High-temperature-resistant oil-based drilling fluid and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant oil-based drilling fluid and a preparation method thereof. The high-temperature-resistant oil-based drilling fluid comprises white oil, saline water, an emulsifier, modified bentonite and calcium hydroxide, the modified bentonite is obtained by modifying bentonite with a mixed coupling agent, and the mixed coupling agent comprises a titanate coupling agent, an aluminate coupling agent and an aluminum-zirconium coupling agent in a mass ratio of 1: (2-3): (0.5-1). The bentonite is synergistically modified by using three specific coupling agents in a specific mass ratio, so that not only are the standing stability, suspension stability and electrical stability of an oil-based drilling fluid emulsion prepared by taking white oil as an oil phase effectively improved, but also the high temperature resistance of the oil-based drilling fluid is remarkably improved, the long-term suspension stability can be maintained at 232 DEG C, and the oil-based drilling fluid has a good application prospect. And the construction stability and safety of drilling deep wells and ultra-deep wells can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil-based drilling fluid, and particularly relates to a high-temperature-resistant oil-based drilling fluid and a preparation method thereof. BACKGROUND

[0002] With the global oil and gas resources exploration and development extending to deep strata and complex geological structures (such as deep sea, ultra-deep well, shale oil and gas, etc.), the high-temperature and high-pressure environment faced by drilling operations is becoming increasingly severe. Under such harsh conditions, water-based drilling fluids often cannot meet the operation requirements due to the sharp deterioration of performance, therefore, oil-based drilling fluids with excellent lubricity, inhibition and thermal stability become an indispensable technical choice. The core of the oil-based drilling fluid lies in the stability of the system, especially the long-term maintenance of suitable rheological property and suspension stability under high temperature and high pressure, so as to prevent the failure of drilling fluid function and ensure the safety of wellbore. In the oil-based drilling fluid, organic bentonite can form a three-dimensional network structure, enhance the suspension and cleaning capacity of the drilling fluid, and also reduce the filtration loss, so the organic bentonite is often called "flow type regulator" and "filtration loss reducer", and is an important component indispensable to the oil-based drilling fluid.

[0003] Due to the strong hydrophilicity of bentonite, its dispersibility in non-polar medium is poor, so the surface modification is often performed on the bentonite to improve the stability. The modified bentonite is called organic bentonite, which has good rheological property and cuttings carrying capacity, and can effectively lubricate drilling and prevent corrosion. At present, the surface modification methods for bentonite include surfactant method and surface grafting method, etc., but the physical adsorption of surfactant and the chemical bond formed by surface grafting are relatively weak, and under high temperature and high pressure environment, the combination between the modifier and the solid particles is easily destroyed, the modifier molecules are detached from the solid particles, which leads to the occurrence of oil-water separation or particle aggregation, etc., resulting in the instability of the oil-based drilling fluid system and seriously threatening the safety of drilling operations.

[0004] In addition, for environmental protection consideration, the use of biologically friendly base oil (such as white oil) to replace traditional mineral oil has become an important development trend. However, such biologically friendly oil phase usually has special polarity and molecular structure, and there is a problem of poor adaptability between the traditional organic bentonite optimized for mineral oil. Direct use often leads to insufficient dispersion of organic bentonite, low swelling efficiency, and difficulty in forming a gel structure with sufficient strength, so that the drilling fluid performs poorly in the initial configuration stage, and it is even more difficult to withstand the test of high temperature aging.

[0005] Therefore, there is an urgent need for an oil-based drilling fluid which can maintain long-term system stability at high temperature, so as to be suitable for drilling of deep well and ultra-deep well. SUMMARY

[0006] To solve the problem that the oil phase of the current oil-based drilling fluid and the organic bentonite have poor adaptability, and the poor high-temperature stability of the organic bentonite leads to the difficulty of keeping the prepared oil-based drilling fluid stable for a long time, especially in a high-temperature environment, and the system is prone to instability, the present application provides a high-temperature-resistant oil-based drilling fluid and a preparation method thereof, wherein three specific coupling agents with specific mass ratios are used to modify the bentonite in a synergistic manner, which not only effectively improves the standing stability, suspension stability and electrical stability of the oil-based drilling fluid emulsion prepared by using white oil as the oil phase, but also significantly improves the high-temperature resistance of the oil-based drilling fluid, and the long-term suspension stability can be maintained at 232 DEG C, thereby effectively improving the construction stability and safety of drilling deep and ultra-deep wells.

