Ultra-high-temperature-resistant high-density organic-salt-weighted fracturing fluid, and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of petroleum exploitation, and discloses an ultra-high-temperature-resistant high-density organic-salt-weighted fracturing fluid, and a preparation method therefor and the use thereof. The ultra-high-temperature-resistant high-density organic-salt-weighted fracturing fluid comprises: a thickener A, a low-temperature cleanup additive B, a high-temperature cleanup additive C, a weighting agent, and a solvent. The ultra-high-temperature-resistant high-density organic-salt-weighted fracturing fluid provided by the present invention has a high density (up to 1.568 g / cm3), ultra-high-temperature resistance (withstanding a temperature up to 270°C) and shear resistance, and can improve the success rate of fracturing operations. The preparation method for an ultra-high-temperature-resistant high-density organic-salt-weighted fracturing fluid provided by the present invention involves preparation based on a contact reaction, is simple in terms of process, has low requirements for equipment, and is suitable for industrial production.

Description

An ultra-high temperature and high density organic salt weighted fracturing fluid, a preparation method and application thereof

[0001] Cross-reference to Related Applications

[0002] This application claims the benefit of Chinese Patent Application No. 202411377580.6, filed September 30, 2024, the contents of which are incorporated by reference herein. TECHNICAL FIELD

[0003] The present application relates to the technical field of oil exploitation, in particular to an ultra-high temperature and high density organic salt weighted fracturing fluid, a preparation method and application thereof. BACKGROUND

[0004] With the continuous deepening of oil and gas exploration and development, the discovery of conventional shallow oil and gas resources becomes more difficult, and the exploration and development of deep and ultra-deep oil and gas resources becomes inevitable. At the same time, the continuous development of geophysical prospecting, drilling, well logging, and well completion technologies also promotes the development and utilization of deep and ultra-deep oil and gas resources. Deep and ultra-deep reservoirs have characteristics such as high temperature (generally exceeding 200℃) and high implementation pressure (usually above 90MPa), which puts higher requirements on fracturing equipment and fracturing fluid performance. The maximum pressure of the current fracturing truck group is only 103.4MPa, and forced fracturing not only affects the safety of construction, but also reduces the success rate of construction.

[0005] The density of fracturing fluid is increased by using salt weighting agents to increase the liquid column pressure, thereby reducing the wellhead construction pressure and improving the success rate of fracturing construction. This method is called weighted fracturing fluid technology. This technology not only reduces the requirements on fracturing equipment, but also improves the success rate of field construction. Chao Mingguang et al. used KCl and NaNO3 as weighting agents to increase the density of fracturing fluid to 1.35g / cm 3 , and the temperature resistance of guanidine gum gel was up to 178℃. Kirk M. Bartko et al. used NaBr and KBr as weighting agents to increase the density of fracturing fluid to 1.48g / cm 3 , and achieved high-temperature delayed crosslinking with the highest temperature resistance of 190℃ in laboratory tests. X. J. Yang et al. used a three-time release crosslinking strategy based on hydrophobically modified guanidine gum and organic delayed zirconium-boron crosslinking agents to achieve high-temperature delayed crosslinking with the highest temperature resistance of 180℃, and used potassium formate to increase the density of fracturing fluid to 1.33g / cm 3 . Zhou Jianping et al. developed CaCl2 weighted fracturing fluid with the highest temperature resistance of 170℃ and a density of 1.35g / cm 3 . D. V. Satya Gupta et al. used NaCl, NaBr, CaCl2, CaBr2 or composite salt as weighting agents, and the density of fracturing fluid reached 1.30-2.28g / cm 3The system formula is simple: amphoteric polymer + gelling agent + surfactant + breaker, but the temperature resistance is only 120 DEG C. It can be seen that the existing weighting fracturing fluid has limited density, generally not more than 1.35 g / cm 3 ; and the temperature resistance is limited, generally below 200 DEG C. It is difficult to meet the requirements of high density and ultra-high temperature resistance at the same time.

[0006] On the other hand, the current ultra-high temperature fracturing fluid generally uses synthetic polymer and metal crosslinking agent to improve the temperature resistance limit of the fracturing fluid. In this system, the concentration of the high-temperature thickening agent is too large, and the amount generally exceeds 0.6%, which leads to large base fluid viscosity and difficult injection. The metal crosslinking agent itself also has defects, and the crosslinking speed with the thickening agent is too fast, which causes the viscosity of the crosslinked gel at room temperature to be too large, and is prone to cause a large additional fluid friction, which is not conducive to the fracturing operation of high-temperature deep wells. The domestic research institutions and manufacturers are separated, and the stability of the thickening agent product is relatively poor, and there is a lack of stable supply channel, and the product cannot be quickly updated and replaced.

[0007] Therefore, it has a significant practical significance to develop an ultra-high temperature high-density organic salt weighting fracturing fluid with excellent performance by developing a stable thickening agent and a suitable non-metal crosslinking agent, so as to meet the fracturing and reconstruction requirements of ultra-deep wells, abnormally high temperature and pressure wells, and abnormally high stress wells. SUMMARY

[0008] The purpose of the present application is to overcome the problems of low density, poor temperature resistance, and high viscosity of fracturing fluid containing metal crosslinking agent in the prior art, and to provide an ultra-high temperature high-density organic salt weighting fracturing fluid with high density, ultra-high temperature resistance, shear resistance, simple preparation, low equipment requirement, and suitable for industrial production, as well as a preparation method and application thereof.

[0009] According to a first aspect of the present application, an ultra-high temperature high-density organic salt weighting fracturing fluid is provided, which includes: a thickening agent A, a low-temperature cleanup agent B, a high-temperature cleanup agent C represented by formula (I), and a weighting fluid, wherein the low-temperature cleanup agent B includes: an anionic surfactant, a cationic surfactant, and a viscoelastic surfactant; and the weighting fluid includes: a weighting agent and a solvent.

[0010] In formula (I), R8 and R9 are connected to PEI through a chemical bond, PEI is polyethyleneimine, the structural formula of R8 is The structural formula of R9 is Wherein, R 10 is selected from C12-C18 alkyl.

[0011] According to a second aspect of the present application, the present application provides a preparation method of the super-high-temperature high-density organic salt weighted fracturing fluid, the method comprising: mixing the thickening agent A, the low-temperature cleanup agent B, the high-temperature cleanup agent C and the weighting agent in the presence of a solvent.

[0012] According to a third aspect of the present application, the present application provides application of the super-high-temperature high-density organic salt weighted fracturing fluid in oil exploitation.

