization water and have excellent salt resistance.

[0006] Another object of the present invention is to provide a method for preparing a fast-soluble hydrophobic associating polymer for reinjection water for fracturing, which adopts a ternary hydrophobic functional monomer containing multi-component synergistic supramolecular forces to achieve the stability regulation of the associating micelles, thereby obtaining a three-dimensional network structure of a salt-resistant polymer with a dense associating network and a strong associating effect. By introducing a polarity regulator containing a non-ionic hydrophilic structure, a hydration layer is formed on the surface of the associating micelles by self-assembly, which weakens the water-phase aggregation effect and ion shielding effect of the hydrophobic structure, facilitates the stretching of molecules in the water phase, and thus obtains a dissolution efficiency similar to that of conventional polyacrylamide polymers.

[0007] In order to solve the above technical problems, the technical solutions adopted in this application are:

[0008] On the one hand, the embodiments of the present application provide a fast-soluble hydrophobic associating polymer for reinjection water for fracturing, the molecular formula of which is shown in Formula 1:

[0009]

[0010] Wherein, by mass, i is 60-65%; j is 15-39%; k is 0-15%; l is 0-3%; m is 0-2%; and n is 0-4%. R1 is a hydrophobic functional monomer 1, comprising a nonionic active group, a quaternary ammonium salt structure, and a long carbon chain structure; R2 is a hydrophobic functional monomer 2, which is an alkyl acrylamide mono- or poly-sulfonate; R3 is a hydrophobic functional monomer 3, comprising a poly-nonionic hydrophilic group and a hydrophobic carbon chain containing a monounsaturated double bond; the weight-average molecular weight of the hydrophobically associating polymer is 5×10 6 -8×10 6 .

[0011] Furthermore, the structural formula of the hydrophobic functional monomer 1 is shown in Formula 2, wherein the double bond structure and the quaternary ammonium salt structure can be connected through a nonionic polar group;

[0012]

[0013] In formula 2, R4 can be a is 1-4;

[0014] Or an active group containing an ester group, as shown in Formula 3:

[0015]

[0016] In formula 3, b is 0-2, c is 0-2;

[0017] Or an active group containing an amide group, as shown in Formula 4:

[0018]

[0019] In formula 4, d is 0-2, e is 0-2;

[0020] Or an active group containing ethoxy, as shown in Formula 5:

[0021]

[0022] In formula 5, f is 0-2, g is 1-10, and h is 0-2;

[0023] In formula 2, R5 is a straight-chain alkyl group having 8 to 22 carbon atoms.

[0024] Furthermore, the structural formula of the hydrophobic functional monomer 2 is shown in Formula 6:

[0025]

[0026] In formula 6, R6 and R7 can be -H, -OH, -COO - 、-SO3 - 、-SO4 - 、-PO4- One of the following, in the same molecule, has at least one anion structure; R8 is a straight-chain alkyl group with 8-14 C atoms.

[0027] Furthermore, the structural formula of the hydrophobic functional monomer 3 is shown in Formula 7:

[0028]

[0029] In formula 7, R9 is a polyvalent nonionic hydrophilic group, and its active group is at least one of an alcohol group, an ether group, an amino group, and a carbonyl functional group;

[0030] Furthermore, the structure of R9 can be shown as Formula 8-10:

[0031]

[0032]

[0033] R 10 The structural formula is shown in Formula 11:

[0034]

[0035] In formula 11, o is 4-12; p is 5-10; and the spatial conformation of the carbon chain has a certain fold angle.

[0036] On the other hand, an embodiment of the present application provides a method for preparing a fast-soluble hydrophobic associating polymer for reinjection water for fracturing, comprising the following steps: S1. adding a hydrophobic functional monomer to water, adding a non-ionic polarity regulator and mixing to obtain a polymerizable hydrophobic associating micelle solution, the hydrophobic functional monomer including one or more of hydrophobic functional monomer 1, hydrophobic functional monomer 2 and hydrophobic functional monomer 3, S2. adding the polymerizable hydrophobic associating micelle solution to a conventional monomer aqueous solution, and forming a total monomer system by the hydrophobic functional monomer and the conventional monomer, fixing the total monomer mass to 65-75% of the total mass of the aqueous solution, to obtain a mixed solution A, S3. using a molecular weight regulator to regulate the molecular weight of the copolymer in the mixed solution A to obtain a mixed solution B, S4. adding an initiator to the mixed solution B, keeping it warm and standing for 2-4 hours to complete the reaction, and obtaining a hydrophobic associating polymer after granulation, drying and crushing.

