Composite fracturing fluid densifier for oil and gas well and preparation process of composite fracturing fluid densifier

Abstract

The invention relates to the technical field of thickening agents for fracturing fluids, and particularly discloses a composite fracturing fluid thickening agent for an oil and gas well and a preparation process of the composite fracturing fluid thickening agent. The invention relates to a composite fracturing fluid densifier for oil and gas wells. The composite fracturing fluid densifier comprises 30-50 parts of acrylamide; 20 to 35 parts of 2-acrylamide-2-methyl propane sulfonic acid; 10 to 25 parts of acryloyl morpholine; 3-8 parts of a polyether amine modified organic zirconium cross-linking agent; 2-6 parts of sulfonated konjac gum; 1-5 parts of a salt-tolerant synergistic aid; 0.5-2 parts of a composite initiator; 0.1 to 0.8 part of an inhibitor; and 150 to 180 parts of deionized water. The fracturing fluid thickening agent provided by the invention has the advantages of high viscosity, high temperature resistance and high salt resistance.

Description

Technical Field

[0001] This application relates to the field of thickeners for fracturing fluids, and more specifically, to a composite fracturing fluid thickener for oil and gas wells and its preparation process. Background Technology

[0002] In the field of oil and gas exploration and development, with the continuous depletion of conventional oil and gas reservoir reserves, the focus of exploitation is gradually shifting to unconventional oil and gas reservoirs with low permeability, ultra-low permeability, and deep high temperature, such as tight sandstone gas, coalbed methane, and shale gas. Hydraulic fracturing technology, as a core means for the efficient development of these difficult-to-extract oil and gas resources, relies directly on the comprehensive performance of the fracturing fluid for its operational effectiveness. Thickeners, as key functional components of water-based gel fracturing fluids, play a crucial role in increasing the viscosity of the fracturing fluid, reducing filtrate loss, and suspending and carrying proppant into formation fractures. Water-based gel fracturing fluids, through the incomplete cross-linking reaction of thickener polymers and cross-linking agents, form a gel system with specific viscoelasticity. With advantages such as high viscosity, low friction, and strong proppant suspension capacity, it has been applied to production enhancement operations in major oil and gas fields across China. Especially in low-permeability oilfield blocks such as the Changqing Oilfield, fracturing operations contribute more than 30% to the improvement in oil recovery, becoming a core technological support for ensuring stable oil and gas production.

[0003] In related technologies, such as application document CN119614177A, a thickener for fracturing fluid and its preparation method are disclosed. The thickener comprises a liquid component and a solid component in a mass ratio of 1:(2.2-2.4). The liquid component is composed of deionized water and N-methylpyrrolidone, with a mass ratio of deionized water to N-methylpyrrolidone of 8.5:1.5. The solid component comprises the following raw materials in parts by weight: 20-30 parts 2-acrylamide-2-methylpropanesulfonic acid, 10-20 parts acrylic acid, 10-20 parts acrylamide, 8-10 parts hydroxypropyl methacrylate, 4-6 parts konjac gum, 2-4 parts chitosan, 1-3 parts diatomaceous earth, and 0.4-0.6 parts... The thickener contains 0.4-0.6 parts of ceramsite, 0.2-0.4 parts of disodium ethylenediaminetetraacetate, and 0.2-0.4 parts of chain transfer agent and initiator. By adding konjac powder during the preparation of the thickener, after mixing, reaction and curing, the amino functional groups in the konjac powder molecules can undergo cross-linking reactions with the aldehyde groups of glutaraldehyde, so that water molecules are wrapped in the cross-linked network structure, increasing the internal friction force during fluid flow, which plays a role in increasing the viscosity of the thickener. The hydroxyl groups on the konjac gum molecular chain undergo condensation reactions with the aldehyde groups of glutaraldehyde to form covalent bonds, which plays a cross-linking role, so that a stable chemical cross-linked network structure is formed between the konjac gum molecular chains, effectively improving the cross-linking performance of the thickener.

[0004] However, existing thickeners still have significant performance shortcomings when facing complex geological conditions. Their molecular structures are not fully adapted to the high-temperature, high-salinity environment, and the functional components lack sufficient resistance to degradation. Therefore, they are not suitable for use in deep oil and gas reservoirs with high temperatures (some blocks exceeding 200℃) and high salinity (formation water salinity exceeding 5×10⁻⁶). 4 Under conditions of (mg / L), the performance of thickeners degrades rapidly, failing to meet the requirements of fracturing operations. Regarding temperature resistance, most existing thickeners are linear polymers; high temperatures intensify the thermal motion of molecular chains, disrupting weak intermolecular interactions, leading to decreased chain entanglement and a sharp drop in viscosity. Regarding salt resistance, metal cations in high-salt environments can complex with the hydrophilic groups of the thickener, compressing the hydration layer and causing molecular chains to clump together, weakening the thickening effect and even causing flocculation. Even with the introduction of natural components such as konjac gum, the lack of salt-resistant functional groups makes it difficult to resist high-salt corrosion. In summary, thickeners in related technologies suffer from insufficient temperature and salt resistance. Summary of the Invention

[0005] To enhance the temperature and salt resistance of composite fracturing fluid thickeners for oil and gas wells, this application provides a composite fracturing fluid thickener for oil and gas wells and its preparation process.

