Low-oil-water-ratio oil-based drilling fluid, and preparation method and application thereof

Abstract

The application provides a low oil-water ratio oil-based drilling fluid and a preparation method and application thereof, the low oil-water ratio oil-based drilling fluid comprises an oil phase, a water phase, an emulsifier, an organic-inorganic hybrid flow pattern regulator, an organic soil, a filtrate reducer, an alkalinity regulator, an ultra-fine particle material and a weighting agent, and the oil-water ratio of the drilling fluid is 50:50-75:25. The low oil-water ratio strong plugging oil-based drilling fluid of the application not only has good rheological property and strong plugging property, but also can maintain a stable emulsified state under high temperature and high pressure conditions, and is suitable for complex environments of deep layer, super deep layer and shale oil and gas drilling.

Description

Technical Field

[0001] This invention belongs to the technical field of oil-based drilling fluids for petroleum drilling, and relates to a low oil-water ratio oil-based drilling fluid, its preparation method, and its application. Background Technology

[0002] Currently, oil-based drilling fluids are the primary drilling fluid technology for shale oil and gas development. Existing oil-based drilling fluid technologies can basically meet the requirements for well completion, but they are costly, with base oil accounting for over 70% of the total cost. To reduce costs and increase efficiency, the oil-water ratio of oil-based drilling fluids must be lowered. However, this presents challenges such as poor emulsion stability, poor plugging properties, and difficulty in rheological control. Therefore, there is an urgent need to develop a low-oil-water-ratio, high-plugging oil-based drilling fluid.

[0003] Patent ZL201711246730X discloses a low oil-water ratio drilling fluid system with a filtration loss greater than 3 mL at temperatures exceeding 150°C and a maximum density of 2.2 g / cm³. 3 Patent ZL2015104796058 discloses an oil-based drilling fluid with an ultra-low oil-water ratio, but its temperature resistance is only 120℃. Based on the examples given, its performance fluctuates significantly and is difficult to control. Patent ZL2016102737967 discloses a low oil-water ratio drilling fluid system with a temperature resistance of only 150℃. Patent ZL2014100247413 discloses a soil-free oil-based drilling fluid system with a temperature resistance of only 150℃. CN118085836A discloses a high-efficiency emulsifier, a low oil-water ratio, and low soil-phase oil-based drilling fluid and its preparation method, with a temperature resistance of up to 180℃, but its density is only up to 2.0 g / cm³. 3 .

[0004] In recent years, with the continuous development of oil-based drilling fluid technology in my country, significant progress has been made in low oil-water ratio oil-based drilling fluid technology, reducing the oil-water ratio from 80:20 to 50:50, and achieving a density of 2.2 g / cm³. 3 However, as exploration and development continue to deepen, the requirements for drilling fluids in deep and ultra-deep shale oil and gas drilling are becoming increasingly stringent. Under conditions of high temperature, high pressure, and low oil-water ratio, oil-based drilling fluids still face challenges such as poor emulsion stability, rheological stability, and plugging properties. There is an urgent need to innovate research and development approaches and develop high-temperature, high-density, low oil-water ratio oil-based drilling fluids to provide technical support for the safe and economical development of deep and ultra-deep shale oil and gas exploration. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a low oil-water ratio oil-based drilling fluid, its preparation method, and its application.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a low oil-water ratio oil-based drilling fluid, which includes an oil phase, a water phase, an emulsifier, an organic-inorganic hybrid flow pattern modifier, an organic clay, a filtration loss reducer, an alkalinity modifier, ultrafine particulate material, and a weighting agent, wherein the oil-water ratio of the drilling fluid is 50:50-75:25.

[0008] In this invention, the emulsion droplets are moderately flocculated by using an organic-inorganic hybrid flow modifier to form a weak gel structure, which makes the emulsion stable and has good rheological properties, as well as high-temperature stability. The use of ultrafine particulate materials enables the low oil-water ratio oil-based drilling fluid of this invention to form a low viscosity and high shear weak gel structure, and has a strong wellbore sealing effect, making it suitable for complex formation wells such as highly deviated directional wells and shale horizontal wells.

