Modified nano calcium carbonate material, preparation method and application thereof, and fracturing fluid

Abstract

The invention relates to a petrochemical technology, in particular to a modified nano calcium carbonate material, a preparation method and application thereof and fracturing fluid. The molecular aggregate fluid dynamic diameter D10 of the modified nano calcium carbonate material in water is 2-10 [mu] m, the molecular aggregate fluid dynamic diameter D50 is 8-31 [mu] m, and the molecular aggregate fluid dynamic diameter D90 is 20-90 [mu] m. The preparation method of the modified nano calcium carbonate material comprises the following steps: carrying out hydroxylation treatment on unsaturated fat monobasic acid, and carrying out contact reaction on the hydroxylated unsaturated fat monobasic acid and a nano calcium carbonate raw material; and carrying out amination treatment on the product of the contact reaction. The modified nano calcium carbonate material not only has degradation performance meeting fracturing construction requirements, but also can realize multi-size plugging in tight reservoirs and improve the plugging rate of pore throats, and can enter the pore throats to adsorb and occupy space so as to reduce retention volume of fracturing fluid and reduce damage to the reservoirs.

Description

Technical Field

[0001] The present invention relates to petrochemical technology, in particular to a modified nano-calcium carbonate material, a preparation method and application thereof, and a fracturing fluid containing the modified nano-calcium carbonate material as a plugging agent. Background Art

[0002] In the development of low-permeability oil and gas reservoirs, fracturing is a primary production-increasing measure. Its purpose is to create a crack within the low-permeability reservoir, increasing the drainage area and boosting oil and gas production. Temporary fracturing uses plugging agents to form a filter cake in front of the high-permeability layer or increase the flow resistance of the high-permeability layer, thereby diverting the working fluid into the low-permeability layer.

[0003] Calcium carbonate, an acid-soluble material, has been used in plugging agent product development. After performing its plugging action, it can be acid-dissolved to promote flowback of the working fluid. However, since calcium carbonate particles can only form bridges and seal at pore throats or fractures, the plugging effect is poor. Furthermore, after temporary plugging as a plugging agent, the acid-dissolved material degrades rapidly, resulting in unstable working fluid system operation, poor flowback, and potential formation damage.

[0004] Existing technologies often modify calcium carbonate particles before using them as plugging agents. Although this can improve the plugging effect, there are still some difficult-to-overcome problems in their application. For example, calcium carbonate particles or existing modified calcium carbonate still have low adsorption capacity and low plugging rate for pore throats of multiple sizes when plugging reservoir pores and throats. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art and provide a modified nano-calcium carbonate material, a preparation method and application thereof, and a fracturing fluid. The modified nano-calcium carbonate material not only has degradation performance that meets the requirements of fracturing construction, but also can achieve multi-size plugging in tight reservoirs, improve the plugging rate of pore throats, and can enter the pore throats to absorb and occupy space, thereby reducing the retention of fracturing fluid and reducing damage to the reservoir.

[0006] In order to achieve the above object, the first aspect of the present invention provides a modified nano calcium carbonate material, wherein the hydrodynamic diameter D of the molecular aggregate of the modified nano calcium carbonate material in water is 10 2-10μm, D 50 8-31μm, D 90 20-90μm.

[0007] The second aspect of the present invention provides a method for preparing a modified nano-calcium carbonate material, comprising: subjecting an unsaturated fatty monocarboxylic acid to a hydroxylation treatment and then subjecting the resulting unsaturated fatty acid to a contact reaction with a nano-calcium carbonate raw material; and subjecting the product of the contact reaction to an amination treatment.

[0008] The third aspect of the present invention provides the use of the modified nano-calcium carbonate material as described above or the modified nano-calcium carbonate material prepared according to the method as described above in oil production working fluid, preferably as a plugging agent for fracturing fluid.

[0009] A fourth aspect of the present invention provides a fracturing fluid containing the modified nano-calcium carbonate material as described above or the modified nano-calcium carbonate material prepared according to the method as described above.

[0010] Through the above technical solution, the beneficial effects of the present invention are as follows: the modified nano-calcium carbonate material provided by the present invention not only has strong adsorption groups and rigid groups, but also has a specific molecular aggregate hydrodynamic diameter in water, which can achieve multi-size plugging in tight reservoirs, improve the plugging rate of pore throats, and can enter the pore throats to adsorb and occupy space to reduce the retention of fracturing fluid, thereby reducing the damage of the thickener in the fracturing fluid to the reservoir; and the acid-soluble degradation rate of the modified nano-calcium carbonate material can meet the construction process requirements of tight reservoirs, reduce damage to the formation after the plugging operation, utilize the acidification process to effectively degrade the modified nano-calcium carbonate material, promote the return of the working fluid, reduce the filtration loss of the fracturing fluid system, and solve the formation damage problem easily caused by general inorganic material plugging agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is an infrared spectrum of the modified nano-calcium carbonate material obtained in Example 1;

[0012] Figure 2 1 is a scanning electron microscope morphology image and EDS spectrum image of the modified nano-calcium carbonate material obtained in Example 1;

[0013] Figure 3 This is the scanning electron microscope morphology and EDS spectrum of unmodified nano calcium carbonate particles;

[0014] Figure 4 This is an optical microscope observation image of the aqueous solution of the modified nano-calcium carbonate material obtained in Example 1;

[0015] Figure 5 is an optical microscope observation of unmodified nano calcium carbonate particles;

[0016] Figure 6 This is an optical microscope observation of an aqueous solution of unmodified nano-calcium carbonate particles. DETAILED DESCRIPTION

[0017] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0018] The first aspect of the present invention provides a modified nano calcium carbonate material, wherein the hydrodynamic diameter D of the molecular aggregate of the modified nano calcium carbonate material in water is 10 2-10 μm, specifically 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, or any value between the above two values; D 50 8-31 μm, specifically 8 μm, 15 μm, 20 μm, 25 μm, 31 μm, or any value between the above two values; D 90 It is 20-90 μm, specifically 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or any value between the above two values.

[0019] The inventors of the present invention unexpectedly discovered during the research and development process that the nano calcium carbonate raw material was modified so that it has a specific molecular aggregate hydrodynamic diameter D in water. 10 、D 50 、D 90 Not only does the acid-soluble degradation time of the modified nano-calcium carbonate material meet the construction process requirements of tight reservoirs, reducing damage to the formation after the plugging operation, but the acidification process is used to effectively degrade the modified nano-calcium carbonate material, promote the return of the working fluid, reduce the filtration loss of the fracturing fluid system, and solve the formation damage problem that is easily caused by general inorganic plugging agents; the material also has good rock adsorption properties, which can achieve multi-size plugging in tight reservoirs, improve the plugging rate of pore throats, and enter the pore throats to absorb and occupy space to reduce the retention of fracturing fluid and reduce damage to the reservoir.

[0020] In the present invention, the hydrodynamic diameter of the molecular aggregates of the modified nano-calcium carbonate material in water refers to the apparent diameter of the molecular aggregates formed by the modified nano-calcium carbonate material in water. The test method is as follows: the modified nano-calcium carbonate material is subjected to wet measurement using a Fritsch 22 laser particle size analyzer. The test software MaScontrol is opened and the cleaning and calibration program is clicked to complete the cleaning and calibration of the instrument before the measurement is performed. The test sample is prepared and added to the funnel in small amounts and multiple times using a spatula. The sample is dispersed using clean water and ultrasound. After the addition of the sample is completed, the instrument automatically performs three sets of parallel data tests. If the error does not exceed 5%, the test dynamic particle size distribution report is output. After the test is completed, the instrument is cleaned and dried, and then turned off. 10 、D 20 、D 50 、D 70 and D 90 They respectively represent the particle sizes corresponding to when the cumulative particle size distribution number of the sample reaches 10%, 20%, 50%, 70% and 90% (manually accumulate the percentages of all particle sizes before or after this particle size); its physical meaning is that the number of particles with a size smaller than this particle size accounts for 10%, 20%, 50%, 70% and 90% of the total number of particles.

