Water-in-oil drilling fluid with temperature and pressure synergistic thickening effect and application

Abstract

This invention belongs to the field of oil-based drilling fluid technology for oil and gas field drilling, specifically relating to a water-in-oil drilling fluid with a synergistic thickening effect of temperature and pressure and its application. The drilling fluid comprises a base oil phase, a brine phase, organic clay, a high-temperature resistant emulsifier, a wetting agent, a thickening regulator, a flow stabilizer, an alkaline substance, a filtration loss reducer, a plugging material, and a weighting material. The thickening regulator is a compound composition of a cyclic polyacid or its modified organic cyclic acid and an amidation product of an organic amine, possessing a multi-branched or network structure, which can significantly improve the low-shear rate viscosity and dynamic shear force of the drilling fluid under high temperature and high pressure. The plugging material in this invention is a temperature-sensitive intelligent polymer microsphere with temperature-responsive characteristics, capable of shrinking and agglomerating at high temperatures to achieve adaptive plugging. The drilling fluid of this invention exhibits excellent rheological stability, suspension capacity, and plugging performance under high temperature and high pressure conditions, making it suitable for the development of deep, ultra-deep, and extra-deep oil and gas wells.

Description

Technical Field

[0001] This invention belongs to the field of oil-based drilling fluid technology for oil and gas field drilling, specifically relating to a water-in-oil drilling fluid with a synergistic thickening effect of temperature and pressure and its application. Background Technology

[0002] Oil-in-water drilling fluids, with oil as the primary base fluid, exhibit rheological properties sensitive to temperature changes. Although increased pressure slightly raises the fluid viscosity, in deep well environments where both temperature and pressure rise, the overall fluid tends to "thicken" more. This leads to a significant decrease in viscosity and shear stress at high temperatures, weakening rheological and gel thixotropic properties. Consequently, this results in drilling fluid instability, reduced slurry carrying capacity, and impacts wellbore cleanliness and pump pressure. Therefore, optimizing the rheological properties and suspension capacity of oil-in-water drilling fluids for different deep-layer environments is a crucial technical challenge that urgently needs to be addressed.

[0003] To meet the demands of deep, harsh environments for water-in-oil drilling fluids, it is necessary to enhance fluid structure by introducing flow modifiers and specifically modify low-shear rate viscosity and dynamic shear force under different temperature and pressure conditions to improve the dynamic proppant carrying capacity and static cuttings suspension capacity of the drilling fluid. Simultaneously, excessive increases in apparent viscosity and plastic viscosity must be avoided, balancing mechanical drilling rate and economic efficiency to achieve "simultaneous optimization of environmental conditions and performance." However, current drilling fluid development and performance evaluation largely rely on parameters under conventional temperature and pressure conditions, with insufficient research on rheological changes under actual wellbore temperature and pressure. There is a lack of accurate real-time rheological parameter assessments of thickening and thinning trends and performance stability, making it difficult to construct water-in-oil drilling fluid systems suitable for the high-temperature, high-pressure environment of deep wells.

[0004] In existing technologies, the optimization of the rheological properties of water-in-oil drilling fluids largely relies on organoclay and other flow modifiers. Organoclay can swell in the base fluid to form a thixotropic gel, improving the viscosity and dispersion stability of the drilling fluid. However, conventional organoclay has a better thickening effect at low temperatures, but its performance degrades at high temperatures, making it difficult to adapt to deep-earth drilling environments above 200°C. Although some technologies improve temperature resistance by modifying organoclay (such as CN 110183596 A for lithium saponite modification and CN 108147419 A for montmorillonite modification), single organoclay still cannot meet the requirements of harsh formations.

[0005] Other flow modifiers (such as synthetic polymers, resins, polyacids and their derivatives) exhibit superior thermal stability and can form branched or comb-shaped macromolecules through chain monomers, synergistically enhancing fluid structure forces with organoclay (e.g., CN 104194742 A, CN104169391 A, CN 103012180 B, CN 103666414 B). However, these modifiers are mostly based on linear structures and lack multi-directional star-shaped structures, limiting the rheological control limits and potentially leading to drilling fluid instability under sustained high temperature and pressure.

[0006] Furthermore, traditional plugging agents (asphalt-based, calcium carbonate, graphite, etc.) are prone to failure or drilling fluid loss when facing micro-fractured formations in deep, high-temperature, and high-pressure wells. Moreover, their plugging behavior is static and passive, lacking intelligent response to downhole temperature. The plugging effectiveness deteriorates at high temperatures, resulting in a "spatial mismatch between plugging demand and plugging effectiveness," which restricts the improvement of wellbore stability and drilling efficiency.

[0007] In summary, there is an urgent need to develop a thickened water-in-oil drilling fluid with strong structural force and intelligent response sealing capabilities under high temperature and high pressure environments to meet the needs of deep oil and gas resource exploration and development. Summary of the Invention

[0008] To address the problems of water-in-oil drilling fluids being prone to thickening and instability under high temperature and pressure, and the lack of intelligent response in traditional plugging agents, this invention provides a water-in-oil drilling fluid with a synergistic thickening effect of temperature and pressure, and its application. This drilling fluid can significantly improve low shear rate viscosity and dynamic shear force under high temperature and pressure, while also possessing temperature-sensitive intelligent plugging capabilities, making it suitable for the development of deep, ultra-deep, and extra-deep oil and gas wells.

[0009] To overcome the shortcomings of the prior art, the present invention provides the following technical solution:

[0010] A water-in-oil drilling fluid with a synergistic thickening effect of temperature and pressure includes a base oil phase, a brine phase, organic clay, a high-temperature resistant emulsifier, a wetting agent, a thickening regulator, a flow pattern stabilizer, an alkaline substance, a filtration loss reducer, a plugging substance, and a weighting material.