[0013] The super-high-temperature high-density organic salt weighted fracturing fluid has high density (up to 1.568 g / cm 3 ), high temperature resistance (up to 270 DEG C), shear resistance and can improve the success rate of fracturing operation.

[0014] Further, the present application provides a preparation method of the super-high-temperature high-density organic salt weighted fracturing fluid, the preparation process is a contact reaction, the process is simple, the requirement for equipment is low and the method is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0015] Fig. 1 is a rheological curve diagram of Example 1;

[0016] Fig. 2 is a rheological curve diagram of Example 2;

[0017] Fig. 3 is a rheological curve diagram of Example 3;

[0018] Fig. 4 is a rheological curve diagram of Example 4;

[0019] Fig. 5 is a rheological curve diagram of Example 5. DETAILED DESCRIPTION

[0020] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application. The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values disclosed herein should be understood to be approximate. For numeric ranges, the endpoints of the various ranges, the endpoints of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numeric ranges, which should be considered to be specifically disclosed herein.

[0021] The present application provides a super-high-temperature high-density organic salt weighted fracturing fluid, the super-high-temperature high-density organic salt weighted fracturing fluid comprising: a thickening agent A, a low-temperature cleanup agent B, a high-temperature cleanup agent C shown in formula (I), and a weighting fluid, wherein the low-temperature cleanup agent B comprises: an anionic surfactant, a cationic surfactant, and a viscoelastic surfactant; and the weighting fluid comprises: a weighting agent and a solvent.

[0022] In formula (I), R8 and R9 are connected to PEI by a chemical bond, PEI is polyethyleneimine, the structural formula of R8 is the structural formula of R9 is wherein, R 10 is selected from C12-C18 alkyl.

[0023] In the present application, high-temperature cleanup aid C represented by formula (I) means that polyethyleneimine is modified by R8 and R9 connected by a chemical bond, and the group represented by formula (I) does not represent the number of R8 and R9.

[0024] The super-high-temperature high-density organic salt weighting fracturing fluid with the aforementioned technical features has the advantages of high density, super-high-temperature resistance, shear resistance, simple preparation, low equipment requirement, and suitability for industrial production.

[0025] In the present application, the alkylene group of C0 represents the absence of the group, and the groups at both ends of the group are directly connected.

[0026] In the present application, the volume ratio of the gelling agent A, the low-temperature cleanup aid B, the high-temperature cleanup aid C, and the weighting fluid can be selected within a wide range, and the following exemplary descriptions are provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the volume ratio of the gelling agent A, the low-temperature cleanup aid B, the high-temperature cleanup aid C, and the weighting fluid is 1.5-4:0.5-1:0.5-1.5:100. By using the aforementioned preferred volume ratio, the temperature resistance of the prepared super-high-temperature high-density organic salt weighting fracturing fluid can be further improved.

[0027] In the present application, the type of the gelling agent A can be selected within a wide range, and the following exemplary descriptions are provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the gelling agent A contains a polymer represented by formula (II).

[0028] In the present application, the type of R1 can be selected within a wide range, and the following exemplary descriptions are provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, R1 is selected from C0-C6 alkylene, and is preferably selected from C0-C3 alkylene.

[0029] In the present application, the type of R2 can be selected within a wide range, and the following exemplary descriptions are provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, R2 is selected from C0-C6 alkylene, and is preferably selected from C0-C3 alkylene.

[0030] In the present application, the type of R3 can be selected within a wide range, and the following exemplary descriptions are provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, R3 is selected from C0-C6 alkylene, and is preferably selected from C0-C3 alkylene.

[0031] In the present application, the type of R4 can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, R4 is selected from C12 to C18 alkyl, preferably selected from C12 to C15 alkyl.

[0032] According to a preferred embodiment of the present application, the complex solvent in the thickening agent A is water and white oil.

[0033] In the present application, the content ratio of the polymer represented by formula (II) to water in the thickening agent A can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, the polymer represented by formula (II) accounts for 40-80% of the total mass of water and the polymer represented by formula (II).

[0034] In the present application, the content ratio of water to white oil in the thickening agent A can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, the mass ratio of water to white oil is 1:1-2.

[0035] In the present application, the type of anionic surfactant can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, the structure of the anionic surfactant is represented by formula (III).

[0036] In the present application, the type of R5 can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, R5 is selected from C12 to C18 alkyl.

[0037] In the present application, the type of cationic surfactant can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, the structure of the cationic surfactant is represented by formula (IV).

[0038] In the present application, the type of R6 can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, R6 is selected from C12 to C18 alkyl, preferably selected from C12 to C15 alkyl.

[0039] In the present application, the type of viscoelastic surfactant can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, the structure of the viscoelastic surfactant is represented by formula (V).

[0040] In the present application, the type of R7 can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, R7 is selected from C16-C24 alkyl and / or alkenyl, preferably selected from C16-C19 alkyl and / or alkenyl.

[0041] In the present application, the number average molecular weight of PEI can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, the number average molecular weight of PEI is 100-200 thousand, preferably 70-100 thousand. By using the preferred PEI described above, the product has good temperature resistance and low cost.

[0042] In the present application, the type of R 10 can be selected from a wide range, which is exemplarily described below, but does not limit the scope of the present application. According to a preferred embodiment of the present application, R 10 is selected from C12-C15 alkyl.

[0043] According to a preferred embodiment of the present application, R1 is C0 alkylene.

[0044] According to a preferred embodiment of the present application, R2 is C0 alkylene.

[0045] According to a preferred embodiment of the present application, R3 is C1 alkylene.

[0046] According to a preferred embodiment of the present application, R4 is C12 alkyl.

[0047] According to a preferred embodiment of the present application, R5 is selected from one or more of C12 alkyl, C14 alkyl, C16 alkyl, and C18 alkyl.

[0048] According to a preferred embodiment of the present application, R6 is C14 alkyl.

[0049] According to a preferred embodiment of the present application, R7 is CH3-(CH2)7-CH=CH-(CH2)8- alkenyl.

[0050] According to a preferred embodiment of the present application, R 10 is C12 alkyl.

[0051] In the present application, the polymer represented by formula (II) is a random polymer, and formula (II) only represents the structural unit constituting the polymer and its proportion, without limiting the connection mode and order of the structural unit.

[0052] In the present application, the proportion of the three structural units in the polymer represented by formula (II) can be selected within a wide range, and the following exemplary description is provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, in formula (II), x is 70-85%, y is 10-29.5%, and z = 100%-x-y.