[0021] According to the present invention, preferably, the hydrodynamic diameter D of the molecular aggregate of the modified nano calcium carbonate material in water is 20 4-22μm, D 70 The inventors have found that under this preferred embodiment, the fluid loss can be effectively reduced during the fracturing process, and multi-scale plugging of reservoirs of different sizes can be achieved during fracturing. It has a high degree of compatibility with the pore throats of tight sandstone reservoirs and can meet the fracturing transformation technology requirements of more low-permeability tight gas reservoirs.

[0022] According to the present invention, the modified nano-calcium carbonate material preferably has an acid solubility of 50-80%, more preferably 65-80%, in a 15% by weight hydrochloric acid solution at 90°C for 1 hour; and an acid solubility of 90% or more after 2 hours at 90°C. In this manner, the modified nano-calcium carbonate material not only ensures the return of working fluid after oil extraction operations, but also has a degradation rate that better meets the time requirements of the post-fracture operation process.

[0023] In the present invention, the specific detection process of the acid solubility rate is as follows: 2g of the modified nano-calcium carbonate material is placed in an oven and dried to constant weight, recorded as m1, added to 250mL of a 15% by weight hydrochloric acid solution, stirred evenly, covered and kept at a temperature of 90°C for 1h or 2h, stopped heating, taken out and filtered, dried to constant weight and weighed, recorded as m2, and then the acid solubility rate S is calculated according to formula (I):

[0024] S=(m1-m2) / m1×100% Formula (I),

[0025] Where: S is the acid solubility (%); m1 is the sample mass (g); m2 is the residue mass (g).

[0026] According to the present invention, preferably, the modified nano-calcium carbonate material has a retention reduction rate of 4.5% or more, preferably 25% or more, for a fracturing fluid composed of 99.7wt% solvent + 0.1wt% thickener + 0.1wt% drainage agent + 0.1wt% clay stabilizer and a retention amount of 12.5 mg / g, so as to further reduce the adsorption damage of the working fluid system to the reservoir.

[0027] To verify the adsorption and space-occupying effect of the modified nano-calcium carbonate material provided by the present invention on sandstone, thereby preventing acrylamide homopolymer in the fracturing fluid system from entering the sandstone pores, by testing its effect on the retention of the acrylamide homopolymer fracturing fluid system in the reservoir, it was found that the modified nano-calcium carbonate material provided by the present invention can be adsorbed in the tiny pore throats of the sandstone, preventing the adsorption of the polyacrylamide system, allowing more polyacrylamide to flow out, and reducing the retention amount, thereby indicating that the modified nano-calcium carbonate material can effectively improve the pore throat plugging rate of the fracturing fluid.

[0028] The specific detection process for the effect of the acrylamide homopolymer system on the retention of the reservoir is as follows: first, the sandstone sample is made into 0.21-0.30 mm (70-50 mesh) sandstone particles and loaded into a sand filling tube. The core of the sand filling tube with a diameter of 2.5 cm and a length of 15 cm is dried and weighed; a solution (1000 mg / L anionic polyacrylamide solution) is prepared, and the modified nano-calcium carbonate material provided by the present invention is added to each of the solutions and displaced at 1 mL / min for 5 hours. The solution concentration in the outflow sample is measured by the starch-chromium iodide method, and the retention of the polyacrylamide in the formation is calculated using the material balance method according to formula (II);

[0029] Q = (ρ0V0-ρ1V1) / W Formula (II), retention of polyacrylamide in the core, mg / g;

[0030] ρ0-concentration of injected polyacrylamide solution, mg / L; V0-volume of injected polyacrylamide, mL; ρ1-concentration of the sample flowing out of the core outlet, mg / L; V1-volume of the sample flowing out of the core outlet, mL; W-dry mass of the core, g.

[0031] The retention reduction rate refers to the ratio of the change in retention before and after the addition of the composition provided by the present invention (the addition amount of the composition is preferably 0.5-2 weight %) to the initial retention of the fracturing fluid, and the calculation formula is shown in Formula (III);

[0032]

[0033] In formula (III):

[0034] ΔQ——reduction rate of fracturing fluid retention, %;

[0035] Q0 - retention amount of the fracturing fluid when the composition provided by the present invention is not added, mg / g;

[0036] Q1 - retention amount of the fracturing fluid after adding the composition provided by the present invention, mg / g.

[0037] In the present invention, the solvent for the fracturing fluid can be water, the thickener can be any substance that can serve as a thickener in fracturing fluid, the drainage aid can be any substance that can serve as a drainage aid in fracturing fluid, and the clay stabilizer can be any substance that can serve as a clay stabilizer in fracturing fluid. Exemplarily, the thickener is an acrylamide homopolymer and / or a copolymer of acrylamide and another monomer, wherein the other monomer is selected from at least one of acryloyloxyethyltrimethylammonium chloride, sodium acrylate, and acrylic acid. More preferably, the copolymer of acrylamide and another monomer is at least one of an acrylamide-acryloyloxyethyltrimethylammonium chloride copolymer, an acrylamide-sodium acrylate-acrylic acid copolymer, and an acrylamide-acryloyloxyethyltrimethylammonium chloride-sodium acrylate-acrylic acid copolymer. Furthermore, preferably, the molecular weight of the acrylamide homopolymer is greater than 18 million, and the molecular weight of the copolymer of acrylamide and another monomer is greater than 18 million. The drainage aid is polyoxyethylene amine ether and / or polyoxyethylene fatty alcohol ether, preferably oleylamine polyoxyethylene ether and / or rosin amine polyoxyethylene ether, and preferably at least one of polyoxyethylene lauryl alcohol ether, polyoxyethylene tetradecyl alcohol ether, polyoxyethylene cetyl alcohol ether, and polyoxyethylene octadecyl alcohol ether. The clay stabilizer is dimethylamine quaternary ammonium salt and / or polyquaternium salt, preferably polyquaternium-126.

[0038] In the present invention, a fracturing fluid comprising a solvent, a thickener, a drainage aid, and a clay stabilizer with a retention rate of 12.5 mg / g can be formulated as follows: 99.7 wt% water + 0.1 wt% acrylamide homopolymer with a relative molecular weight of 18 million + 0.1 wt% drainage aid + 0.1 wt% dimethylamine quaternary ammonium salt. Fracturing fluids meeting these requirements can be, for example, the SPR series of fracturing fluids produced by Dongying Shipurui Petroleum Engineering Technology Co., Ltd., for example, a mixture of acrylamide homopolymer (thickener SPR-08), oleylamine polyoxyethylene ether (drainage aid SPR-201), and dimethylamine quaternary ammonium salt (clay stabilizer SPR-103) in the aforementioned proportions.

[0039] According to the present invention, preferably, the modified nano-calcium carbonate material contains calcium carbonate particles and a modifier attached to the surface of the calcium carbonate particles, wherein the modifier is a derivative formed by replacing at least one hydroxyl group in a polyhydroxy fatty acid with an amino-containing substituent. The carboxyl group contained in the modifier can form a stable chemical bond with calcium carbonate to attach to the surface of the calcium carbonate particles. The modifier makes the modified nano-calcium carbonate material an organic / inorganic nano-composite material. Combined with the bridging effect of inorganic nanoparticles and the deformation properties of organic particles, it forms a specific molecular aggregate hydrodynamic diameter in water, has good dispersion properties and pore throat plugging properties, and when applied to oil production working fluid systems, it can be used as an excellent plugging agent to achieve multi-size plugging in tight reservoirs, improve the plugging rate of pore throats, and enter the pore throats to adsorb and occupy space, making the plugging of formations more successful. The invention effectively improves the plugging rate during temporary plugging and fracturing in oil production and reduces the retention of fracturing fluid. The modifier on the surface of the calcium carbonate of the modified nano-calcium carbonate material can be hydrolyzed and fallen off under the combined action of high temperature and acidic conditions, exposing the calcium carbonate particles coated inside. The calcium carbonate particles then decompose when exposed to acid, so that the material has excellent acid solubility and forms a suitable degradation rate. After the temporary plugging and fracturing construction is completed, the acidification process can be used to effectively degrade the modified nano-calcium carbonate material, promote the return of the working fluid, and reduce the filtration loss during the fracturing process. The degradation rate and degradation time can meet the time requirements of the post-fracturing construction process of the tight reservoir.