[0011] The volume ratio of the base oil phase to the brine phase is 80:20~90:10; based on a total volume of 1L for the base oil phase and the brine phase, the dosage of each component is as follows: 10~20g organic clay, 20~50g high-temperature emulsifier, 5~10g wetting agent, 5~20g thickening regulator, 10~20g flow stabilizer, 30~40g alkaline substance, 50~80g filtration loss reducer, 40~50g sealing substance, and 1500~1700g weighting material;

[0012] The sealing material is a thermosensitive smart polymer microsphere, which is prepared by copolymerization of thermosensitive monomers, rigid reinforcing monomers, ionic monomers and crosslinking agents. By weight fraction, the feeding ratio of each monomer is: 80-95 parts of thermosensitive monomer, 3-15 parts of rigid reinforcing monomer, 2-8 parts of ionic monomer, and 0.5-2 parts of crosslinking agent.

[0013] Furthermore, the thermosensitive monomer is selected from N-isopropylacrylamide, N-vinylcaprolactam, and polyethylene glycol methacrylate; the rigidity-reinforcing monomer is selected from N-vinylcarbazole or styrene; the ionic monomer is selected from 2-acrylamido-2-methylpropanesulfonic acid, sodium salt, potassium salt, or calcium salt of AMPS; the crosslinking agent is N,N'-methylenebisacrylamide; and the minimum critical dissolution temperature of the thermosensitive smart polymer microspheres is 85~120℃.

[0014] Furthermore, the preparation method of the temperature-sensitive smart polymer microspheres includes the following steps:

[0015] S1. Dissolve 1-5 parts of polyvinyl alcohol in 100 parts of deionized water as the aqueous phase, and dissolve the thermosensitive monomer, rigid reinforcing monomer, ionic monomer, and crosslinking agent in 50-150 parts of toluene as the oil phase;

[0016] S2. The oil phase is added to the aqueous phase to form a crude emulsion, which is then homogenized under high pressure of 40~60MPa to obtain a fine emulsion;

[0017] S3. Add 0.1 to 0.5 parts of potassium persulfate to the fine emulsion, and carry out the polymerization reaction at 70 to 80°C under an inert atmosphere for 6 to 12 hours;

[0018] S4. After the reaction is complete, the thermosensitive smart polymer microspheres are obtained by centrifugation, washing and vacuum drying at 40°C.

[0019] Furthermore, the thickening regulator is a composition of an effective component and a solvent; the effective component includes cyclic polyacids and amidation products, modified organic cyclic acids and amidation products, and the solvent is a polar organic solvent of polyol ethers; the mass ratio of the effective component to the solvent is 60:40 to 80:20.

[0020] Further, the cyclic polyacid is a saturated or unsaturated cyclic structure containing 3 to 4 carboxylic acid groups; selected from one or more mixtures of trimellitic acid, pyromellitic acid, benzophenanthrene tricarboxylic acid, triphenyl tricarboxylic acid, cyclobutanetetracarboxylic acid, cyclopentanetetracarboxylic acid, pyromellitic tetracarboxylic acid, biphenyltetracarboxylic acid, hydrogenated biphenyltetracarboxylic acid, benzophenone tetracarboxylic acid, di(dicarboxyphenyl) ether, naphthalenetetracarboxylic acid, perylenetetracarboxylic acid, and pyrenetetracarboxylic acid.

[0021] Further, the amidation product of the cyclic polyacid is prepared by reacting the cyclic polyacid with an organic amine at 150-170°C for 2-4 hours; the organic amine is monoethanolamine, diethanolamine, or ethylenediamine; wherein the molar ratio of the three-membered cyclic acid to monoethanolamine or diethanolamine is 1:(3.05-3.3), the molar ratio of the four-membered cyclic acid to monoethanolamine or diethanolamine is 1:(4.1-4.5), the molar ratio of the three-membered cyclic acid to ethylenediamine is (1.3-3):3, and the molar ratio of the four-membered cyclic acid to ethylenediamine is (1.5-4):4.

[0022] Further, the modified organic cyclic acid is prepared by cycloaddition reaction of a cyclic fatty acid containing an unsaturated diene bond with a dienophilic anhydride at 200-230°C for 3-4 hours; wherein the cyclic fatty acid is selected from rosin acid or dibenzylsuccinic acid, and the dienophilic anhydride is selected from maleic anhydride, tetrahydrophthalic anhydride, or cyclohexadiene-dicarboxylic anhydride; its amidation product is prepared by amidation reaction of the modified organic cyclic acid with monoethanolamine or diethanolamine at 150-170°C for 2-3 hours.

[0023] Furthermore, the base oil phase includes at least one of mineral oil, diesel oil, and hydrocarbon synthetic oil; the brine phase is an aqueous solution of calcium chloride with a concentration of 25-30%.

[0024] Furthermore, the organic clay is organically modified lithium saponite; the high-temperature emulsifier is maleic fatty acid amide; the wetting agent is a straight-chain alkanolamide with a fatty chain containing 14-22 carbon atoms; the flow stabilizer is one or more styrene-butadiene-styrene block copolymers; the alkaline substance is calcium oxide or calcium hydroxide; the filtration loss reducing agent includes organically modified lignite, natural asphalt, or a combination thereof; and the weighting material is barite.

[0025] In addition, the present invention also provides the application of the oil-in-water drilling fluid described above in the development of deep, ultra-deep and extra-deep oil and gas wells.