[0006] This application provides a composite fracturing fluid thickener for oil and gas wells, employing the following technical solution: A composite fracturing fluid thickener for oil and gas wells is made from raw materials comprising the following components: Acrylamide 30-50 parts; 20-35 parts of 2-acrylamide-2-methylpropanesulfonic acid; Acryloylmorpholine 10-25 parts; 3-8 parts of polyetheramine-modified organozirconium crosslinking agent; 2-6 parts of sulfonated konjac gum; Salt-tolerant synergist 1-5 parts; 0.5-2 parts of composite initiator; Inhibitor 0.1-0.8 parts; 150-180 parts of deionized water; The polyetheramine-modified organozirconium crosslinking agent is obtained by coordination polymerization of zirconium oxychloride, polyetheramine D230, ethylene glycol monomethyl ether, and triethanolamine. The sulfonated konjac gum was obtained by modifying konjac gum with chlorosulfonic acid.

[0007] By employing the above technical solutions, acrylamide (AM) provides the basic polymerization framework, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) contains a strong hydrophilic sulfonic acid group (-SO3H), and the negatively charged layer formed after its ionization can resist the corrosion of metal cations in high-salt environments, preventing molecular chain coiling; acrylomorpholine contains a six-membered heterocyclic structure, and the conjugated system formed by nitrogen and oxygen atoms within the ring can enhance the rigidity of the molecular chain and suppress thermal motion at high temperatures. The combination of these three components not only ensures the basic adhesion of the polymer, but also synergistically improves its temperature and salt resistance through functional groups. The polyetheramine-modified organozirconium crosslinking agent molecule formed by coordination polymerization of zirconium oxychloride, polyetheramine D230, etc., simultaneously contains zirconium-oxygen-carbon covalent bonds, polyether segments, and amino functional groups. At high temperatures, the zirconium-oxygen-carbon bonds are not easily broken, maintaining the integrity of the crosslinking network; in high-salt environments, the steric hindrance effect of the polyether segments can hinder the contact between metal cations and the hydrophilic groups of the polymer, solving the problem of crosslinking failure of traditional crosslinking agents under complex working conditions. Natural konjac gum lacks salt-resistant functional groups and is prone to aggregation in high-salt environments. However, sulfonated konjac gum modified with chlorosulfonic acid introduces sulfonic acid groups, whose negative charge forms a "double salt-resistant barrier" with the sulfonic acid groups of AMPS. At the same time, the polysaccharide chains of konjac gum can form an interpenetrating network with the polymer backbone, further enhancing the viscosity stability of the system and avoiding viscosity decay caused by the decrease in molecular chain entanglement at high temperatures.

[0008] In summary, the design of the above-mentioned raw materials addresses the core defects of existing thickeners in terms of insufficient temperature and salt resistance from three dimensions: molecular structure, cross-linking network, and environmental adaptability. This can meet the fracturing requirements of deep oil and gas reservoirs under high temperature and high salt conditions.

[0009] Optionally, the polyetheramine-modified organozirconium crosslinking agent is prepared by the following method: Zirconium oxychloride was dissolved in ethylene glycol monomethyl ether and stirred at 40-60℃ for 30-60 min until completely dissolved to obtain a zirconium salt solution. Polyetheramine D230 was added dropwise to the zirconium salt solution over a period of 30-45 min. After the addition was complete, the temperature was raised to 70-85℃ and the reaction was maintained for 2-4 h. Triethanolamine was then added and the reaction was continued for 1-2 h. The mixture was cooled to room temperature and unreacted ethylene glycol monomethyl ether was removed by rotary evaporation to obtain a polyetheramine-modified organozirconium crosslinking agent.

[0010] Optionally, the molar ratio of zirconium oxychloride, polyetheramine D230, ethylene glycol monomethyl ether and triethanolamine is 1:(0.8-1.2):(1.5-2.5):(0.5-1).