[0040] According to the present invention, preferably, the structural formula of the modifier is as shown in formula (I) and the carbon chain length is greater than 20.

[0041] Among them, R I 、R II Each is independently hydrogen or C1-C3 alkyl, specifically hydrogen, methyl, ethyl, n-propyl, isopropyl; R III is hydrogen or C1-C20 alkyl (including linear alkyl, branched alkyl, cycloalkyl), for example, hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, etc.; m is an integer of 0-20; R IV and R V One of them is an amino-containing substituent and the other is hydrogen, or both are amino-containing substituents; the amino-containing substituent can be an amino group, an imino group, a nitro group, an alkyl group having an amino group, an aromatic group having an amino group, etc.

[0042] In the present invention, the morphology of the modified nano-calcium carbonate material can be detected by the following steps: after drying the modified nano-calcium carbonate material by irradiation with an infrared lamp, a small amount of the material is placed on a conductive tape on a copper tray, and lightly pressed with lint-free paper to firmly adhere the sample particles, and the powder sample adhering to the side of the copper tray is removed; the material is placed in a device, vacuumed, and conductive, and the morphology and elemental analysis of the sample powder is performed using a Quanta 250 scanning electron microscope. Figure 1 As shown, the modified nano calcium carbonate material provided by the present invention is Figure 2 Compared with the calcium carbonate shown, it is obvious that there are modified units attached to the surface of the particles.

[0043] According to the present invention, preferably, the carbon chain content of the modifier is 5-15% by weight, based on the total amount of the modified nano-calcium carbonate material; further preferably, the amino group content is 0.05-0.6% by weight. The inventors have found that under this preferred embodiment, the fluid loss during the fracturing process and the retention of the fracturing fluid in the pore throat can be further reduced.

[0044] In the present invention, the carbon and amino content can be determined by combining H NMR spectroscopy, C NMR spectroscopy and infrared detection, or by combining infrared detection with scanning electron microscopy.

[0045] The second aspect of the present invention provides a method for preparing a modified nano-calcium carbonate material, comprising: subjecting an unsaturated fatty monocarboxylic acid to a hydroxylation treatment and then subjecting the resulting unsaturated fatty acid to a contact reaction with a nano-calcium carbonate raw material; and subjecting the product of the contact reaction to an amination treatment.

[0046] The preparation method of the modified nano-calcium carbonate material provided by the present invention not only has a specific molecular aggregate hydrodynamic diameter in water, forming good dispersion performance and rock adsorption performance, but also significantly improves the multi-size plugging rate during construction, can enter the pore throat to absorb and occupy space, and reduce the retention of fracturing fluid, but also has an acid-soluble degradation rate that meets the construction process requirements of tight reservoirs, thereby reducing damage to the formation after the plugging operation.

[0047] In the present invention, the particle size of the nano calcium carbonate raw material is nanometer scale, preferably 30-150 nm, and can be commercially obtained.

[0048] In the present invention, preferably, the structural formula of the unsaturated fatty monocarboxylic acid is as shown in formula (II) and the carbon chain length is greater than 20.

[0049] Among them, R I 、R II are each independently hydrogen or C1-C3 alkyl, R IIIis hydrogen or a C1-C20 alkyl group, and m is an integer from 0 to 20. For example, the unsaturated fatty monocarboxylic acid may be docos-13-enoic acid, hexacos-7-enoic acid, pentacos-9-enoic acid, tetracos-20-enoic acid, octacos-10-enoic acid, etc., preferably hexacos-7-enoic acid and / or docos-13-enoic acid, and more preferably docos-13-enoic acid. The inventors have discovered that this preferred embodiment further enhances the rock adsorption of the modified nano-calcium carbonate material and improves the plugging rate.

[0050] According to the present invention, preferably, the hydroxylation process comprises: mixing the unsaturated fatty monobasic acid with a hydroxylating agent in the presence of a C1-C5 organic acid. The C1-C5 organic acid may be formic acid, acetic acid, propionic acid, butyric acid, or valeric acid, preferably formic acid.

[0051] According to the present invention, preferably, the hydroxylation agent is a peroxide, more preferably hydrogen peroxide. The inventors have found that under this preferred embodiment, it is beneficial to promote the addition reaction of formic acid and monounsaturated fatty acids and improve the reaction efficiency.

[0052] According to the present invention, preferably, the first reaction comprises: mixing the unsaturated fatty monobasic acid with a C1-C5 organic acid, dropwise adding the hydroxylation reagent at 30-35°C, and then heating to 65-70°C for 4-6 hours. The inventors have discovered that this preferred embodiment improves the efficiency of polyhydroxy fatty acid synthesis.

[0053] According to the present invention, the weight ratio of the unsaturated fatty acid, C1-C5 organic acid and hydroxylating agent is 1-2:1-2:1. The inventors have found that under this preferred embodiment, the conversion rate of the addition reaction between the hydroxylating agent and the monounsaturated fatty acid is improved.

[0054] In the present invention, the reaction solution obtained by the mixed reaction can be separated into layers to remove the water layer, the oil layer can be washed with hot water until neutral, a small amount of acetone can be added to dissolve the oil layer, and the water and solvent can be removed by rotary evaporation to obtain the first product (polyhydroxy fatty acid).

[0055] According to the present invention, preferably, the weight ratio of the hydroxylated unsaturated fatty monocarboxylic acid to the nano-calcium carbonate raw material is 1:4-8.

[0056] According to the present invention, preferably, the contact reaction conditions include: a temperature of 30-70°C, specifically 30°C, 40°C, 50°C, 60°C, 70°C, or any value therebetween; and a time of 0.5-1.5 hours, specifically 0.5 hours, 0.7 hours, 0.9 hours, 1.1 hours, 1.3 hours, 1.5 hours, or any value therebetween. The inventors have found that this preferred embodiment facilitates the modification of calcium carbonate by polyhydroxy fatty acids and improves reaction efficiency.

[0057] In the present invention, the contact reaction is carried out in the presence of a solvent. For example, the nano-calcium carbonate raw material can be dispersed in anhydrous ethanol, and then the nano-calcium carbonate raw material and the first product are subjected to contact reaction by shaking and stirring in an ultrasonic stirrer, and the product of the contact reaction is obtained by filtering and drying.

[0058] According to the present invention, preferably, the amination treatment process comprises: reacting the product of the contact reaction with an aromatic sulfonyl halide in a first stage, and then reacting the product with a diamine in the presence of a catalyst in a second stage.

[0059] According to the present invention, the aromatic sulfonyl halide can be benzenesulfonyl chloride, benzenesulfonyl fluoride, benzenesulfonyl bromide, or benzenesulfonyl iodide. Preferably, the aromatic sulfonyl halide is benzenesulfonyl chloride, more preferably at least one of p-toluenesulfonyl chloride, p-ethylbenzenesulfonyl chloride, m-toluenesulfonyl chloride, and m-ethylbenzenesulfonyl chloride; further preferably, p-toluenesulfonyl chloride. The diamine is selected from at least one of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl, and 4,4'-diaminodiphenyl sulfone; further preferably, p-phenylenediamine. The inventors have discovered that this preferred embodiment facilitates surface modification of the contact reaction product, improving the blocking effect.

[0060] According to the present invention, preferably, the weight ratio of the aromatic sulfonyl halide to the product of the contact reaction is 1:0.8-1.2.

[0061] According to the present invention, preferably, the first stage reaction process includes: adding the product of the contact reaction to the solution containing the aromatic sulfonyl halide in multiple portions. The inventors have found that under this preferred embodiment, the reaction efficiency of the aromatic sulfonyl halide and the product of the contact reaction is improved.

[0062] Further preferably, the solvent of the solution containing the aromatic sulfonyl halide is a strong base solution with a concentration of 20-30% by weight or pyridine, and the strong base is preferably sodium hydroxide and / or potassium hydroxide; the solvent of the solution containing the aromatic sulfonyl halide is further preferably pyridine.