[0026] Compared with the prior art, the technical solution of the present invention has at least the following technical effects:

[0027] This invention provides a water-in-oil drilling fluid with a synergistic thickening effect of temperature and pressure. The high-temperature thickening agent used here employs polycyclic cyclic carboxylic acids and modified fatty acids with more complex unit structures as substrates. By compounding these with their amidation products, a composition with multi-branched or network structures is formed. Compared to linear or regularly branched macromolecular systems, this composition exhibits higher structural strength. Based on its multi-directional extension characteristics, it can exert stronger internal structural forces in the drilling fluid system. When applied to drilling fluids, it can stably improve the rheological properties of the drilling fluid under ultra-high temperature conditions. After hot rolling at 200℃, the resulting water-in-oil drilling fluid shows a significant improvement in low shear rate and dynamic shear force values ​​under simulated deep well high-temperature and high-pressure environments compared to conventional systems, demonstrating excellent thickening performance and a significantly improved tendency for sedimentation instability in ultra-high temperature environments. A temperature-sensitive intelligent plugging mechanism is introduced, overcoming the challenge of high-temperature plugging. The innovative temperature-sensitive polymer microspheres respond to changes in formation temperature: they shrink and aggregate at high temperatures, automatically activating the plugging function and forming a tight-sealed plugging layer at micro-fractures. Experiments have shown that its sand bed penetration depth is much lower than that of traditional plugging agents, solving the wellbore instability problem caused by high temperature failure and passive plugging of traditional technologies. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0029] Figure 1 This is a scanning electron microscope image of the temperature-sensitive intelligent polymer microspheres of the present invention;

[0030] Figure 2 The graph shows the results of the settling resistance changes of drilling fluids in Examples 4, 5, and 6 and Comparative Example 1. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0032] The endpoints and any values ​​of the ranges disclosed in this invention 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0033] According to a first aspect of the present invention, a water-in-oil drilling fluid with a synergistic thickening effect of temperature and pressure is provided, comprising a base oil phase, a brine phase, an organoclay, a high-temperature resistant emulsifier, a wetting agent, a thickening regulator, a flow pattern stabilizer, an alkaline substance, a filtration loss reducer, a plugging substance, and a weighting material;

[0034] The volume ratio of the base oil phase to the brine phase is 80:20~90:10; based on a total volume of 1L for the base oil phase and the brine phase, the dosage of each component is as follows: 10~20g organic clay, 20~50g high-temperature emulsifier, 5~10g wetting agent, 5~20g thickening regulator, 10~20g flow stabilizer, 30~40g alkaline substance, 50~80g filtration loss reducer, 40~50g sealing substance, and 1500~1700g weighting material;

[0035] The sealing material is a thermosensitive smart polymer microsphere, which is prepared by copolymerization of thermosensitive monomers, rigid reinforcing monomers, ionic monomers and crosslinking agents. By weight fraction, the feeding ratio of each monomer is: 80-95 parts of thermosensitive monomer, 3-15 parts of rigid reinforcing monomer, 2-8 parts of ionic monomer, and 0.5-2 parts of crosslinking agent.

[0036] The plugging material in this invention is a temperature-sensitive intelligent polymer microsphere. This microsphere hydrophilically swells below its lowest critical dissolution temperature (LCST) and hydrophobically shrinks and aggregates into chain segments above its LCST, significantly increasing its volume. This allows it to automatically activate its plugging function in high-temperature formations, achieving intelligent and adaptive plugging of microfractures. This invention, through the synergistic effect of a rheological control system centered on a thickening agent and an intelligent plugging system centered on temperature-sensitive microspheres, creates a mutually supportive and functionally complementary effect under high-temperature and high-pressure conditions. This solves the problems of high-temperature thickening and suspension instability in traditional drilling fluids and overcomes the bottleneck of passive failure of traditional plugging agents. Ultimately, it achieves the integrated performance of long-term rheological stability and adaptive plugging required for deep and ultra-deep oil and gas well development.

[0037] The thermosensitive smart polymer microspheres were prepared via free radical copolymerization. They were formed by copolymerizing thermosensitive monomers, rigidity-reinforcing monomers, ionic monomers, and crosslinking agent N,N'-methylenebisacrylamide under the action of potassium persulfate as an initiator, resulting in a crosslinked polymer with a three-dimensional network structure. The reaction equation is as follows:

[0038] ;

[0039] Where, n1:n2:n3:n4 = (90~98):(2~10):(1~5):1. In the formula... X This represents the total number of repeating structures in the polymer chain. Its specific value is controlled by the amount of initiator and reaction conditions in the reaction system. It is only necessary to ensure that the final microspheres meet the performance requirement of a minimum critical dissolution temperature of 85~120℃.

[0040] The raw material components of the temperature-sensitive smart polymer microspheres are as follows:

[0041] (a) Thermosensitive monomer: one of N-isopropylacrylamide (NIPAM), N-vinylcaprolactam (NVCL) and oligoethylene glycol methacrylate (OEGMA), which provides the main thermosensitive properties of the polymer;

[0042] (b) Rigid reinforcing monomer: one of N-vinylcarbazole or styrene, used to improve the mechanical strength and thermal stability of polymer microspheres and prevent them from being compressed and destroyed under high temperature and high pressure;

[0043] (c) Ionic monomer: 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) or a salt thereof. The salt includes, but is not limited to, its alkali metal salt, alkaline earth metal salt, ammonium salt, or organic amine salt. Preferably, the salt is a sodium salt, potassium salt, or calcium salt. More preferably, it is sodium 2-acrylamido-2-methylpropanesulfonate;

[0044] (d) Crosslinking agent: N,N'-methylenebisacrylamide (MBA), used to form a three-dimensional network structure and maintain the integrity of the microsphere morphology.

[0045] The mass ratio of the monomers is as follows: 80-95 parts of thermosensitive monomer, 3-15 parts of rigidity-reinforcing monomer, 2-8 parts of ionic monomer, and 0.5-2 parts of crosslinking agent N,N'-methylenebisacrylamide.

[0046] The method for preparing the temperature-sensitive smart polymer microspheres includes the following steps:

[0047] S1. Preparation of aqueous and oil phases: Dissolve 1-5 parts by weight of polyvinyl alcohol in 100 parts by weight of deionized water as the aqueous phase; dissolve all of the above monomers (a), (b), (c), and (d) in 50-150 parts by weight of toluene as the oil phase;

[0048] S2. Pre-emulsification: The oil phase is slowly added to the aqueous phase at a stirring speed of 300~500 rpm to form a coarse emulsion. Then, high-pressure homogenization is carried out at a pressure of 40~60 MPa to obtain a stable fine emulsion.

[0049] S3. Initiating polymerization: Nitrogen gas is introduced into the fine emulsion obtained in step S2 for 30 minutes to remove oxygen, and then 0.1~0.5 parts by mass of water-soluble initiator potassium persulfate is added. The reaction is carried out in an oil bath at 70~80°C under nitrogen protection for 6~12 hours.