[0007] Specifically, the following technical solutions are provided:

[0008] The first aspect of the present application provides a high-temperature-resistant oil-based drilling fluid, which comprises white oil, salt water, emulsifier, modified bentonite and calcium hydroxide; the modified bentonite is obtained by modifying the bentonite with a mixed coupling agent, and the mixed coupling agent comprises a titanate coupling agent, an aluminate coupling agent and an aluminum-zirconium coupling agent with a mass ratio of 1:(2-3):(0.5-1).

[0009] The present application optimizes the types of modifiers for bentonite, uses a specific mixed coupling agent to modify and treat bentonite, so that the modified bentonite has better adaptability with white oil-based drilling fluid, and effectively improves the system stability of the oil-based drilling fluid under high-temperature conditions. Specifically as follows:

[0010] The present application uses three coupling agents, i.e., a titanate coupling agent, an aluminate coupling agent and an aluminum-zirconium coupling agent, to modify and treat bentonite in a synergistic manner. On the one hand, the titanate coupling agent has high reactivity and can quickly react with the hydroxyl groups on the surface of bentonite, thereby greatly reducing the surface energy of the particles, preventing the agglomeration of bentonite, and achieving good dispersion. At the same time, the titanate coupling agent can effectively break the interaction between the layers of bentonite, significantly reduce the apparent viscosity of the drilling fluid system, and improve its flowability during circulation, thereby reducing the pump pressure loss. The addition of the aluminate coupling agent is conducive to forming a more compact coating on the surface of bentonite, thereby effectively improving the thermal stability of the modified bentonite, so that it can maintain structural stability in a high-temperature downhole environment and avoid deterioration of the stability of the drilling fluid system due to high temperature. On this basis, the present application further introduces an appropriate amount of aluminum-zirconium coupling agent, which forms intermolecular forces between the zirconium with strong oxygen affinity on the surface of bentonite and the functional groups of the titanate and aluminate, thereby playing a bridging and reinforcing role, so that the modified layer is more firm, and the structural stability of the modified bentonite is further improved. Under the synergistic action of the above three coupling agents, the modified bentonite not only has good dispersibility and high thermal stability, but also has high adaptability with white oil, so that the white oil-based drilling fluid containing the above modified bentonite can maintain long-term stability under high-temperature conditions.

[0011] In addition, in this invention, in order to take into account the dispersibility and high-temperature stability of modified bentonite in oil-based drilling fluids, the addition amounts of titanate coupling agent, aluminate coupling agent and aluminum zirconium coupling agent in the coupling agent used for modified bentonite need to be controlled within a suitable range, for example, 1:(2-3):(0.5-1). If the mass ratio of titanate coupling agent in the coupling agent is less than 1 / 4, the prepared modified bentonite cannot be effectively dispersed in oil-based drilling fluids. If the mass ratio of titanate coupling agent in the coupling agent is greater than 1 / 2, although the prepared modified bentonite has good dispersibility in oil-based drilling fluids, the aluminate coupling agent and aluminum zirconium coupling agent are insufficient to form a dense and stable protective layer, resulting in a significant decrease in the rheological properties of the modified bentonite after high-temperature aging, making it unsuitable for use in high-temperature downhole environments. Extensive experiments have shown that the addition amounts of titanate coupling agent, aluminate coupling agent and alumina-zirconium coupling agent in the coupling agent of modified bentonite need to be controlled within the range of 1:(2-3):(0.5-1), for example 1:2.5:0.75. The modified bentonite prepared can achieve both excellent dispersibility and high-temperature stability in oil-based drilling fluids.

[0012] In this invention, the calcium hydroxide in the oil-based drilling fluid is in a finely dispersed state, which is beneficial to improving the structural strength of the system, increasing the thermal stability of the system, and can be used to adjust the pH value of the system to meet the requirements of the system.