[0063] According to the present invention, preferably, the conditions for the first stage reaction include: a temperature of -5 to 5°C, specifically -5°C, -3°C, -1°C, 0°C, 1°C, 3°C, 5°C, or any value therebetween; and a reaction time of 4 to 7 hours, specifically 4 hours, 5 hours, 6 hours, 7 hours, or any value therebetween. The inventors have found that under this preferred embodiment, the reaction efficiency is improved.

[0064] Illustratively, the process of the first stage reaction is: dissolving the aromatic sulfonyl halide in pyridine, stirring in an ice bath, adding the product of the contact reaction in small amounts and multiple times, and reacting for a total of 4-7 hours.

[0065] According to the present invention, preferably, the weight ratio of the product of the first stage reaction to the diamine is 2.4-3: 1. The inventors have found that under this preferred embodiment, it is beneficial to introduce amino groups on the surface of the third product, thereby increasing the yield of the modified nano-calcium carbonate material.

[0066] According to the present invention, preferably, described second stage reaction adopts concentrated strong alkali solution as reaction solvent, and described strong alkali is preferably 20-30 weight % sodium hydroxide and / or potassium hydroxide in concentration.The inventor finds that under this preferred embodiment, is conducive to improving the adhesion effect of structural unit a on modified nano-calcium carbonate material.

[0067] According to the present invention, preferably, the catalyst is a phase transfer catalyst, more preferably tetrabutylammonium bromide and / or benzyltriethylammonium chloride. The inventors have found that under this preferred embodiment, it is beneficial to improve the conversion rate of amino groups introduced into the surface of the product of the first stage reaction.

[0068] According to the present invention, preferably, the conditions of the second stage reaction include: using a strong alkaline solution with a concentration of 20-30% by weight as the reaction solvent, a temperature of 95-105° C., and a time of 7-12 hours. The inventors have found that under this preferred embodiment, it is beneficial to increase the yield of the modified nano-calcium carbonate material with structural unit a attached.

[0069] The third aspect of the present invention provides the use of the modified nano-calcium carbonate material as described above or the modified nano-calcium carbonate material prepared according to the method as described above in oil production working fluid.

[0070] In the present invention, the oil production working fluid can be a fracturing fluid, a drilling fluid, a completion fluid or any other working fluid; preferably, the above-mentioned modified nano-calcium carbonate material is used as a plugging agent for the fracturing fluid. During on-site construction, it plays the role of a plugging agent, has good dispersibility and rock adsorption, high plugging strength and good stability, can enter the pore throat and absorb and occupy space to reduce the retention of the fracturing fluid; after the construction is completed, the modified nano-calcium carbonate material can be acidified and degraded based on its own acid solubility, effectively reducing the residue content of the working fluid, reducing damage to the reservoir matrix, and can effectively reduce the filtration loss of the working fluid, promote the rapid return of the fracturing fluid to the reservoir, and improve the return efficiency of the working fluid.

[0071] A fourth aspect of the present invention provides a fracturing fluid containing the modified nano-calcium carbonate material as described above.

[0072] According to the present invention, preferably, the content of the modified nano-calcium carbonate material is 0.5-2% by weight based on the total amount of the fracturing fluid. The inventors have found that under this preferred embodiment, it is beneficial to better improve the sealing strength and stability, reduce the filtration loss of the fracturing fluid, and reduce the damage of the fluid to the formation.

[0073] According to the present invention, preferably, the fracturing fluid further comprises, based on the total amount of the fracturing fluid, 0.1-1% by weight of a thickener, 0.1-1% by weight of a drainage aid, and 0.1-1% by weight of a clay stabilizer, with the remainder being a solvent (e.g., water). The fracturing fluid provided by the present invention, incorporating the modified nano-calcium carbonate material provided above, based on existing conventional fracturing fluid systems, can significantly improve the plugging rate compared to the initial fracturing fluid system and enhance the flowback efficiency of the working fluid after construction.

[0074] According to the present invention, preferably, the thickener is an acrylamide homopolymer and / or a copolymer of acrylamide and another monomer, wherein the other monomer is selected from at least one of acryloyloxyethyltrimethylammonium chloride, sodium acrylate, and acrylic acid. Further preferably, the copolymer of acrylamide and another monomer is at least one of an acrylamide-acryloyloxyethyltrimethylammonium chloride copolymer, an acrylamide-sodium acrylate-acrylic acid copolymer, and an acrylamide-acryloyloxyethyltrimethylammonium chloride-sodium acrylate-acrylic acid copolymer. Further preferably, the molecular weight of the acrylamide homopolymer is greater than 18 million, and the molecular weight of the copolymer of acrylamide and another monomer is greater than 18 million.

[0075] According to the present invention, preferably, the drainage aid is polyoxyethylene amine ether and / or polyoxyethylene fatty alcohol ether. Further preferably, the polyoxyethylene amine ether is oleylamine polyoxyethylene ether and / or rosin amine polyoxyethylene ether; and the polyoxyethylene fatty alcohol ether is at least one of polyoxyethylene lauryl alcohol ether, polyoxyethylene tetradecyl alcohol ether, polyoxyethylene cetyl alcohol ether, and polyoxyethylene stearyl alcohol ether.

[0076] According to the present invention, preferably, the clay stabilizer is dimethylamine quaternary ammonium salt and / or polyquaternium salt, and the polyquaternium salt is preferably polyquaternium-126.

[0077] The present invention will be described in detail below through examples.

[0078] In the following examples, the nano-calcium carbonate raw material was purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., with a product model of XFI11-2 and a particle size of 50-100 nm; erucic acid (docosa-13-enoic acid) was purchased from Shanghai Aladdin Technology Co., Ltd. with a CAS number of 112-86-7; hexacos-7-enoic acid was purchased from Shanghai Aladdin Technology Co., Ltd. with a CAS number of 66274-43-9; unless otherwise specified, the remaining raw materials and reagents were conventional commercially available products.

[0079] In the following examples, the specific detection process of the acid solubility rate is as follows: 2 g of the modified nano-calcium carbonate material is placed in an oven and dried to constant weight, recorded as m1, added to 250 mL of a 15 wt % hydrochloric acid solution, stirred evenly, covered and kept at a temperature of 90 ° C for 1 h or 2 h, stopped heating, taken out and filtered, dried to constant weight and weighed, recorded as m2, and then the acid solubility rate S is calculated according to formula (I):

[0080] S=(m1-m2) / m1×100% formula (I),

[0081] Where: S is the acid solubility (%); m1 is the sample mass (g); m2 is the residue mass (g).

[0082] The test method for the particle size of the modified nano-calcium carbonate material is: using a Fritsch 22 laser particle size analyzer, and referring to the measurement method in the standard GB / T 19077-2016 "Particle Size Analysis by Laser Diffraction Method" for testing.

[0083] In order to verify whether the modified calcium carbonate blocks the pore throats, the filtration loss of the fracturing fluid with modified nano-calcium carbonate material added is measured using a high-temperature and high-pressure filter loss instrument. The specific filtration loss test is carried out using a rock plate processed from a core of a tight sandstone reservoir. The pore diameter of the sample is between 0.01 and 20 μm. The detection process refers to the industry standard "SY / T 5107-2016 Performance Evaluation Method of Water-Based Fracturing Fluid".

[0084] In order to verify the adsorption and occupying effect of the modified nano-calcium carbonate material provided by the present invention on sandstone, thereby preventing acrylamide homopolymer in the fracturing fluid system from entering the sandstone pores, the retention of the fracturing fluid after adding the modified nano-calcium carbonate material and the retention reduction rate before and after addition were measured. The specific process is: first, the sandstone sample is made into 0.21-0.3mm (70-50 mesh) sandstone particles and loaded into the sand filling tube, and the sand filling tube core with a diameter of 2.5cm and a length of 15cm is dried and weighed; a solution (1000mg / L anionic polyacrylamide solution) is prepared, and the modified nano-calcium carbonate material is added respectively and displaced at 1mL / min for 5h, and the starch-chromium iodide method is used to determine the solution concentration in the outflow sample, and the material balance method is used to calculate the retention of polyacrylamide in the formation according to formula (II);

[0085] Q = (ρ0V0-ρ1V1) / W Formula (II), retention of polyacrylamide in the core, mg / g;

[0086] ρ0-concentration of injected polyacrylamide solution, mg / L; V0-volume of injected polyacrylamide, mL; ρ1-concentration of the sample flowing out of the core outlet, mg / L; V1-volume of the sample flowing out of the core outlet, mL; W-dry mass of the core, g.