[0011] By employing the above technical solution, zirconium oxychloride is dissolved in ethylene glycol monomethyl ether to form a zirconium salt solution, followed by the dropwise addition of polyetheramine D230 for coordination polymerization. Triethanolamine is then added to continue the reaction, ultimately yielding a polyetheramine-modified organozirconium crosslinking agent. This stepwise reaction method allows for precise control of the reaction process and extent between the raw materials, ensuring the formation of a stable coordination structure. At high temperatures, the zirconium-oxygen-carbon bond exhibits high stability and is not easily broken, thus maintaining the integrity of the crosslinking network and preventing the thickener's performance degradation due to crosslinking structure destruction caused by high temperatures. In high-salt environments, the steric hindrance effect of the polyether segments effectively hinders the contact between metal cations and the polymer's hydrophilic groups, avoiding the crosslinking failure of traditional crosslinking agents under high-salt conditions due to metal cation interference, thereby improving the thickener's temperature and salt resistance.

[0012] Optionally, the sulfonated konjac gum is prepared by the following method: Konjac gum was dissolved in deionized water and stirred at 30-40℃ to form a colloidal solution. Then, chlorosulfonic acid was added, and the temperature was raised to 55-65℃ and kept at this temperature for 3-5 hours. After the reaction was completed, the pH was adjusted to neutral with a 10%-15% sodium hydroxide solution. The mixture was then centrifuged, washed until no chloride ions were found, dried, and pulverized to obtain sulfonated modified konjac gum.

[0013] Optionally, the mass ratio of the konjac gum, deionized water and chlorosulfonic acid is 1:(12-18):(1.2-1.8).

[0014] By employing the above technical solution, konjac gum is first dissolved in deionized water to form a colloidal solution, then chlorosulfonic acid is added for sulfonation. After adjusting the pH to neutral, the solution is centrifuged, washed, dried, and pulverized to obtain sulfonated modified konjac gum. Chlorosulfonic acid modification introduces sulfonic acid groups into the konjac gum molecule. Natural konjac gum lacks salt-resistant functional groups and is prone to aggregation in high-salt environments. The sulfonic acid groups introduced into the modified sulfonated konjac gum carry a negative charge. The negatively charged layer formed after ionization can synergistically interact with the sulfonic acid groups of AMPS to form a "double salt-resistant barrier," effectively resisting the erosion of metal cations in high-salt environments and preventing molecular chain aggregation. Simultaneously, the polysaccharide chains of konjac gum can form an interpenetrating network with the polymer backbone, further enhancing the viscosity stability of the system, preventing viscosity decay due to decreased molecular chain entanglement at high temperatures, and improving the temperature and salt resistance of the thickener.

[0015] Optionally, the salt tolerance synergist is prepared by the following method: Montmorillonite was added to deionized water and ultrasonically dispersed for 20-30 minutes to form a montmorillonite suspension. Aminotrimethylenephosphonic acid was added and stirred at 70-85℃ for 4-6 hours. After cooling, the mixture was centrifuged, washed 3-5 times with deionized water, vacuum dried at 80-90℃ for 8-10 hours, and ground through a 200-mesh sieve to obtain aminotrimethylenephosphonic acid modified montmorillonite.

[0016] Optionally, the mass ratio of montmorillonite, deionized water and aminotrimethylenephosphonic acid is 1:(30-50):(0.3-0.6).

[0017] By employing the above technical solution, montmorillonite is ultrasonically dispersed in deionized water to form a suspension. Aminotrimethylene phosphonic acid is then added and stirred to react. Following centrifugation, washing, drying, and grinding, aminotrimethylene phosphonic acid-modified montmorillonite is obtained. Aminotrimethylene phosphonic acid can modify montmorillonite, imparting new properties. It reacts fully with montmorillonite, improving its surface properties. The modified montmorillonite can play a synergistic role in thickener systems, enhancing the thickener's tolerance to high-salt environments and further improving its salt resistance, thus meeting the requirements for use in deep oil and gas reservoirs under high-temperature and high-salt conditions.

[0018] Optionally, the composite initiator is potassium sulfite and sodium bisulfite in a mass ratio of (2-3):1.

[0019] By adopting the above technical solution, the composite initiator with the above mass ratio can provide suitable initiation conditions. During the polymerization reaction, the reaction rate and degree of polymerization can be precisely controlled, so that monomers such as acrylamide, AMPS, and acryloylmorpholine can be fully polymerized to form a polymer skeleton with good molecular structure and performance. This provides a stable thickening basis for the thickener and also helps to work synergistically with other functional components to improve the overall temperature and salt resistance of the thickener.

[0020] Optionally, the inhibitor is either sodium formate or hydroxypropyl methylcellulose.

[0021] Secondly, this application provides a method for preparing a composite fracturing fluid thickener for oil and gas wells, employing the following technical solution: A method for preparing a composite fracturing fluid thickener for oil and gas wells includes the following steps: S1. Mix acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acrylmorpholine, inhibitor and deionized water according to the ratio, stir for 1-2 hours to obtain a prepolymer solution, add a composite initiator to the prepolymer solution, and polymerize at 40-50℃ for 4-8 hours under nitrogen protection to obtain a polymer gel. S2. Add sulfonated konjac gum, salt-resistant synergist and polyetheramine-modified organozirconium crosslinking agent to the polymer gel, heat to 50-60℃ and continue stirring for 1-3 hours; then dry with forced air at 80-100℃ for 6-12 hours to obtain a composite fracturing fluid thickener for oil and gas wells.