[0013] Furthermore, the mass ratio of the mixed coupling agent to the bentonite is 1:100-1:10.

[0014] Furthermore, the white oil in the high-temperature resistant oil-based drilling fluid is No. 3 white oil.

[0015] Furthermore, the brine is a calcium chloride aqueous solution with a mass concentration of 25 wt%.

[0016] Further, the emulsifier includes a primary emulsifier and a secondary emulsifier; preferably, the primary emulsifier is Schlumberger EZ-MUL, the secondary emulsifier is Baker Hughes VERSACOAT, and the mass ratio of the primary emulsifier to the secondary emulsifier is 2:1.

[0017] Furthermore, the bentonite is sodium-based bentonite.

[0018] Furthermore, the particle size of the modified bentonite is preferably less than 75 μm. The particle size of the modified bentonite directly affects the dispersibility and gelation efficiency of the sample. The finer the particles, the easier they are to disperse, and the larger the specific surface area. The solvent can penetrate into the interior of the particles more quickly, causing the interlayer to expand rapidly, thereby forming a gel more quickly, achieving a higher final viscosity, and making the three-dimensional network structure more uniform and stable.

[0019] Furthermore, the volume ratio of white oil to brine in the high-temperature resistant oil-based drilling fluid is preferably 7.5:2.5-8.5:1.5, and more preferably 8:2.

[0020] Furthermore, the mass percentage of emulsifier in the high-temperature oil-based drilling fluid is preferably 3%-5%, such as 3%, 4%, 5%, etc., including but not limited to the mass percentages listed above.

[0021] Furthermore, the modified bentonite in the high-temperature oil-based drilling fluid preferably accounts for 3%-5% by mass, such as 3%, 4%, 5%, etc., including but not limited to the mass percentages listed above.

[0022] Furthermore, the mass percentage of calcium hydroxide in the high-temperature resistant oil-based drilling fluid is preferably 3%-5%, such as 3%, 4%, 5%, etc., including but not limited to the mass percentages listed above.

[0023] Furthermore, the high-temperature resistant oil-based drilling fluid also contains barite to increase the concentration of the dispersed phase, thereby increasing the viscosity shear of the system and reducing the filtration loss. The mass percentage of barite in the high-temperature resistant oil-based drilling fluid does not exceed 25%, for example, 5%, 10%, 15%, 20%, etc.

[0024] Furthermore, the preparation of the modified bentonite includes the following steps: adding titanate coupling agent, aluminate coupling agent and aluminum zirconium coupling agent into a solvent and stirring evenly, then adding bentonite and heating and stirring, separating the solid, and washing and drying to obtain the modified bentonite; preferably, the temperature of the heating and stirring treatment is 50-70℃ and the time is not less than 4h.

[0025] Furthermore, the high-temperature resistant oil-based drilling fluid meets the following conditions: after aging at 232℃ for 16 hours, the emulsion, after standing at 25±5℃ for 5 days, has a stability rate of not less than 95%, a sedimentation factor of not more than 0.51, and a demulsification voltage of not less than 1000V, more preferably, a demulsification voltage of not less than 1200V.

[0026] A second aspect of this invention provides a method for preparing the high-temperature resistant oil-based drilling fluid described in the first aspect, comprising the following steps:

[0027] S1. According to the formula amount, mix the white oil and emulsifier evenly, then add modified bentonite, calcium hydroxide, barite and brine for the first stirring treatment to obtain an emulsion.

[0028] S2. The emulsion is subjected to constant temperature rolling under a protective atmosphere and aging temperature, and after cooling to room temperature, it is subjected to a second stirring treatment to obtain the high temperature resistant oil-based drilling fluid.

[0029] Furthermore, in step S1, the speed of the first stirring treatment is preferably 8000-15000 rpm, and the time is preferably 20-60 min.

[0030] Further, in step S2, the aging temperature is preferably 60-232℃, and the rolling time is preferably 8-16h; the speed of the second stirring treatment is preferably 8000-15000rpm, and the time is preferably 20-60min.

