A thickening agent for fracturing fluid and its preparation method

Abstract

The present invention relates to the technical field of thickeners, and specifically to a thickener for fracturing fluid and a preparation method thereof: including a liquid material and a solid material, the mass ratio of the liquid material to the solid material is 1:(2.2 - 2.4), and the liquid material is composed of deionized water and N-methylpyrrolidone. In the present invention, by adding konjac powder in the preparation of the thickener, after the konjac powder undergoes a mixing reaction and a curing treatment, the amino functional groups in the konjac molecules can undergo a cross-linking reaction 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, that is, playing a role in enhancing the viscosity of the thickener. The hydroxyl groups on the konjac gum molecular chain undergo a condensation reaction with the aldehyde groups of glutaraldehyde to form covalent bonds, playing a cross-linking role, and forming a stable chemical cross-linked network structure between the konjac gum molecular chains, effectively improving the cross-linking performance of the thickener.

Description

Technical Field

[0001] The present invention relates to the technical field of thickeners, and particularly to a thickener for fracturing fluid and a preparation method thereof. Background Art

[0002] The thickener for fracturing fluid is a chemical additive used to increase the viscosity of fracturing fluid and plays a key role in the fracturing operation of oil and gas exploitation.

[0003] In the prior art, during the fracturing operation, as the formation depth increases and the temperature rises, the intermolecular force between molecular chains will be weakened at high temperature, resulting in a decrease in the entanglement degree of molecular chains and affecting the viscosity performance of fracturing fluid. Based on this, the present invention provides a thickener for fracturing fluid and a preparation method thereof. Summary of the Invention

[0004] The purpose of the present invention is to provide a thickener for fracturing fluid and a preparation method thereof. The thickener for fracturing fluid prepared by the present invention not only has good viscosity but also excellent cross-linking performance, effectively improving the use performance of the thickener.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] In the first aspect, the present invention provides a thickener for fracturing fluid, including a liquid material and a solid material, and the mass ratio of the liquid material to the solid material is 1:(2.2 - 2.4);

[0007] The liquid material is composed of deionized water and N-methylpyrrolidone, and the mass ratio of the deionized water to N-methylpyrrolidone is 8.5:1.5;

[0008] The solid material includes the following raw materials in parts by weight: 20 - 30 parts of 2-acrylamide-2-methylpropanesulfonic acid, 10 - 20 parts of acrylic acid, 10 - 20 parts of acrylamide, 8 - 10 parts of hydroxypropyl methacrylate, 4 - 6 parts of konjac gum, 2 - 4 parts of chitosan, 1 - 3 parts of diatomite, 0.4 - 0.6 parts of ceramsite, 0.4 - 0.6 parts of disodium ethylenediaminetetraacetate, 0.2 - 0.4 parts of chain transfer agent, and 0.2 - 0.4 parts of initiator;

[0009] The konjac gum is subjected to modification treatment, and the modification treatment of the konjac gum includes the following steps:

[0010] S1: Mix and react the konjac gum to obtain a mixed solution;

[0011] S2: Carry out solidification treatment on the mixed solution to complete the modification treatment of the konjac gum.

[0012] Further, the chain transfer agent is selected from at least one of sodium formate, sodium sulfate, and sodium citrate.

[0013] Further, the initiator is selected as sodium bisulfite.

[0014] Further, the konjac gum is selected as a powder with a particle size of 140 - 200 mesh.

[0015] Further, the mixed solution is prepared by the following method: the konjac gum and the glutaraldehyde solution are added into a mixer, and the mixer is set to stir at 220 - 240 r / min for 8 - 12 min. After mixing evenly, it is added into a water bath and heated to 50 - 60 °C. Stirring is maintained during the heating process, and then it is kept for a reaction for 16 - 20 min. After cooling to room temperature, a sodium carbonate solution is added, stirred evenly, and left standing for 6 - 10 min to obtain the mixed solution.

[0016] Further, the mass of the glutaraldehyde solution is 2 - 3 times that of the konjac gum, the concentration of the glutaraldehyde solution is 2 - 4%, the mass of the sodium carbonate solution is 10 - 20% of the mass of the konjac gum, and the concentration of the sodium carbonate solution is 4 - 6%.