[0009] This invention, through the balanced combination of its components—oil phase, aqueous phase, emulsifier, organic-inorganic hybrid flow modifier, organic clay, filtration reducer, alkalinity regulator, ultrafine particulate material, and weighting agent—enables a low oil-water ratio oil-based drilling fluid that addresses the problems of poor emulsion stability, poor plugging properties, and difficulty in rheological control inherent in existing oil-based drilling fluids with low oil-water ratios. The drilling fluid of this invention maintains good emulsion stability and rheological properties even under low oil-water ratio conditions. Furthermore, this drilling fluid exhibits strong plugging properties and maintains a stable emulsion state under high temperature and high pressure conditions, making it suitable for the complex environments of high-temperature deep, ultra-deep, and shale oil and gas drilling.

[0010] Preferably, the oil phase is white oil or diesel oil, more preferably No. 3 white oil or No. 0 diesel oil.

[0011] In this invention, the oil-water ratio of the drilling fluid is low, ranging from 50:50 to 75:25, namely 50:50, 53:47, 55:45, 58:42, 60:40, 63:37, 65:35, 68:32, 70:30, 73:27, 75:25, etc.

[0012] Preferably, the aqueous phase is a salt solution, and the mass fraction of the solute in the salt solution is 20-35%, for example, 20%, 23%, 25%, 28%, 30%, 33% or 35%.

[0013] Preferably, the salt solution is an aqueous solution of calcium chloride, sodium chloride, potassium chloride, or sodium formate.

[0014] Preferably, the emulsifier includes a primary emulsifier and a secondary emulsifier.

[0015] Preferably, the primary emulsifier is a fatty acid amide-based high-efficiency emulsifier. This emulsifier has polyamide groups, which can significantly improve the oil-water emulsification effect and increase the stability of the emulsion. More preferably, it is DR-EM (a product of China Petroleum Engineering Technology Research Institute Co., Ltd.).

[0016] Preferably, the amount of the main emulsifier added, expressed in grams, is 3 to 5% of the total volume of the oil and water phases, for example, 3%, 3.5%, 4%, 4.5%, or 5%.

[0017] Preferably, the co-emulsifier is a fatty acid-modified alkanolamide. The co-emulsifier works synergistically with the main emulsifier to further enhance the stability of the emulsion. More preferably, it is DR-CO (a product of China Petroleum Engineering Technology Research Institute Co., Ltd.).

[0018] Preferably, the amount of the co-emulsifier added is 1 to 3% of the total volume of the oil phase and the aqueous phase, for example, 1%, 1.5%, 1.8%, 2%, 2.5%, 2.8% or 3%.

[0019] Preferably, the organic-inorganic hybrid flow pattern modifier is nano-silica modified with silane coupling agent and polymer.

[0020] Preferably, the amount of the organic-inorganic hybrid flow pattern modifier added, in grams, is 0.5%-2% of the total volume of the oil and water phases, for example, 0.5%, 0.8%, 1%, 1.5%, 1.8% or 2%.

[0021] Preferably, the particle size of the nano-silica is 20-100 nanometers, such as 20 nanometers, 25 nanometers, 30 nanometers, 40 nanometers, 50 nanometers, 60 nanometers, 70 nanometers, 80 nanometers, 90 nanometers, or 100 nanometers. Commercially available high-purity nano-silica can be selected.

[0022] Preferably, the silane coupling agent is selected from one or a combination of at least two of vinyltrimethoxysilane, vinylethoxysilane, and vinyltriethoxysilane.

[0023] Preferably, the amount of the silane coupling agent is 15% to 50% of the mass of nano-silica, for example, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%.

[0024] Preferably, the polymer monomers are styrene and methyl methacrylate.

[0025] Preferably, the molar ratio of styrene to methyl methacrylate is 3:1 to 2:1, for example 3:1, 2.8:1, 2.5:1, 2.3:1 or 2:1.

[0026] Preferably, the molar ratio of the polymeric monomer to the silane coupling agent is 1:1 to 2:1, for example, 1:1, 1.3:1, 1.5:1, 1.8:1 or 2:1.

[0027] Preferably, the preparation method of the organic-inorganic hybrid flow pattern regulator includes the following steps:

[0028] (1) Disperse nano-silica in a solvent, add silane coupling agent, react, and obtain silane coupling agent modified nano-silica;

[0029] (2) The nano-silica modified by silane coupling agent is dispersed in an organic solvent, and a polymerization monomer and an initiator are added to react and obtain the organic-inorganic hybrid flow pattern regulator.