[0022] By employing the above technical solution, in step S1, acrylamide, AMPS, acrylomorpholine, inhibitor, and deionized water are mixed and stirred to obtain a prepolymer solution. A composite initiator is then added, and polymerization is carried out under nitrogen protection to obtain a polymer gel. This step, through precise control of reaction conditions and raw material ratios, ensures that the three monomers undergo polymerization under the action of the initiator, forming a polymer backbone with a specific molecular structure. Acrylamide provides the basic polymerization backbone, while the strong hydrophilic sulfonic acid groups of AMPS and the six-membered heterocyclic structure of acrylomorpholine work synergistically to ensure the polymer's thickening base and enhance its temperature and salt resistance through functional group synergy. In step S2, sulfonated konjac gum, a salt-resistant synergist, and a polyetheramine-modified organozirconium crosslinking agent are added to the polymer gel. After heating and stirring, the mixture is dried by blowing air to obtain a thickener. In this step, the sulfonated konjac gum, salt-resistant synergist, and polyetheramine-modified organozirconium crosslinking agent are thoroughly mixed and reacted with the polymer gel. The "double salt resistance barrier" and interpenetrating network structure of sulfonated konjac gum, the synergistic effect of salt resistance synergists, and the stable crosslinking network of polyetheramine-modified organozirconium crosslinking agent jointly improve the temperature and salt resistance of the thickener, enabling it to meet the fracturing construction requirements under high temperature and high salt conditions in deep oil and gas reservoirs.

[0023] In summary, this application has the following beneficial effects: 1. Because this application uses acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and acrylomorpholine as basic polymerization components, acrylamide provides the basic polymerization skeleton, 2-acrylamido-2-methylpropanesulfonic acid contains a strong hydrophilic sulfonic acid group, and the negative charge layer formed after its ionization can resist the corrosion of metal cations in high-salt environments and avoid molecular chain coiling; acrylomorpholine contains a six-membered heterocyclic structure, and the conjugated system formed by nitrogen atoms and oxygen atoms in the ring can enhance the rigidity of the molecular chain and inhibit thermal motion at high temperatures. The synergistic effect of the three not only ensures the thickening basis of the polymer, but also significantly improves the temperature and salt resistance of the thickener through the synergistic effect of functional groups, effectively solving the defects of insufficient temperature and salt resistance of existing thickeners when facing complex geological conditions, and can meet the fracturing requirements of deep oil and gas reservoirs under high temperature and high salt conditions.

[0024] 2. This application preferably uses a polyetheramine-modified organozirconium crosslinking agent, which is obtained by coordination polymerization of zirconium oxychloride, polyetheramine D230, ethylene glycol monomethyl ether, and triethanolamine. Its molecule simultaneously contains zirconium-oxygen-carbon covalent bonds, polyether segments, and amino functional groups. At high temperatures, the zirconium-oxygen-carbon bonds are not easily broken, maintaining the integrity of the crosslinking network. In high-salt environments, the steric hindrance effect of the polyether segments hinders the contact between metal cations and the polymer's hydrophilic groups, solving the problem of crosslinking failure of traditional crosslinking agents under complex working conditions. This further enhances the temperature and salt resistance of the thickener, ensuring its stability and effectiveness under extreme conditions. Detailed Implementation

[0025] The present application will be further described in detail below with reference to the embodiments.

[0026] Preparation example of polyetheramine modified organozirconium crosslinking agent Preparation Example 1 The polyetheramine-modified organozirconium crosslinking agent was prepared by the following method: Weigh the raw materials zirconium oxychloride, polyetheramine D230, ethylene glycol monomethyl ether, and triethanolamine according to a molar ratio of 1:0.8:1.5:0.5. Dissolve zirconium oxychloride in ethylene glycol monomethyl ether and stir at 40°C for 30 min until completely dissolved to obtain a zirconium salt solution. Add polyetheramine D230 dropwise to the zirconium salt solution over a period of 30 min. After the addition is complete, raise the temperature to 70°C and maintain the reaction for 2 h. Then add triethanolamine and continue the reaction for 1 h. Cool to room temperature and remove unreacted ethylene glycol monomethyl ether by rotary evaporation to obtain the polyetheramine-modified organozirconium crosslinking agent.