[0017] Further, the method of the curing treatment is as follows: the mixed solution is subjected to filtration and separation treatment to obtain a solid product, the solid product is washed, and then sent into an oven. The oven is set to dry at 60 - 70 °C for 40 - 50 min. After the drying treatment, it is ground and sieved. The sieve aperture is 140 - 200 mesh, and the modification treatment of the konjac gum is completed.

[0018] Further, the acrylic acid and hydroxypropyl methacrylate are pretreated to obtain an additive solution, and the additive solution is prepared by the following method: acrylic acid and hydroxypropyl methacrylate are mixed in a reaction kettle. Deionized water and sodium dodecylbenzenesulfonate are added into the reaction kettle. The mass of the deionized water is 70 - 80% of the mass of the acrylic acid, and the mass ratio of the deionized water to the sodium dodecylbenzenesulfonate is 1:(0.1 - 0.3). After mixing evenly, an ammonium persulfate solution is added, and the temperature is raised to 60 - 80 °C. The reaction kettle is kept in a stirring state with a rotation speed of 120 - 160 r / min. After heating, a p-toluenesulfonic acid solution is added, and the reaction is kept for 2 - 3 h. Ammonia water is added to adjust the pH value to 8 - 9 to obtain the additive solution. Among them, the mass of the ammonium persulfate solution is 6 - 10% of the mass of the acrylic acid, the concentration is 2 - 4%, the mass of the p-toluenesulfonic acid solution is 4 - 6% of the mass of the acrylic acid, and the concentration is 1 - 3%.

[0019] Further, the chitosan, diatomite, and ceramsite are all selected as powders with a particle size of 200 - 300 mesh.

[0020] Second, the present invention also provides a preparation method of a thickening agent for a fracturing fluid, including the following steps:

[0021] Step 1: Weigh deionized water, N-methylpyrrolidone, and 2-acrylamido-2-methylpropanesulfonic acid as needed and add them to the reaction kettle. Set the mixing speed at 80 - 120 r / min and mix for 6 - 10 min. After mixing, add the additive solution, set the mixing speed at 120 - 160 r / min and mix for 12 - 16 min to obtain a preliminary reaction solution.

[0022] Step 2: Weigh the modified konjac gum as needed in the preliminary reaction solution, let it stand and react for 20 - 30 min. Then weigh acrylamide, chitosan, diatomite, ceramsite, disodium ethylenediaminetetraacetate, and chain transfer agent as needed. Set the mixing speed at 80 - 120 r / min and mix for 20 - 30 min. Continuously introduce nitrogen during the mixing process. After mixing, add the initiator, mix well and react for 3 - 6 h to prepare the thickening agent for fracturing fluid.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. In the present invention, by adding konjac powder in the preparation of the thickening agent, after the konjac powder undergoes mixing reaction and curing treatment, the amino functional groups in the konjac molecules can cross-link 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, that is, playing a role in increasing the viscosity of the thickening agent. The hydroxyl groups on the konjac gum molecular chain undergo a condensation reaction with the aldehyde groups of glutaraldehyde to form covalent bonds, playing a cross-linking role, and forming a stable chemical cross-linked network structure between the konjac gum molecular chains, effectively improving the cross-linking performance of the thickening agent.

[0025] 2. In the present invention, by adding chitosan, diatomite, and ceramsite, using the hydrophilic groups contained in the chitosan molecular chain, which can form hydrogen bonds with water molecules, are evenly distributed in the fracturing fluid and play a tangling role, effectively increasing the viscosity of the fracturing fluid and enhancing its sand-carrying capacity. Using the rich pore structure of diatomite and ceramsite, with a relatively large specific surface area, it can form tiny filtration channels in the fracturing fluid to prevent solid particles and impurities in the fracturing fluid from entering the formation, reducing the filtration loss and improving the fracturing effect. Through the addition of the above natural materials, the natural materials can be naturally degraded in the natural environment, reducing the pollution to the formation soil.

[0026] 3. In the present invention, through the pretreatment of acrylic acid and hydroxypropyl methacrylate, the acrylic acid and hydroxypropyl methacrylate undergo a cross-linking reaction to form a branched structure in the acrylic acid molecular chain, reducing the freely moving molecular chains and increasing the fluid resistance, thereby achieving the purpose of increasing the viscosity of the fracturing fluid. Detailed implementation mode

[0027] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.