[0053] In the present application, the number average molecular weight of the polymer represented by formula (II) can be selected within a wide range, and the following exemplary description is provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the number average molecular weight of the polymer represented by formula (II) is 2-9 million.

[0054] In the present application, the thickening agent A can achieve the purpose of the present application as long as it has the aforementioned technical features, and there is no special requirement for its preparation method. According to a preferred embodiment of the present application, the preparation method of the thickening agent A comprises: (1) adding enamide, enoate, double-tailed carboxybetaine type functional monomer represented by formula (VI), and disodium ethylenediaminetetraacetate into water to obtain an aqueous phase; (2) adding an emulsifier into white oil to obtain an oil phase; (3) adding the aqueous phase into the oil phase to emulsify to obtain an emulsion; (4) purging with inert gas to remove oxygen, adding an oxidizing agent, then adding a reducing agent, and after reaction, adding a phase transfer agent to obtain the thickening agent A.

[0055] In the present application, in step (1) of the preparation method of the thickening agent A, the total amount of enamide, enoate, and double-tailed carboxybetaine type functional monomer can be selected within a wide range, and the following exemplary description is provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the total mass of enamide, enoate, and double-tailed carboxybetaine type functional monomer is 40-80% of the total mass of the aqueous phase.

[0056] In the present application, in step (1) of the preparation method of the thickening agent A, the amount of disodium ethylenediaminetetraacetate can be selected within a wide range, and the following exemplary description is provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the mass of disodium ethylenediaminetetraacetate is 0.01-0.2% of the total mass of enamide, enoate, and double-tailed carboxybetaine type functional monomer.

[0057] In the present application, in step (2) of the preparation method of the thickening agent A, the amount of emulsifier can be selected within a wide range, and the following exemplary description is provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the mass of emulsifier is 5-15% of the total mass of the oil phase.

[0058] In the present application, in step (3) of the preparation method of the thickening agent A, the use amount ratio of the water phase and the oil phase can be selected in a wide range, and the following is exemplarily described, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the use amount ratio of the water phase and the oil phase is 1-1.8:1 by mass.

[0059] In the present application, in step (4) of the preparation method of the thickening agent A, the use amount ratio of the oxidizing agent and the reducing agent can be selected in a wide range, and the following is exemplarily described, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the use amount ratio of the oxidizing agent and the reducing agent is 1-4:1 by mass.

[0060] In the present application, in step (4) of the preparation method of the thickening agent A, the use amount of the oxidizing agent can be selected in a wide range, and the following is exemplarily described, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the mass of the oxidizing agent is 0.01-0.04% of the total mass of the enamide, the enoate, and the double-tailed carboxybetaine functional monomer.

[0061] In the present application, in step (4) of the preparation method of the thickening agent A, the use amount of the phase transfer agent can be selected in a wide range, and the following is exemplarily described, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the mass of the phase transfer agent is 1-3% of the total mass of the emulsion.

[0062] In the present application, the type of the emulsifier can be selected in a wide range, and the types commonly used in the art can be applied to the present application, and the following is exemplarily described, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the emulsifier is Span-80.

[0063] In the present application, the type of the oxidizing agent can be selected in a wide range, and the types commonly used in the art can be applied to the present application, and the following is exemplarily described, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the oxidizing agent is selected from one or more of ammonium persulfate, potassium persulfate, tert-butyl hydroperoxide, potassium bromate, and sodium bromate.

[0064] In the present application, the type of the reducing agent can be selected in a wide range, and the types commonly used in the art can be applied to the present application, and the following is exemplarily described, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the reducing agent is selected from one or more of sodium sulfite, sodium bisulfite, tetramethyl ethylenediamine, ammonium formate, and ammonium oxalate.

[0065] In the present application, the providing form of the oxidizing agent and the reducing agent is not particularly limited, and for example, the oxidizing agent and the reducing agent can be provided in the form of an aqueous solution.

[0066] In the present application, the type of phase transfer agent can be selected from a wide range, the type commonly used in the art can be applied to the present application, the following exemplary description, but not therefore limit the scope of the present application. According to a preferred embodiment of the present application, the phase transfer agent is OP-10.

[0067] In the present application, in order to mix the water phase and the oil phase uniformly, step (3) is carried out under shearing conditions. According to a preferred embodiment of the present application, the shearing speed is 5000-8000 r / min.

[0068] In the present application, in step (3) of the preparation method of thickening agent A, the emulsification time can be selected from a wide range, the following exemplary description, but not therefore limit the scope of the present application. According to a preferred embodiment of the present application, the emulsification time is 10-15 min.

[0069] In the present application, in order to mix the reactants uniformly, step (4) is carried out under shearing conditions. According to a preferred embodiment of the present application, the shearing speed is 300-500 r / min.

[0070] In the present application, in step (4) of the preparation method of thickening agent A, the reaction time can be selected from a wide range, the following exemplary description, but not therefore limit the scope of the present application. According to a preferred embodiment of the present application, the reaction time is 3-6 h.

[0071] Using the preferred thickening agent A described above, the stability of the super-high-temperature high-density organic salt weighting fracturing fluid is enhanced, and the temperature resistance of the super-high-temperature high-density organic salt weighting fracturing fluid is improved.

[0072] In the present application, in low-temperature cleanup agent B, the content of anionic surfactant can be selected from a wide range, the following exemplary description, but not therefore limit the scope of the present application. According to a preferred embodiment of the present application, the content of anionic surfactant is 8-12 wt%.

[0073] In the present application, in low-temperature cleanup agent B, the content of cationic surfactant can be selected from a wide range, the following exemplary description, but not therefore limit the scope of the present application. According to a preferred embodiment of the present application, the content of cationic surfactant is 0.5-2 wt%.

[0074] In the present application, in low-temperature cleanup agent B, the content of viscoelastic surfactant can be selected from a wide range, the following exemplary description, but not therefore limit the scope of the present application. According to a preferred embodiment of the present application, the content of viscoelastic surfactant is 0.5-10 wt%.

[0075] According to a preferred embodiment of the present application, low-temperature cleanup agent B also contains water-soluble solvent.

[0076] The foregoing preferred low-temperature cleanup agent B has the advantages of enhancing the stability of the super-high-temperature high-density organic salt weighted fracturing fluid in a low-temperature environment and increasing the temperature range applicable to the super-high-temperature high-density organic salt weighted fracturing fluid.

