Modified cellulose thickener for fracturing fluid, fracturing fluid and preparation method thereof
By modifying carboxymethyl cellulose with double-terminal aminopolysiloxane and sulfonated nano-montmorillonite, the problems of easy degradation and high residue of cellulose derivatives at high temperatures were solved, the application of fracturing fluid under high temperature and high shear conditions was realized, and formation damage was reduced.
Patent Information
- Application Number
- CN202510788390.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-13
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2045-06-13
AI Technical Summary
Existing cellulose derivative thickeners are easily degraded at high temperatures and have poor shear resistance, which cannot meet the construction requirements of long fracturing sections. In addition, the residue content after gel breaking is high, which can easily cause secondary blockage of the reservoir.
Carboxymethyl cellulose is grafted with double-terminated amino polysiloxane to prepare a modified cellulose derivative, which is then combined with sulfonated nano-montmorillonite to form a stable cross-linked network, thereby improving the heat resistance and shear resistance while controlling the gel breaking performance.
Modified cellulose derivatives have excellent heat and shear resistance above 160°C, low residue content after gel breaking, reducing formation damage and meeting construction requirements under high temperature and high shear conditions.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of oil and gas extraction, and in particular to a modified cellulose thickener for fracturing fluid, fracturing fluid, and a preparation method thereof. Background Art
[0002] Fracturing technology, as a key measure for increasing oil and gas reservoir production, has rapidly developed and become widely used. Fracturing fluid, a crucial component of this technology, is a heterogeneous, unstable chemical system composed of multiple additives in specific proportions. Its primary function is to transmit high pressure from the surface to the formation, transporting proppant into the fractures and spreading it there. To achieve efficient transport during the delivery process, fracturing fluids must possess a high suspension capacity and a high low-shear viscosity. In recent years, thickeners have been commonly used to achieve this effect. Currently, the most commonly used thickeners in domestic water-based fracturing fluids include natural plant gums and their derivatives, cellulose derivatives, and synthetic polymers. Natural plant gums and their derivatives mainly include guar gum, hydroxypropyl guar gum, carboxymethyl guar gum, carboxymethyl hydroxypropyl guar gum, sesbania gum, modified fenugreek gum, modified konjac gum, saponin gum and leucanthemum gum; cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl hydroxyethyl cellulose; synthetic polymers such as polyacrylamide, partially hydrolyzed polyacrylamide, methylene polyacrylamide, polyvinyl alcohol, and copolymers of acrylamide and hydrophobic monomers, 2-acrylamido-2-methylpropanesulfonic acid (sodium), vinyl pyrrolidone, polyvinyl alcohol, etc.
[0003] Cellulose is a widely available natural resource with excellent thickening and compatibility. However, common cellulose derivatives, such as carboxymethyl cellulose and hydroxypropyl cellulose, have poor temperature resistance. Carboxymethyl cellulose degrades rapidly above 80°C and exhibits poor salt and shear resistance, while hydroxypropyl cellulose degrades rapidly above 120°C and exhibits poor shear resistance. Both are unable to meet the requirements of long fracturing stages. Therefore, to improve the applicability of cellulose in oil and gas reservoir development, researchers have begun modifying it.
[0004] Patent CN117924718A discloses a modified sodium carboxymethyl cellulose and a preparation method thereof. A hydrophobic quaternary ammonium salt is synthesized from epichlorohydrin and N,N-diethyl-N'-oleoylethylenediamine, and then free radical polymerized with acrylamide and 2-acrylamido-2-methylpropanesulfonic acid to obtain a polymer powder. The polymer powder is then grafted onto sodium carboxymethyl cellulose through an etherification reaction to obtain modified sodium carboxymethyl cellulose. However, the modified sodium carboxymethyl cellulose prepared by this technology has a temperature resistance of only 120°C and cannot be adapted to the development of oil and gas reservoirs at higher temperatures.