[0037] Furthermore, the conventional monomers are composed of one or more of acrylamide, sodium acrylate, and sodium 2-acrylamide-2-methylpropanesulfonate.

[0038] Furthermore, the nonionic polarity regulator is a small molecule active substance having nonionic active groups, or a copolymer containing nonionic active groups; the amount of the nonionic polarity regulator added does not exceed 3 wt % of the total monomers.

[0039] Furthermore, the above-mentioned small molecule active substance with non-ionic active groups is composed of a hydrophobic chain portion and a hydrophilic active group, the hydrophobic chain portion is one or more of alkyl alcohol, alkylamine and alkylphenol structures; the hydrophilic active group is one or more of polyoxyethylene block, glucoside group, polyglycerol group and cyclodextrin group.

[0040] Furthermore, the above-mentioned copolymer containing nonionic active groups is copolymerized by one or more polymerizable monomers, and has a degree of polymerization of 100-500. The polymerizable monomers are composed of a hydrophobic chain portion and a hydrophilic active group, and the hydrophobic chain portion is one or more of an alkyl alcohol, an alkylamine and an alkylphenol structure; and the hydrophilic active group is one or more of a polyoxyethylene block, a glucoside group, a polyglycerol group and a cyclodextrin group.

[0041] Furthermore, the molecular weight regulator is one or more of sodium formate, sodium acetate, isopropyl alcohol, sodium hypophosphite and urea, and the added amount of the molecular weight regulator is 0.002 wt% to 0.004 wt% of the total monomers.

[0042] Furthermore, in the above step S4, the initiator includes a first-stage initiator and a second-stage initiator, the first-stage initiator includes 0.01%-0.025% of the total monomer system mass of sodium formaldehyde sulfoxylate and 0.005%-0.015% of the total monomer system mass of ammonium persulfate; the second-stage initiator is 0.05%-0.08% of the total monomer system mass of azobisisobutyronitrile

[0043] Furthermore, in the above step S4, the crushing mesh size is 100-120 meshes.

[0044] Furthermore, water is selected as the solvent. In order to show the quick dissolution and salt resistance of the polymer, the selected solvent may be a solvent containing Na + , K + , Ca 2+ Mg 2+ 、Cu 2+ 、Fe 2+ 、Fe 3+ , Pb 2+ and Cr 2+ Isocationic brine or actual flowback mineral water.

[0045] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0046] 1. A ternary hydrophobic monomer synergistic combination is adopted. By optimizing the structure of the hydrophobic functional monomer, the combined effects of ionic force, hydrogen bond force, hydrophobic force and spatial physical entanglement are balanced to obtain a tight hydrophobic association structure, showing excellent salt resistance.

[0047] 2. The hydrophobic associating micelles are doped with non-ionic active substances, which weakens the ionic effect, reduces the aggregation of the hydrophobic associating structure, and facilitates the diffusion of water molecules into the interior, thereby having rapid solubility in salt water.

[0048] 3. By constructing a self-assembled hydrophobic association structure, a fracturing fluid with high drag reduction and high sand carrying performance can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0050] Figure 1 A process flow diagram and principle diagram of a method for preparing a fast-soluble hydrophobically associating polymer for reinjection water for fracturing provided by an embodiment of the present invention;

[0051] Figure 2 This is a schematic diagram of the dissolution state of polymer particles after dissolving in reinjection water for 2 minutes according to Example 1 of the present invention;

[0052] Figure 3 This is a schematic diagram of the dissolution state of polymer particles in comparative example 1 of the present invention after being dissolved in reinjected water for 2 minutes;