[0027] Preparation Example 2 The polyetheramine-modified organozirconium crosslinking agent was prepared by the following method: Weigh the raw materials zirconium oxychloride, polyetheramine D230, ethylene glycol monomethyl ether, and triethanolamine according to a molar ratio of 1:1:2:0.8. Dissolve zirconium oxychloride in ethylene glycol monomethyl ether and stir at 50°C for 45 min until completely dissolved to obtain a zirconium salt solution. Add polyetheramine D230 dropwise to the zirconium salt solution over a period of 40 min. After the addition is complete, raise the temperature to 78°C and maintain the reaction for 3 h. Then add triethanolamine and continue the reaction for 1.5 h. Cool to room temperature and remove unreacted ethylene glycol monomethyl ether by rotary evaporation to obtain the polyetheramine-modified organozirconium crosslinking agent.

[0028] Preparation Example 3 The polyetheramine-modified organozirconium crosslinking agent was prepared by the following method: Weigh out the raw materials zirconium oxychloride, polyetheramine D230, ethylene glycol monomethyl ether, and triethanolamine in a molar ratio of 1:1.2:2.5:1. Dissolve zirconium oxychloride in ethylene glycol monomethyl ether and stir at 60°C for 60 min until completely dissolved to obtain a zirconium salt solution. Add polyetheramine D230 dropwise to the zirconium salt solution over a period of 45 min. After the addition is complete, raise the temperature to 78°C and maintain the reaction for 3 h. Then add triethanolamine and continue the reaction for 1.5 h. Cool to room temperature and remove unreacted ethylene glycol monomethyl ether by rotary evaporation to obtain the polyetheramine-modified organozirconium crosslinking agent.

[0029] Preparation example of sulfonated konjac gum Preparation Example 4 Sulfonated konjac gum is prepared by the following method: 10 kg of konjac gum was dissolved in 120 kg of deionized water and stirred at 30 °C to form a colloidal solution. Then, 12 kg of chlorosulfonic acid was added, the temperature was raised to 55 °C, and the reaction was maintained for 3 h. After the reaction was completed, the pH was adjusted to neutral with a 10% sodium hydroxide solution. The mixture was then centrifuged, washed until no chloride ions were found, dried, and pulverized to obtain sulfonated modified konjac gum.

[0030] Preparation Example 5 Sulfonated konjac gum is prepared by the following method: 10 kg of konjac gum was dissolved in 150 kg of deionized water and stirred at 35 °C to form a colloidal solution. Then, 15 kg of chlorosulfonic acid was added, the temperature was raised to 60 °C, and the reaction was maintained for 4 h. After the reaction was completed, the pH was adjusted to neutral with a 12% sodium hydroxide solution. The mixture was then centrifuged, washed until no chloride ions were found, dried, and pulverized to obtain sulfonated modified konjac gum.

[0031] Preparation Example 6 Sulfonated konjac gum is prepared by the following method: 10 kg of konjac gum was dissolved in 180 kg of deionized water and stirred at 40 °C to form a colloidal solution. Then, 18 kg of chlorosulfonic acid was added, the temperature was raised to 65 °C, and the reaction was maintained for 5 h. After the reaction was completed, the pH was adjusted to neutral with a 15% sodium hydroxide solution. The mixture was then centrifuged, washed until no chloride ions were found, dried, and pulverized to obtain sulfonated modified konjac gum.

[0032] Preparation example of salt-tolerant synergist Preparation Example 7 Salt-tolerant synergist was prepared using the following method: 1 kg of montmorillonite was added to 30 kg of deionized water and ultrasonically dispersed for 20 min to form a montmorillonite suspension. Aminotrimethylenephosphonic acid was added and stirred at 70 °C for 4 h. After cooling, the mixture was centrifuged, washed three times with deionized water, vacuum dried at 80 °C for 8 h, and ground through a 200-mesh sieve to obtain aminotrimethylenephosphonic acid modified montmorillonite.

[0033] Preparation Example 8 Salt-tolerant synergist was prepared using the following method: 1 kg of montmorillonite was added to 40 kg of deionized water and ultrasonically dispersed for 25 min to form a montmorillonite suspension. Aminotrimethylenephosphonic acid was added and stirred at 75 °C for 5 h. After cooling, the mixture was centrifuged, washed 4 times with deionized water, vacuum dried at 85 °C for 9 h, and ground through a 200-mesh sieve to obtain aminotrimethylenephosphonic acid modified montmorillonite.

[0034] Preparation Example 9 Salt-tolerant synergist was prepared using the following method: 1 kg of montmorillonite was added to 50 kg of deionized water and ultrasonically dispersed for 30 min to form a montmorillonite suspension. Aminotrimethylenephosphonic acid was added and stirred at 85 °C for 6 h. After cooling, the mixture was centrifuged, washed 5 times with deionized water, vacuum dried at 90 °C for 10 h, and ground through a 200-mesh sieve to obtain aminotrimethylenephosphonic acid modified montmorillonite.