[0050] S4. Post-processing: After the reaction is completed, the mixture is naturally cooled to room temperature, and solid microspheres are obtained by centrifugation. The microspheres are then washed three times with ethanol and deionized water, and finally dried to constant weight in a vacuum drying oven at 40°C to obtain the temperature-sensitive smart polymer microspheres.

[0051] The LCST of the temperature-sensitive smart polymer microspheres can be adjusted by the monomer ratio, with a preferred range of 85~120℃, to adapt to deep drilling environments with different geothermal gradients.

[0052] In the aforementioned water-in-oil drilling fluid, as a preferred embodiment, the thickening regulator comprises a composition of a cyclic polyacid and its amide derivative, wherein the composition comprises: an active ingredient and a solvent. The active ingredient comprises: a cyclic polyacid and its amidated product, a modified organic cyclic acid and its amidated product, and the solvent is an alcohol ether.

[0053] The effective components of the above-described composition are a cyclic polycarboxylic acid and an amidation product. The cyclic polycarboxylic acid is characterized by a saturated or unsaturated cyclic structure containing 3-4 carboxylic acid groups, including tricarboxylic acid products such as trimellitic acid, pyromellitic acid, benzo[a]phenanthrene tricarboxylic acid, triphenyl tricarboxylic acid, etc., or a mixture of one or more of these; including tetracarboxylic acid products such as cyclobutanetetracarboxylic acid, cyclopentanetetracarboxylic acid, pyromellitic tetracarboxylic acid, biphenyltetracarboxylic acid, hydrogenated biphenyltetracarboxylic acid, tetrabenzophenone tetracarboxylate, di(dicarboxyphenyl) ether, naphthalenetetracarboxylic acid, perylenetetracarboxylic acid, pyrenetetracarboxylic acid, etc.; and similar stable structures resulting from substitution of other parts with halogen or olefin chains. The amidation derivative of the cyclic polycarboxylic acid is obtained by a high-temperature amidation reaction of the above structure with an organic amine, preferably monoethanolamine, diethanolamine, or ethylenediamine.

[0054] Optionally, the molar ratio of the ternary cyclic acid to monoethanolamine or diethanolamine is 1:(3.05~3.3), and the molar ratio of the tetracyclic acid to monoethanolamine or diethanolamine is 1:(4.1~4.5); the molar ratio of the ternary cyclic acid to ethylenediamine is (1.3~3):3, and the molar ratio of the tetracyclic acid to ethylenediamine is (1.5~4):4; the reaction temperature is 150~170 °C, and the time is 2~4 h. Preferably, benzo[a]phenanthrene tricarboxylic acid and monoethanolamine are reacted at a molar ratio of less than 1:3, preferably 1:3.2, and subjected to an intermolecular amidation dehydration reaction at 150~160 °C for 2.5 h to prepare a product dominated by triamide groups. Preferably, pyromellitic acid and ethylenediamine are reacted at a molar ratio of more than 1:4, preferably 1.9:4, and subjected to an intermolecular amidation dehydration reaction at 150~160 °C for 3 h to prepare a multi-branched amidated product.

[0055] Optionally, in the above-described compositions, the cyclic polyacid is 40-50 parts by weight, and the amide derivative reacting with the alcohol amine is 50-60 parts by weight; or the cyclic polyacid is 30-40 parts by weight, and the amide derivative reacting with the ethylenediamine is 60-70 parts by weight.

[0056] In a preferred embodiment, the above-described composition is a modified organic cyclic acid and its amidation product. The modified organic cyclic acid is prepared by cycloaddition reaction of a cyclic fatty acid containing an unsaturated diene bond with a dienophilic anhydride under high temperature or catalytic conditions. The cyclic fatty acid includes rosin acid, dibenzylidene succinic acid, and similar stable structures containing simple substituents at other sites. The dienophilic anhydride includes maleic anhydride, tetrahydrophthalic anhydride, cyclohexadiene-dicarboxylic anhydride, and similar stable structures containing simple substituents at other sites. The amidation derivative is prepared by high-temperature amidation reaction of the above structure with an organic amine, preferably monoethanolamine or diethanolamine.

[0057] Optionally, the mass ratio of the above-mentioned cyclic fatty acid to monoanhydride is 10:(2~3), preferably 10:3, the cycloaddition reaction temperature is 200~230 ℃, preferably 210 ℃, and the reaction time is 3~4 h to obtain the modified organic cyclic acid. Wherein, the mass ratio of cyclic fatty acid:monoanhydride:alkanolamine is 10:(2~3):(2~4), the monocarboxylic acid substrate is preferably 10:3:3, the dicarboxylic acid substrate is preferably 10:2.8:3.5, the amidation reaction temperature is 150~170 ℃, and the reaction time is 2~3 h. Preferably, rosin acid and maleic anhydride are subjected to a high-temperature diene cycloaddition reaction to graft maleic anhydride onto rosin acid, and then the adduct is reacted with monoethanolamine to obtain maleic rosin acid alkylolamide. The mass ratio of rosin acid: maleic anhydride: monoethanolamine is 10:(2~3):(2~4), preferably 10:3:3. The cycloaddition reaction temperature is 210 ℃, the reaction time is 3 h, and the amidation reaction temperature is 160 ℃, the reaction time is 2 h.

[0058] Optionally, in the above-described composition, the modified organic cyclic acid is 20-40 parts by weight, and the amidation product is 60-80 parts by weight.

[0059] In a preferred embodiment, the solvent of the above-described composition is a polar organic solvent of polyol ethers, including but not limited to triethylene glycol methyl / ethyl / propylene / butyl / isopropyl ether, diethylene glycol methyl / ethyl / propylene / butyl / isopropyl ether, ethylene glycol methyl / ethyl / propylene / butyl / isopropyl ether, propylene glycol methyl / ethyl / propylene / butyl / isopropyl ether, and preferably triethylene glycol butyl ether.