[0053] Figure 4 1 is a comparison chart of the difference in particle size of the monomer solutions in Example 1 of the present invention and Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0054] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0055] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0056] In order to solve the problem of salt resistance of polymers, the present invention adopts a ternary hydrophobic functional monomer containing multi-element cooperative supramolecular forces, and the three monomers are cationic, anionic, and non-ionic structures respectively. Among them, hydrophobic functional monomer 1 and hydrophobic functional monomer 2 are mainly combined by ionic forces; hydrophobic functional monomer 3 is a hydrogen bond donor, which is combined with the other two monomers by hydrogen bond forces. The spatial conformation of its hydrophobic tail chain is bent, which enhances the entanglement of the hydrophobic chains inside the micelles. The combination of ternary monomers realizes the regulation of the stability of the associated micelles, thereby obtaining a three-dimensional network structure of salt-resistant polymers with a dense associated network and a strong associated effect. In order to solve the problem of rapid dissolution in highly mineralized water, the present application introduces a polarity regulator containing a non-ionic hydrophilic structure, utilizes self-assembly to form a hydration layer on the surface of the associated micelles, weakens the water-phase aggregation effect and ion shielding effect of the hydrophobic structure, and is conducive to the stretching of molecules in the water phase, thereby obtaining the online mixing and rapid dissolution efficiency of the reinjected water.

[0057] Faced with the problems of conventional linear polymers not being salt-resistant and hydrophobic associating polymers being slow to dissolve or even insoluble in large-scale hydraulic fracturing reinjection water, the hydrophobic functional monomer structure design and the optimization of the surface hydration layer of the hydrophobic associating micelles are used to simultaneously achieve the effect of rapid dissolution of the polymer in highly mineralized water and excellent salt resistance.

[0058] like Figure 1 As shown, based on the basic theoretical concept of the present invention, a method for preparing a fast-soluble hydrophobic associating polymer for reinjection water for fracturing is proposed, comprising the following steps:

[0059] S1. In parts by mass, 9-11 parts of acrylamide, 3-5 parts of sodium acrylate and 1-2 parts of sodium 2-acrylamide-2-methylpropanesulfonate are added to 18-22 parts of water, and the pH is adjusted to 6.5-7.5 to obtain a conventional monomer aqueous solution;

[0060] S2. Adding a hydrophobic functional monomer to water, adding a nonionic polarity regulator, the amount of the nonionic polarity regulator not exceeding 3% by mass of the total monomer system, the nonionic polarity regulator being a small molecule active substance having a nonionic active group, or a copolymer containing a nonionic active group, stirring at 200 r / min for 24 hours to obtain a polymerizable hydrophobic associating micelle solution, the hydrophobic functional monomer comprising one or more of hydrophobic functional monomer 1, hydrophobic functional monomer 2 and hydrophobic functional monomer 3, the structural formula of hydrophobic functional monomer 1 being as shown in Formula 2:

[0061]

[0062] The structural formula of the hydrophobic functional monomer 2 is shown in Formula 6:

[0063]

[0064] The structural formula of the hydrophobic functional monomer 3 is shown in Formula 7:

[0065]

[0066] S3. The polymerizable hydrophobically associating micelle solution is added to a conventional aqueous monomer solution, the total monomer system consisting of a hydrophobic functional monomer and a conventional monomer, the total monomer mass being fixed at 65-75% of the mass of water to obtain a mixed solution A;

[0067] S4. The molecular weight of the copolymer in the mixed solution A is regulated by a molecular weight regulator, wherein the molecular weight regulator is one or more of sodium formate, sodium acetate, isopropyl alcohol, sodium hypophosphite and urea; the weight average molecular weight of the copolymer after regulation is 5×10 6 -8×10 6 , the molecular weight regulator is added in an amount of 0.002% to 0.004% by mass of the total monomer system to obtain a mixed solution B;

[0068] S5. An initiator is added to the mixed solution B, wherein the initiator includes a first-stage initiator and a second-stage initiator, wherein the first-stage initiator includes 0.01%-0.025% by weight of the total monomer system of sodium formaldehyde sulfoxylate and 0.005%-0.015% by weight of the total monomer system of ammonium persulfate; the second-stage initiator is 0.05%-0.08% by weight of the total monomer system of azobisisobutyronitrile. The mixture is kept warm and allowed to stand for 2-4 hours to complete the reaction, and then granulated, dried, and crushed to 100-120 mesh to obtain a hydrophobically associating polymer.