[0077] In the present application, the number average molecular weight of the high-temperature cleanup agent C can be selected in a wide range, which is exemplarily described below, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the number average molecular weight of the high-temperature cleanup agent C is 100,000 to 2,000,000, preferably 500,000 to 1,000,000. The foregoing preferred number average molecular weight of the high-temperature cleanup agent C has the advantages of enhancing the stability of the super-high-temperature high-density organic salt weighted fracturing fluid in a high-temperature environment and improving the temperature resistance of the super-high-temperature high-density organic salt weighted fracturing fluid, while the cost is relatively low.

[0078] According to a preferred embodiment of the present application, the high-temperature cleanup agent C contains a water-soluble solvent.

[0079] In the present application, the content ratio of the organic matter represented by formula (I) to the water-soluble solvent in the high-temperature cleanup agent C can be selected in a wide range, which is exemplarily described below, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the organic matter represented by formula (I) accounts for 5-20% of the total mass of the water-soluble solvent and the organic matter represented by formula (I).

[0080] According to a preferred embodiment of the present application, the weighting agent is provided in the form of a weighting fluid.

[0081] In the present application, the density of the weighting fluid can be selected in a wide range, which is exemplarily described below, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the density of the weighting fluid is 1.5 g / cm 3 The foregoing preferred density of the weighting fluid has the advantages of further increasing the density of the super-high-temperature high-density organic salt weighted fracturing fluid and improving the success rate of fracturing operation.

[0082] In the present application, the type of the weighting agent can be selected in a wide range, and the types commonly used in the art can be applied to the present application. The types are exemplarily described below, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the weighting agent is an organic salt weighting agent.

[0083] In the present application, the type of the organic salt weighting agent can be selected in a wide range, and the types commonly used in the art can achieve the purpose of the present application. The types are exemplarily described below, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the organic salt weighting agent is selected from one or more of potassium formate, cesium formate, bismuth formate, potassium acetate, cesium acetate, bismuth acetate, potassium propionate, cesium propionate, and bismuth propionate.

[0084] The super-high-temperature high-density organic salt weighted fracturing fluid with the foregoing features can achieve the purpose of the present application, and the preparation method thereof has no special requirements, and the following exemplary description is provided, but the scope of the present application is not limited thereto. According to an embodiment of the present application, the preparation method of the super-high-temperature high-density organic salt weighted fracturing fluid comprises mixing the thickening agent A, the low-temperature cleanup agent B, the high-temperature cleanup agent C and the weighting agent in the presence of a solvent. The preparation method of the super-high-temperature high-density organic salt weighted fracturing fluid with the foregoing technical features has the advantages of simple process, low equipment requirement and suitability for industrial production, and the obtained super-high-temperature high-density organic salt weighted fracturing fluid has the advantages of high density, high temperature resistance and shear resistance.

[0085] In the present application, in the preparation method of the fracturing fluid, the mixing can be carried out under dynamic conditions as needed for sufficient mixing. According to a preferred embodiment of the present application, the rotation speed is 300-2000 r / min.

[0086] In the present application, in the preparation method of the fracturing fluid, the order of the mixing has no special requirements, and a person skilled in the art can design it as needed, and the following exemplary description is provided, but the scope of the present application is not limited thereto. For example, the weighting agent and the solvent can be mixed first, and then mixed with the thickening agent A, the low-temperature cleanup agent B and the high-temperature cleanup agent C.

[0087] The super-high-temperature high-density organic salt weighted fracturing fluid of the present application is particularly suitable for application in oil exploitation.

[0088] Further, the super-high-temperature high-density organic salt weighted fracturing fluid of the present application is particularly suitable for application in oil exploitation at 150-270℃, such as application in oil exploitation at 170℃, 190℃, 210℃, 230℃ and 250℃.

[0089] In the present application, the low-temperature cleanup agent B only needs to have the foregoing technical features to achieve the purpose of the present application, and the preparation method thereof has no special requirements, and the following exemplary description of the preparation method of the low-temperature cleanup agent B is provided, but the scope of the present application is not limited thereto. For example, the preparation method of the low-temperature cleanup agent B comprises dissolving an anionic surfactant, a cationic surfactant and a viscoelastic surfactant in water to obtain the low-temperature cleanup agent B.

[0090] In the present application, the high-temperature cleanup agent C only needs to have the foregoing technical features to achieve the purpose of the present application, and the preparation method thereof has no special requirements, and the following exemplary description of the preparation method of the high-temperature cleanup agent C is provided, but the scope of the present application is not limited thereto. For example, the preparation method of the high-temperature cleanup agent C comprises dissolving polyethyleneimine, 2-acrylamide-2-methyl propane sulfonic acid sodium and 2,3-epoxypropyl-N,N-dimethyl alkyl ammonium halide in water, and reacting at 50-80℃ for 6-12 h to obtain the high-temperature cleanup agent C.

[0091] In the present application, the weighting fluid can achieve the purpose of the present application as long as it has the aforementioned technical features, and there is no special requirement for the preparation method thereof. The preparation method of the weighting fluid is exemplarily described below, but the scope of the present application is not limited thereto. For example, the preparation method of the weighting fluid comprises: dissolving the organic salt weighting agent in water to obtain the weighting fluid.

[0092] In the present application, in the preparation methods of the thickening agent A, the low-temperature cleanup aid B, the high-temperature cleanup aid C and the weighting fluid, in order to fully dissolve or mix or react, the dissolution and / or mixing and / or reaction can be carried out under dynamic conditions according to the needs.

[0093] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various specific technical features in any suitable manner. In order to avoid unnecessary repetition, the present application does not further describe various possible combination manners. However, these simple modifications and combinations should also be regarded as the disclosed content of the present application and belong to the protection scope of the present application.

[0094] The present application will be described in detail below through examples. It is necessary to point out here that the following examples are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above content of the present application.

[0095] The specific experimental steps or conditions not indicated in the examples and comparative examples can be carried out according to the conventional experimental steps described in the literature in the art or the operation or conditions. The reagents or instruments not indicated by the manufacturer are all conventional reagent products that can be obtained by market purchase.

[0096] Example 1

[0097] (1) Preparation of the thickening agent A:

[0098] (1-1) Preparation of the aqueous phase:

[0099] 47.4 parts by mass of acrylamide, 12 parts by mass of sodium acrylate, 0.6 parts by mass of 4-(benzyl(3-(dodecyldimethylamino)-2-hydroxypropyl)amino)-maleamic acid salt and 0.06 parts by mass of disodium ethylenediaminetetraacetate were dissolved in 50 parts by mass of water, and stirred until the solution was clear and transparent to obtain an aqueous phase solution.

[0100] (1-2) Preparation of the oil phase:

[0101] 10 parts by mass of Span-80 was dissolved in 90 parts by mass of white oil, and stirred uniformly to obtain an oil phase solution.