[0005] Patent CN110257041A discloses a guar gum-nanocellulose fiber cross-linked thickener for fracturing fluid. After cross-linking pyridine-type cationic nanocellulose fibers with guar gum, they are further moderately cross-linked with fatty alcohol polyvinyl ether and acrylic acid. When used in combination with nanoparticles, the agent has excellent temperature and salt resistance. However, it does not solve the problem of high guar gum residue content and the easy occurrence of secondary blockage after reservoir reconstruction.
[0006] Therefore, although certain progress has been made in the research of thickeners, current thickeners still need to be improved. Summary of the Invention
[0007] In response to the deficiencies in the prior art, the present application provides a modified cellulose thickener for fracturing fluid, a fracturing fluid, and a preparation method thereof, which have good temperature resistance, low residue content after gel breaking, and little damage to the formation.
[0008] To achieve the above objectives, the technical solutions adopted in this application are as follows:
[0009] According to one aspect of the present application, a modified cellulose thickener for fracturing fluid is provided, comprising a carboxymethyl cellulose derivative obtained by grafting carboxymethyl cellulose modified by a double-terminal amino polysiloxane.
[0010] Furthermore, the mass ratio of the carboxymethyl cellulose to the double-terminated aminopolysiloxane is 1:(1-1.8).
[0011] Preferably, the mass ratio of the carboxymethyl cellulose to the double-terminated aminopolysiloxane is 1:1.3.
[0012] Furthermore, the molecular weight of the carboxymethyl cellulose is 20,000-100,000, and the degree of carboxymethyl substitution is 0.54-0.68, preferably 0.61.
[0013] Furthermore, the molecular weight of the dual-terminated amino polysiloxane is 2000-8000.
[0014] Preferably, the molecular weight of the dual-terminated amino polysiloxane is 5000.
[0015] The amount of monohydroxyl-terminated polysiloxane used should not be too much, which will lead to a decrease in swelling properties. The amount introduced and the degree of carboxylmethylation should be controlled to maintain excellent swelling properties and excellent temperature resistance.
[0016] Furthermore, the preparation method of the above-mentioned cellulose derivative comprises the following steps:
[0017] Dissolve carboxymethyl cellulose in dimethyl sulfoxide solvent, add double-terminated amino polysiloxane and catalyst p-toluenesulfonic acid, react at 50-60°C for 12-24 hours, cool after the reaction is completed, filter and dry to obtain a cellulose derivative.
[0018] Optionally, the mass ratio of the carboxymethyl cellulose to the solvent dimethyl sulfoxide is 1:(5-10).
[0019] Optionally, the catalyst is used in an amount of 0.1-1% by weight of the carboxymethyl cellulose.
[0020] In the present application, carboxymethyl cellulose is grafted and modified by using a double-terminal amino polysiloxane. The amino groups in the double-terminal amino polysiloxane undergo an amidation reaction with the carboxyl groups in the carboxymethyl cellulose to form a cellulose derivative with polysiloxane side chains. Compared with carboxymethyl cellulose, the introduction of polysiloxane chain segments into the cellulose derivative gives it higher resistance to temperature and shearing.
[0021] Some of the amino groups in the double-ended amino polysiloxane are unreacted, and a certain degree of cross-linking will occur with the cross-linking agent and other ingredients when preparing the fracturing fluid. Therefore, it is necessary to control the amount and molecular weight of the double-ended amino polysiloxane to avoid too high a proportion of the double-ended amino polysiloxane or too large a molecular weight, which will lead to excessive cross-linking of the fracturing fluid and difficulty in complete gel breaking, resulting in more cross-linked structures remaining after gel breaking, increasing the residue content; excessive use of the double-ended amino polysiloxane or too large a molecular weight will also affect the uniformity of the formed solution, and affect the temperature resistance, shear resistance and salt resistance; in addition, it will also affect the gel breaking performance of the fracturing fluid. Therefore, the present application prefers a double-terminated aminopolysiloxane with a molecular weight of 2000-8000, controls the carboxymethyl substitution degree of carboxymethyl cellulose in the range of 0.54-0.68, the mass ratio of the double-terminated aminopolysiloxane in the range of 1:(1-1.8), and the carboxymethyl degree of carboxymethyl cellulose, thereby controlling the branch length, carboxyl content, etc., so that it has high temperature and shear resistance, while ensuring excellent swelling and gel breaking properties.