[0087] The retention reduction rate refers to the ratio of the change in retention before and after the addition of the composition provided by the present invention (the addition amount of the composition is preferably 0.5-2 weight %) to the initial retention of the fracturing fluid, and is calculated as shown in formula (III);

[0088]

[0089] In formula (III):

[0090] ΔQ——reduction rate of fracturing fluid retention, %;

[0091] Q0 - retention amount of the fracturing fluid when the composition provided by the present invention is not added, mg / g;

[0092] Q1 - retention amount of the fracturing fluid after adding the composition provided by the present invention, mg / g.

[0093] The test method for the hydrodynamic diameter of molecular aggregates of modified nano-calcium carbonate materials in water is as follows: the modified nano-calcium carbonate material is used to determine the particle size of the modified calcium carbonate dispersed in water using a Fritsch 22 laser particle size analyzer using a wet method, and the wet method test is performed with reference to the liquid medium (using water) dispersion and measurement method in the standard GB / T 19077-2016 "Particle Size Analysis Laser Diffraction Method". The specific process is: open the test software MaScontrol and click the cleaning and calibration program to complete the cleaning and calibration of the instrument, and then perform the measurement; prepare the test sample, add the sample to the funnel in small amounts and multiple times with a medicine spoon, and disperse the sample with clean water and ultrasound. After the addition is completed, the instrument automatically performs three sets of parallel data tests. If the error does not exceed 5%, the test dynamic particle size distribution report is output. After the test is completed, the instrument is cleaned and dried, and then the instrument is turned off.

[0094] Example 1

[0095] 1) 16 g of erucic acid and 14 g of formic acid were placed in a four-necked reaction flask equipped with an electric stirrer, a thermometer, a dropping funnel, and a condenser. The reaction flask was placed in a constant temperature water bath and heated to 32° C. with stirring. 10 g of hydrogen peroxide was then added dropwise at a uniform rate. The system temperature was adjusted to 68° C., the reaction temperature, and the reaction was stopped after 5 h to obtain a reaction solution I. The reaction solution was transferred to a separatory funnel, the water layer was separated, the oil layer was washed with hot water until neutral, a small amount of acetone was added to dissolve the oil layer, and the water and solvent were removed by rotary evaporation to obtain the first product (white solid, polyhydroxy erucic acid); 90 g of nano-calcium carbonate raw material (powder) was dispersed in 200 mL of anhydrous ethanol, and the first product was added to the mixture. The mixture was stirred and shaken in an ultrasonic stirrer at 65° C. for 1 h. The mixture was filtered and dried to obtain the second product (polyhydroxy erucic acid-grafted nano-calcium carbonate);

[0096] 2) 10 g of p-toluenesulfonyl chloride was dissolved in 20 mL of pyridine and stirred in an ice bath. A total of 10 g of the second product was added in small amounts (about 0.5 g each time) for a total of 6 hours to obtain a third product (alkyl p-toluenesulfonate grafted nano-calcium carbonate). In the presence of a phase transfer catalyst, tetrabutylammonium bromide, 28 g of the third product and 10 g of p-phenylenediamine were mixed in a 25 wt% sodium hydroxide solution. The mixture was stirred with a magnetic stirrer and heated to 100° C. under reflux for 10 hours. The modified nano-calcium carbonate material was obtained after drying, filtration, and rotary evaporation.

[0097] Example 2

[0098] 1) 20 g of erucic acid and 18 g of formic acid were placed in a four-necked reaction flask equipped with an electric stirrer, a thermometer, a dropping funnel, and a condenser. The reaction flask was placed in a constant temperature water bath and heated to 35° C. with stirring. 10 g of hydrogen peroxide was then added dropwise at a uniform rate. The system temperature was adjusted to 70° C. and the reaction was stopped after 4 h to obtain a reaction solution I. The reaction solution was transferred to a separatory funnel, the water layer was separated, the oil layer was washed with hot water until neutral, a small amount of acetone was added to dissolve the oil layer, and the water and solvent were removed by rotary evaporation to obtain the first product (white solid, polyhydroxy erucic acid); 100 g of nano-calcium carbonate raw material (powder) was dispersed in 200 mL of anhydrous ethanol, and the first product was added. The mixture was stirred and reacted in an ultrasonic stirrer at 70° C. for 0.5 h. The mixture was filtered and dried to obtain the second product (polyhydroxy erucic acid-grafted nano-calcium carbonate);

[0099] 2) 10 g of p-toluenesulfonyl chloride was dissolved in a 20 wt% sodium hydroxide solution, stirred in an ice bath, and a total of 9 g of the second product was added in small amounts (about 0.4 g each time) for a total reaction of 7 h to obtain a third product (alkyl p-toluenesulfonate grafted nano-calcium carbonate); 24 g of the third product was mixed with 10 g of p-phenylenediamine in a 20 wt% sodium hydroxide solution in the presence of a phase transfer catalyst, tetrabutylammonium bromide, and magnetic stirring. The mixture was heated to 95° C. and refluxed for 12 h. The modified nano-calcium carbonate material was obtained after drying, filtration, and rotary evaporation.

[0100] Example 3

[0101] 1) 12 g of erucic acid and 10 g of formic acid were placed in a four-necked reaction flask equipped with an electric stirrer, a thermometer, a dropping funnel, and a condenser. The reaction flask was placed in a constant temperature water bath and heated to 30° C. with stirring. 10 g of hydrogen peroxide was then added dropwise at a uniform rate. The system temperature was adjusted to 65° C. and the reaction was stopped after 6 h to obtain a reaction solution I. The reaction solution was transferred to a separatory funnel, the water layer was separated, the oil layer was washed with hot water until neutral, a small amount of acetone was added to dissolve the oil layer, and the water and solvent were removed by rotary evaporation to obtain the first product (white solid, polyhydroxy erucic acid); 80 g of nano-calcium carbonate raw material (powder) was dispersed in 200 mL of anhydrous ethanol, and the first product was added. The mixture was stirred and shaken in an ultrasonic stirrer at 30° C. for 1.5 h. The reaction was filtered and dried to obtain the second product (polyhydroxy erucic acid-grafted nano-calcium carbonate);

[0102] 2) 10 g of p-ethylbenzenesulfonyl chloride was dissolved in a 30 wt% sodium hydroxide solution, stirred in an ice bath, and a total of 12 g of the second product was added in small amounts (about 0.6 g each time) for a total of 4 h to obtain a third product (alkyl p-toluenesulfonate grafted nano-calcium carbonate); 30 g of the third product was mixed with 10 g of p-phenylenediamine in a 30 wt% sodium hydroxide solution in the presence of a phase transfer catalyst, benzyltriethylammonium chloride, and stirred with a magnetic stirrer. The mixture was heated to 105° C. and refluxed for 7 h. The modified nano-calcium carbonate material was obtained after drying, filtration, and rotary evaporation.

[0103] Example 4

[0104] The modified nano-calcium carbonate material was prepared according to the method of Example 1, except that the erucic acid in step 1) was replaced by hexacos-7-enoic acid.

[0105] Example 5

[0106] The modified nano-calcium carbonate material was prepared according to the method of Example 1, except that the p-phenylenediamine in step 2) was replaced by 1,4-butanediamine.