[0060] In a preferred embodiment, the mass ratio of the effective component to the solvent in the above-described composition is 60:40 to 80:20, preferably 70:30.

[0061] In the above-mentioned water-in-oil drilling fluid, as a preferred embodiment, the base oil phase includes at least one of mineral oil, diesel oil, and hydrocarbon synthetic oil; the brine phase is a calcium chloride aqueous solution with a concentration of 25-30%.

[0062] The organic clay is organically modified lithium saponite; the high-temperature emulsifier is maleic fatty acid amide; the wetting agent is a straight-chain alkanolamide with a fatty chain containing 14-22 carbon atoms; the flow stabilizer is a composition of one or more styrene-butadiene-styrene block copolymers; the alkaline substance is calcium oxide or calcium hydroxide; the filtration loss reducing agent includes organically modified lignite, natural bitumen, or a combination thereof; and the weighting material is barite.

[0063] According to a second aspect of the present invention, the application of the water-in-oil drilling fluid as described above in the development of deep, ultra-deep and extra-deep oil and gas wells is provided, wherein the geothermal temperature of the oil and gas well is ≥150°C and the target layer temperature is ≥200°C.

[0064] The present invention will now be described in detail with reference to embodiments thereof. These examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present invention encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0065] In the embodiments of the present invention, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0066] (a) Preparation of high-temperature thickening regulator

[0067] Example 1: Preparation of compositions of cyclic tricarboxylic acids and amide derivatives:

[0068] S1. Take 72.5g of benzo[a]phenanthrene-2,6,10-tricarboxylic acid and place it in a four-necked flask. Add 100 mL of dimethylformamide to dissolve the reactants. Assemble a reflux condenser, an inert gas vent, a thermometer, and a stirrer.

[0069] S2. Install the reaction system on an automatic oil bath and stir at a speed of 150 rpm. Heat to 75 °C and maintain this temperature while stirring for 30 min. At this temperature, add 39.1 g of monoethanolamine dropwise to the reactor and maintain the temperature while stirring for another 30 min.

[0070] S3. Heat to 150 °C, introduce nitrogen gas into the reactor, and react for 2-2.5 h. Terminate the reaction after the liquid level in the separator has stabilized for approximately 30 min, yielding an amidated derivative.

[0071] S4. Cool to 80 °C, add 90 g of benzo[2,6,10-tricarboxylic acid], dissolve, and remove the reaction solvent by vacuum distillation at the same temperature. The resulting product is a combination of carboxylic acid and amidation product.

[0072] S5. Cool to 60 ℃, take 70 g of the above effective components composition, add 30 g of triethylene glycol butyl ether solvent, the effective component concentration is 70%, and obtain thickening regulator CA-AM(I).

[0073] Example 2: Preparation of compositions of cyclic tetracarboxylic acids and amide derivatives:

[0074] S1. Place 76.3 g of pyromellitic acid in a four-necked flask, add 100 mL of dimethylformamide to dissolve the reactants, and assemble a reflux condenser, an inert gas vent, a thermometer, and a stirrer.

[0075] S2. Install the reaction system on an automatic oil bath and stir at a speed of 150 rpm. Heat to 75 ℃ and maintain this temperature while stirring for 30 min. At this temperature, add 38 g of ethylenediamine dropwise to the reactor and maintain the temperature while stirring for another 30 min.

[0076] S3. Heat to 150 °C, introduce nitrogen gas into the reactor, and react for 3-4 h. Terminate the reaction after the liquid level in the separator has stabilized for approximately 30 min, yielding an amidated derivative.

[0077] S4. Cool to 80 °C, add 85 g of pyromellitic acid, dissolve, and remove the reaction solvent by vacuum distillation at this temperature. The resulting product is a combination of carboxylic acid and amidation product.

[0078] S5. Cool to 60 ℃, take 70 g of the above effective components composition, add 30 g of triethylene glycol butyl ether solvent, the effective component concentration is 70%, and obtain thickening regulator CA-AM(II).

[0079] Example 3: Preparation of compositions of modified organic cyclic acids and amide derivatives:

[0080] S1. Place 100g of rosin acid in a four-necked flask and assemble a reflux condenser, an inert gas vent, a thermometer, and a stirrer.

[0081] S2. Install the reaction system on an automatic oil bath and stir at a speed of 120 rpm. Heat to 75 ℃ and maintain this temperature while stirring for 10 min. Add 30 g of maleic anhydride at this temperature and continue stirring for 20 min.

[0082] S3. Heat to 140-160 ℃, stir at 150 rpm, and maintain stirring at this temperature for 30 min to promote the co-solubility of the reactants and form the isomer rosinic acid, which can undergo addition reaction.

[0083] S4. Heat to 210-220 ℃ and stir the reaction at this temperature for 3 h. The product obtained is modified maleic astringent.

[0084] S5. Cool down to 80-90 ℃, add about 30 g of monoethanolamine dropwise, and continue stirring for 30 min while maintaining the temperature.

[0085] S6. Heat to 150 °C, introduce nitrogen gas into the reactor, and react for 2-3 h. Terminate the reaction after the liquid level in the separator has stabilized for approximately 30 min. The resulting product is modified maleic rosin alkanolamide.

[0086] S7. Cool to 90 °C, add 40 g of rosin acid, and dissolve to obtain a composition of carboxylic acid and amidation product. Cool to 60 °C, take 70 g of the above effective component composition, add 30 g of triethylene glycol butyl ether solvent, the effective component concentration is 70%, and obtain thickening regulator CA-AM(III).

[0087] (II) Preparation of drilling fluid with temperature / pressure thickening effect

[0088] Example 4: Preparation of thickened water-in-oil drilling fluid (I):

[0089] S1. At a speed of 11000 r / min, add 3 parts by weight of high-temperature emulsifier, 1 part by weight of wetting agent, and 1-1.5 parts by weight of high-temperature thickener CA-AM(I) to 80 parts by volume of base oil, and stir for 20 min; add 20 parts by volume of calcium chloride brine with a concentration of 25%, and stir for 30 min.