[0069] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0070] Example 1

[0071] This embodiment 1 provides a method for preparing a fast-soluble hydrophobically associating polymer for reinjection water for fracturing, comprising the following steps:

[0072] S1. In parts by mass, 10.3 parts of acrylamide, 4.2 parts of sodium acrylate and 1.8 parts of sodium 2-acrylamide-2-methylpropanesulfonate were added to 20 parts of water, and the pH was adjusted to 6.5-7.5 to obtain a conventional monomer aqueous solution;

[0073] S2. 0.32 parts of hydrophobic functional monomer 1 and 0.21 parts of hydrophobic functional monomer 2 were added to 13 parts of clean water, 0.36 parts of nonionic polarity regulator were added, and stirred at 200 r / min for 24 hours until the liquid was homogeneous to obtain a polymerizable hydrophobically associating micelle solution. The hydrophobic functional monomer 1 was 2-acrylamide triethoxydimethyl dodecyl ammonium chloride, and its structural formula is as shown in Formula 12:

[0074]

[0075] The hydrophobic functional monomer 2 is sodium 2-acrylamidododecylsulfonate, and its structural formula is shown in Formula 13:

[0076]

[0077] The nonionic polarity regulator is dodecyl glucoside;

[0078] S3. The polymerizable hydrophobically associating micelle solution is added to a conventional monomer aqueous solution, the total monomer system consisting of a hydrophobic functional monomer and a conventional monomer, the total monomer mass being fixed at 70% of the mass of water to obtain a mixed solution A;

[0079] S4 were added to the mixed solution A 0.0003 parts of a molecular weight regulator sodium hypophosphite, a first-stage initiator 0.0012 parts of sodium formaldehyde sulfoxylate and 0.0008 parts of ammonium persulfate, and a second-stage initiator 0.005 parts of azobisisobutyronitrile;

[0080] S5. Keep the mixture at room temperature for 2-4 hours until the reaction is complete to obtain polymer lumps, which are then granulated, dried, and crushed to 120 mesh to obtain a hydrophobically associating polymer.

[0081] Example 2

[0082] This embodiment 2 provides a method for preparing a fast-soluble hydrophobically associating polymer for reinjection water for fracturing, comprising the following steps:

[0083] S1. In parts by mass, 10.3 parts of acrylamide, 4.2 parts of sodium acrylate and 1.8 parts of sodium 2-acrylamide-2-methylpropanesulfonate were added to 20 parts of water, and the pH was adjusted to 6.5-7.5 to obtain a conventional monomer aqueous solution;

[0084] S2. 0.26 parts of hydrophobic functional monomer 1, 0.12 parts of hydrophobic functional monomer 2 and 0.21 parts of hydrophobic functional monomer 3 were added to 13 parts of clean water, 0.3 parts of nonionic polarity regulator were added, and stirred at 200 r / min for 24 hours until the liquid was homogeneous to obtain a polymerizable hydrophobically associating micelle solution. The hydrophobic functional monomer 1 was ethyl acrylate dimethyl dodecyl ammonium chloride, and its structural formula was as shown in Formula 14:

[0085]

[0086] The hydrophobic functional monomer 2 is sodium 2-acrylamidododecyl disulfonate, and its structural formula is shown in Formula 15:

[0087]

[0088] The hydrophobic functional monomer 3 is 2-acrylamidotriglycerol oleate, and its structural formula is shown in Formula 16:

[0089]

[0090] The nonionic polarity regulator is dodecyl glucoside;

[0091] S3. The polymerizable hydrophobically associating micelle solution is added to a conventional monomer aqueous solution, the total monomer system consisting of a hydrophobic functional monomer and a conventional monomer, the total monomer mass being fixed at 70% of the mass of water to obtain a mixed solution A;

[0092] S4 were added 0.0003 parts of a molecular weight regulator sodium hypophosphite, a first-stage initiator 0.0012 parts of sodium formaldehyde sulfoxylate and 0.0008 parts of ammonium persulfate, and a second-stage initiator 0.005 parts of azobisisobutyronitrile;

[0093] S5. Keep the mixture at room temperature for 2-4 hours until the reaction is complete to obtain polymer lumps, which are then granulated, dried, and crushed to 120 mesh to obtain a hydrophobically associating polymer.