[0107] Example 6

[0108] The modified nano-calcium carbonate material was prepared according to the method of Example 1, except that step 1) was replaced by:

[0109] 1) 16 g of erucic acid, 14 g of formic acid, and 10 g of hydrogen peroxide were placed in a four-necked reaction flask equipped with an electric stirrer, a thermometer, a dropping funnel, and a condenser. The reaction flask was placed in a constant temperature water bath and heated to 68° C. with stirring. The reaction was stopped after 5 h to obtain a reaction solution I. The reaction solution was transferred to a separatory funnel, the water layer was separated, the oil layer was washed with hot water until neutral, a small amount of acetone was added to dissolve the oil layer, and the water and solvent were removed by rotary evaporation to obtain the first product (white solid, polyhydroxy erucic acid). 90 g of nano-calcium carbonate raw material (powder) was dispersed in 200 mL of anhydrous ethanol, and the first product was added to the mixture. The mixture was stirred and shaken in an ultrasonic stirrer at room temperature (25° C.) for 1 h. The mixture was filtered and dried to obtain the second product (polyhydroxy erucic acid-grafted nano-calcium carbonate).

[0110] Example 7

[0111] The modified nano-calcium carbonate material was prepared according to the method of Example 1, except that step 2) was replaced by:

[0112] 2) 10 g of p-toluenesulfonyl chloride was dissolved in a 25 wt% sodium hydroxide solution, stirred in an ice bath, and then mixed with 10 g of the second product and reacted for 6 h to obtain a third product (alkyl p-toluenesulfonate grafted nano-calcium carbonate); 28 g of the third product was mixed with 10 g of p-phenylenediamine in a 25 wt% sodium hydroxide solution in the presence of a phase transfer catalyst, tetrabutylammonium bromide, and magnetically stirred. The mixture was heated to 100° C. and refluxed for 10 h. The modified nano-calcium carbonate material was obtained after drying, filtration, and rotary evaporation.

[0113] Example 8

[0114] The modified nano-calcium carbonate material was prepared according to the method of Example 1, except that step 1) was replaced by:

[0115] 1) 16 g of erucic acid and 14 g of formic acid were placed in a four-necked reaction flask equipped with an electric stirrer, a thermometer, a dropping funnel, and a condenser. The reaction flask was placed in a constant temperature water bath and heated to 32° C. with stirring. 10 g of hydrogen peroxide was then added dropwise at a uniform rate. The system temperature was adjusted to 55° C. and the reaction was stopped after 5 h to obtain a reaction solution I. The reaction solution was transferred to a separatory funnel, the water layer was separated, the oil layer was washed with hot water until neutral, a small amount of acetone was added to dissolve the oil layer, and the water and solvent were removed by rotary evaporation to obtain the first product (white solid, polyhydroxy erucic acid). 90 g of nano-calcium carbonate raw material (powder) was dispersed in 200 mL of anhydrous ethanol, and the first product was added thereto. The mixture was stirred and shaken in an ultrasonic stirrer at room temperature (25° C.) for 1 h. The mixture was filtered and dried to obtain the second product (polyhydroxy erucic acid-grafted nano-calcium carbonate).

[0116] Example 9

[0117] The modified nano-calcium carbonate material was prepared according to the method of Example 1, except that step 2) was replaced by:

[0118] 2) 10 g of p-toluenesulfonyl chloride was dissolved in a 25 wt% sodium hydroxide solution, stirred at room temperature (25° C.), and a total of 10 g of the second product was added in small amounts (about 0.5 g each time) for a total of 6 h to obtain a third product (alkyl p-toluenesulfonate grafted nano-calcium carbonate); 28 g of the third product was mixed with 10 g of p-phenylenediamine in a 25 wt% sodium hydroxide solution in the presence of a phase transfer catalyst, tetrabutylammonium bromide, and magnetic stirring. The mixture was heated to 100° C. and refluxed for 10 h. The modified nano-calcium carbonate material was obtained after drying, filtration, and rotary evaporation.

[0119] Example 10

[0120] The modified nano-calcium carbonate material was prepared according to the method of Example 1, except that step 2) was replaced by:

[0121] 2) 10 g of p-toluenesulfonyl chloride was dissolved in a 25 wt% sodium hydroxide solution, stirred in an ice bath, and a total of 10 g of the second product was added in small amounts (about 0.5 g each time) for a total of 6 h to obtain a third product (alkyl p-toluenesulfonate grafted nano-calcium carbonate); 28 g of the third product was mixed with 10 g of p-phenylenediamine in a 25 wt% sodium hydroxide solution, stirred with a magnetic stirrer, heated to 100° C. and refluxed for 10 h. The mixture was dried, filtered, and rotary evaporated to obtain a modified nano-calcium carbonate material.

[0122] Comparative Example 1

[0123] 16 g of erucic acid and 14 g of formic acid were placed in a four-necked reaction flask equipped with an electric stirrer, a thermometer, a dropping funnel, and a condenser. The reaction flask was placed in a constant temperature water bath and heated to 32° C. with stirring. 10 g of hydrogen peroxide was then added dropwise at a uniform rate. The system temperature was adjusted to a reaction temperature of 68° C. The reaction was stopped after 5 h to obtain reaction solution I. The reaction solution was transferred to a separatory funnel, the water layer was separated, the oil layer was washed with hot water until neutral, a small amount of acetone was added to dissolve the oil layer, and the water and solvent were removed by rotary evaporation to obtain the first product (white solid, polyhydroxy erucic acid). 90 g of nano-calcium carbonate raw material (powder) was dispersed in 200 mL of anhydrous ethanol, and the first product was added. The mixture was stirred and shaken in an ultrasonic stirrer at 65° C. for 1 h. The second product (polyhydroxy erucic acid-grafted nano-calcium carbonate) was filtered and dried to obtain a modified nano-calcium carbonate material.

[0124] Comparative Example 2

[0125] 90 g of nano-calcium carbonate raw material (powder) was dispersed in 200 mL of anhydrous ethanol, and 16 g of erucic acid was added. The mixture was stirred and reacted at 65° C. in an ultrasonic stirrer for 1 h. The second product (erucic acid-grafted nano-calcium carbonate) was obtained by filtration and drying as a modified nano-calcium carbonate material.

[0126] Comparative Example 3

[0127] 16g of erucic acid, 10g of hydrogen peroxide, 90g of nano-calcium carbonate raw material (powder), 10g of p-toluenesulfonyl chloride and 10g of p-phenylenediamine were physically mixed (forming a suspension with calcium carbonate floating on the surface of other liquid solutions), dried, filtered and rotary evaporated to obtain modified nano-calcium carbonate material.

[0128] Comparative Example 4

[0129] 90 g of nano-calcium carbonate raw material (powder) was dispersed in 200 mL of anhydrous ethanol, 10 g of p-toluenesulfonyl chloride was dissolved in 20 mL of pyridine, and the mixture was stirred in an ice bath. A total of 10 g of calcium carbonate ethanol solution was added in small amounts (about 0.5 g each time) for a total reaction time of 6 hours to obtain a first product. In the presence of a phase transfer catalyst, tetrabutylammonium bromide, 28 g of the first product and 10 g of p-phenylenediamine were mixed in a 25 wt% sodium hydroxide solution, magnetically stirred, heated to 100° C. and refluxed for 10 hours. The modified nano-calcium carbonate material was obtained after drying, filtration, and rotary evaporation.

[0130] Comparative Example 5

[0131] 1) 16 g of octadecanoic acid and 14 g of formic acid were placed in a four-necked reaction flask with an electric stirrer, a thermometer, a dropping funnel, and a condenser, and the reaction flask was placed in a thermostatic water bath. After the temperature was raised to 32° C. under stirring, 10 g of hydrogen peroxide was uniformly added dropwise, the system temperature was adjusted to a reaction temperature of 68° C., and the reaction was stopped after 5 h to obtain a reaction solution I. The reaction solution was transferred to a separatory funnel, the water layer was separated, the oil layer was washed with hot water until neutral, a small amount of acetone was added to dissolve the oil layer, and water and solvent were removed by rotary evaporation to obtain a first product; 90 g of nano calcium carbonate raw material (powder) was dispersed with 200 mL of anhydrous ethanol, and the first product was added thereto. The mixture was stirred and shaken in an ultrasonic stirrer at 65° C. for 1 h, filtered, and dried to obtain the first product (stearic acid-grafted nano calcium carbonate);

[0132] 2) 10 g of p-toluenesulfonyl chloride was dissolved in 20 mL of pyridine and stirred in an ice bath. A total of 10 g of the first product was added in small amounts (about 0.5 g each time) for a total reaction time of 6 h to obtain a second product (alkyl p-toluenesulfonate grafted nano-calcium carbonate); 28 g of the second product was mixed with 10 g of p-phenylenediamine in a 25 wt% sodium hydroxide solution in the presence of a phase transfer catalyst, tetrabutylammonium bromide, and magnetic stirring was performed. The mixture was heated to 100° C. and refluxed for 10 h. The modified nano-calcium carbonate material was obtained after drying, filtration, and rotary evaporation.