[0030] Preferably, the dispersion in step (1) is achieved by ultrasonic treatment to ensure uniform dispersion of nano-silica.

[0031] The ultrasonic treatment time is generally 10 to 15 minutes, and the frequency can be selected above 40 kHz to ensure that the nano-silica is fully dispersed.

[0032] Preferably, the solvent in step (1) is a mixed solvent of ethanol and water, and the volume ratio of ethanol / water is 70:30 to 90:10, such as 70:30, 75:25, 78:22, 80:20, 83:17, 85:15, 88:12 or 90:10. Using such a mixed solvent can promote the hydrolysis of silane coupling agent and its reaction with the hydroxyl groups on the surface of nano silica.

[0033] Preferably, the reaction in step (1) is carried out under stirring at a speed of 100-300 rpm, such as 100 rpm, 130 rpm, 150 rpm, 200 rpm, 250 rpm, 280 rpm or 300 rpm.

[0034] Preferably, the reaction in step (1) is carried out at 60°C-70°C (e.g., 60°C, 63°C, 65°C, 68°C or 70°C) for 4 to 6 hours (e.g., 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours).

[0035] Preferably, after the reaction in step (1) is completed, the mixture is filtered, washed, dried and pulverized to obtain the silane coupling agent modified nano-silica.

[0036] Preferably, the washing is performed using anhydrous ethanol or a mixture of ethanol and water, and the washing is preferably performed three times.

[0037] Preferably, the drying temperature is 60°C and the drying time is 12 hours.

[0038] Preferably, the organic solvent in step (2) is toluene, because it has good solubility and a high boiling point, making it suitable for free radical polymerization reactions.

[0039] Preferably, the initiator in step (2) is selected from azobisisobutyronitrile (AIBN), ammonium persulfate (APS), azobiscyclohexyl cyanide (ADCN), etc., and the selection depends on the type of monomer and the reaction temperature.

[0040] Preferably, the amount of the initiator added is 1%-2% of the mass of the polymerizing monomer, for example, 1%, 1.3%, 1.5%, 1.8% or 2%.

[0041] Preferably, the reaction temperature in step (2) is 80-90°C (e.g., 80°C, 83°C, 85°C, 88°C or 90°C), and the reaction time is 3-5 hours (e.g., 3 hours, 4 hours or 5 hours).

[0042] Preferably, the reaction in step (2) is carried out under nitrogen protection.

[0043] Preferably, after the reaction in step (2) is completed, the product is separated by centrifugation, washed multiple times, and finally dried to obtain an organic-inorganic hybrid flow pattern regulator.

[0044] Preferably, after the reaction in step (2) is completed, the mixture is washed multiple times with toluene and ethanol to remove unreacted monomers and residual initiators.

[0045] Preferably, the drying temperature is controlled at 60°C and the time is 10 hours.

[0046] Preferably, the organic soil is organically modified montmorillonite, used to improve drilling fluid viscosity and shear force. More preferably, it is organic soil DR-OC (a product of China Petroleum Engineering Technology Research Institute Co., Ltd.).

[0047] Preferably, the amount of organic soil added, expressed in grams, is 1% to 3% of the total volume of the oil and water phases, for example, 1%, 1.5%, 2%, 2.5%, or 3%.

[0048] Preferably, the filtration loss reducer is a modified lignite and bitumen-based filtration loss reducer, which can effectively reduce filtration loss under high temperature and high pressure environments and enhance the wellbore sealing effect. More preferably, it is FLRA (a product of China Petroleum Engineering Technology Research Institute Co., Ltd.).

[0049] Preferably, the amount of the filtration loss reducer added, expressed in grams, is 2 to 4% of the total volume of the oil and water phases, for example, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.5%, 3.8%, or 4%.

[0050] Preferably, the alkalinity regulator is calcium oxide, used to adjust the alkalinity of the drilling fluid system.

[0051] Preferably, the amount of alkalinity regulator added, expressed in grams, is 3-5% of the total volume of the oil and water phases, specifically 3%, 3.5%, 4%, 4.5%, or 5%.