[0028] This embodiment provides a thickening agent for fracturing fluid, which includes a liquid material and a solid material, and the mass ratio of the liquid material to the solid material is 1:(2.2 - 2.4);

[0029] The liquid material is composed of deionized water and N-methylpyrrolidone, and the mass ratio of deionized water to N-methylpyrrolidone is 8.5:1.5;

[0030] The solid material includes the following raw materials in parts by weight: 20 - 30 parts of 2-acrylamide-2-methylpropanesulfonic acid, 10 - 20 parts of acrylic acid, 10 - 20 parts of acrylamide, 8 - 10 parts of hydroxypropyl methacrylate, 4 - 6 parts of konjac gum, 2 - 4 parts of chitosan, 1 - 3 parts of diatomite, 0.4 - 0.6 parts of ceramsite, 0.4 - 0.6 parts of disodium ethylenediaminetetraacetate, 0.2 - 0.4 parts of chain transfer agent, and 0.2 - 0.4 parts of initiator;

[0031] The konjac gum is subjected to a modification treatment, and the modification treatment of the konjac gum includes the following steps:

[0032] S1: Mix and react the konjac gum to obtain a mixed solution;

[0033] S2: Carry out a solidification treatment on the mixed solution to complete the modification treatment of the konjac gum.

[0034] In some embodiments, the chain transfer agent is selected from at least one of sodium formate, sodium sulfate, and sodium citrate.

[0035] In some embodiments, the initiator is selected as sodium bisulfite.

[0036] In some embodiments, the konjac gum is selected as a powder with a particle size of 140 - 200 mesh.

[0037] In some embodiments, the mixed solution is obtained by the following method: Add the konjac gum and glutaraldehyde solution into a mixer, set the mixer to stir at 220 - 240 r / min for 8 - 12 min, after mixing evenly, add it into a water bath, heat to 50 - 60 °C, keep stirring during the heating process, then carry out a heat preservation reaction for 16 - 20 min, after cooling to room temperature, add a sodium carbonate solution, stir evenly, and stand for 6 - 10 min to obtain the mixed solution.

[0038] In some embodiments, the mass of the glutaraldehyde solution is 2 to 3 times the mass of the konjac gum, the concentration of the glutaraldehyde solution is 2 to 4%, the mass of the sodium carbonate solution is 10 to 20% of the mass of the konjac gum, and the concentration of the sodium carbonate solution is 4 to 6%.

[0039] In some embodiments, the method of curing treatment is as follows: the mixed solution is subjected to filtration separation treatment to obtain a solid product, the solid product is washed, and then sent into an oven. The oven is set at 60 - 70°C for drying treatment at 40 - 50°C. After drying treatment, it is ground and sieved. The sieve diameter is 140 - 200 mesh, and the modification treatment of konjac gum is completed.

[0040] In some embodiments, acrylic acid and hydroxypropyl methacrylate are pretreated to obtain an additive solution, which is prepared by the following method: acrylic acid and hydroxypropyl methacrylate are mixed in a reaction kettle. Deionized water and sodium dodecylbenzenesulfonate are added to the reaction kettle. The mass of the deionized water is 70 - 80% of the mass of acrylic acid, and the mass ratio of deionized water to sodium dodecylbenzenesulfonate is 1:(0.1 - 0.3). After mixing evenly, ammonium persulfate solution is added, and the temperature is raised to 60 - 80°C. The reaction kettle is kept in a stirring state with a rotation speed of 120 - 160 r / min. After heating, p-toluenesulfonic acid solution is added, and the reaction is kept for 2 - 3 h. Ammonia water is added to adjust the pH value to 8 - 9 to obtain the additive solution. Among them, the mass of the ammonium persulfate solution is 6 - 10% of the mass of acrylic acid, the concentration is 2 - 4%, the mass of the p-toluenesulfonic acid solution is 4 - 6% of the mass of acrylic acid, and the concentration is 1 - 3%.

[0041] In some embodiments, chitosan, diatomite, and ceramsite are all selected as powders with a particle size of 200 - 300 mesh.