[0133] Test Example 1

[0134] The modified nano-calcium carbonate powder prepared in Example 1 was pressed into a KBr pellet and analyzed by a Shimadzu IRPrestige-21 Fourier transform infrared spectrometer. The infrared spectrum was as follows: Figure 1 shown. Figure 1 The absorption peak of NH in -NH2 of phenylenediamine is at 3420 cm -1 The -CH=CH- bending vibration peaks of the benzene ring are at 1583, 1492, and 1400 cm -1 , indicating that the modified nano-calcium carbonate material contains aniline structure; in addition, 1700cm -1 and 2923cm-1 The stretching vibration peaks of C=O and methylene CH2 in polyhydroxy erucic acid appeared, and the absorption peak of -OH in polyhydroxy erucic acid partially overlapped with the peak of NH; at the same time, the characteristic absorption peaks of CaCO3 mainly appeared at 1700, 1460, 875, and 715 cm -1 It is proved that the modified nano calcium carbonate material finally prepared in Example 1 contains calcium carbonate particles and is grafted with a modifier having a fatty acid carbon chain and an amino group.

[0135] The fine powder of the modified nano-calcium carbonate material prepared in Example 1 was dried by irradiation with an infrared lamp, and a small amount was placed on a conductive tape on a copper tray. It was lightly pressed with lint-free paper to firmly adhere the sample particles, and the powder sample adhering to the side of the copper tray was removed. The sample was loaded into the equipment, vacuumed, and conductive. The morphology and elemental analysis of the sample powder were performed using a Quanta 250 scanning electron microscope. The morphology and EDS spectrum of the modified calcium carbonate provided by the present invention are shown as follows: Figure 2 As shown, Figure 3 Compared with the calcium carbonate particle morphology and EDS spectrum shown, it is obvious that there is a modifier attached to the particle surface. The EDS spectrum shows that element N exists in the modified nano calcium carbonate. The content of amino groups can be inferred based on the content of element N.

[0136] The carbon chain content and amino group content in the modified nano-calcium carbonate materials prepared in Examples 1 to 10 and Comparative Examples 1 to 5 were determined by combining infrared detection and scanning electron microscopy. The results are shown in Table 2.

[0137] The aqueous solution of modified nano calcium carbonate material obtained in Example 1 was observed under an optical microscope. Figure 4 As shown, the particles of modified calcium carbonate are composed of many tiny crystallites and are evenly distributed.

[0138] The unmodified nano calcium carbonate particles and their aqueous solution were observed under an optical microscope. Figure 5-Figure 6 As shown in the figure, the nano calcium carbonate particles are uniform in size in the dry powder state; after adding water, they are agglomerated, but the size is inconsistent and the distribution is uneven.

[0139] The hydrodynamic diameter D of the molecular aggregates of the modified nano-calcium carbonate materials prepared in test examples 1 to 10 and comparative examples 1 to 5 in water is 10 、D 20 、D 50 、D 70 and D 90 The results are shown in Table 1. The acid solubility of the modified nano-calcium carbonate materials prepared in Examples 1 to 10 and Comparative Examples 1 to 5 was tested, with calcium carbonate as a reference. The results are shown in Table 2.

[0140] Table 1

[0141]

[0142] Table 2

[0143] serial number Carbon chain content / weight% Amino content / weight% 90℃, 1h acid solubility / % 90℃, 2h acid solubility / % Example 1 7.82 0.55 74 100 Example 2 8.17 0.48 78 100 Example 3 7.09 0.39 78 95 Example 4 10.32 0.41 80 98 Example 5 11.53 0.26 75 100 Example 6 13.45 0.19 67 92 Example 7 14.56 0.05 68 96 Example 8 9.24 0.43 71 94 Example 9 10.35 0.06 71 100 Example 10 13.45 0.09 66 98 Comparative Example 1 20.31 0 73 100 Comparative Example 2 24.20 0 65 90 Comparative Example 3 2.35 0 100 100 Comparative Example 4 0 0 100 100 Comparative Example 5 20.12 0.04 77 91 Calcium carbonate raw materials 0 0 100 100

[0144] Test Example 2

[0145] Step 1) 0.1 g of polyacrylamide with a weight average molecular weight of 18 million (purchased from Dongying Shipurui Petroleum Engineering Technology Co., Ltd., product model is thickener SPR-08) is added to 99.7 g of clean water. The addition speed is controlled during the addition process to prevent the formation of fish eyes, and the speed is adjusted at all times to ensure a vortex state until it is fully dissolved to form a uniform solution; then 0.1 g of oleylamine polyoxyethylene ether (purchased from Dongying Shipurui Petroleum Engineering Technology Co., Ltd., product model is drainage agent SPR-201) and 0.1 g of dimethylamine quaternary ammonium salt (purchased from Dongying Shipurui Petroleum Engineering Technology Co., Ltd., product model is clay stabilizer SPR-103) are added and stirred evenly.

[0146] Step 2) While maintaining the stirring state, 0.5 g of the modified nano-calcium carbonate material obtained in Examples 1 to 10 was added to the solution obtained in Step 1) respectively, and stirred to obtain the fracturing fluid.

[0147] Test Example 3

[0148] Step 1) 0.1 g of polyacrylamide with a weight average molecular weight of 18 million (purchased from Dongying Shipurui Petroleum Engineering Technology Co., Ltd., product model is thickener SPR-08) is added to 99.7 g of clean water. The addition speed is controlled during the addition process to prevent the formation of fish eyes, and the speed is adjusted at all times to ensure a vortex state until it is fully dissolved to form a uniform solution; then 0.1 g of oleylamine polyoxyethylene ether (purchased from Dongying Shipurui Petroleum Engineering Technology Co., Ltd., product model is drainage agent SPR-201) and 0.1 g of dimethylamine quaternary ammonium salt (purchased from Dongying Shipurui Petroleum Engineering Technology Co., Ltd., product model is clay stabilizer SPR-103) are added and stirred evenly.

[0149] Step 2) While maintaining the stirring state, add 2 g of the modified nano-calcium carbonate material obtained in Example 1 to the solution obtained in step 1) and stir to obtain the fracturing fluid.

[0150] Test Example 4

[0151] The fracturing fluid was prepared according to the method of Test Example 3, except that the amount of the modified nano-calcium carbonate material prepared in Example 1 in step 2) was replaced with 1.5 g.

[0152] Comparative test example 1

[0153] The fracturing fluid was prepared according to the method of Test Example 2, except that 0.5 g of the modified nano-calcium carbonate material prepared in Example 2) was replaced by 0.5 g of the modified nano-calcium carbonate material prepared in Comparative Example 1.

[0154] Comparative test example 2

[0155] The fracturing fluid was prepared according to the method of Test Example 2, except that 0.5 g of the modified nano-calcium carbonate material prepared in Example 2 was replaced with 0.5 g of the modified nano-calcium carbonate material prepared in Comparative Example 2 in step 2).

[0156] Comparative test example 3

[0157] A fracturing fluid was prepared according to the method of Test Example 2, except that 0.5 g of the modified nano-calcium carbonate material prepared in Example 2) was replaced with 0.5 g of the modified nano-calcium carbonate material prepared in Comparative Example 3. Because the physical mixing followed by filtration, drying, and rotary evaporation in Comparative Example 3 only produced calcium carbonate powder partially contaminated with erucic acid, which remained floating when dissolved in aqueous solvent, and no fracturing fluid system could be obtained. Therefore, the filtration loss and retention of the fracturing fluid could not be effectively measured.

[0158] Comparative test example 4

[0159] The fracturing fluid was prepared according to the method of Test Example 2, except that 0.5 g of the modified nano-calcium carbonate material prepared in Example 2) was replaced by 0.5 g of the modified nano-calcium carbonate material prepared in Comparative Example 4.