[0052] Preferably, the particle size of the ultrafine particulate material is 600-3000 mesh, such as 600 mesh, 700 mesh, 800 mesh, 900 mesh, 1000 mesh, 1200 mesh, 1500 mesh, 1800 mesh, 2000 mesh, 2300 mesh, 2500 mesh, 2800 mesh or 3000 mesh.

[0053] Preferably, the ultrafine particulate material is ultrafine calcium carbonate.

[0054] Preferably, the ultrafine calcium carbonate comprises 600 mesh, 1200 mesh, 2000 mesh and 3000 mesh calcium carbonate in a 1:1:1:1 ratio. This mixture forms a reasonable particle size distribution, effectively sealing micro-cracks in the well wall and improving well wall stability.

[0055] Preferably, the amount of the ultrafine particulate material added, expressed in grams, is 3-5% of the total volume of the oil and water phases, specifically 3%, 3.5%, 4%, 4.5%, or 5%.

[0056] Preferably, the barite comprises micronized barite;

[0057] Preferably, the micronized barite has a particle size D90 of less than 5 micrometers and a D50 of less than 3 micrometers, which enables it to maintain good rheological properties under low oil-water ratio conditions.

[0058] Preferably, the mass percentage of micronized barite in the barite is 5-20%, for example 5%, 8%, 10%, 12%, 15%, 18% or 20%, preferably 10%.

[0059] Preferably, the amount of weighting agent added, expressed in grams, is 0.5-4.5 times the total volume of the oil and water phases, for example, 0.5 times, 1 time, 1.5 times, 1.8 times, 2 times, 2.5 times, 2.8 times, 3 times, 3.5 times, 3.8 times, or 4 times.

[0060] On the other hand, the present invention provides a method for preparing the low oil-water ratio oil-based drilling fluid as described above. The preparation method involves uniformly mixing the oil phase, water phase, emulsifier, organic-inorganic hybrid flow pattern modifier, organic clay, filtration loss reducer, alkalinity modifier, ultrafine particulate material and weighting agent to obtain the low oil-water ratio oil-based drilling fluid.

[0061] On the other hand, the present invention provides the application of the low oil-water ratio oil-based drilling fluid described above in deep oil and gas drilling, ultra-deep oil and gas drilling or shale oil and gas drilling.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] (1) Emulsion stability: By employing a high-efficiency emulsifier with polyamide groups and a fatty acid-modified co-emulsifier, and by using amphiphilic nanoparticles to enhance the strength of the oil-water interface film, this invention significantly improves the emulsion stability of drilling fluids with low oil-water ratios. Even at an oil-water ratio of 50:50, the emulsion can still maintain high stability, with a demulsification voltage exceeding 600V.

[0064] (2) Sealing performance: It is compounded with broad-spectrum ultrafine calcium carbonate and modified nano silica, which enables the drilling fluid to form a weak gel structure with low viscosity and high shear, and has a strong well wall sealing effect. It is suitable for complex formation wells such as high-angle directional wells and shale horizontal wells.

[0065] (3) Rheological regulation: The organic-inorganic hybrid flow pattern regulator is based on the adsorption and bridging of amphiphilic molecules and modified nanoparticles with multi-branched multipolar groups at the emulsion droplet interface, so that the emulsion droplets are moderately flocculated and form a weak gel structure; the combination of micronized barite and ordinary barite results in a more reasonable particle size distribution and a lower viscosity effect, making the emulsion stable and having good rheological properties, and able to remain stable at a high temperature of 200℃.

[0066] (4) Temperature resistance: The drilling fluid of the present invention has a temperature resistance of up to 200℃ and a filtration loss of less than 3mL, making it suitable for drilling operations in high temperature and high pressure environments. Detailed Implementation

[0067] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0068] In the following embodiments, unless otherwise stated, all raw materials used are conventional materials and are commercially available. The methods used in the embodiments, unless otherwise specified, are existing technologies.

[0069] In the materials used in the examples, No. 3 white oil was purchased from Guangzhou Maoming Petrochemical Co., Ltd., and No. 0 diesel oil came from Ziyang Oil Depot in Sichuan.