[0035] Example Example 1 A composite fracturing fluid thickener for oil and gas wells, the raw material components and formulations of which are shown in Table 1, wherein the polyetheramine-modified organozirconium crosslinking agent is the polyetheramine-modified organozirconium crosslinking agent prepared in Preparation Example 1, the sulfonated konjac gum is the sulfonated konjac gum prepared in Preparation Example 4, the salt-resistant synergist is the salt-resistant synergist prepared in Preparation Example 7, the composite initiator is potassium sulfite and sodium bisulfite in a mass ratio of 2:1, and the inhibitor is sodium formate.

[0036] A composite fracturing fluid thickener for oil and gas wells, the preparation method of which includes the following steps: S1. Mix acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acrylamide morpholine, inhibitor and deionized water according to the ratio, stir for 1 hour to obtain a prepolymer solution, add a composite initiator to the prepolymer solution, and polymerize at 40°C for 4 hours under nitrogen protection to obtain a polymer gel. S2. Add sulfonated konjac gum, salt-resistant synergist and polyetheramine-modified organozirconium crosslinking agent to the polymer gel, heat to 50℃ and continue stirring for 1 hour; then dry at 80℃ for 6 hours to obtain a composite fracturing fluid thickener for oil and gas wells.

[0037] Example 2 A composite fracturing fluid thickener for oil and gas wells, the raw material components and formulations of which are shown in Table 1, wherein the polyetheramine-modified organozirconium crosslinking agent is the polyetheramine-modified organozirconium crosslinking agent prepared in Preparation Example 2, the sulfonated konjac gum is the sulfonated konjac gum prepared in Preparation Example 5, the salt-resistant synergist is the salt-resistant synergist prepared in Preparation Example 8, the composite initiator is potassium sulfite and sodium bisulfite in a mass ratio of 2.5:1, and the inhibitor is hydroxypropyl methylcellulose.

[0038] A composite fracturing fluid thickener for oil and gas wells, the preparation method of which includes the following steps: S1. Acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acrylmorpholine, inhibitor and deionized water are mixed according to the formula and stirred for 1.5 h to obtain a prepolymer solution. A composite initiator is added to the prepolymer solution and polymerized at 45°C for 6 h under nitrogen protection to obtain a polymer gel. S2. Add sulfonated konjac gum, salt-resistant synergist and polyetheramine-modified organozirconium crosslinking agent to the polymer gel, heat to 55℃ and continue stirring for 2 hours; then dry at 90℃ for 9 hours to obtain a composite fracturing fluid thickener for oil and gas wells.

[0039] Example 3 A composite fracturing fluid thickener for oil and gas wells, the raw material components and formulations of which are shown in Table 1, wherein the polyetheramine-modified organozirconium crosslinking agent is the polyetheramine-modified organozirconium crosslinking agent prepared in Preparation Example 3, the sulfonated konjac gum is the sulfonated konjac gum prepared in Preparation Example 6, the salt-resistant synergist is the salt-resistant synergist prepared in Preparation Example 9, the composite initiator is potassium sulfite and sodium bisulfite in a mass ratio of 3:1, and the inhibitor is hydroxypropyl methylcellulose.

[0040] A composite fracturing fluid thickener for oil and gas wells, the preparation method of which includes the following steps: S1. Mix acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acrylmorpholine, inhibitor and deionized water according to the ratio, stir for 2 hours to obtain a prepolymer solution, add a composite initiator to the prepolymer solution, and polymerize at 50°C for 8 hours under nitrogen protection to obtain a polymer gel. S2. Add sulfonated konjac gum, salt-resistant synergist and polyetheramine-modified organozirconium crosslinking agent to the polymer gel, heat to 60℃ and continue stirring for 3 hours; then dry at 100℃ for 12 hours to obtain a composite fracturing fluid thickener for oil and gas wells.

[0041] Table 1. Raw material components and proportions (kg) of the composite fracturing fluid thickener for oil and gas wells in Examples 1-3.

[0042] Example 4 A composite fracturing fluid thickener for oil and gas wells differs from Example 1 in that the inhibitor used in this example is hydroxypropyl methylcellulose.

[0043] Example 5 A composite fracturing fluid thickener for oil and gas wells differs from Example 1 in that the composite initiator in this example is potassium sulfite and sodium bisulfite in a mass ratio of 1:1.

[0044] Example 6 A composite fracturing fluid thickener for oil and gas wells differs from Example 1 in that the salt-tolerant synergist in this example is untreated montmorillonite.

[0045] Comparative Example Comparative Example 1 The thickener for fracturing fluid was prepared according to the method in Example 1 of the application document with publication number CN119614177A entitled "A Thickener for Fracturing Fluid and its Preparation Method".

[0046] Comparative Example 2 A composite fracturing fluid thickener for oil and gas wells differs from Example 1 in that an equal amount of sodium tetraborate decahydrate crosslinking agent is used instead of polyetheramine-modified organozirconium crosslinking agent in this comparative example.