[0090] S2. At a speed of 11000 r / min, add 3.5 parts by weight of quicklime and 1.5 parts by weight of organic modified clay to the system and stir for 20 min; add 5 parts by weight of organic lignite and 2.5 parts by weight of natural bitumen and stir for 20 min; add 1 part by weight of flow-stabilized block copolymer and stir for 20 min.

[0091] S3. Preparation of temperature-sensitive smart polymer microspheres TSM-1:

[0092] A) Dissolve 3g of polyvinyl alcohol (PVA-1788) in 100g of deionized water to prepare an aqueous phase. Dissolve 90g of N-isopropylacrylamide (NIPAM), 6g of N-vinylcarbazole, 3g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and 1g of N,N'-methylenebisacrylamide (MBA) in 100g of toluene to prepare an oil phase.

[0093] B) While stirring at 400 rpm, the oil phase is slowly poured into the aqueous phase and stirred for 30 minutes to form a coarse emulsion. The coarse emulsion is then subjected to high-pressure homogenization at 50 MPa for 10 minutes each time to obtain a fine emulsion with uniform particle size distribution.

[0094] C) Transfer the fine emulsion to a four-necked flask equipped with a condenser, nitrogen delivery tube, and stirrer, and purge with nitrogen for 30 minutes. Then add 0.3 g of potassium persulfate (KPS).

[0095] D) Heat to 75℃ and react for 8 hours under nitrogen protection and stirring at 300 rpm. After the reaction, cool, centrifuge, wash three times alternately with ethanol and deionized water, and dry under vacuum at 40℃ for 12 hours to obtain a white powder product TSM-1, with the following microstructure: Figure 1 As shown.

[0096] S4. At a rotation speed of 11000 r / min, add 5 parts by weight of TSM-1 to the system, and adjust the drilling fluid density to 1.8 g / cm³ using barite. 3 Stir for 45 minutes to prepare high-temperature thickened water-in-oil drilling fluid (I).

[0097] Example 5:

[0098] Preparation of thickened water-in-oil drilling fluid (II): Replace the high-temperature thickener with the preparation process of Example 4, and add the high-temperature thickener CA-AM(II) at 0.8-1 parts by weight. The remaining preparation steps are the same as in Example 4.

[0099] Example 6:

[0100] Preparation of thickened water-in-oil drilling fluid (III): Replace the high-temperature thickener with the preparation process of Example 4, add 1-2 parts by weight of high-temperature thickener CA-AM (III), and the rest of the preparation steps are the same as in Example 4.

[0101] (III) Preparation of comparative drilling fluid

[0102] Comparative Example 1:

[0103] Preparation of conventional thickened water-in-oil drilling fluid (IV): Replace the high-temperature thickener with the preparation process of Example 4, add 0.8-1.5 parts by weight of linear fatty acid polyamide flow modifier, and the rest of the preparation steps are the same as in Example 4.

[0104] Comparative Example 2:

[0105] Preparation of conventional thickened water-in-oil drilling fluid (V): The preparation process is the same as in Example 4, except that the sealing material, temperature-sensitive intelligent polymer microspheres TSM-1, is replaced with calcium carbonate, while the other components and preparation steps remain unchanged.

[0106] Performance testing:

[0107] (i) Referring to GB / T 16783.2, the basic rheological properties, demulsification voltage, and high-temperature and high-pressure filtration performance of drilling fluids (I) to (IV) in Examples 4, 5, 6, and Comparative Example 1 before and after hot rolling at 200℃ for 16 h were tested. The test results are shown in Table 1.

[0108] Table 1. Basic properties of drilling fluid under conventional test conditions

[0109]

[0110]

[0111] As shown in Table 1, drilling fluids (I) to (III) all exhibit good rheological stability after aging at 200 ℃ for 16 h: the values ​​of Ф6 and Ф3 remain stable in the range of 10-12, without significant decrease and are higher than those of drilling fluid (IV) in Comparative Example 1; the plastic viscosity and dynamic shear stress are close to those of the comparative example, with the plastic viscosity maintained at 45-55 mPa·s and the dynamic shear stress at 8-12 Pa; at the same time, the demulsification voltage is higher than >1200 V and the high-temperature and high-pressure filtration loss is <5 mL, showing good rheological properties in performance tests under normal temperature / pressure conditions.

[0112] (II) A series of gradient temperature and pressure parameters were set to simulate the wellbore environment. The rheological properties of the water-in-oil drilling fluids (I) to (IV) in Examples 4-6 and Comparative Example 1 were tested using a high-temperature and high-pressure rheometer during the simulated temperature and pressure increase process. The test results are shown in Tables 2-5:

[0113] Table 2. High-Temperature and High-Pressure Rheological Properties of Drilling Fluid (I)

[0114]

[0115] Table 3. High-Temperature and High-Pressure Rheological Properties of Drilling Fluid (II)

[0116]

[0117] Table 4. High-Temperature and High-Pressure Rheological Properties of Drilling Fluid (III)

[0118]

[0119] Table 5. High-Temperature and High-Pressure Rheological Properties of Drilling Fluid (IV)

[0120]

[0121] As shown in Tables 2-5, the test results of Comparative Example 1, water-in-oil drilling fluid (IV), exhibited a slight decrease in both high and low shear rate viscosities during the process of heating to 200 ℃ and pressurizing to approximately 150 MPa. However, these viscosities rebounded somewhat during the same temperature gradient pressurization, consistent with the general variation pattern of oil-based drilling fluids. Although the overall rheological properties were relatively stable, the low shear rate viscosity was relatively low. Meanwhile, its plastic viscosity did not change significantly, while the dynamic shear force showed a certain decreasing trend. These results indicate that drilling fluids constructed using conventional linear fatty acid polyamide structures as flow modifiers possess a certain degree of stability in high-temperature and high-pressure environments, but the fluid exhibits a de-thickening trend and does not possess clear thickening characteristics. In Examples 4-6, the water-in-oil drilling fluids (I)-(III) all employed different complex cyclic polyacids and their amide derivatives as thickeners in high-temperature environments. During the heating and pressurization process, the plastic viscosity was similar to that of the comparative examples, indicating that the thickeners did not significantly affect the high shear rate viscosity and plastic viscosity of the drilling fluids in these examples. Simultaneously, the low shear rate viscosity and dynamic shear force of the drilling fluids were significantly improved, exhibiting a clear trend of relative viscosity enhancement and shear strength improvement. These results demonstrate that the water-in-oil drilling fluid prepared according to this invention can achieve improved directional properties of low shear viscosity and dynamic shear force in high-temperature and high-pressure environments. It can improve the suspension capacity of the drilling fluid and, to a certain extent, reduce the increase in mechanical pressure loss caused by the overall viscosity increase, achieving a relatively ideal thickening effect.