[0070] Deionized water, anhydrous ethanol, calcium oxide, and calcium chloride were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and were of analytical grade.

[0071] Vinyltrimethoxysilane, vinylethoxysilane, and vinyltriethoxysilane were purchased from Guangzhou Zhongjie Chemical Technology Co., Ltd., with a purity of ≥98%.

[0072] Nano-silica (20nm) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., and was of analytical grade.

[0073] The main emulsifier, co-emulsifier, filtration loss reducer, and organic soil were all produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0074] The barite was purchased from Ankang Liyuan Mining Co., Ltd.

[0075] Example 1

[0076] 1. Preparation of organic-inorganic hybrid flow pattern modifiers:

[0077] 15g of nano-silica was added to 100mL of ethanol / water (90:10) solution and sonicated for 10 minutes. Then, 3g of vinyltrimethoxysilane was added. The reaction temperature was maintained at 65℃, the stirring speed was 150 rpm, and the reaction time was 5 hours. After modification, the nano-silica was filtered, dried, and pulverized to obtain modified nano-silica. The modified nano-silica was then added to toluene, nitrogen gas was introduced into the reaction vessel, and the stirring speed was set to 200 rpm. Azobisisobutyronitrile (1% of the total monomer molar amount) was added as an initiator according to a styrene to methyl methacrylate molar ratio of 3:1 and a total monomer addition to silane coupling agent molar ratio of 1:1. The reaction temperature was maintained at 90℃, and the reaction time was 2 hours. After the reaction, the nano-silica was filtered, dried, and pulverized to obtain an organic-inorganic hybrid flow modifier.

[0078] 2. Prepare low oil-water ratio, high-sealability oil-based drilling fluid

[0079] Maintaining a stirring speed of 11,000 rpm, add 20g of the primary emulsifier fatty acid amide (primary emulsifier DR-EM) and 4g of the secondary emulsifier alkanolamide (secondary emulsifier DR-CO) to 200mL of diesel oil, and stir at high speed for 10min; add 2g of organic clay, and stir at high speed for 10min; add 200mL of CaCl2 aqueous solution (mass concentration of 20%), and stir at high speed for 20min; add 16g of calcium oxide, and stir at high speed for 10min; add 10g of filtration loss reducer, and stir at high speed for 10min; add 6g of the organic-inorganic hybrid flow pattern regulator prepared in step 1, and stir at high speed for 10min; add 8g of broad-spectrum ultrafine calcium, and finally add 216g of ordinary barite and 54g of micronized barite, and stir for 30min to obtain a low oil-water ratio, strong plugging oil-based drilling fluid with an oil-water ratio of 50:50 and a density of 1.4g / cm³. 3 .

[0080] Example 2

[0081] 1. Preparation of organic-inorganic hybrid flow pattern modifiers:

[0082] Same as Example 1.

[0083] 2. Prepare low oil-water ratio, high-sealability oil-based drilling fluid

[0084] Maintaining a stirring speed of 11,000 rpm, add 16g of the primary emulsifier fatty acid amide (primary emulsifier DR-EM) and 4g of the co-emulsifier alkanolamide compound (co-emulsifier DR-CO) to 260mL of diesel oil, and stir at high speed for 10min; add 4g of organic clay, and stir at high speed for 10min; add 140mL of CaCl2 aqueous solution (mass concentration of 20%), and stir at high speed for 20min; add 12g of calcium oxide, and stir at high speed for 10min; add 12g of filtration loss reducer, and stir at high speed for 10min; add 6g of the organic-inorganic hybrid flow pattern regulator prepared in step 1, and stir at high speed for 10min; add 8g of broad-spectrum ultrafine calcium carbonate, and finally add 720g of ordinary barite and 80g of micronized barite, and stir for 30min to obtain a low oil-water ratio, strong plugging oil-based drilling fluid with an oil-water ratio of 65:35 and a density of 2.0g / cm³. 3 .

[0085] Example 3

[0086] 1. Preparation of organic-inorganic hybrid flow pattern modifiers:

[0087] Same as Example 1.