[0047] Comparative Example 3 A composite fracturing fluid thickener for oil and gas wells differs from Example 1 in that an equal amount of unmodified konjac gum is used instead of sulfonated konjac gum in this comparative example.

[0048] Comparative Example 4 A composite fracturing fluid thickener for oil and gas wells differs from Example 1 in that no salt-resistant synergist is added in this comparative example, and the difference is made up with acrylamide.

[0049] Performance testing I. Thickener Viscosity Testing The initial viscosity of the fracturing fluid base fluid prepared by the thickener was determined according to SY / T5107-2016 "Performance Evaluation Method of Water-based Fracturing Fluid". The test results are shown in Table 2.

[0050] II. Thickener Temperature Resistance Test According to SY / T5107-2016 "Performance Evaluation Method of Water-based Fracturing Fluid", the viscosity retention rate of the gel after the thickener crosslinks was measured to simulate the high temperature environment (220℃) of deep oil and gas reservoirs, and its temperature resistance stability was evaluated. The test results are shown in Table 2.

[0051] III. Thickener Salt Resistance Test According to SY / T5107-2016 "Performance Evaluation Method of Water-Based Fracturing Fluids", a salinity-simulating brine was prepared using NaCl, CaCl2, and MgCl2 in a mass ratio of 8:1:1 to simulate the high-salinity environment of deep oil and gas reservoirs (salinity 8×10⁻⁶). 4 ~9×10 4 The viscosity retention rate of the gel after crosslinking with thickener was determined by the concentration of mg / L, and its salt resistance stability was evaluated. The test results are shown in Table 2.

[0052] Table 2 Detection Results

[0053] As shown in Table 2, the viscosity of the thickeners in Examples 1-3 is between 132-137 mPa·s, the temperature resistance viscosity retention rate is between 90.8%-93.1%, and the salt resistance viscosity retention rate is between 91.6%-94.7%. This indicates that the thickeners prepared under different raw material ratios all have good viscosity, temperature resistance, and salt resistance, and the adjustment of the raw material ratio has a relatively stable effect on performance within a certain range.

[0054] The difference between Example 4 and Example 1 is that the inhibitor used is hydroxypropyl methylcellulose. The test results show that its viscosity, temperature resistance viscosity retention rate and salt resistance viscosity retention rate are not much different from those of Example 1, indicating that in the technical solution of this application, the use of sodium formate or hydroxypropyl methylcellulose as an inhibitor has little impact on the overall performance of the thickener.

[0055] The difference between Example 5 and Example 1 lies in the different mass ratio of the composite initiator. The test results show that its viscosity, temperature-resistant viscosity retention rate, and salt-resistant viscosity retention rate are all lower than those of Example 1. This indicates that when the mass ratio of the composite initiator is 2:1, it can better provide suitable initiation conditions, accurately control the reaction rate and degree of polymerization, and make the thickener performance better.

[0056] The difference between Example 6 and Example 1 is that the salt-resistant synergist used is untreated montmorillonite. The test results show that its salt-resistant viscosity retention rate is significantly lower than that of Example 1, indicating that aminotrimethylene phosphonic acid modified montmorillonite, as a salt-resistant synergist, can better enhance the thickener's tolerance to high-salt environments and improve its salt resistance performance.

[0057] The test results of the thickener in Comparative Example 1 showed that its viscosity, temperature resistance viscosity retention rate, and salt resistance viscosity retention rate were all lower than those of the embodiments of this application, indicating that the thickener prepared by the technical solution of this application is superior to the thickeners in related technologies in terms of temperature and salt resistance performance.

[0058] Comparative Example 2 used an equal amount of sodium tetraborate decahydrate crosslinking agent instead of polyetheramine-modified organozirconium crosslinking agent. The test results showed that its viscosity, temperature resistance viscosity retention rate, and salt resistance viscosity retention rate were all lower than those of Example 1. This indicates that polyetheramine-modified organozirconium crosslinking agent has a significant advantage in improving the temperature and salt resistance performance of thickeners. Traditional crosslinking agents are prone to crosslinking failure under complex working conditions.

[0059] Comparative Example 3 used an equal amount of unmodified konjac gum instead of sulfonated konjac gum. The test results showed that its temperature resistance viscosity retention rate and salt resistance viscosity retention rate were both lower than those of Example 1. This indicates that the "double salt resistance barrier" formed by the sulfonic acid groups introduced by sulfonated konjac gum and the interpenetrating network structure formed with the polymer skeleton play an important role in improving the temperature and salt resistance performance of the thickener. Natural konjac gum is difficult to meet the requirements.