[0094] Example 3

[0095] This embodiment 3 provides a method for preparing a fast-soluble hydrophobically associating polymer for reinjection water for fracturing, comprising the following steps:

[0096] S1. In parts by mass, 10.3 parts of acrylamide, 4.2 parts of sodium acrylate and 1.8 parts of sodium 2-acrylamide-2-methylpropanesulfonate were added to 20 parts of water, and the pH was adjusted to 6.5-7.5 to obtain a monomer aqueous solution;

[0097] S2. 0.55 parts of hydrophobic functional monomer 1 and hydrophobic functional monomer 3 were added to 13 parts of clean water, 0.38 parts of nonionic polarity regulator were added, and stirred at 200 r / min for 24 hours until the liquid was homogeneous to obtain a polymerizable hydrophobically associating micelle solution. The hydrophobic functional monomer 1 was ethyl acrylate dimethyl hexadecyl ammonium chloride, and its structural formula was as shown in Formula 17:

[0098]

[0099] The hydrophobic functional monomer 3 is 2-acrylamidotriethanolamine erucate, and its structural formula is shown in Formula 18:

[0100]

[0101] The nonionic polarity regulator is dodecyl glucoside;

[0102] S3. The polymerizable hydrophobically associating micelle solution is added to a conventional monomer aqueous solution, the total monomer system consisting of a hydrophobic functional monomer and a conventional monomer, the total monomer mass being fixed at 70% of the mass of water to obtain a mixed solution A;

[0103] S4 were added 0.0003 parts of a molecular weight regulator sodium hypophosphite, a first-stage initiator 0.0012 parts of sodium formaldehyde sulfoxylate and 0.0008 parts of ammonium persulfate, and a second-stage initiator 0.005 parts of azobisisobutyronitrile;

[0104] S5. Keep the mixture at room temperature for 2-4 hours until the reaction is complete to obtain polymer lumps, which are then granulated, dried, and crushed to 120 mesh to obtain a hydrophobically associating polymer.

[0105] Example 4

[0106] This embodiment 4 provides a method for preparing a fast-soluble hydrophobically associating polymer for reinjection water for fracturing, comprising the following steps:

[0107] S1. In parts by mass, 10.3 parts of acrylamide, 4.2 parts of sodium acrylate and 1.8 parts of sodium 2-acrylamide-2-methylpropanesulfonate were added to 20 parts of water, and the pH was adjusted to 6.5-7.5 to obtain a conventional monomer aqueous solution;

[0108] S2. 0.32 parts of hydrophobic functional monomer 1 and 0.21 parts of hydrophobic functional monomer 2 were added to 13 parts of clean water, 0.41 parts of nonionic polarity regulator were added, and stirred at 200 r / min for 24 hours until the liquid was homogeneous to obtain a polymerizable hydrophobically associating micelle solution, wherein the hydrophobic functional monomer 1 was 2-acrylamide triethoxydimethyl dodecyl ammonium chloride, having the structural formula shown in Formula 12 above, the hydrophobic functional monomer 2 was 2-acrylamide sodium dodecyl sulfonate, having the structural formula shown in Formula 13 above, and the nonionic polarity regulator was triethylamine polyoxyethylene ether, having a degree of polymerization of 150, having the structural formula shown in Formula 19:

[0109]

[0110] S3. The polymerizable hydrophobically associating micelle solution is added to a conventional monomer aqueous solution, the total monomer system consisting of a hydrophobic functional monomer and a conventional monomer, the total monomer mass being fixed at 70% of the mass of water to obtain a mixed solution A;

[0111] S4 were added 0.0003 parts of a molecular weight regulator sodium hypophosphite, a first-stage initiator 0.0012 parts of sodium formaldehyde sulfoxylate and 0.0008 parts of ammonium persulfate, and a second-stage initiator 0.005 parts of azobisisobutyronitrile;

[0112] S5. Keep the mixture at room temperature for 2-4 hours until the reaction is complete to obtain polymer lumps, which are then granulated, dried, and crushed to 120 mesh to obtain a hydrophobically associating polymer.