[0022] According to another aspect of the present application, a fracturing fluid is provided, comprising the modified cellulose thickener for fracturing fluid and a cross-linking agent; wherein,
[0023] The amount of the modified cellulose thickener for the fracturing fluid is 0.30-45% of the total weight of the fracturing fluid;
[0024] The amount of the cross-linking agent used accounts for 0.1-0.3% of the total weight of the fracturing fluid.
[0025] Furthermore, the crosslinking agent is selected from at least one of an organic boron crosslinking agent, a borate, and an organic boron zirconium crosslinking agent, for example, triethanolamine borate, ethylene glycol borate, zirconium oxychloride, tetrabutyl zirconate, and the like.
[0026] Furthermore, the fracturing fluid also contains a guar gum derivative, the amount of which accounts for 0.05-0.1% of the total weight of the fracturing fluid; the guar gum derivative is selected from any one of hydroxypropyl guar gum, carboxymethyl guar gum, and carboxymethyl hydroxypropyl guar gum, and the molecular weight of the guar gum derivative is 200,000-500,000.
[0027] Furthermore, the fracturing fluid further comprises a fungicide, the amount of which accounts for 0-0.1%, preferably 0.05-0.1%, of the total weight of the fracturing fluid; the fungicide is selected from at least one of formaldehyde and isothiazolinone fungicides.
[0028] Furthermore, the fracturing fluid further comprises a clay stabilizer, the amount of the clay stabilizer accounting for 0-1%, preferably 0.5-1%, of the total weight of the fracturing fluid; the clay stabilizer is selected from at least one of potassium chloride, ammonium chloride, and sodium chloride.
[0029] Furthermore, the fracturing fluid further comprises a drainage aid, the amount of which accounts for 0-1%, preferably 0.5-1%, of the total weight of the fracturing fluid; the drainage aid is selected from at least one of fluorocarbon surfactants and alkylphenol polyoxyethylene ethers.
[0030] Furthermore, the fracturing fluid further comprises a pH regulator, which is added to adjust the pH of the fracturing fluid to 10-11; the pH regulator is selected from sodium hydroxide or sodium carbonate.
[0031] Furthermore, the fracturing fluid further comprises a breaker, and the amount of the breaker accounts for 0-0.05% of the total weight of the fracturing fluid, preferably 0.005-0.05%; the breaker is selected from potassium persulfate or sodium persulfate.
[0032] In a further preferred embodiment, sulfonated nano-montmorillonite is further added to the fracturing fluid, and the amount of sulfonated nano-montmorillonite added to the fracturing fluid is 0-0.5%, preferably 0.2-0.5%, by weight.
[0033] The lamellar structure of nano-montmorillonite can remain relatively stable at high temperatures, and adding it to fracturing fluid can improve its heat and shear resistance. However, the dispersibility of nano-montmorillonite is poor, and it is easy to agglomerate in the fracturing fluid, which cannot play a good reinforcing effect. The present application utilizes sulfonated nano-montmorillonite modified by vinyl silane coupling agent and sulfonic acid group-containing polymerizable monomer, and its dispersibility is improved, so that the nano-montmorillonite can play the role of enhancing heat and shear resistance. The sulfonated nano-montmorillonite and cellulose molecules can also form stable chemical bonds and other interactions, thereby further improving the heat resistance and shear resistance of the thickener, so that it has a higher viscosity retention rate at high temperature and high shear rate; however, nano-montmorillonite will increase the cross-linked network structure of the fracturing fluid, increase the cross-linking density, and reduce the gel breaking performance. The present application introduces a polymer formed by vinyl silane coupling agent and sulfonic acid group-containing polymerizable monomer on the surface of nano-montmorillonite, which can also adjust the interfacial properties of the fracturing fluid to a certain extent, reduce the surface tension, and make the gel breaker more easily penetrate, thereby improving the gel breaking performance.