[0102] (1-3) High-speed emulsification:

[0103] The prepared water phase was slowly added to the oil phase under a stirring speed of 5000 r / min, and emulsified for 15 min.

[0104] (1-4) Polymerization reaction:

[0105] The stirring speed was reduced to 400 r / min, and oxygen was removed by nitrogen. After 30 min, 2 parts by mass of a 0.6 wt% ammonium persulfate solution was added, and after uniform stirring, 20 parts by mass of a 0.06 wt% sodium bisulfite solution was slowly added. After 4 h of reaction, 2.5 parts by mass of OP-10 was added, and stirring was continued for 15 min to obtain the thickening agent A.

[0106] In the polymer represented by formula (II), x is 83.8%, y is 16.0%, and z is 0.2%.

[0107] (2) Preparation of low-temperature cleanup aid B:

[0108] 9 parts by mass of sodium lauryl polyoxyethylene ether (3) carboxylate, 1 part by mass of N-tetradecyl-N-(2-hydroxyethyl)-N,N-dimethyl ammonium bromide, and 5 parts by mass of 3-((dimethyl(3-oleoylamido)propyl)ammonium)-propane-1-sulfonate were dissolved in 85 parts by mass of water, and stirred uniformly to obtain the low-temperature cleanup aid B.

[0109] (3) Preparation of high-temperature cleanup aid C:

[0110] 5 parts by mass of polyethyleneimine (molecular weight 50,000), 1 part by mass of 2-acrylamide-2-methylpropane sulfonic acid sodium, and 2 parts by mass of 2,3-epoxypropyl-N,N-dimethyldodecyl ammonium chloride were dissolved in 92 parts by mass of water, and stirred uniformly at 50°C for 6 h to obtain the high-temperature cleanup aid C. The molecular weight of the high-temperature cleanup aid C was 50,000.

[0111] (4) Preparation of weighting fluid:

[0112] 2300 parts by mass of potassium formate was dissolved in 1000 parts by mass of water to obtain a weighting fluid with a density of 1.502 g / cm 3 .

[0113] (5) Preparation of fracturing fluid:

[0114] 100 parts by volume of the weighting fluid was taken, and 0.5 parts by volume of the low-temperature cleanup aid B and 0.75 parts by volume of the high-temperature cleanup aid C were added under a stirring speed of 500 r / min. Then, 2.5 parts by volume of the thickening agent A was added under a stirring speed of 1500 r / min, and stirring was continued for 0.5 min to obtain the super-high-temperature high-density organic salt weighting fracturing fluid.

[0115] Performance test:

[0116] The test temperature is increased from 30℃ to 220℃, the temperature increasing rate is 6℃ / min, and the shear rate is 100s 1 The test data of the rheological property of the super-high-temperature high-density organic salt weighting fracturing fluid are shown in Figure 1.

[0117] As shown in Figure 1, the viscosity is still above 200 mPa·s, higher than 50 mPa·s after shearing for 90 min at 220℃, so the super-high-temperature high-density organic salt weighting fracturing fluid in the application can resist temperature up to 220℃, and can be used for fracturing operation in super-high-temperature super-deep well.

[0118] Example 2

[0119] (1) Preparation of thickening agent A:

[0120] (1-1) Preparation of water phase:

[0121] 62.4 parts by mass of acrylamide, 16 parts by mass of sodium acrylate, 1.6 parts by mass of 4-(benzyl(3-(dodecyldimethylamino)-2-hydroxypropyl)amino)-maleamic acid salt and 0.08 parts by mass of disodium ethylenediaminetetraacetate are dissolved in 50 parts by mass of water, and stirred until the solution is clear and transparent to obtain a water phase solution.

[0122] (1-2) Preparation of oil phase:

[0123] 11 parts by mass of Span-80 is dissolved in 89 parts by mass of white oil, and stirred uniformly to obtain an oil phase solution.

[0124] (1-3) High-speed emulsification:

[0125] The prepared water phase is slowly added to the oil phase under a stirring speed of 5000r / min, and emulsified for 15 min.

[0126] (1-4) Polymerization reaction:

[0127] The stirring speed is reduced to 400r / min, and oxygen is removed by nitrogen gas. After 30 min, 1 part by mass of 0.8% ammonium persulfate solution is added, and after uniform stirring, 10 parts by mass of 0.08% sodium bisulfite solution is slowly added. After 4h of reaction, 2.5 parts by mass of OP-10 is added, and the stirring is continued for 10-15 min to obtain the thickening agent A.

[0128] In the polymer represented by formula (II), x is 83.5%, y is 16.2%, and z is 0.3%.

[0129] (2) Preparation of low-temperature cleanup aid B:

[0130] Sodium 9.5 parts by mass of tetradecanol polyoxyethylene ether (3) carboxylate, 0.5 parts by mass of N-tetradecyl-N-(2-hydroxyethyl)-N,N-dimethyl ammonium bromide, 5 parts by mass of 3-((dimethyl(3-oleoylamido)propyl)ammonium)-propane-1-sulfonate are dissolved in 85 parts by mass of water, and stirred uniformly to obtain low-temperature cleanup aid B.

[0131] (3) Preparation of high-temperature cleanup aid C:

[0132] 5 parts by mass of polyethyleneimine (molecular weight 70,000), 1 part by mass of sodium 2-acrylamido-2-methylpropane sulfonate, and 2 parts by mass of 2,3-epoxypropyl-N,N-dimethyldodecyl ammonium chloride are dissolved in 92 parts by mass of water, stirred uniformly, and reacted at 60°C for 6 hours to obtain high-temperature cleanup aid C. The molecular weight of the high-temperature cleanup aid C is 70,000.

[0133] (4) Preparation of weighting fluid:

[0134] 3000 parts by mass of potassium formate is dissolved in 1000 parts by mass of water to obtain a weighting fluid with a density of 1.568 g / cm 3 .

[0135] (5) Preparation of fracturing fluid:

[0136] 100 parts by volume of the weighting fluid is taken, 0.5 parts by volume of low-temperature cleanup aid B and 1 part by volume of high-temperature cleanup aid C are added under a stirring speed of 500 r / min, 3 parts by volume of thickening agent A is added under a stirring speed of 1500 r / min, and the stirring is continued for 0.5-2 min to obtain the ultra-high-temperature high-density organic salt weighting fracturing fluid.