[0113] Comparative Example 1

[0114] This comparative example 1 is basically the same as Example 1, except that no nonionic polarity regulator is added to verify the beneficial effect of the nonionic polarity regulator on the rapid dissolution of the polymer, and the solubility difference is analyzed by comparing the viscosity at different dissolution times.

[0115] Comparative Example 2

[0116] This comparative example 2 is basically the same as Example 2, except that hydrophobic functional monomer 2 and hydrophobic functional monomer 3 are not added, and the amount of hydrophobic functional monomer 1 is increased to 0.59 parts. The difference in salt resistance between the synergistic effect of the multi-component hydrophobic monomers and the single hydrophobic functional monomer 1 is compared to verify the efficient salt resistance effect of the hydrophobic association formed by the supramolecular action of the ternary hydrophobic monomers.

[0117] Comparative Example 3

[0118] Comparative Example 3 is basically the same as Example 2, except that hydrophobic functional monomer 1 is not added, and the amount of hydrophobic functional monomer 2 is increased to 0.59 parts, and the difference in salt resistance between the synergistic effect of multiple hydrophobic monomers and the single hydrophobic functional monomer 2 is compared.

[0119] Comparative Example 4

[0120] Comparative Example 4 is substantially the same as Example 1, except that hydrophobic functional monomer 1 and hydrophobic functional monomer 2 are not added, and the solubility and salt resistance of the polymer are compared when no hydrophobic monomer is present.

[0121] Test Case

[0122] Gas well flowback water samples were used as the source for polymer performance testing. Their salinity is shown in Table 1. According to the principles for preparing on-site reinjection water, the flowback water samples were mixed with clean water at a ratio of 4:1 to obtain simulated reinjection water samples. Unless otherwise specified, these samples are referred to as reinjection water.

[0123] Table 1 Mineralization of on-site flowback water samples

[0124] Test items Unit of measurement Test results Remark <![CDATA[F - ]]> mg / L / Ion chromatography <![CDATA[Cl - ]]> mg / L 40068.46 <![CDATA[SO4 2- ]]> mg / L 522.39 <![CDATA[NO3 - ]]> mg / L 467.87 <![CDATA[HCO3 - ]]> mg / L 220.94 <![CDATA[CO3 2- ]]> mg / L Not detected Indicator method <![CDATA[Li + ]]> mg / L 2.80 <![CDATA[Na + ]]> mg / L 7996.01 <![CDATA[K + ]]> mg / L 904.50 <![CDATA[Mg 2+ ]]> mg / L 303.36 <![CDATA[Ca 2+ ]]> mg / L 11349.40 <![CDATA[Sr 2+ ]]> mg / L 6144.22 <![CDATA[Ba 2+ ]]> mg / L / Ion chromatography Mineralization mg / L 67979.95

[0125] The polymers obtained in the above examples and comparative examples were dissolved in reinjection water at a concentration of 0.1%. A 500mL beaker was filled with 400mL of reinjection water and mechanical stirring was started at 500 rpm. The polymer was then added to the water over a 10s period. The viscosity at different time points was measured using a six-speed rotational viscometer to obtain the polymer dissolution rate relationship. The results are shown in Table 2:

[0126] Table 2 Dissolution rates of different polymers

[0127]

[0128] For Examples 1-4, when the polymer was mixed with water for reinjection, the viscosity release rate reached more than 65% in 30 seconds, and the complete release state was achieved within 2 minutes, achieving the quick dissolution effect in the mixed water for reinjection. However, since Comparative Example 1 did not use non-ionic polarity regulator for optimization, its viscosity at 10 minutes was only 6 mPa·s, which was much lower than that of Example 1. This is because the polymer did not dissolve within the specified dissolution time and all showed the state of swollen particles. For example, the polymer in Example 1 was basically completely dissolved after 2 minutes, and there were no obvious particles on the wall of the beaker. Figure 2 As shown; while in Comparative Example 1, after dissolving for 2 minutes, the polymer swelled and showed a large number of particles, such as Figure 3 As shown. This comparison shows that the optimization of micelle polarity regulation is a key step in achieving rapid dissolution of polymers in reinjection water. During the dissolution process of reinjection water in Comparative Examples 2-4, it was observed from the experiment that the polymers were basically dissolved in 10 minutes, and there were no large amounts of swollen particles on the wall. However, its viscosity is still relatively low. This is because the self-assembled large-scale hydrophobic associating structure is not obtained, so the salt resistance is poor. Even if the polymer is dissolved, its viscosity is still much lower than that of Example 1. At the same time, for Comparative Example 4, since it does not contain hydrophobic monomers, the viscosity is released within 1 minute, and it has more significant rapid solubility than hydrophobic associating polymers. However, Examples 1-4 can still be dissolved within 1-2 minutes, and have the rapid dissolution effect of online mixing.