[0088] 2. Prepare low oil-water ratio, high-sealability oil-based drilling fluid

[0089] Maintaining a stirring speed of 11,000 rpm, add 16g of the primary emulsifier fatty acid amide (primary emulsifier DR-EM) and 4g of the co-emulsifier alkanolamide compound (co-emulsifier DR-CO) to 300mL of diesel oil, and stir at high speed for 10min; add 4g of organic clay, and stir at high speed for 10min; add 100mL of CaCl2 aqueous solution (mass concentration of 20%), and stir at high speed for 20min; add 12g of calcium oxide, and stir at high speed for 10min; add 12g of filtration loss reducer, and stir at high speed for 10min; add 6g of the organic-inorganic hybrid flow pattern regulator prepared in step 1, and stir at high speed for 10min; add 8g of broad-spectrum ultrafine calcium carbonate, and finally add 955g of ordinary barite and 238g of micronized barite, and stir for 30min to obtain a low oil-water ratio, strong plugging oil-based drilling fluid with an oil-water ratio of 75:25 and a density of 2.3g / cm³. 3 .

[0090] Example 4

[0091] 1. Preparation of organic-inorganic hybrid flow pattern modifiers:

[0092] 15g of nano-silica was added to 100mL of ethanol / water (90:10) solution and sonicated for 10 minutes. Then, 3g of vinyltrimethoxysilane was added. The reaction temperature was maintained at 65℃, the stirring speed was 150 rpm, and the reaction time was 5 hours. After modification, the nano-silica was filtered, dried, and pulverized to obtain modified nano-silica. The modified nano-silica was then added to toluene, nitrogen gas was introduced into the reaction vessel, and the stirring speed was set to 200 rpm. Azobisisobutyronitrile (1% of the total monomer molar amount) was added as an initiator according to a styrene to methyl methacrylate molar ratio of 2:1 and a total monomer addition to silane coupling agent molar ratio of 1:1. The reaction temperature was maintained at 90℃, and the reaction time was 2 hours. After the reaction, the nano-silica was filtered, dried, and pulverized to obtain an organic-inorganic hybrid flow modifier.

[0093] 2. Prepare low oil-water ratio, high-sealability oil-based drilling fluid

[0094] Same as Example 2.

[0095] Example 5

[0096] 1. Preparation of organic-inorganic hybrid flow pattern modifiers:

[0097] Same as Example 2

[0098] 2. Prepare low oil-water ratio, high-sealability oil-based drilling fluid

[0099] Maintaining a stirring speed of 11,000 rpm, add 16g of the primary emulsifier fatty acid amide (primary emulsifier DR-EM) and 4g of the co-emulsifier alkanolamide compound (co-emulsifier DR-CO) to 260mL of white oil, and stir at high speed for 10min; add 4g of organic clay, and stir at high speed for 10min; add 140mL of CaCl2 aqueous solution (mass concentration of 20%), and stir at high speed for 20min; add 12g of calcium oxide, and stir at high speed for 10min; add 12g of filtration loss reducer, and stir at high speed for 10min; add 6g of the organic-inorganic hybrid flow pattern regulator prepared in step 1, and stir at high speed for 10min; add 8g of broad-spectrum ultrafine calcium carbonate, and finally add 720g of ordinary barite and 80g of micronized barite, and stir for 30min to obtain a low oil-water ratio, strong plugging oil-based drilling fluid with an oil-water ratio of 65:35 and a density of 2.0g / cm³. 3 .

[0100] Comparative Example 1

[0101] No organic-inorganic hybrid flow pattern modifier was used; otherwise, it was the same as in Example 2.

[0102] Comparative Example 2

[0103] Broad-spectrum ultrafine calcium carbonate was not used; otherwise, it was the same as in Example 2.

[0104] Comparative Example 3

[0105] Micronized barite was not used; the amount of ordinary barite added was 800g, and the rest was the same as in Example 2.

[0106] The drilling fluid performance of Examples 1-5 and Comparative Examples 1-3 was tested according to the test method in 16783.2.