[0137] Performance test:

[0138] The test temperature is increased from 30°C to 240°C at a rate of 6°C / min, and the shear rate is 100 s 1 . The test data of the rheological properties of the ultra-high-temperature high-density organic salt weighting fracturing fluid are shown in FIG. 2.

[0139] As shown in FIG. 2, the viscosity is still above 150 mPa·s, higher than 50 mPa·s, after shearing at 240°C for 90 min. Therefore, the ultra-high-temperature high-density organic salt weighting fracturing fluid in the present application can withstand a temperature of 240°C and can be used for fracturing operations in ultra-high-temperature and ultra-deep wells.

[0140] Example 3

[0141] (1) Preparation of thickening agent A:

[0142] (1-1) Preparation of water phase:

[0143] Sodium acrylate, 20 parts by mass, 1.6 parts by mass of 4-(benzyl(3-(dodecyldimethylamino)-2-hydroxypropyl)amino)-maleic amide acid salt, and 0.1 part by mass of ethylenediaminetetraacetic acid disodium salt were dissolved in 80 parts by mass of water, and stirred until the solution became clear and transparent, to obtain an aqueous phase solution.

[0144] (1-2) Preparation of an oil phase:

[0145] Span-80, 12 parts by mass, was dissolved in 88 parts by mass of white oil, and stirred until uniform, to obtain an oil phase solution.

[0146] (1-3) High-speed emulsification:

[0147] The prepared aqueous phase was slowly added to the oil phase at a stirring speed of 5000 r / min, and emulsified for 15 min.

[0148] (1-4) Polymerization reaction:

[0149] The stirring speed was reduced to 400 r / min, and oxygen was removed by nitrogen gas. After 30 min, 2 parts by mass of 0.8% ammonium persulfate solution was added, and after uniform stirring, 20 parts by mass of 0.08% sodium bisulfite solution was slowly added. After 4 h of reaction, 2.5 parts by mass of OP-10 was added, and stirring was continued for 10-15 min, to obtain the densifier A.

[0150] In the polymer represented by formula (II), x is 79.2%, y is 20.5%, and z is 0.3%.

[0151] (2) Preparation of low-temperature cleanup aid B:

[0152] Sodium carboxylate of hexadecanol polyoxyethylene ether (3), 9 parts by mass, N-tetradecyl-N-(2-hydroxyethyl)-N,N-dimethylammonium bromide, 1 part by mass, 3-((dimethyl(3-oleoylamido)propyl)ammonio)-propane-1-sulfonate, 5 parts by mass, were dissolved in 85 parts by mass of water, and stirred until uniform, to obtain the low-temperature cleanup aid B.

[0153] (3) Preparation of high-temperature cleanup aid C:

[0154] Polyethyleneimine (molecular weight 70,000), 8 parts by mass, sodium 2-acrylamido-2-methylpropane sulfonate, 1 part by mass, and 2,3-epoxypropyl-N,N-dimethyldodecylammonium chloride, 2 parts by mass, were dissolved in 89 parts by mass of water, and stirred until uniform. The mixture was reacted at 70°C for 6 h, to obtain the high-temperature cleanup aid C. The molecular weight of the high-temperature cleanup aid C was 70,000.

[0155] (4) Preparation of weighting fluid:

[0156] Dissolve 1500 parts by mass of potassium formate, 1000 parts by mass of potassium acetate in 1000 parts by mass of water to obtain a weighting fluid with a density of 1.512 g / cm 3 .

[0157] (5) Preparation of the fracturing fluid:

[0158] Take 100 parts by volume of the weighting fluid, add 0.5 parts by volume of low-temperature cleanup agent B and 1 part by volume of high-temperature cleanup agent C under a stirring speed of 500 r / min, add 3.5 parts by volume of thickening agent A under a stirring speed of 1500 r / min, and continue stirring for 0.5-2 min to obtain the super-high-temperature high-density organic salt weighting fracturing fluid.

[0159] Performance test:

[0160] The test temperature is increased from 30℃ to 260℃ at a rate of 6℃ / min, and the shear rate is 100 s 1 . The test data of the rheological properties of the super-high-temperature high-density organic salt weighting fracturing fluid are shown in FIG. 3.

[0161] As shown in FIG. 3, the viscosity is still above 300 mPa·s, higher than 50 mPa·s after shearing at 260℃ for 90 min, so the super-high-temperature high-density organic salt weighting fracturing fluid in the application can withstand a temperature of 260℃ and can be used for fracturing operation in super-high-temperature super-deep wells.

[0162] Example 4

[0163] (1) Preparation of thickening agent A:

[0164] (1-1) Preparation of the water phase:

[0165] Dissolve 58 parts by mass of acrylamide, 20 parts by mass of sodium acrylate, 2 parts by mass of 4-(benzyl(3-(dodecyldimethylamino)-2-hydroxypropyl)amino)-maleamic acid salt and 0.12 parts by mass of disodium ethylenediaminetetraacetate in 50 parts by mass of water, and stir until the solution is clear and transparent to obtain the water phase solution.

[0166] (1-2) Preparation of the oil phase:

[0167] Dissolve 13 parts by mass of Span-80 in 87 parts by mass of white oil, and stir uniformly to obtain the oil phase solution.

[0168] (1-3) High-speed emulsification:

[0169] Slowly add the prepared water phase into the oil phase under a stirring speed of 5000 r / min, and emulsify for 10 min.

[0170] (1-4) Polymerization reaction:

[0171] The stirring speed was reduced to 400 r / min, and the oxygen was removed by nitrogen. After 30 min, 3 parts by mass of 0.8% ammonium persulfate solution was added, and after stirring, 30 parts by mass of 0.08% sodium bisulfite solution was slowly added. After 4 h of reaction, 2.5 parts by mass of OP-10 was added, and stirring was continued for 10-15 min to obtain the thickening agent A.

[0172] In the polymer represented by formula (II), x is 79.0%, y is 20.6%, and z is 0.4%.

[0173] (2) Preparation of low-temperature cleanup aid B:

[0174] 9 parts by mass of sodium carboxylate of cetyl polyoxyethylene ether (3), 1.5 parts by mass of N-tetradecyl-N-(2-hydroxyethyl)-N,N-dimethyl ammonium bromide, and 4.5 parts by mass of 3-((dimethyl(3-oleoylamido)propyl)ammonium)-propane-1-sulfonate were dissolved in 85 parts by mass of water, and stirred to obtain the low-temperature cleanup aid B.