[0129] The polymer obtained in Example 1 was dissolved in reinjection water with different flowback dilution ratios to obtain simulated reinjection water with different salinities. The rheological properties, viscoelasticity, drag reduction, and static sand carrying performance of the obtained solutions were tested according to the standard "SY / T 7627-2021 Technical Requirements for Water-Based Fracturing Fluids". The results are shown in Table 3:

[0130] Table 3 Salt resistance of polymers

[0131]

[0132]

[0133] Under low viscosity conditions (6mPa·s), the liquid drag reduction rate is 78%. When the viscosity increases to 30mPa·s, its drag reduction rate is 72%. It also has significant elastic characteristics, which can keep the 70 / 140 quartz sand proppant completely suspended without settling. As the mineralization of the reinjection water increases, its elastic modulus can reach 5.65Pa under the corresponding dosage, and it can still keep the proppant in a fully suspended state.

[0134] The polymerizable hydrophobic functional monomer solution obtained in step S2 of Example 1 and the corresponding polymerizable hydrophobic functional monomer solutions of Comparative Examples 1 and 2 were prepared into different concentrations and their average particle sizes were tested. The results are as follows: Figure 4The hydrophobic functional monomer micelles obtained in Example 1 reached their maximum size at 300 mg / L, with an average size of 318 nm, which is larger than those in Comparative Examples 1 and 2. Larger micelle size facilitates the formation of a more compact associative cross-linked structure, thus significantly enhancing the salt resistance of the polymer.

[0135] The test results of the above examples demonstrate that the polymer proposed in this application has the ability to achieve online mixing and rapid dissolution in reinjection water. Furthermore, it has excellent salt resistance, and the fracturing fluid prepared in highly salinized water has outstanding advantages in drag reduction and sand carrying.

[0136] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A fast-soluble hydrophobic associating polymer for reinjection water for fracturing, characterized in that: The molecular formula is shown in Formula 1: Formula 1; Wherein, by mass fraction, i is 60-65%; j is 15-39%; k is 0-15%; l is 0-3%; m is 0-2%; n is 0-4%; and l and m are not 0; R1 is a hydrophobic functional monomer 1, and its structural formula is shown in Formula 2, wherein the double bond structure and the quaternary ammonium salt structure are connected by a nonionic polar group: Formula 2; In formula 2, R4 is , a is 1-4; Or an active group containing an ester group, as shown in Formula 3: Formula 3; In formula 3, b is 0-2, c is 0-2; Or an active group containing an amide group, as shown in Formula 4: Formula 4; In formula 4, d is 0-2, e is 0-2; Or an active group containing ethoxy, as shown in Formula 5: Formula 5; In formula 5, f is 0-2, g is 1-10, and h is 0-2; In formula 2, R5 is a straight-chain alkyl group having 8 to 22 carbon atoms; R2 is a hydrophobic functional monomer 2, and its structural formula is shown in Formula 6: Formula 6; In formula 6, R6 and R7 are -H, -OH, -COO - 、-SO3 - 、-SO4 - 、-PO4 - One of the following, in the same molecule, has at least one anionic structure; R8 is a straight-chain alkyl group with 8 to 14 carbon atoms; R3 is a hydrophobic functional monomer 3, and its structural formula is shown in Formula 7: Formula 7; In formula 7, R9 is a polyvalent nonionic hydrophilic group, R 10 It is a hydrophobic carbon chain containing a monounsaturated double bond, and the structural formula of R9 is shown in Formula 8-10: Formula 8; or Formula 9; or Formula 10; R 10 The structural formula is shown in Formula 11: Formula 11; In formula 11, o is 4-12; p is 5-10; the carbon chain spatial conformation has a fold angle; The weight average molecular weight of the hydrophobically associating polymer is 5×10 6 - 8×10 6 , the preparation method of the hydrophobically associating polymer comprises the following steps: S1. adding a hydrophobic functional monomer to water, adding a nonionic polarity modifier and mixing to obtain a polymerizable hydrophobically associating micelle solution, wherein the hydrophobic functional monomer comprises one or more of the hydrophobic functional monomer 1, the hydrophobic functional monomer 2 and the hydrophobic functional monomer 3; the nonionic polarity modifier is a small molecule active substance having a nonionic active group or a copolymer containing a nonionic active group; S2. The polymerizable hydrophobically associating micelle solution is added to a conventional monomer aqueous solution, the total monomer system consisting of a hydrophobic functional monomer and a conventional monomer, the total monomer mass is fixed to 65-75% of the total mass of the aqueous solution to obtain a mixed solution A; S3. Using a molecular weight regulator to regulate the molecular weight of the copolymer in the mixed solution A to obtain a mixed solution B; S4. Add an initiator to the mixed solution B, keep it warm and let it stand for 2-4 hours to complete the reaction, and then granulate, dry and crush to obtain a hydrophobically associating polymer.