[0042] In some embodiments, a preparation method of a thickening agent for a fracturing fluid includes the following steps:

[0043] Step 1: Weigh deionized water, N-methylpyrrolidone, and 2-acrylamide-2-methylpropanesulfonic acid as required and add them to a reaction kettle. Set the mixing speed at 80 - 120 r / min for 6 - 10 min. After mixing, add the additive solution, and set the mixing speed at 120 - 160 r / min for 12 - 16 min to obtain a preliminary reaction solution;

[0044] Step 2: Weigh the modified konjac gum as required in the preliminary reaction solution, let it stand for reaction for 20 - 30 min, and then weigh acrylamide, chitosan, diatomite, ceramsite, disodium ethylenediaminetetraacetate, and a chain transfer agent as required. Set the mixing speed at 80 - 120 r / min for 20 - 30 min. Nitrogen is continuously introduced during the mixing process. After mixing, add an initiator, and after mixing evenly, react for 3 - 6 h to obtain a thickening agent for a fracturing fluid.

[0045] In this embodiment, by adding konjac powder in the preparation of the thickening agent, after the konjac powder undergoes a mixing reaction and a curing treatment, the amino functional groups in the konjac molecules can undergo a crosslinking reaction with the aldehyde groups of glutaraldehyde, so that water molecules are wrapped in the crosslinked network structure, increasing the internal friction during fluid flow, that is, playing a role in increasing the viscosity of the thickening agent. The hydroxyl groups on the konjac gum molecular chain undergo a condensation reaction with the aldehyde groups of glutaraldehyde to form covalent bonds, playing a crosslinking role, and forming a stable chemical crosslinked network structure between the konjac gum molecular chains, effectively improving the crosslinking performance of the thickening agent. By adding chitosan, diatomite and ceramsite, using the hydrophilic groups contained in the chitosan molecular chain, hydrogen bonds can be formed with water molecules, evenly distributed in the fracturing fluid and playing a tangling role, effectively increasing the viscosity of the fracturing fluid and enhancing its sand-carrying capacity. Utilizing the rich pore structures of diatomite and ceramsite, with a relatively large specific surface area, tiny filtration channels can be formed in the fracturing fluid to prevent solid particles and impurities in the fracturing fluid from entering the formation, reducing the filtration loss and improving the fracturing effect. By adding the above natural materials, the natural materials can be naturally degraded in the natural environment, reducing the pollution to the formation soil. By pre-treating acrylic acid and hydroxypropyl methacrylate, a crosslinking reaction occurs between acrylic acid and hydroxypropyl methacrylate, forming a branched structure in the acrylic acid molecular chain, reducing the freely moving molecular chains and increasing the fluid resistance, thereby achieving the purpose of increasing the viscosity of the fracturing fluid.

[0046] Based on the foregoing embodiments, the following multiple groups of experiments were carried out:

[0047] It should be noted that the raw materials used in the following experiments are all commercially available raw materials.

[0048] Experiment 1:

[0049] Raw material preparation: The mass ratio of the liquid material to the solid material is 1:(2.2);

[0050] The liquid material consists of deionized water and N-methylpyrrolidone, and the mass ratio of deionized water to N-methylpyrrolidone is 8.5:1.5;

[0051] The solid material includes the following raw materials by weight: 20 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10 parts of acrylic acid, 10 parts of acrylamide, 8 parts of hydroxypropyl methacrylate, 4 parts of konjac gum, 2 parts of chitosan, 1 part of diatomite, 0.4 part of ceramsite, 0.4 part of disodium ethylenediaminetetraacetate, 0.2 part of chain transfer agent and 0.2 part of initiator. The chain transfer agent is selected as sodium formate, the initiator is selected as sodium bisulfite, the konjac gum is selected as a powder with a particle size of 140 mesh, and the chitosan, diatomite and ceramsite are all selected as powders with a particle size of 200 mesh;

[0052] The konjac gum is subjected to a modification treatment, and the modification treatment of the konjac gum includes the following steps:

[0053] S1: Mix konjac gum to carry out a reaction to obtain a mixed solution;

[0054] The mixed solution is obtained by the following method: Konjac gum and glutaraldehyde solution are added to a mixer. The mixer is set to stir at 220 r / min for 8 min. After mixing evenly, it is added to a water bath and heated to 50 °C. Stirring is maintained during the heating process. Then, it is kept for a reaction for 16 min. After cooling to room temperature, sodium carbonate solution is added, stirred evenly, and left standing for 6 min to obtain the mixed solution. The mass of the glutaraldehyde solution is 2 times the mass of the konjac gum, the concentration of the glutaraldehyde solution is 2%, the mass of the sodium carbonate solution is 10% of the mass of the konjac gum, and the concentration of the sodium carbonate solution is 4%;