[0031] The beneficial effects of this invention are:

[0032] This invention provides a high-temperature resistant oil-based drilling fluid. It employs three coupling agents—titanium ester coupling agent, aluminate coupling agent, and aluminum zirconium coupling agent—in a specific mass ratio to synergistically modify bentonite. This not only effectively improves the static stability, suspension stability, and electrical stability of the oil-based drilling fluid emulsion prepared with white oil as the oil phase, but also significantly enhances the high-temperature resistance of the oil-based drilling fluid. It can maintain long-term suspension stability at 232℃, which is beneficial for improving the construction stability and safety of drilling deep and ultra-deep wells.

[0033] The coupling agent used in this invention for modifying bentonite has a high proportion of low-cost aluminate coupling agent, which helps to reduce the production cost of the product.

[0034] The high-temperature resistant oil-based drilling fluid provided by this invention uses bio-friendly white oil as the oil phase. The prepared oil-based drilling fluid is non-toxic, harmless, and environmentally friendly. Attached Figure Description

[0035] Figure 1 A schematic diagram of the process flow for preparing modified bentonite in Example 1;

[0036] Figure 2 Images of the oil-based drilling fluid prepared in Example 1 after high-temperature aging and standing for different times;

[0037] Figure 3 Images of the oil-based drilling fluid prepared in Example 2 after high-temperature aging and standing for different times;

[0038] Figure 4 Images of the oil-based drilling fluid prepared for Comparative Example 1 after high-temperature aging and standing for different times;

[0039] Figure 5 Images of the oil-based drilling fluid prepared for Comparative Example 2 after being aged at high temperature and left to stand for different times;

[0040] Figure 6 Images of the oil-based drilling fluid prepared for Comparative Example 3 after being aged at high temperature and left to stand for different times. Detailed Implementation

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. The terms “comprising” or “including” as used herein may also be replaced with the closed form “is” or “consisting of”.

[0042] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0043] The manufacturers and models of the raw materials used in the following examples and comparative examples are as follows:

[0044]

[0045] Example 1

[0046] This embodiment relates to the preparation of a high-temperature resistant oil-based drilling fluid, specifically including the following steps:

[0047] (1) Preparation of modified bentonite: 2g of titanate coupling agent, 5g of aluminate coupling agent and 1.5g of aluminum zirconium coupling agent were added to 1000mL of anhydrous ethanol, and then 100g of bentonite particles were added and stirred in a water bath at 60℃ for 5h. After centrifugation, washing, drying, grinding and sieving, modified bentonite with a particle size of 44-75μm was obtained. The mass ratio of titanate coupling agent to aluminate coupling agent and aluminum zirconium coupling agent was 1:2.5:0.75.

[0048] (2) Preparation of oil-based drilling fluid: Add 3g of emulsifier (2g Schlumberger EZ-MUL + 1g Baker Hughes VERSACOAT) to 80mL of No. 3 white oil and stir at 15000rpm for 20min; then add 3g of modified bentonite, 3g of calcium hydroxide, 25g of barite and 20mL of 25% calcium chloride aqueous solution, and stir at 15000rpm for 20min to obtain an emulsion. The volume ratio of white oil to 25% calcium chloride aqueous solution is 8:2.

[0049] (3) The emulsion prepared in step (2) is loaded into an ultra-high temperature pressure vessel, filled with nitrogen, placed in a roller heating furnace, and rolled at a constant temperature of 232°C for 16 hours. After naturally cooling to room temperature, it is taken out and stirred at a speed of 15000rpm for 20 minutes to obtain a high temperature resistant oil-based drilling fluid.

[0050] The static stability, suspension stability, and electrical stability of the emulsion of the high-temperature resistant oil-based drilling fluid after high-temperature aging were tested after standing at 25±5℃ for 5 days. The specific test methods are as follows:

[0051] Static stability: Pour the emulsion into a stoppered graduated cylinder and record its initial volume (V). s ), observe the oil separation (V) of the emulsion at regular intervals. o ), water separation (V) w The stability of an emulsion (E, %) is equal to the remaining emulsion volume (V) at a given moment. s -V o -V w ) and the initial emulsion volume V s The ratio.

[0052] Suspension stability: The emulsion was poured into a stoppered graduated cylinder, and the density at the top and bottom of the drilling fluid column was measured. The suspension factor SF of the emulsion = bottom density / bottom plus top density. Generally, it is considered that when SF = 0.50, no static sedimentation occurred in the drilling fluid system; when SF > 0.52, static sedimentation was significant, and the suspension performance was poor.