[0175] (3) Preparation of high-temperature cleanup aid C:

[0176] 8 parts by mass of polyethyleneimine (molecular weight 100,000), 1 part by mass of 2-acrylamide-2-methyl propane sulfonic acid sodium, and 2.5 parts by mass of 2,3-epoxypropyl-N,N-dimethyldodecyl ammonium chloride were dissolved in 88.5 parts by mass of water, and stirred to obtain the high-temperature cleanup aid C. The molecular weight of the high-temperature cleanup aid C was 100,000.

[0177] (4) Preparation of weighting fluid:

[0178] 1000 parts by mass of potassium formate, 2000 parts by mass of potassium acetate were dissolved in 1000 parts by mass of water to obtain a weighting fluid with a density of 1.520 g / cm 3 .

[0179] (5) Preparation of fracturing fluid:

[0180] 100 parts by volume of the weighting fluid was taken, and 0.5 parts by volume of the low-temperature cleanup aid B and 1.2 parts by volume of the high-temperature cleanup aid C were added under a stirring speed of 500 r / min. Then, 3.5 parts by volume of the thickening agent A was added under a stirring speed of 1500 r / min, and stirring was continued for 2 min to obtain the super-high-temperature high-density organic salt weighting fracturing fluid.

[0181] Performance test:

[0182] The test temperature was increased from 30°C to 270°C at a rate of 6°C / min, and the shear rate was 100 s 1 . The test data of the rheological properties of the super-high-temperature high-density organic salt weighting fracturing fluid are shown in FIG. 4.

[0183] As shown in Figure 4, the viscosity is still above 380 mPa·s, higher than 50 mPa·s after shearing for 90 min at 270℃, so the temperature resistance of the super-high-temperature high-density organic salt weighted fracturing fluid in the application can reach 270℃, and can be used for fracturing operation in super-high-temperature super-deep wells.

[0184] Example 5

[0185] (1) Preparation of thickening agent A:

[0186] (1-1) Preparation of water phase:

[0187] 62.4 parts by mass of acrylamide, 16 parts by mass of sodium acrylate, 1.6 parts by mass of 4-(benzyl(3-(dodecyldimethylamino)-2-hydroxypropyl)amino)-maleamic acid salt and 0.1 part by mass of disodium ethylenediaminetetraacetate were dissolved in 50 parts by mass of water, and stirred until the solution was clear and transparent to obtain a water phase solution.

[0188] (1-2) Preparation of oil phase:

[0189] 13 parts by mass of Span-80 was dissolved in 87 parts by mass of white oil, and stirred uniformly to obtain an oil phase solution.

[0190] (1-3) High-speed emulsification:

[0191] The prepared water phase was slowly added to the oil phase under a stirring speed of 5000 r / min, and emulsified for 10 min.

[0192] (1-4) Polymerization reaction:

[0193] The stirring speed was reduced to 400 r / min, and nitrogen was introduced to remove oxygen. After 30 min, 3 parts by mass of 0.8% ammonium persulfate solution was added, and after uniform stirring, 30 parts by mass of 0.08% sodium bisulfite solution was slowly added. After 4 h of reaction, 2.5 parts by mass of OP-10 was added, and the stirring was continued for 15 min to obtain the thickening agent A.

[0194] In the polymer represented by formula (II), x is 83.5%, y is 16.2%, and z is 0.3%.

[0195] (2) Preparation of low-temperature cleanup agent B:

[0196] 9 parts by mass of sodium octadecyl polyoxyethylene ether (3) carboxylate, 1 part by mass of N-tetradecyl-N-(2-hydroxyethyl)-N,N-dimethyl ammonium bromide, and 10 parts by mass of 3-((dimethyl(3-oleoylamido)propyl)ammonium)-propane-1-sulfonate were dissolved in 85 parts by mass of water, and stirred uniformly to obtain the low-temperature cleanup agent B.

[0197] (3) Preparation of high-temperature cleanup agent C:

[0198] 10 parts by mass of polyethyleneimine (molecular weight 100,000), 2 parts by mass of 2-acrylamide-2-methylpropane sulfonic acid sodium and 5 parts by mass of 2,3-epoxypropyl-N,N-dimethyl dodecyl ammonium chloride were dissolved in 83 parts by mass of water, stirred uniformly, reacted at 80 DEG C for 10 h to obtain high-temperature cleanup additive C, and the molecular weight of the high-temperature cleanup additive C was 100,000.

[0199] (4) Preparation of the weighting fluid:

[0200] 2500 parts by mass of potassium acetate and 5000 parts by mass of potassium propionate were dissolved in 1000 parts by mass of water to obtain a weighting fluid with a density of 1.516 g / cm 3 .

[0201] (5) Preparation of the fracturing fluid:

[0202] 100 parts by volume of the weighting fluid were taken, 0.5 parts by volume of the low-temperature cleanup additive B and 0.5 parts by volume of the high-temperature cleanup additive C were added under a stirring speed of 500 r / min, 1.5 parts by volume of the thickening agent A were added under a stirring speed of 1500 r / min, and the stirring was continued for 2 min to obtain the super-high-temperature high-density organic salt weighting fracturing fluid.

[0203] Performance test:

[0204] The test temperature was increased from 30 DEG C to 240 DEG C at a rate of 6 DEG C / min, the shear rate was 100 s 1 , and the test data of the rheological properties of the super-high-temperature high-density organic salt weighting fracturing fluid are shown in Fig. 5.

[0205] As shown in Fig. 5, the viscosity was still above 270 mPa·s, higher than 50 mPa·s after shearing at 240 DEG C for 90 min, so the super-high-temperature high-density organic salt weighting fracturing fluid in the application can resist a temperature of 240 DEG C and can be used for fracturing operation in super-high-temperature super-deep wells.

Claims

1. An ultra-high temperature high-density organic salt weighted fracturing fluid, characterized in that, The super-high-temperature high-density organic salt weighted fracturing fluid comprises: a thickening agent A, a low-temperature cleanup agent B, a high-temperature cleanup agent C shown in formula (I), and a weighting fluid, wherein, The low-temperature cleanup agent B comprises: an anionic surfactant, a cationic surfactant, and a viscoelastic surfactant. The weighting fluid includes: a weighting agent, a solvent; In formula (I), R8and R9are connected to PEI through a chemical bond, PEI is polyethyleneimine, the structural formula of R8is R9is of the formula wherein R 10 is selected from C12-C18 alkyl.

2. The ultra-high temperature high density organic salt weighted fracturing fluid according to claim 1, characterized in that, The volume ratio of the thickening agent A, the low-temperature cleanup agent B, the high-temperature cleanup agent C, and the weighting fluid is 1.5-4:0.5-1:0.5-1.5:

100.