[0055] S2: Carry out solidification treatment on the mixed solution to complete the modification treatment of konjac gum;

[0056] The method of solidification treatment is: The mixed solution is subjected to filtration and separation treatment to obtain a solid product. The solid product is washed, and then sent into an oven. The oven is set to dry at 60 °C for 40 °C. After drying, it is ground and sieved. The sieve diameter is 140 mesh to complete the modification treatment of konjac gum;

[0057] Acrylic acid and hydroxypropyl methacrylate are pretreated to obtain an additive solution. The additive solution is obtained by the following method: Acrylic acid and hydroxypropyl methacrylate are mixed in a reaction kettle. Deionized water and sodium dodecylbenzenesulfonate are added to the reaction kettle. The mass of the deionized water is 70% of the mass of the acrylic acid. The mass ratio of the deionized water to the sodium dodecylbenzenesulfonate is 1:(0.1). After mixing evenly, ammonium persulfate solution is added, and the temperature is raised to 60 °C. The reaction kettle is kept stirring at a speed of 120 r / min. After heating, p-toluenesulfonic acid solution is added, and the reaction is kept for 2 h. Ammonia water is added to adjust the pH value to 8 to obtain the additive solution. Among them, the mass of the ammonium persulfate solution is 6% of the mass of the acrylic acid, the concentration is 2%, and the mass of the p-toluenesulfonic acid solution is 4% of the mass of the acrylic acid, and the concentration is 1%;

[0058] Preparation of thickening agent for fracturing fluid:

[0059] Step 1: Weigh deionized water, N-methylpyrrolidone, and 2-acrylamido-2-methylpropanesulfonic acid as needed and add them to a reaction kettle. Set the mixing treatment at 80 r / min for 6 min. After mixing, add the additive solution and set the mixing treatment at 120 r / min for 12 min to obtain a preliminary reaction solution;

[0060] Step 2: Weigh the konjac gum that has completed the modification treatment as needed in the preliminary reaction solution, let it stand for reaction for 20 min. Then, weigh acrylamide, chitosan, diatomite, ceramsite, disodium ethylenediaminetetraacetate, and chain transfer agent as needed, set the mixing treatment at 80 r / min for 20 min. Nitrogen is continuously introduced during the mixing process. After mixing, add an initiator, mix evenly, and react for 3 h to obtain the thickening agent for fracturing fluid.

[0061] Experiment 2:

[0062] Raw material preparation: The mass ratio of the liquid material to the solid material is 1:(2.3);

[0063] The liquid material consists of deionized water and N-methylpyrrolidone, and the mass ratio of deionized water to N-methylpyrrolidone is 8.5:1.5;

[0064] The solid material includes the following raw materials by weight: 25 parts of 2-acrylamide-2-methylpropanesulfonic acid, 15 parts of acrylic acid, 15 parts of acrylamide, 9 parts of hydroxypropyl methacrylate, 5 parts of konjac gum, 3 parts of chitosan, 2 parts of diatomite, 0.5 part of ceramsite, 0.5 part of disodium ethylenediaminetetraacetate, 0.3 part of chain transfer agent and 0.3 part of initiator. The chain transfer agent is selected as sodium sulfate, the initiator is selected as sodium bisulfite. The konjac gum is selected as powder with a particle size of 170 mesh, and the chitosan, diatomite and ceramsite are all selected as powder with a particle size of 250 mesh;

[0065] The konjac gum is subjected to modification treatment, and the modification treatment of the konjac gum includes the following steps:

[0066] S1: Mix and react the konjac gum to obtain a mixed solution;

[0067] The mixed solution is obtained by the following method: The konjac gum and glutaraldehyde solution are added to a mixer. The mixer is set to stir at 230 r / min for 10 min. After mixing evenly, it is added to a water bath and heated to 55 °C. Stirring is maintained during the heating process, and then the reaction is kept warm for 18 min. After cooling to room temperature, sodium carbonate solution is added, stirred evenly, and left standing for 8 min to obtain the mixed solution. The mass of the glutaraldehyde solution is 2.5 times that of the konjac gum, the concentration of the glutaraldehyde solution is 3%, the mass of the sodium carbonate solution is 15% of the mass of the konjac gum, and the concentration of the sodium carbonate solution is 5%;