[0122] (III) The oil-in-water drilling fluids (I) to (IV) from Examples 4, 5, and 6, and Comparative Example 1, were left to stand at 200 °C for 7 days. The changes in settling resistance of the drilling fluids after prolonged standing in a high-temperature environment were tested using a settling stability meter to compare the settling stability of different samples. The specific test methods are as follows:

[0123] This experiment was conducted using the RF-990LA / 2 settling resistance tester from Chengdu Ruifeng Instrument Equipment Co., Ltd. Drilling fluids (I) through (IV) were placed in high-temperature aging tanks and vertically stabilized for 7 days in an electrically heated drying oven at 200 ℃. Afterwards, without disrupting the settling of the drilling fluids, the aging tanks containing the drilling fluids were removed, cooled to room temperature, and then opened. The settling resistance tester was turned on, and the probe test direction was set to "compression," the control mode to "constant speed," and the control quantity to "200 mm / min." The aging tanks were placed on the test platform. Based on the height of the aging tank containing the drilling fluids, the instrument probe was adjusted to the top of the tank and zeroed. The distance from the bottom of the probe to the bottom of the aging tank was measured at this point. The instrument test switching condition and condition value were set to "deformation ≥ 280 mm." The purpose of this setting was to collect the real-time fluid resistance experienced by the probe as it descended vertically at a constant speed of 280 mm, penetrating the drilling fluid through the aging tank to the bottom, thus reflecting the settling of each drilling fluid. The higher the overall resistance curve and the peak value of the maximum resistance during the test, the more severe the solid phase deposition of the fluid in the tank, i.e., the worse the settling stability of the drilling fluid. After setting the above parameters and adjusting the instrument, click "Start" to complete and record the fluid resistance and settling of drilling fluids (I) to (IV) under normal temperature and pressure after long-term high-temperature aging. The test can obtain the relevant parameters of probe deformation distance and real-time resistance. Plotting the two parameters together yields the following results, as shown in the appendix. Figure 2 :

[0124] From the appendix Figure 2 The test results show that drilling fluids (I) to (IV) all exhibited varying degrees of solid deposition after standing at high temperature for 7 days, with maximum settling resistances of 1.57, 1.66, 1.64, and 2.05 N, respectively. The drilling fluid (IV) of Comparative Example 1 exhibited the highest maximum settling resistance, indicating more severe solid deposition in this example, meaning its suspension capacity was weaker than that of the thickened drilling fluid. These results demonstrate that the systems (I) to (III) of the present invention exhibit better rheological properties than the drilling fluid (IV) of Comparative Example 1, and therefore possess better settling stability, which is beneficial for improving the tendency of water-in-oil drilling fluids to become unstable under actual temperature / pressure conditions.

[0125] (iv) Evaluation of the plugging performance of drilling fluid (V) in Comparative Example 2: 100-mesh quartz sand was loaded into a high-temperature, high-pressure filtration analyzer as a sand bed. The drilling fluid to be tested was added, and pressure differences of 0.7 MPa and 3.5 MPa were applied at ambient temperature (25℃) and high temperature (120℃), respectively. The penetration depth of the sand bed after the drilling fluid completely penetrated for 30 minutes was measured. The shallower the penetration depth and the lower the filtration loss, the higher the plugging efficiency of the plugging agent and the denser the plugging layer formed. The results are shown in Table 6:

[0126] Table 6 Evaluation Results of Drilling Fluid Pouring Performance

[0127]

[0128] Test results show that the drilling fluid system of this invention is significantly superior to traditional solutions. Drilling fluids (I) to (III) innovatively incorporate the temperature-sensitive intelligent plugging agent TSM-1, which is activated at high temperatures, achieving "intelligent plugging." The sand bed penetration depth of the drilling fluid in this example at room temperature is approximately 4-5 cm, slightly lower than that of drilling fluid (V) in Comparative Example 2 (5.2 cm) using a conventional calcium carbonate plugging agent, indicating that TSM-1 can maintain good plugging performance at room temperature. However, at 120℃, the sand bed penetration depth of drilling fluids (I) to (III) is significantly lower than at room temperature, proving that TSM-1 is activated at high temperatures and effectively plugs the sand bed pores. In contrast, the sand bed penetration depth of drilling fluid (V) without TSM-1 does not change much at high temperatures and is higher than that of drilling fluids (I) to (III), indicating that conventional plugging agents lack an intelligent, adaptive plugging mechanism under high-temperature conditions. The above results demonstrate that the TSM-1 plugging agent can actively respond to high-temperature environments and form an extremely dense plugging layer, solving the core pain points of passive plugging and high-temperature failure in traditional technologies. Among them, the TSM-1 microspheres are specifically activated at high temperatures, and their molecular chains undergo phase transition, shrinkage, and tight aggregation, achieving a qualitative change from "physical filling" to "intelligent adaptive wall building," which produces a significant synergistic effect with the thickener network.

[0129] In summary, this invention successfully constructs an intelligent drilling fluid system that responds to deep high-temperature and high-pressure environments by combining a high-temperature thickener with an intelligent plugging agent. This not only solves the problem of ineffective plugging caused by the high-temperature failure and single mechanism of traditional plugging agents, but also surpasses the performance bottleneck of single thickening technology, providing a reliable technical guarantee for achieving safe and efficient drilling in deep and ultra-deep environments.