[0034] Furthermore, the sulfonated nano-montmorillonite is prepared by sequentially modifying nano-montmorillonite with a vinyl silane coupling agent and a polymerizable monomer containing a sulfonic acid group, and the preparation method thereof comprises the following steps:
[0035] (1) dispersing nano-montmorillonite powder in solvent I, adding a vinyl silane coupling agent to react, filtering and drying after the reaction to obtain an intermediate product;
[0036] (2) The intermediate product is dispersed in solvent II, a polymerizable monomer containing a sulfonic acid group is added, an initiator is added to react, and after the reaction is completed, the mixture is filtered and dried to obtain sulfonated nano-montmorillonite.
[0037] Optionally, the weight ratio of the nano-montmorillonite, the vinyl silane coupling agent, and the polymerizable monomer containing a sulfonic acid group is 1:(1-2):(0.5-0.7).
[0038] Optionally, in step (1), the particle size of the nano-montmorillonite is 200-600 nm.
[0039] Optionally, in step (1), the vinyl silane coupling agent is selected from at least one of vinyl triethoxysilane, vinyl trimethoxysilane, vinyl tripropoxysilane, and vinyl tris(β-methoxyethoxy)silane.
[0040] Optionally, in step (1), the solvent I is selected from any one of n-hexane, n-heptane, dichloromethane, and toluene, and the mass ratio of the nano-montmorillonite powder to the solvent I is 1:10-15.
[0041] Optionally, in step (1), the reaction temperature is 80-100°C and the reaction time is 3-10 hours.
[0042] Optionally, in step (2), the solvent II is selected from any one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and N,N-dimethylacetamide.
[0043] Optionally, in step (2), the polymerizable monomer containing a sulfonic acid group is selected from at least one of 2-methacrylamide-2-methylpropanesulfonic acid, 2-acrylamideethanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 3-acryloyloxypropanesulfonic acid and 2-methacryloyloxypropanesulfonic acid.
[0044] Optionally, in step (2), the initiator is selected from azo initiators and peroxide initiators, illustratively including but not limited to azobisisobutyronitrile, 2,2'-azo-bis-(2-methylbutyronitrile), azobis(2,4-dimethylvaleronitrile), azobisisoheptanenitrile, dilauroyl peroxide, or tert-butyl peroxyneodecanoate, dibenzoyl peroxide, diisopropylbenzene peroxide, etc.
[0045] Optionally, in step (2), the reaction temperature is 70-90°C and the reaction time is 2-6 hours.
[0046] According to another aspect of the present application, a method for preparing a fracturing fluid is provided, comprising the following steps:
[0047] S1. Add water to the guar gum derivative and stir to swell for 5-10 minutes, then add a fungicide, a clay stabilizer, and a drainage agent and mix evenly, adjust the pH to 10-11 with a pH adjuster, and add a cross-linking agent to obtain a base liquid;
[0048] S2. Add a modified cellulose thickener for fracturing fluid to the base fluid, add a gel breaker, and stir to form a mesh-like jelly.
[0049] Furthermore, the above operations are all carried out at room temperature.
[0050] Compared with the prior art, this application has the following beneficial effects:
[0051] 1. The present application provides a modified cellulose thickener for fracturing fluid. The thickener is a cellulose derivative obtained by modifying carboxymethyl cellulose with a double-terminal amino polysiloxane. Compared with conventional cellulose derivative thickeners such as carboxymethyl cellulose, the cellulose derivative of the present application has higher temperature resistance and shear resistance. The fracturing fluid prepared with guar gum derivatives has a temperature resistance of over 160°C and a low residue content, thereby reducing damage to the formation.
[0052] 2. The present application also provides a fracturing fluid containing the above-mentioned thickener, which has thorough gel breaking, low residue, and meets the construction requirements of reservoirs with a temperature of ≥160°C.
[0053] 3. Sulfonated nano-montmorillonite is also added to the fracturing fluid of the present application. The dispersibility of the sulfonated nano-montmorillonite in the fracturing fluid is improved, which can improve the temperature and shear resistance of the fracturing fluid and also help improve the gel breaking performance. DETAILED DESCRIPTION
[0054] The following non-limiting examples are provided to enable those skilled in the art to more fully understand the present application, but are not intended to limit the present application in any way. The following contents are merely illustrative of the scope of protection claimed in the present application. Those skilled in the art may make various changes and modifications to the invention of the present application based on the disclosed contents, and such changes and modifications shall also fall within the scope of protection claimed in the present application.