[0068] S2: Carry out solidification treatment on the mixed solution to complete the modification treatment of the konjac gum;

[0069] The method of solidification treatment is: The mixed solution is subjected to filtration and separation treatment to obtain a solid product. The solid product is washed, and then sent to an oven. The oven is set to dry at 65 °C for 45 °C. After drying, it is ground and sieved. The sieving particle size is 170 mesh to complete the modification treatment of the konjac gum;

[0070] Acrylic acid and hydroxypropyl methacrylate are pretreated to prepare an additive liquid, and the additive liquid is prepared by the following method: acrylic acid and hydroxypropyl methacrylate are mixed in a reactor, deionized water and sodium dodecylbenzene sulfonate are added to the reactor, the mass of deionized water is 75% of the mass of acrylic acid, and the mass ratio of deionized water to sodium dodecylbenzene sulfonate is 1:(0.2), and after mixing, ammonium persulfate solution is added, and the temperature is raised to 70°C. The reactor is kept in a stirring state with a speed of 140r / min. After heating, p-toluenesulfonic acid solution is added, and the temperature is kept for reaction for 2.5h, and ammonia water is added to adjust the pH value to 8.5 to prepare an additive liquid, wherein the mass of the ammonium persulfate solution is 8% of the mass of acrylic acid and the concentration is 3%, and the mass of the p-toluenesulfonic acid solution is 5% of the mass of acrylic acid and the concentration is 2%;

[0071] Preparation of fracturing fluid thickener:

[0072] Step 1: Weigh deionized water, N-methylpyrrolidone and 2-acrylamide-2-methylpropanesulfonic acid as needed and add them into the reactor, set the mixing speed at 100 r / min for 8 minutes, add the additive liquid after mixing, set the mixing speed at 140 r / min for 14 minutes to obtain a preliminary reaction solution;

[0073] Step 2: Weigh the modified konjac gum in the preliminary reaction solution as needed, let it react for 25 minutes, then weigh acrylamide, chitosan, diatomaceous earth, ceramsite, disodium ethylenediaminetetraacetic acid and chain transfer agent as needed, set the mixing speed to 100r / min for 25 minutes, continuously introduce nitrogen during the mixing process, add the initiator after the mixing is completed, mix well and react for 4.5 hours to obtain a thickener for fracturing fluid.

[0074] Experiment 3:

[0075] Raw material preparation: The mass ratio of liquid material to solid material is 1:(2.4);

[0076] The liquid material is composed of deionized water and N-methylpyrrolidone, and the mass ratio of deionized water to N-methylpyrrolidone is 8.5:1.5;

[0077] The solid material comprises the following raw materials in parts by weight: 30 parts of 2-acrylamide-2-methylpropane sulfonic acid, 20 parts of acrylic acid, 20 parts of acrylamide, 10 parts of hydroxypropyl methacrylate, 6 parts of konjac glucomannan, 4 parts of chitosan, 3 parts of diatomaceous earth, 0.6 parts of ceramsite, 0.6 parts of disodium ethylenediaminetetraacetate, 0.4 parts of chain transfer agent and 0.4 parts of initiator, wherein the chain transfer agent is sodium citrate, the initiator is sodium bisulfite, the konjac glucomannan is powdered material with a particle size of 200 meshes, and the chitosan, diatomaceous earth and ceramsite are all powdered material with a particle size of 300 meshes;

[0078] Konjac glucomannan is subjected to modification treatment, and the modification treatment of konjac glucomannan comprises the following steps:

[0079] S1: Mix konjac gum to carry out a reaction to obtain a mixed solution;

[0080] The mixed solution is obtained by the following method: Add konjac gum and glutaraldehyde solution into a mixer. The mixer is set to stir at 240 r / min for 12 min. After mixing evenly, add it into a water bath and heat to 60 °C. Keep stirring during the heating process. Then carry out a heat preservation reaction for 20 min. After cooling to room temperature, add sodium carbonate solution, stir evenly, and let it stand for 10 min to obtain the mixed solution. The mass of the glutaraldehyde solution is 3 times that of the konjac gum, the concentration of the glutaraldehyde solution is 4%, the mass of the sodium carbonate solution is 20% of the mass of the konjac gum, and the concentration of the sodium carbonate solution is 6%;