[0160] Comparative test example 5

[0161] The fracturing fluid was prepared according to the method of Test Example 2, except that 0.5 g of the modified nano-calcium carbonate material prepared in Example 2) was replaced by 0.5 g of the modified nano-calcium carbonate material prepared in Comparative Example 5.

[0162] Comparative Test Example 6

[0163] The fracturing fluid was prepared according to the method of Test Example 2, except that 0.5 g of the modified nano-calcium carbonate material prepared in Example was not added in step 2).

[0164] The fracturing fluid prepared in Comparative Test Example 6 is used as the original fracturing fluid.

[0165] The filtration loss, retention volume and retention volume reduction rate of each fracturing fluid corresponding to the modified nano-calcium carbonate materials prepared in Test Examples 2-4 and Comparative Test Examples 1-6 were measured. The results are shown in Table 3.

[0166] Table 3

[0167]

[0168]

[0169] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A modified nano calcium carbonate material, characterized in that, The hydrodynamic diameter D of the molecular aggregates of the modified nano-calcium carbonate material in water is 10 2-10μm, D 50 8-31μm, D 90 20-90μm.

2. modified nano calcium carbonate material according to claim 1, wherein, The hydrodynamic diameter D of the molecular aggregates of the modified nano-calcium carbonate material in water is 20 4-22μm, D 70 12-70μm.

3. modified nano calcium carbonate material according to claim 1 or 2, wherein, The modified nano-calcium carbonate material has an acid solubility of 50-80% in a hydrochloric acid solution with a concentration of 15% by weight and degraded at 90° C. for 1 hour, and an acid solubility of more than 90% in a hydrochloric acid solution with a concentration of 15% by weight and degraded at 90° C. for 2 hours.

4. The modified nano calcium carbonate material according to any one of claims 1 to 3, wherein The modified nano-calcium carbonate material has a retention reduction rate of 4.5% or more, preferably 25% or more, for a fracturing fluid composed of 99.7wt% solvent+0.1wt% thickener+0.1wt% drainage aid+0.1wt% clay stabilizer and a retention amount of 12.5mg / g.

5. The modified nano calcium carbonate material according to any one of claims 1 to 4, wherein The modified nano calcium carbonate material contains calcium carbonate particles and a modifier attached to the surface of the calcium carbonate particles, wherein the modifier contains a derivative formed by replacing at least one hydroxyl group in a polyhydroxy fatty acid with an amino-containing substituent. Preferably, the structural formula of the modifier is as shown in formula (I) and the carbon chain length is greater than 20. Among them, R I 、R II are each independently hydrogen or C1-C3 alkyl, R III is hydrogen or C1-C20 alkyl, m is an integer of 0-20; R IV and R V One of them is an amino-containing substituent and the other is a hydroxyl group, or both are amino-containing substituents.

6. modified nano calcium carbonate material according to claim 5, wherein, Based on the total amount of the modified nano-calcium carbonate material, the carbon chain content in the modifier is 5-15% by weight, and the amino group content is 0.05-0.6% by weight.

7. A method for preparing a modified nano-calcium carbonate material, characterized in that: The method comprises: subjecting unsaturated fatty monocarboxylic acid to hydroxylation treatment, and then subjecting the unsaturated fatty monocarboxylic acid to a contact reaction with a nanometer calcium carbonate raw material; and subjecting the product of the contact reaction to an amination treatment.

8. The preparation method according to claim 7, characterized in that The structural formula of the unsaturated fatty monocarboxylic acid is shown in formula (II) and the carbon chain length is greater than 20. Among them, R I 、R II are each independently hydrogen or C1-C3 alkyl, R III is hydrogen or C1-C20 alkyl, and m is an integer from 0 to 20; The hydroxylation treatment process includes: mixing the unsaturated fatty monobasic acid with a hydroxylation agent in the presence of a C1-C5 organic acid; Preferably, the hydroxylation agent is a peroxide, more preferably hydrogen peroxide; The weight ratio of the unsaturated fatty monocarboxylic acid, the C1-C5 organic acid and the hydroxylation agent is 1-2:1-2:

1.

9. The preparation method according to claim 8, characterized in that The mixing reaction conditions include: mixing the unsaturated fatty monobasic acid and the C1-C5 organic acid, adding the hydroxylation reagent dropwise at a temperature of 30-35° C., and then heating to 65-70° C. for reaction for 4-6 hours.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The weight ratio of the hydroxylated unsaturated fatty monocarboxylic acid to the nano-calcium carbonate raw material is 1:4-8; Preferably, the contact reaction conditions include: temperature of 30-70° C. and time of 0.5-1.5 h.

11. The preparation method according to any one of claims 7 to 10, characterized in that: The amination treatment process includes: reacting the product of the contact reaction with an aromatic sulfonyl halide in a first stage, and then reacting the product with a diamine in the presence of a catalyst in a second stage; Preferably, the aromatic sulfonyl halide is benzenesulfonyl chloride, more preferably at least one of p-toluenesulfonyl chloride, p-ethylbenzenesulfonyl chloride, m-toluenesulfonyl chloride and m-ethylbenzenesulfonyl chloride; The diamine is selected from at least one of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl and 4,4'-diaminodiphenyl sulfone; The catalyst is a phase transfer catalyst, more preferably tetrabutylammonium bromide and / or benzyltriethylammonium chloride; Preferably, the weight ratio of the aromatic sulfonyl halide to the product of the contact reaction is 1:0.8-1.2, and the weight ratio of the product of the first stage reaction to the diamine is 2.4-3:

1.

12. The preparation method according to claim 11, characterized in that The first stage reaction process includes: adding the product of the contact reaction to the solution containing the aromatic sulfonyl halide in multiple times to react; The conditions of the first stage reaction include: temperature of -5 to 5°C, time of 4-7h; Preferably, the conditions for the second stage reaction include: using a strong alkaline solution with a concentration of 20-30 wt% as the reaction solvent, a temperature of 95-105° C., and a reaction time of 7-12 h.

13. Use of the modified nano-calcium carbonate material according to any one of claims 1 to 6 or the modified nano-calcium carbonate material prepared according to the method according to any one of claims 7 to 12 in oil production working fluid, preferably as a plugging agent in fracturing fluid.

14. A fracturing fluid containing the modified nano-calcium carbonate material according to any one of claims 1 to 6 or the modified nano-calcium carbonate material prepared according to the method according to any one of claims 7 to 12.

15. The fracturing fluid according to claim 14, wherein: Based on the total amount of the fracturing fluid, the content of the modified nano-calcium carbonate material is 0.5-2% by weight.

16. The fracturing fluid according to claim 14 or 15, wherein: The fracturing fluid also contains, based on the total amount of the fracturing fluid, 0.1-1 weight percent of a thickener, 0.1-1 weight percent of a drainage aid, and 0.1-1 weight percent of a clay stabilizer; Preferably, the thickener is an acrylamide homopolymer and / or a copolymer of acrylamide and other monomers, wherein the other monomers are selected from at least one of acryloyloxyethyltrimethylammonium chloride, sodium acrylate, and acrylic acid; further preferably, the copolymer of acrylamide and other monomers is at least one of acrylamide-acryloyloxyethyltrimethylammonium chloride copolymer, acrylamide-sodium acrylate-acrylic acid copolymer, and acrylamide-acryloyloxyethyltrimethylammonium chloride-sodium acrylate-acrylic acid copolymer; Preferably, the drainage aid is polyoxyethylene amine ether and / or polyoxyethylene fatty alcohol ether; Preferably, the polyoxyethylene amine ether is oleylamine polyoxyethylene ether and / or rosin amine polyoxyethylene ether; the polyoxyethylene fatty alcohol ether is at least one of polyoxyethylene lauryl alcohol ether, polyoxyethylene tetradecyl alcohol ether, polyoxyethylene cetyl alcohol ether and polyoxyethylene stearyl alcohol ether; Preferably, the clay stabilizer is dimethylamine quaternary ammonium salt and / or polyquaternium salt.

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