[0060] Comparative Example 4, without the addition of salt-resistant synergist, showed that its salt-resistant viscosity retention rate was significantly lower than that of Example 1, indicating that the salt-resistant synergist is indispensable for improving the salt resistance of the thickener.

[0061] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A composite fracturing fluid thickener for oil and gas wells, characterized in that, It is made from raw materials containing the following components: Acrylamide 30-50 parts; 20-35 parts of 2-acrylamide-2-methylpropanesulfonic acid; Acryloylmorpholine 10-25 parts; 3-8 parts of polyetheramine-modified organozirconium crosslinking agent; 2-6 parts of sulfonated konjac gum; Salt-tolerant synergist 1-5 parts; 0.5-2 parts of composite initiator; Inhibitor 0.1-0.8 parts; 150-180 parts of deionized water; The polyetheramine-modified organozirconium crosslinking agent is obtained by coordination polymerization of zirconium oxychloride, polyetheramine D230, ethylene glycol monomethyl ether, and triethanolamine. The sulfonated konjac gum was obtained by modifying konjac gum with chlorosulfonic acid.

2. The composite fracturing fluid thickener for oil and gas wells according to claim 1, characterized in that, The polyetheramine-modified organozirconium crosslinking agent was prepared by the following method: Zirconium oxychloride was dissolved in ethylene glycol monomethyl ether and stirred at 40-60℃ for 30-60 min until completely dissolved to obtain a zirconium salt solution. Polyetheramine D230 was added dropwise to the zirconium salt solution over a period of 30-45 min. After the addition was complete, the temperature was raised to 70-85℃ and the reaction was maintained for 2-4 h. Triethanolamine was then added and the reaction was continued for 1-2 h. The mixture was cooled to room temperature and unreacted ethylene glycol monomethyl ether was removed by rotary evaporation to obtain a polyetheramine-modified organozirconium crosslinking agent.

3. The composite fracturing fluid thickener for oil and gas wells according to claim 2, characterized in that, The molar ratio of zirconium oxychloride, polyetheramine D230, ethylene glycol monomethyl ether and triethanolamine is 1:(0.8-1.2):(1.5-2.5):(0.5-1).

4. The composite fracturing fluid thickener for oil and gas wells according to claim 2, characterized in that, The sulfonated konjac gum was prepared by the following method: Konjac gum was dissolved in deionized water and stirred at 30-40℃ to form a colloidal solution. Then, chlorosulfonic acid was added, and the temperature was raised to 55-65℃ and kept at this temperature for 3-5 hours. After the reaction was completed, the pH was adjusted to neutral with a 10%-15% sodium hydroxide solution. The mixture was then centrifuged, washed until no chloride ions were found, dried, and pulverized to obtain sulfonated modified konjac gum.

5. A composite fracturing fluid thickener for oil and gas wells according to claim 4, characterized in that, The mass ratio of konjac gum, deionized water and chlorosulfonic acid is 1:(12-18):(1.2-1.8).

6. The composite fracturing fluid thickener for oil and gas wells according to claim 1, characterized in that, The salt tolerance synergist was prepared by the following method: Montmorillonite was added to deionized water and ultrasonically dispersed for 20-30 minutes to form a montmorillonite suspension. Aminotrimethylenephosphonic acid was added and stirred at 70-85℃ for 4-6 hours. After cooling, the mixture was centrifuged, washed 3-5 times with deionized water, vacuum dried at 80-90℃ for 8-10 hours, and ground through a 200-mesh sieve to obtain aminotrimethylenephosphonic acid modified montmorillonite.

7. A composite fracturing fluid thickener for oil and gas wells according to claim 6, characterized in that, The mass ratio of montmorillonite, deionized water and aminotrimethylenephosphonic acid is 1:(30-50):(0.3-0.6).

8. The composite fracturing fluid thickener for oil and gas wells according to claim 1, characterized in that, The composite initiator is potassium sulfite and sodium bisulfite in a mass ratio of (2-3):

1.

9. A composite fracturing fluid thickener for oil and gas wells according to claim 1, characterized in that, The inhibitor is either sodium formate or hydroxypropyl methylcellulose.

10. A method for preparing a composite fracturing fluid thickener for oil and gas wells according to any one of claims 1-9, characterized in that, The steps include the following: S1. Mix acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acrylmorpholine, inhibitor and deionized water according to the ratio, stir for 1-2 hours to obtain a prepolymer solution, add a composite initiator to the prepolymer solution, and polymerize at 40-50℃ for 4-8 hours under nitrogen protection to obtain a polymer gel. S2. Add sulfonated konjac gum, salt-resistant synergist and polyetheramine-modified organozirconium crosslinking agent to the polymer gel, heat to 50-60℃ and continue stirring for 1-3 hours; then dry with forced air at 80-100℃ for 6-12 hours to obtain a composite fracturing fluid thickener for oil and gas wells.

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