[0053] Electrical stability: The electrical stability meter is calibrated, and then the electrode probe is inserted into the emulsion. The voltage is increased to a critical value, which is the emulsion demulsification voltage (ES). Each sample is tested in parallel three times, and the average value is taken.

[0054] The test results are as follows: the emulsion stability rate is 99%, the sedimentation factor SF is 0.5, and the demulsification voltage is 1315V.

[0055] Example 2

[0056] This embodiment relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that the mass ratio of titanate coupling agent to aluminate coupling agent and alumina-zirconium coupling agent is 1:2:1, and the total mass of the added mixed coupling agent is the same as in Example 1; all other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0057] The high-temperature resistant oil-based drilling fluid prepared in this embodiment, after being aged at high temperature, has an emulsion stability rate of 97% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.51, and a demulsification voltage of 1231V.

[0058] Example 3

[0059] This embodiment relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that the mass ratio of titanate coupling agent to aluminate coupling agent and aluminozirconium coupling agent is 1:3:0.5, and the total mass of the mixed coupling agent added is the same as in Example 1; all other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0060] The high-temperature resistant oil-based drilling fluid prepared in this embodiment, after being aged at high temperature, has an emulsion stability rate of 98% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.51, and a demulsification voltage of 1285V.

[0061] Example 4

[0062] This embodiment relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that the volume ratio of white oil to 25% calcium chloride aqueous solution is 7.5:2.5, and the total volume of white oil and 25% calcium chloride aqueous solution is the same as in Example 1. All other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0063] The high-temperature resistant oil-based drilling fluid prepared in this embodiment, after being aged at high temperature, has an emulsion stability rate of 97% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.51, and a demulsification voltage of 1145V.

[0064] Example 5

[0065] This embodiment relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that the volume ratio of white oil to 25% calcium chloride aqueous solution is 8.5:1.5, and the total volume of white oil and 25% calcium chloride aqueous solution is the same as in Example 1. All other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0066] The high-temperature resistant oil-based drilling fluid prepared in this embodiment, after being aged at high temperature, has an emulsion stability rate of 97% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.51, and a demulsification voltage of 1069V.

[0067] Comparative Example 1

[0068] This comparative example relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that no modified bentonite was added to the oil-based drilling fluid; all other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0069] The high-temperature resistant oil-based drilling fluid prepared in this comparative example, after being aged at high temperature, showed an emulsion stability rate of 62% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.55, and a demulsification voltage of 223V.

[0070] Comparative Example 2

[0071] This comparative example relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that an equal amount of unmodified bentonite is added to the oil-based drilling fluid to replace the modified bentonite; all other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0072] The high-temperature resistant oil-based drilling fluid prepared in this comparative example, after being aged at high temperature, showed an emulsion stability rate of 74% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.54, and a demulsification voltage of 351V.

[0073] Comparative Example 3

[0074] This comparative example relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that an equal volume of environmentally friendly synthetic oil is used instead of white oil; all other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0075] The high-temperature resistant oil-based drilling fluid prepared in this comparative example, after being aged at high temperature, showed an emulsion stability rate of 92% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.52, and a demulsification voltage of 425V.

[0076] Comparative Example 4

[0077] This comparative example relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that an equal amount of silane coupling agent is used to replace the titanate coupling agent, aluminate coupling agent, and aluminum zirconium coupling agent; all other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0078] The high-temperature resistant oil-based drilling fluid prepared in this comparative example, after being aged at high temperature, showed an emulsion stability rate of 93% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.51, and a demulsification voltage of 596V.

[0079] Comparative Example 5

[0080] This comparative example relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that an equal amount of titanate coupling agent is used instead of aluminate coupling agent and aluminum zirconium coupling agent; all other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0081] The high-temperature resistant oil-based drilling fluid prepared in this comparative example, after being aged at high temperature, showed an emulsion stability rate of 95% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.52, and a demulsification voltage of 387V.