[0081] S2: Carry out solidification treatment on the mixed solution to complete the modification treatment of konjac gum;

[0082] The method of solidification treatment is: Carry out filtration and separation treatment on the mixed solution to obtain a solid product. Wash the solid product, and then send it into an oven. The oven is set to dry at 70 °C for 50 °C. After drying, carry out pulverization and sieving treatment. The sieving particle size is 200 mesh to complete the modification treatment of konjac gum;

[0083] Pre-treat acrylic acid and hydroxypropyl methacrylate to obtain an additive solution. The additive solution is obtained by the following method: Mix acrylic acid and hydroxypropyl methacrylate in a reaction kettle. Add deionized water and sodium dodecylbenzenesulfonate into the reaction kettle. The mass of deionized water is 80% of the mass of acrylic acid. The mass ratio of deionized water to sodium dodecylbenzenesulfonate is 1:(0.3). After mixing evenly, add ammonium persulfate solution, heat up to 80 °C. The reaction kettle keeps stirring at a speed of 160 r / min. After heating, add p-toluenesulfonic acid solution and carry out a heat preservation reaction for 3 h. Add ammonia water to adjust the pH value to 9 to obtain the additive solution. Among them, the mass of the ammonium persulfate solution is 10% of the mass of acrylic acid, the concentration is 4%, the mass of the p-toluenesulfonic acid solution is 6% of the mass of acrylic acid, and the concentration is 3%;

[0084] Preparation of thickening agent for fracturing fluid:

[0085] Step 1: Weigh deionized water, N-methylpyrrolidone, and 2-acrylamido-2-methylpropanesulfonic acid as needed and add them into a reaction kettle. Set to mix at 120 r / min for 10 min. After mixing, add the additive solution and set to mix at 160 r / min for 16 min to obtain a preliminary reaction solution;

[0086] Step 2: Weigh the modified konjac gum as needed in the preliminary reaction solution, let it stand for reaction for 30 min, then weigh acrylamide, chitosan, diatomite, ceramsite, disodium ethylenediaminetetraacetate and chain transfer agent as needed, set the mixing treatment at 120 r / min for 30 min, continuously introduce nitrogen during the mixing process, add the initiator after completion of mixing, and react for 6 h after mixing evenly to obtain the thickening agent for fracturing fluid.

[0087] Comparative Example 1. The difference between this comparative example and Experiment 1 is that: in this comparative example, acrylic acid and hydroxypropyl methacrylate were not pretreated.

[0088] Comparative Example 2. The difference between this comparative example and Experiment 1 is that: this comparative example does not contain chitosan, diatomite and ceramsite.

[0089] Comparative Example 3. The difference between this comparative example and Experiment 1 is that: this comparative example does not contain konjac gum.

[0090] Comparative Example 4. The difference between this comparative example and Experiment 1 is that: in this comparative example, the konjac gum was not modified.

[0091] Performance test: Perform performance tests on the thickening agents prepared in Experiment 1, Experiment 2, Experiment 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4, and record the obtained test data in the following table:

[0092] Table 1, Performance test table of 0.1% thickening agent concentration:

[0093]

[0094] Table 2, Performance test table of 0.5% thickening agent concentration:

[0095]

[0096] By comparing and analyzing the relevant data in the table, it can be seen that the thickening agent for fracturing fluid prepared by the present invention not only has good viscosity, but also has excellent crosslinking performance. This shows that a thickening agent for fracturing fluid and its preparation method provided by the present invention have a broader market prospect and are more suitable for popularization.