[0055] In the present application, the "double-terminated amino polysiloxane refers to a polysiloxane having two primary amino groups at the end group, and the two primary amino groups are respectively located at two different end groups of the polysiloxane". The double-terminated amino polysiloxane of the present application can achieve the effect of the present application as long as the two ends are capped with primary amino groups and the molecular weight is in the range of 2000-8000. There are no other restrictions. The double-terminated amino polysiloxane can be a commercially available double-terminated amino polydimethylsiloxane or a homemade product. The preparation method is as follows: 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and octamethylcyclotetrasiloxane are used as raw materials, and the double-terminated amino polysiloxane is reacted under the action of a catalyst tetramethylammonium hydroxide pentahydrate to obtain the double-terminated amino polysiloxane. The raw material ratio and dosage are adjusted according to the required molecular weight.
[0056] In the following specific embodiments, methylisothiazolinone (CAS: 2682-20-4) is selected as the fungicide, potassium chloride is selected as the clay stabilizer, octylphenol polyoxyethylene ether (CAS: 9036-19-5) is selected as the drainage agent, 20% by mass sodium hydroxide solution is selected as the pH adjuster, potassium persulfate is selected as the gel breaker, and triethanolamine borate is selected as the cross-linking agent. The selection of the above materials does not constitute a limitation of the present application. It is understandable that the effect of the present application can also be achieved by replacing them with other materials.
[0057] The present invention is further described below by way of specific examples. Unless otherwise specified, the various chemical reagents used in the examples of the present invention were obtained through conventional commercial channels.
[0058] Example 1
[0059] A modified cellulose thickener for fracturing fluid is prepared by the following method:
[0060] Dissolve carboxymethyl cellulose in 5 times the weight of dimethyl sulfoxide, add diamino polysiloxane in a mass ratio of 1:1 between carboxymethyl cellulose and diamino polysiloxane, add terephthalic acid at a rate of 0.1% by weight of carboxymethyl cellulose, and react at 50°C for 12 hours. After the reaction is complete, cool, filter, and dry to obtain the product, which is recorded as thickener 1#.
[0061] In this embodiment, the molecular weight of carboxymethyl cellulose is 20,000, and the degree of carboxylmethyl is 0.54; the molecular weight of the double-terminated aminopolysiloxane is 2,000.
[0062] Example 2
[0063] A modified cellulose thickener for fracturing fluid is prepared by the following method:
[0064] Dissolve carboxymethyl cellulose in 10 times by weight of dimethyl sulfoxide, add diamino polysiloxane at a mass ratio of 1:1.3, and react at 60°C for 18 hours. After the reaction is completed, cool, filter, and dry to obtain the product, which is recorded as thickener 2#.
[0065] In this embodiment, the molecular weight of carboxymethyl cellulose is 80,000, and the degree of carboxylmethyl is 0.61; the molecular weight of the double-terminated aminopolysiloxane is 5,000.
[0066] Example 3
[0067] A modified cellulose thickener for fracturing fluid is prepared by the following method:
[0068] Dissolve carboxymethyl cellulose in 10 times by weight of dimethyl sulfoxide, add diamino polysiloxane at a mass ratio of 1:1.8, and react at 60°C for 24 hours. After the reaction is complete, cool, filter, and dry to obtain the product, which is recorded as thickener 3#.
[0069] In this embodiment, the molecular weight of carboxymethyl cellulose is 100,000, and the degree of carboxylmethyl is 0.68; the molecular weight of the double-terminated aminopolysiloxane is 8,000.
[0070] Example 4
[0071] The difference from Example 2 is that the degree of carboxymethyl substitution of carboxymethyl cellulose is 0.51, and the rest is the same as Example 2. The obtained product is recorded as thickener 4#.
[0072] Example 5
[0073] The difference from Example 2 is that the degree of carboxymethyl substitution of carboxymethyl cellulose is 0.76, and the rest is the same as Example 2. The obtained product is recorded as thickener 5#.