2. The method for preparing a fast-soluble hydrophobically associating polymer for reinjection water for fracturing according to claim 1, characterized in that: The following steps are involved: S1. adding a hydrophobic functional monomer to water, adding a nonionic polarity modifier and mixing to obtain a polymerizable hydrophobically associating micelle solution, wherein the hydrophobic functional monomer comprises one or more of the hydrophobic functional monomer 1, the hydrophobic functional monomer 2 and the hydrophobic functional monomer 3; the nonionic polarity modifier is a small molecule active substance having a nonionic active group or a copolymer containing a nonionic active group; S2. The polymerizable hydrophobically associating micelle solution is added to a conventional monomer aqueous solution, the total monomer system consisting of a hydrophobic functional monomer and a conventional monomer, the total monomer mass is fixed to 65-75% of the total mass of the aqueous solution to obtain a mixed solution A; S3. Using a molecular weight regulator to regulate the molecular weight of the copolymer in the mixed solution A to obtain a mixed solution B; S4. Add an initiator to the mixed solution B, keep it warm and let it stand for 2-4 hours to complete the reaction, and then granulate, dry and crush to obtain a hydrophobically associating polymer.

3. The method for preparing a fast-soluble hydrophobically associating polymer for reinjection water for fracturing according to claim 2, characterized in that: The small molecule active substance with non-ionic active groups is composed of a hydrophobic chain portion and a hydrophilic active group, wherein the hydrophobic chain portion is one or more of an alkyl alcohol, an alkylamine and an alkylphenol structure; and the hydrophilic active group is one or more of a polyoxyethylene block, a glucoside group, a polyglycerol group and a cyclodextrin group.

4. The method for preparing a fast-soluble hydrophobically associating polymer for reinjection water for fracturing according to claim 2, characterized in that: The copolymer containing nonionic active groups is formed by copolymerization of one or more polymerizable monomers, and has a degree of polymerization of 100-500. The polymerizable monomers are composed of a hydrophobic chain portion and a hydrophilic active group, wherein the hydrophobic chain portion is one or more of an alkyl alcohol, an alkylamine, and an alkylphenol structure; and the hydrophilic active group is one or more of a polyoxyethylene block, a glucoside group, a polyglycerol group, and a cyclodextrin group.

5. The method for preparing a fast-soluble hydrophobically associating polymer for reinjection water for fracturing according to claim 2, characterized in that: The molecular weight regulator is one or more of sodium formate, sodium acetate, isopropyl alcohol, sodium hypophosphite and urea.

6. The method for preparing a fast-soluble hydrophobically associating polymer for reinjection water for fracturing according to claim 2, characterized in that: The conventional monomers are composed of one or more of acrylamide, sodium acrylate, and sodium 2-acrylamide-2-methylpropanesulfonate.

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