[0097] In the description of this specification, the descriptions referring to the terms "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0098] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A thickener for fracturing fluid, characterized in that: It includes liquid material and solid material, wherein the mass ratio of the liquid material to the solid material is 1:(2.2-2.4); The liquid material consists of deionized water and N-methylpyrrolidone, and the mass ratio of the deionized water to N-methylpyrrolidone is 8.5:1.5; The solid material comprises the following raw materials in parts by weight: 20 to 30 parts of 2-acrylamide-2-methylpropane sulfonic acid, 10 to 20 parts of acrylic acid, 10 to 20 parts of acrylamide, 8 to 10 parts of hydroxypropyl methacrylate, 4 to 6 parts of konjac gum, 2 to 4 parts of chitosan, 1 to 3 parts of diatomaceous earth, 0.4 to 0.6 parts of ceramsite, 0.4 to 0.6 parts of disodium ethylenediaminetetraacetate, 0.2 to 0.4 parts of chain transfer agent and 0.2 to 0.4 parts of initiator; The acrylic acid and hydroxypropyl methacrylate are pretreated to prepare an additive liquid, and the additive liquid is prepared by the following method: acrylic acid and hydroxypropyl methacrylate are mixed in a reactor, deionized water and sodium dodecylbenzene sulfonate are added to the reactor, the mass of the deionized water is 70-80% of the mass of acrylic acid, and the mass ratio of deionized water to sodium dodecylbenzene sulfonate is 1:(0.1-0.3), after mixing, ammonium persulfate solution is added, the temperature is raised to 60-80°C, the reactor is kept in a stirring state, the speed is 120-160r / min, after heating, p-toluenesulfonic acid solution is added, the temperature is kept for reaction for 2-3h, ammonia water is added to adjust the pH value to 8-9, and the additive liquid is prepared, wherein the mass of the ammonium persulfate solution is 6-10% of the mass of acrylic acid, and the concentration is 2-4%, and the mass of the p-toluenesulfonic acid solution is 4-6% of the mass of acrylic acid, and the concentration is 1-3%; Described konjac glucomannan is subjected to modification treatment, and the modification treatment of described konjac glucomannan comprises the following steps: S1: Konjac gum mixed reaction to obtain a mixed solution; The mixed solution is prepared by the following method: the konjac gum and the glutaraldehyde solution are added to a mixer, the mixer is set at 220-240 r / min and stirred for 8-12 minutes, and after being mixed evenly, they are added to a water bath, heated to 50-60° C., stirred during the heating process, and then kept warm for 16-20 minutes. After cooling to room temperature, sodium carbonate solution is added, stirred evenly, and allowed to stand for 6-10 minutes to obtain a mixed solution, wherein the mass of the glutaraldehyde solution is 2-3 times the mass of the konjac gum, the concentration of the glutaraldehyde solution is 2-4%, the mass of the sodium carbonate solution is 10-20% of the mass of the konjac gum, and the concentration of the sodium carbonate solution is 4-6%; S2: the mixed solution is solidified to complete the modification of konjac gum; The solidification treatment method comprises the following steps: filtering and separating the mixed liquid to obtain a solid product, washing the solid product, and then sending the solid product into an oven, setting the oven at 60-70° C. for drying for 40-50 minutes, grinding and sieving the solid product after drying, wherein the sieved particle size is 140-200 meshes, and thus the modification of the konjac gum is completed.

2. The thickener for fracturing fluid according to claim 1, characterized in that: The chain transfer agent is at least one of sodium formate, sodium sulfate and sodium citrate.

3. The thickener for fracturing fluid according to claim 1, characterized in that: The initiator is sodium bisulfite.

4. The thickener for fracturing fluid according to claim 1, characterized in that: The konjac gum is powdered material with a particle size of 140 to 200 meshes.

5. The thickener for fracturing fluid according to claim 1, characterized in that: The chitosan, diatomaceous earth and ceramsite are all powdered materials with a particle size of 200-300 meshes.

6. A method for preparing a thickener for fracturing fluid according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Weigh deionized water, N-methylpyrrolidone and 2-acrylamide-2-methylpropanesulfonic acid as needed and add them into the reaction kettle, set the mixing process at 80-120 r / min for 6-10 min, add the additive liquid after mixing, set the mixing process at 120-160 r / min for 12-16 min, and obtain a preliminary reaction solution; Step 2: Weigh the modified konjac gum in the preliminary reaction solution as needed, let it stand and react for 20 to 30 minutes, then weigh acrylamide, chitosan, diatomaceous earth, ceramsite, disodium ethylenediaminetetraacetic acid and chain transfer agent as needed, set 80 to 120 r / min to mix for 20 to 30 minutes, continuously introduce nitrogen during the mixing process, add the initiator after mixing, mix well and react for 3 to 6 hours to obtain a thickener for fracturing fluid.

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