[0074] Example 6
[0075] The difference from Example 2 is that the mass ratio of carboxymethyl cellulose to double-terminated aminopolysiloxane is 1:0.8, and the rest is the same as Example 2. The obtained product is recorded as thickener 6#.
[0076] Example 7
[0077] The difference from Example 2 is that the mass ratio of carboxymethyl cellulose to double-terminated aminopolysiloxane is 1:02, and the rest is the same as Example 2. The obtained product is recorded as thickener 7#.
[0078] Example 8
[0079] The difference from Example 2 is that the molecular weight of the dual-terminated amino polysiloxane is 1000, and the rest is the same as Example 2. The obtained product is recorded as thickener 8#.
[0080] Example 9
[0081] The difference from Example 2 is that the molecular weight of the dual-terminated amino polysiloxane is 10,000, and the rest is the same as Example 2. The obtained product is recorded as thickener 9#.
[0082] Example 10
[0083] A method for preparing a fracturing fluid comprises the following steps:
[0084] S1. Add water to the guar gum derivative and stir to swell for 5 minutes, add a fungicide, a clay stabilizer, and a drainage agent and mix evenly, adjust the pH to 10 with a pH adjuster, add a cross-linking agent and mix evenly to obtain a base liquid;
[0085] S2, adding a thickener and a gel breaker to the base liquid, stirring to form a gel;
[0086] The components in the fracturing fluid are calculated by weight percentage and include: carboxymethyl guar gum 0.05-0.1%, thickener 0.30-0.45%, cross-linking agent 0.1-0.3%, fungicide 0.05-0.1%, and clay stabilizer 0.5-1%.
[0087] The following fracturing fluid was prepared according to the above method:
[0088] Fracturing fluid 1#
[0089] Carboxymethyl guar gum (molecular weight 200,000) 0.1%, thickener 1# 0.30%, cross-linking agent 0.1%, bactericide 0.05%, clay stabilizer 0.5%.
[0090] Fracturing fluid 2#
[0091] Carboxymethyl hydroxypropyl guar gum (molecular weight 200,000) 0.05%, thickener 2# 0.45%, cross-linking agent 0.3%, bactericide 0.1%, clay stabilizer 0.1%.
[0092] Fracturing fluid 3#
[0093] Carboxymethyl hydroxypropyl guar gum (molecular weight 200,000) 0.05%, thickener 3# 0.45%, cross-linking agent 0.3%, bactericide 0.1%, clay stabilizer 0.1%.
[0094] Fracturing fluid 4#
[0095] The difference from fracturing fluid 2# is that the thickener is the thickener 4# prepared in Example 4 above.
[0096] Fracturing fluid 5#
[0097] The difference from fracturing fluid 2# is that the thickener is the thickener 5# prepared in Example 5 above.
[0098] Fracturing fluid 6#
[0099] The difference from fracturing fluid 2# is that the thickener is the thickener 6# prepared in Example 6 above.
[0100] Fracturing fluid 7#
[0101] The difference from fracturing fluid 2# is that the thickener is the thickener 7# prepared in Example 7 above.
[0102] Fracturing fluid 8#
[0103] The difference from fracturing fluid 2# is that the thickener is the thickener 8# prepared in Example 8 above.
[0104] Fracturing fluid 9#
[0105] The difference from fracturing fluid 2# is that the thickener is the thickener 9# prepared in Example 9 above.
[0106] Fracturing fluid 10#
[0107] The difference from fracturing fluid 2# is that it also contains 0.2% sulfonated nano-montmorillonite, which is prepared by the following method:
[0108] (1) Dispersing nano-montmorillonite powder with a particle size of 600 nm in 10 times the weight of toluene, adding vinyl triethoxysilane to react, filtering and drying after the reaction to obtain an intermediate product (i.e., silane coupling agent modified nano-montmorillonite); (2) The intermediate product is dispersed in 20 times the weight of the intermediate product N,N-dimethylformamide, adding 2-methylacrylamide-2-methylpropanesulfonic acid, adding an initiator to react, filtering and drying after the reaction to obtain sulfonated nano-montmorillonite; the weight ratio of nano-montmorillonite powder, vinyl triethoxysilane, and 2-methylacrylamide-2-methylpropanesulfonic acid is 1:1:0.5.