[0130] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any technical solutions obtained by means of equivalent substitution or equivalent transformation should be covered within the protection scope of the present invention.

Claims

1. A water-in-oil drilling fluid with a synergistic thickening effect of temperature and pressure, characterized in that, It includes base oil phase, brine phase, organoclay, high-temperature emulsifier, wetting agent, thickening regulator, flow stabilizer, alkaline substance, filtration loss reducer, plugging substance and weighting material; The volume ratio of the base oil phase to the brine phase is 80:20~90:10; based on a total volume of 1L for the base oil phase and the brine phase, the dosage of each component is as follows: 10~20g organic clay, 20~50g high-temperature emulsifier, 5~10g wetting agent, 5~20g thickening regulator, 10~20g flow stabilizer, 30~40g alkaline substance, 50~80g filtration loss reducer, 40~50g sealing substance, and 1500~1700g weighting material; The sealing material is a thermosensitive smart polymer microsphere, which is prepared by copolymerization of thermosensitive monomers, rigidity-reinforcing monomers, ionic monomers and crosslinking agents. By weight fraction, the feeding ratio of each monomer is: 80-95 parts of thermosensitive monomer, 3-15 parts of rigidity-reinforcing monomer, 2-8 parts of ionic monomer, and 0.5-2 parts of crosslinking agent. The method for preparing the temperature-sensitive smart polymer microspheres includes the following steps: S1. Dissolve 1-5 parts of polyvinyl alcohol in 100 parts of deionized water as the aqueous phase, and dissolve the thermosensitive monomer, rigid reinforcing monomer, ionic monomer, and crosslinking agent in 50-150 parts of toluene as the oil phase; S2. The oil phase is added to the aqueous phase to form a crude emulsion, which is then homogenized under high pressure of 40~60MPa to obtain a fine emulsion; S3. Add 0.1 to 0.5 parts of potassium persulfate to the fine emulsion, and carry out the polymerization reaction at 70 to 80°C under an inert atmosphere for 6 to 12 hours; S4. After the reaction is complete, the thermosensitive smart polymer microspheres are obtained by centrifugation, washing and vacuum drying at 40℃. The thickening regulator is a composition of an effective component and a solvent; the effective component includes cyclic polyacids and their amidation products, modified organic cyclic acids and their amidation products, and the solvent is a polar organic solvent of polyol ethers; the mass ratio of the effective component to the solvent is 60:40 to 80:

20. The amidation product of the cyclic polyacid is prepared by reacting the cyclic polyacid with an organic amine at 150-170℃ for 2-4 hours; the organic amine is monoethanolamine, diethanolamine, or ethylenediamine; wherein the molar ratio of the three-membered cyclic acid to monoethanolamine or diethanolamine is 1:(3.05-3.3), the molar ratio of the four-membered cyclic acid to monoethanolamine or diethanolamine is 1:(4.1-4.5), the molar ratio of the three-membered cyclic acid to ethylenediamine is (1.3-3):3, and the molar ratio of the four-membered cyclic acid to ethylenediamine is (1.5-4):4; The modified organic cyclic acid is prepared by cycloaddition reaction of a cyclic fatty acid containing an unsaturated diene bond with a dienophilic anhydride at 200-230°C for 3-4 hours; wherein the cyclic fatty acid is selected from rosin acid or dibenzylsuccinic acid, and the dienophilic anhydride is selected from maleic anhydride, tetrahydrophthalic anhydride, or cyclohexadiene-dicarboxylic anhydride; its amidation product is prepared by amidation reaction of the modified organic cyclic acid with monoethanolamine or diethanolamine at 150-170°C for 2-3 hours.

2. The water-in-oil drilling fluid according to claim 1, characterized in that, The thermosensitive monomer is selected from N-isopropylacrylamide, N-vinylcaprolactam, and oligoethylene glycol methacrylate; the rigidity-reinforcing monomer is selected from N-vinylcarbazole or styrene; the ionic monomer is selected from 2-acrylamido-2-methylpropanesulfonic acid, sodium salt, potassium salt, or calcium salt of AMPS; the crosslinking agent is N,N'-methylenebisacrylamide; and the minimum critical dissolution temperature of the thermosensitive smart polymer microspheres is 85~120℃.

3. The water-in-oil drilling fluid according to claim 1, characterized in that, The cyclic polyacid is a saturated or unsaturated cyclic structure containing 3 to 4 carboxylic acid groups; selected from one or more of trimellitic acid, pyromellitic acid, benzophenanthrene tricarboxylic acid, triphenyl tricarboxylic acid, cyclobutanetetracarboxylic acid, cyclopentanetetracarboxylic acid, pyromellitic tetracarboxylic acid, biphenyltetracarboxylic acid, hydrogenated biphenyltetracarboxylic acid, benzophenone tetracarboxylic acid, di(dicarboxyphenyl) ether, naphthalenetetracarboxylic acid, perylenetetracarboxylic acid, and pyrenetetracarboxylic acid.

4. The water-in-oil drilling fluid according to claim 1, characterized in that, The base oil phase includes at least one of mineral oil, diesel oil, and hydrocarbon synthetic oil; the brine phase is an aqueous solution of calcium chloride with a concentration of 25-30%.

5. The water-in-oil drilling fluid according to claim 1, characterized in that, The organic clay is organically modified lithium saponite; the high-temperature emulsifier is maleic fatty acid amide; the wetting agent is a straight-chain alkanolamide with a fatty chain containing 14-22 carbon atoms; the flow stabilizer is one or more styrene-butadiene-styrene block copolymers; the alkaline substance is calcium oxide or calcium hydroxide; the filtration loss reducing agent includes organically modified lignite, natural asphalt, or a combination thereof; and the weighting material is barite.

6. The application of the water-in-oil drilling fluid as described in any one of claims 1-5 in the development of deep, ultra-deep and extra-deep oil and gas wells.

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