3. The ultra-high temperature high density organic salt weighted fracturing fluid according to claim 1, characterized in that, The thickening agent A contains a polymer of formula (II); In formula (II), R1-R3 are each independently selected from C0-C6 alkylene, preferably selected from C0-C3 alkylene; R4 is selected from C12-C18 alkyl, preferably selected from C12-C15 alkyl.

4. The ultra-high temperature high density organic salt weighted fracturing fluid according to claim 3, characterized in that, The thickening agent A contains a composite solvent, and the composite solvent is water and white oil, wherein, The polymer shown in formula (II) accounts for 40-80% of the total mass of water and the polymer shown in formula (II); and / or The mass ratio of water to white oil is 1:1-2. 5.The super-high-temperature high-density organic salt weighted fracturing fluid according to claim 1, wherein, The structure of the anionic surfactant is shown in formula (III); and / or The structure of the cationic surfactant is shown in formula (IV); and / or The structure of the viscoelastic surfactant is shown as formula (V); In formula (III), R5is selected from C12to C18alkyl groups; In formula (IV), R6is selected from C12to C18alkyl, preferably from C12to C15alkyl; In formula (V), R7 is selected from C16-C24 alkyl and / or alkenyl, preferably selected from C16-C19 alkyl and / or alkenyl.

6. The ultra-high temperature, high density organic salt weighted fracturing fluid according to any one of claims 1-5, characterized in that, The number average molecular weight of the PEI is 100-200 thousand.

7. The ultra-high temperature, high density organic salt weighted fracturing fluid according to any one of claims 1-5, characterized in that, said R 10 selected from C12-C15 alkyl.

8. The ultra-high temperature, high density organic salt weighted fracturing fluid according to any one of claims 1-5, characterized in that, In formula (II), x is 70-85%, y is 10-29.5%, and z=100%-x-y.

9. The ultra-high temperature, high density organic salt weighted fracturing fluid according to any one of claims 1-5, characterized in that, The number average molecular weight of the polymer shown in formula (II) is 2-9 million.

10. The ultra-high temperature, high density organic salt weighted fracturing fluid according to any one of claims 1-5, characterized in that, The preparation method of the thickening agent A comprises: (1) adding enamide, enoate, double-tailed carboxybetaine type functional monomer shown in formula (VI), and disodium ethylenediaminetetraacetate into water to obtain an aqueous phase; (2) adding an emulsifier into white oil to obtain an oil phase; (3) adding the aqueous phase into the oil phase to obtain an emulsion; (4) oxygen is removed by passing inert gas, an oxidizing agent is added, then a reducing agent is added, after reaction, a phase transfer agent is added to obtain thickening agent A; 11. The ultra-high temperature, high density organic salt weighted fracturing fluid of claim 10, wherein, In the preparation method of the thickening agent A, In step (1), the total mass of enamide, enoate, and double-tailed carboxybetaine type functional monomer is 40-80% of the total mass of the aqueous phase; and / or In step (1), the mass of disodium ethylenediaminetetraacetate is 0.01-0.2% of the total mass of enamide, enoate, and double-tailed carboxybetaine type functional monomer; and / or In step (2), the mass of the emulsifier is 5-15% of the total mass of the oil phase; and / or In step (3), the mass ratio of the aqueous phase to the oil phase is 1-1.8:1; and / or In step (4), the mass ratio of the oxidizing agent to the reducing agent is 1-4:1; and / or In step (4), the mass of the oxidizing agent is 0.01-0.04% of the total mass of enamide, enoate, and double-tailed carboxybetaine type functional monomer; In step (4), the mass of the phase transfer agent is 1-3% of the total mass of the emulsion.

12. The ultra-high temperature, high density organic salt weighted fracturing fluid of claim 10, wherein, In the preparation method of the thickening agent A, The emulsifier is Span-80; and / or The oxidizing agent is selected from one or more of ammonium persulfate, potassium persulfate, tert-butyl hydroperoxide, potassium bromate, and sodium bromate; and / or The reducing agent is selected from one or more of sodium sulfite, sodium bisulfite, tetramethyl ethylenediamine, ammonium formate, ammonium oxalate; and / or The phase transfer agent is OP-10.

13. The ultra-high temperature, high density organic salt weighted fracturing fluid of claim 10, wherein, In the preparation method of the thickening agent A, Step (3) is performed under shearing at 5000-8000 r / min; and / or In step (3), the emulsifying time is 10-15 min; and / or Step (4) is performed under shearing at 300-500 r / min; and / or In step (4), the reaction time is 3-6 h.

14. The ultra-high temperature, high density, organic salt weighted fracturing fluid of any of claims 1-5, wherein, In the low-temperature cleanup agent B, the content of anionic surfactant is 8-12 wt%, the content of cationic surfactant is 0.5-2 wt%, the content of viscoelastic surfactant is 0.5-10 wt%, and the rest is water solvent, based on the total amount of the low-temperature cleanup agent B.

15. The super-high-temperature high-density organic salt weighted fracturing fluid according to any one of claims 1-5, characterized in that, The number average molecular weight of the high-temperature cleanup agent C is 100-200 thousand; and / or The high-temperature cleanup agent C contains a water solvent, and the organic matter shown in formula (I) accounts for 5-20% of the total mass of the water solvent and the organic matter shown in formula (I).

16. The ultra-high temperature, high density, organic salt weighted fracturing fluid of any of claims 1-5, wherein, The density of the weighting fluid is 1.5 g / cm 3 The above.

17. The ultra-high temperature, high density organic salt weighted fracturing fluid of any one of claims 16, wherein, The weighting agent is an organic salt weighting agent.

18. The ultra-high temperature, high density organic salt weighted fracturing fluid of claim 17, wherein, The organic salt weighting agent is selected from one or more of potassium formate, cesium formate, bismuth formate, potassium acetate, cesium acetate, bismuth acetate, potassium propionate, cesium propionate, and bismuth propionate.

19. A method for preparing an ultra-high temperature high-density organic salt weighted fracturing fluid, characterized in that, The method comprises mixing the thickening agent A, the low-temperature cleanup agent B, the high-temperature cleanup agent C, and the weighting agent in the presence of a solvent.

20. The method of claim 19, wherein, The mixing is performed under dynamic conditions at a rotation speed of 300-2000 r / min.

21. The use of the super-high-temperature high-density organic salt weighted fracturing fluid according to any one of claims 1-18 in oil exploitation.

22. The use according to claim 21, wherein the super-high-temperature high-density organic salt weighted fracturing fluid is used in oil exploitation at 150-270℃.

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