[0109] Fracturing fluid 11#
[0110] The difference from fracturing fluid 2# is that it also contains 0.5% sulfonated nano-montmorillonite, which is prepared by the following method:
[0111] (1) Dispersing nano-montmorillonite powder with a particle size of 200 nm in 20 times the weight of toluene, adding vinyl triethoxysilane to react, filtering and drying after the reaction to obtain an intermediate product (i.e., silane coupling agent modified nano-montmorillonite); (2) The intermediate product is dispersed in 20 times the weight of N,N-dimethylformamide, adding 2-methylacrylamide-2-methylpropanesulfonic acid, adding an initiator to react, filtering and drying after the reaction to obtain sulfonated nano-montmorillonite; the weight ratio of nano-montmorillonite powder, vinyl triethoxysilane, and 2-methylacrylamide-2-methylpropanesulfonic acid is 1:2:0.7.
[0112] Fracturing fluid 12#
[0113] The difference from fracturing fluid 10# is that in the preparation process of sulfonated nano-montmorillonite, the weight ratio of nano-montmorillonite powder, vinyltriethoxysilane, and 2-methylacrylamide-2-methylpropanesulfonic acid is 1:3:1.
[0114] Fracturing fluid 13#
[0115] The difference from fracturing fluid 10# is that 2-methylacrylamide-2-methylpropanesulfonic acid in the preparation process of sulfonated nano-montmorillonite is replaced by an equal amount of propenesulfonic acid.
[0116] Fracturing fluid 14#
[0117] The difference from fracturing fluid 10# is that the sulfonated nano-montmorillonite is replaced by the silane coupling agent-modified nano-montmorillonite obtained in step (1).
[0118] Comparative Example 1
[0119] The difference from fracturing fluid 2# is that the thickener is replaced with an equal amount of hydroxypropyl cellulose to obtain fracturing fluid 15#.
[0120] Comparative Example 2
[0121] The difference from fracturing fluid 2# is that the thickener is replaced with an equal amount of carboxymethyl cellulose to obtain fracturing fluid 16#.
[0122] Test Example 1
[0123] The temperature resistance, salt resistance, and shear resistance of the above thickeners #1 to #9 were tested and compared with carboxymethyl cellulose; the specific method is as follows:
[0124] (1) At room temperature, thickeners 1 to 9 and carboxymethyl cellulose were added to water to prepare a solution with a mass fraction of 0.5%. After the swelling stabilized, the viscosity A at room temperature was tested (shear speed was 170 s -1 ); Then, the viscosity B and C after shearing at 120°C for 180 minutes were tested respectively, and the viscosity retention rate was calculated to evaluate its heat resistance and anti-shear performance;
[0125] (2) Thickeners 1 to 9 and carboxymethyl cellulose were added to 20000ppm NaCl solution to prepare a solution with a mass fraction of 0.5%. After swelling stabilized, the viscosity D was measured at room temperature (shear speed was 170 s -1 ), the viscosity retention rate was calculated according to the formula D / A to evaluate its salt resistance.
[0126] The measured results are shown in Table 1 below.
[0127] Table 1
[0128]
[0129] As shown in the table, compared with carboxymethyl cellulose, the cellulose derivative provided in the present application has excellent temperature resistance, shear resistance, and salt resistance, which makes up for the shortcomings of existing cellulose derivative thickeners.
[0130] Test Example 2
[0131] According to SYT5107-2016, "Water-Based Fracturing Fluid Performance Evaluation Method," the viscosities of fracturing fluids #1 through #16 were tested after shearing for 180 minutes at 120°C and 160°C. The viscosity retention and the residue content after complete gel breaking were calculated. The results are shown in Table 2 below.