[0107] Table 1. Performance of Oil-Based Drilling Fluids in Examples

[0108]

[0109] Table 2 Comparative Performance of Oil-Based Drilling Fluids

[0110]

[0111] Based on the experimental results in Table 1, the five low oil-to-water ratio oil-based drilling fluids prepared in the examples had densities ranging from 1.4 to 2.3 g / cm³. 3 The oil-water ratios of 50:50 to 75:25 all maintained good performance before and after aging at 180℃, with a demulsification voltage ≥600V and a high-temperature, high-pressure filtration loss of less than 3mL. In Example 2, the low oil-water ratio oil-based drilling fluid remained stable after aging at 200℃, exhibiting temperature resistance up to 200℃. In Example 4, the silane coupling agent in the flow pattern modifier was replaced, resulting in minimal impact on the drilling fluid performance. In Example 5, the base oil was replaced with white oil, and apart from a slight increase in overall rheology, no other adverse effects were observed, indicating that the preparation method of this invention is applicable to both diesel and white oil.

[0112] Based on the experimental results in Table 2, the low oil-water ratio oil-based drilling fluids prepared in Comparative Examples 1-3 were compared with those in Example 2. In Comparative Example 1, the absence of an organic-inorganic hybrid flow modifier resulted in significant changes in the drilling fluid's demulsification voltage, rheology, and plugging properties. In particular, the demulsification voltage after aging was below 400V, failing to meet practical field requirements, indicating that the flow modifier in this invention plays a crucial role in stabilizing the system. In Comparative Example 2, the absence of broad-spectrum plugging calcium carbonate led to an increase in high-temperature, high-pressure filtration loss, demonstrating that the preferred composite broad-spectrum calcium carbonate of this invention plays a key role in reducing filtration loss and plugging. In Comparative Example 3, the absence of micronized barite resulted in increased rheology of the drilling fluid system, negatively impacting parameters such as drilling flow rate and pump pressure, indicating that the preferred composite micronized barite and ordinary barite weighting method of this invention have a positive effect on the rheological regulation of low oil-water ratio oil-based drilling fluids.

[0113] The applicant declares that this invention illustrates the low oil-water ratio oil-based drilling fluid, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A low oil-water ratio oil-based drilling fluid, characterized in that, The low oil-water ratio oil-based drilling fluid includes an oil phase, an aqueous phase, an emulsifier, an organic-inorganic hybrid flow pattern modifier, organic clay, a filtration loss reducer, an alkalinity modifier, ultrafine particulate material, and a weighting agent. The oil-water ratio of the drilling fluid is 50:50-75:

25.

2. The low oil-water ratio oil-based drilling fluid according to claim 1, characterized in that, The oil phase is white oil or diesel oil, preferably No. 3 white oil or No. 0 diesel oil; Preferably, the aqueous phase is a salt solution, and the mass fraction of the solute in the salt solution is 20-35%. Preferably, the salt solution is an aqueous solution of calcium chloride, sodium chloride, potassium chloride, or sodium formate.

3. The low oil-water ratio oil-based drilling fluid according to claim 1 or 2, characterized in that, The emulsifier includes a primary emulsifier and a secondary emulsifier; Preferably, the primary emulsifier is a fatty acid amide emulsifier; Preferably, the amount of the main emulsifier added is 3-5% of the total volume of the oil phase and the aqueous phase.

4. The low oil-water ratio oil-based drilling fluid according to any one of claims 1-3, characterized in that, The co-emulsifier is a fatty acid-modified alkanolamide; Preferably, the amount of the co-emulsifier added, expressed in grams, is 1 to 3% of the total volume of the oil and water phases.

5. The low oil-water ratio oil-based drilling fluid according to any one of claims 1-4, characterized in that, The organic-inorganic hybrid flow pattern modifier is nano-silica modified with silane coupling agent and polymer; Preferably, the amount of the organic-inorganic hybrid flow pattern regulator added is 0.5%-2% of the total volume of the oil and water phases, expressed in g. Preferably, the particle size of the nano-silica is 20-100 nanometers; Preferably, the silane coupling agent is selected from one or a combination of at least two of vinyltrimethoxysilane, vinylethoxysilane, and vinyltriethoxysilane; Preferably, the amount of the silane coupling agent is 15% to 50% of the mass of nano-silica.

6. The low oil-water ratio oil-based drilling fluid according to any one of claims 1-5, characterized in that, The polymer monomers are styrene and methyl methacrylate; Preferably, the molar ratio of styrene to methyl methacrylate is 3:1 to 2:1; Preferably, the molar ratio of the polymeric monomer to the silane coupling agent is 1:1 to 2:

1.