[0132] Table 2
[0133]
[0134] As shown in the table, compared to fracturing fluids 15# and 16# that use cellulose derivatives as thickeners, fracturing fluids 1-3# exhibit higher heat and shear resistance, maintaining high viscosity even under prolonged shear at temperatures of 120°C and 160°C, and are resistant to temperatures up to 160°C. Compared to fracturing fluids 1-3#, fracturing fluids 10# and 11# exhibit higher viscosity retention under prolonged shear at temperatures of 120°C and 160°C, further enhancing their heat and shear resistance.
[0135] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, this application is not limited to the above-described embodiments. Any improvements and modifications made by those skilled in the art based on the disclosure of this application, without departing from the scope of this application, should be within the scope of protection of this application.
Claims
1. A modified cellulose thickener for fracturing fluid, characterized in that: The invention relates to a carboxymethyl cellulose derivative obtained by modifying carboxymethyl cellulose with a double-terminal amino polysiloxane; the mass ratio of the carboxymethyl cellulose to the double-terminal amino polysiloxane is 1:(1-1.8); The molecular weight of the carboxymethyl cellulose is 20,000-100,000, and the degree of carboxymethyl substitution DS is 0.54-0.68; The molecular weight of the dual-terminated aminopolysiloxane is 2000-8000.
2. The modified cellulose thickener for fracturing fluid according to claim 1, characterized in that: The preparation method of the carboxymethyl cellulose derivative comprises the following steps: Add carboxymethyl cellulose to the solvent, add double-terminal amino polysiloxane, add catalyst, react at 60-80°C for 12-24 hours, cool after the reaction is completed, filter and dry to obtain the product.
3. A fracturing fluid, characterized in that: The fracturing fluid comprises the modified cellulose thickener for fracturing fluid according to claim 1 or 2, and a cross-linking agent; wherein, The amount of the modified cellulose thickener for the fracturing fluid is 0.30-0.45% of the total weight of the fracturing fluid; The amount of the cross-linking agent used accounts for 0.1-0.3% of the total weight of the fracturing fluid.
4. The fracturing fluid according to claim 3, characterized in that The fracturing fluid further comprises a guar gum derivative, and the amount of the guar gum derivative accounts for 0.05-0.1% of the total weight of the fracturing fluid.
5. The fracturing fluid according to claim 4, wherein The fracturing fluid also contains the following components: A bactericide, wherein the amount of the bactericide is 0-0.1% of the total weight of the fracturing fluid; and / or Clay stabilizer, wherein the amount of the clay stabilizer is 0-1% of the total weight of the fracturing fluid; and / or A drainage aid, wherein the amount of the drainage aid is 0-1% of the total weight of the fracturing fluid; and / or pH regulator, said pH regulator is added to the fracturing fluid to a pH of 10-11; and / or A gel breaker is used in an amount of 0-0.05% of the total weight of the fracturing fluid.
6. The fracturing fluid according to claim 5, characterized in that Sulfonated nano-montmorillonite is also added to the fracturing fluid, and the amount of the sulfonated nano-montmorillonite added to the fracturing fluid is 0-0.5%; The sulfonated nano-montmorillonite is prepared by sequentially modifying nano-montmorillonite with a vinyl silane coupling agent and a polymerizable monomer containing a sulfonic acid group; The weight ratio of the nano-montmorillonite, the vinyl silane coupling agent, and the polymerizable monomer containing a sulfonic acid group is 1:(1-2):(0.5-0.7); The polymerizable monomer containing a sulfonic acid group is at least one selected from 2-methacrylamide-2-methylpropanesulfonic acid, 2-acrylamideethanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 3-acryloyloxypropanesulfonic acid and 2-methacryloyloxypropanesulfonic acid.
7. A method for preparing a fracturing fluid, characterized in that: The following steps are involved: S1. Add water to the guar gum derivative and stir to swell for 5-10 minutes, then add a fungicide, a clay stabilizer, and a drainage agent and mix evenly, adjust the pH to 10-11 with a pH adjuster, and add a cross-linking agent to obtain a base liquid; S2. Add the modified cellulose thickener for fracturing fluid according to claim 1 or 2 to the base fluid, add a gel breaker, and stir to form a network jelly.