7. The low oil-water ratio oil-based drilling fluid according to any one of claims 1-6, characterized in that, The preparation method of the organic-inorganic hybrid flow pattern regulator includes the following steps: (1) Disperse nano-silica in a solvent, add silane coupling agent, react, and obtain silane coupling agent modified nano-silica; (2) Disperse the silane coupling agent-modified nano-silica in an organic solvent, add the polymerization monomer and initiator, and react to obtain the organic-inorganic hybrid flow pattern regulator; Preferably, the dispersion in step (1) is achieved by ultrasonic treatment; Preferably, the solvent in step (1) is a mixture of ethanol and water, and the volume ratio of ethanol to water is 70:30 to 90:

10. Preferably, the reaction in step (1) is carried out under stirring at a speed of 100-300 rpm; Preferably, the reaction in step (1) is carried out at 60°C-70°C for 4 to 6 hours; Preferably, after the reaction in step (1) is completed, the mixture is filtered, washed, dried and pulverized to obtain the silane coupling agent modified nano-silica; Preferably, the washing is performed using anhydrous ethanol or a mixture of ethanol and water, and the washing is preferably performed three times. Preferably, the drying temperature is 60°C and the time is 12 hours; Preferably, the organic solvent in step (2) is toluene; Preferably, the initiator in step (2) is selected from any one or a combination of at least two of azobisisobutyronitrile, ammonium persulfate, or azobiscyclohexyl cyanide; Preferably, the amount of initiator added is 1%-2% of the mass of the polymerizing monomer; Preferably, the reaction temperature in step (2) is 80-90℃ and the reaction time is 3-5 hours; Preferably, the reaction in step (2) is carried out under nitrogen protection; Preferably, after the reaction in step (2) is completed, the product is separated by centrifugation, washed multiple times, and finally dried to obtain an organic-inorganic hybrid flow pattern regulator; Preferably, after the reaction in step (2) is completed, the mixture is washed multiple times with toluene and ethanol to remove unreacted monomers and residual initiators; Preferably, the drying temperature is controlled at 60°C and the time is 10 hours.

8. The low oil-water ratio oil-based drilling fluid according to any one of claims 1-7, characterized in that, The organic soil is organically modified montmorillonite; Preferably, the amount of organic soil added, expressed in grams, is 1-3% of the total volume of the oil and water phases; Preferably, the filtration loss reducing agent is a modified lignite and bitumen-based filtration loss reducing agent; Preferably, the amount of the filtration loss reducing agent added, expressed in grams, is 2-4% of the total volume of the oil and water phases; Preferably, the alkalinity regulator is calcium oxide; Preferably, the amount of alkalinity regulator added, expressed in grams, is 3-5% of the total volume of the oil and aqueous phases; Preferably, the particle size of the ultrafine particulate material is 600-3000 mesh; Preferably, the ultrafine particulate material is ultrafine calcium carbonate; Preferably, the ultrafine calcium carbonate comprises 600 mesh, 1200 mesh, 2000 mesh, and 3000 mesh calcium carbonate in a 1:1:1:1 ratio. Preferably, the amount of the ultrafine particulate material added, expressed in grams, is 3 to 5% of the total volume of the oil and water phases. Preferably, the weighting agent is barite; Preferably, the barite comprises micronized barite; Preferably, the particle size D90 of the micronized barite is less than 5 micrometers, and the particle size D50 is less than 3 micrometers; Preferably, the mass percentage of micronized barite in the barite is 5-20%, more preferably 10%; Preferably, the amount of the weighting agent added, expressed in grams, is 0.5-4.5 times the total volume of the oil and water phases.

9. The method for preparing low oil-water ratio oil-based drilling fluid according to any one of claims 1-8, characterized in that, The preparation method involves uniformly mixing the oil phase, water phase, emulsifier, organic-inorganic hybrid flow pattern modifier, organic clay, filtration loss reducer, alkalinity modifier, ultrafine particulate material, and weighting agent to obtain the low oil-water ratio oil-based drilling fluid.

10. The application of the low oil-water ratio oil-based drilling fluid according to any one of claims 1-8 in deep oil and gas drilling, ultra-deep oil and gas drilling or shale oil and gas drilling.

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