[0082] Comparative Example 6

[0083] This comparative example relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that an equal amount of aluminum zirconium coupling agent is used to replace the titanate coupling agent and the aluminate coupling agent; all other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0084] The high-temperature resistant oil-based drilling fluid prepared in this comparative example, after being aged at high temperature, showed an emulsion stability rate of 95% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.51, and a demulsification voltage of 837V.

[0085] Comparative Example 7

[0086] This comparative example relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that the mass ratio of titanate coupling agent to aluminate coupling agent and aluminozirconium coupling agent is 1:1:1, and the total mass of the mixed coupling agent added is the same as in Example 1; all other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0087] The high-temperature resistant oil-based drilling fluid prepared in this embodiment, after being aged at high temperature, has an emulsion stability rate of 94% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.52, and a demulsification voltage of 643V.

[0088] Comparative Example 8

[0089] This comparative example relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that the volume ratio of white oil to 25% calcium chloride aqueous solution is 7:3, and the total volume of white oil and 25% calcium chloride aqueous solution is the same as in Example 1. All other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0090] The high-temperature resistant oil-based drilling fluid prepared in this embodiment, after being aged at high temperature, has an emulsion stability rate of 65% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.55, and a demulsification voltage of 357V.

[0091] Comparative Example 9

[0092] This comparative example relates to the preparation of a high-temperature resistant oil-based drilling fluid. The only difference from Example 1 is that the volume ratio of white oil to 25% calcium chloride aqueous solution is 9:1, and the total volume of white oil and 25% calcium chloride aqueous solution is the same as in Example 1. All other operations are the same, and the corresponding high-temperature resistant oil-based drilling fluid is prepared.

[0093] The high-temperature resistant oil-based drilling fluid prepared in this embodiment, after being aged at high temperature, has an emulsion stability rate of 59% after standing for 5 days at 25±5℃, a sedimentation factor (SF) of 0.55, and a demulsification voltage of 376V.

[0094] The relevant process parameters and performance data of the oil-based drilling fluids prepared in the above embodiments and comparative examples are summarized in Table 1 below:

[0095] Table 1

[0096]

[0097]

[0098] In the table: Ti represents titanate coupling agent, Al represents aluminate coupling agent, Al-Zr represents aluminum-zirconium coupling agent, Si represents silane coupling agent, and V represents... 油相 V represents the volume of the oil phase. 水相 This indicates the volume of a 25% calcium chloride aqueous solution.

[0099] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A high-temperature resistant oil-based drilling fluid, characterized in that, The high-temperature resistant oil-based drilling fluid comprises white oil, brine, emulsifier, modified bentonite, and calcium hydroxide; the modified bentonite is obtained by modifying bentonite with a mixed coupling agent, the mixed coupling agent comprising titanate coupling agent, aluminate coupling agent, and aluminum zirconium coupling agent in a mass ratio of 1:(2-3):(0.5-1).

2. The high-temperature resistant oil-based drilling fluid according to claim 1, characterized in that, The white oil in the high-temperature resistant oil-based drilling fluid is No. 3 white oil; The brine is a calcium chloride aqueous solution with a mass concentration of 25 wt%. The emulsifier includes a primary emulsifier and a secondary emulsifier; preferably, the primary emulsifier is Schlumberger EZ-MUL, the secondary emulsifier is Baker Hughes VERSACOAT, and the mass ratio of the primary emulsifier to the secondary emulsifier is 2:

1. The bentonite is sodium-based bentonite; The modified bentonite has a particle size of less than 75 μm.

3. The high-temperature resistant oil-based drilling fluid according to claim 1 or 2, characterized in that, It must contain at least one of the following characteristics: (1) The volume ratio of white oil to brine in the high-temperature resistant oil-based drilling fluid is 7.5:2.5-8.5:1.5; (2) The emulsifier in the high-temperature resistant oil-based drilling fluid accounts for 3%-5% of the total mass; (3) The modified bentonite in the high-temperature oil-based drilling fluid accounts for 3%-5% of the total mass. (4) The mass percentage of calcium hydroxide in the high-temperature resistant oil-based drilling fluid is 3%-5%.

4. The high-temperature resistant oil-based drilling fluid according to claim 3, characterized in that, The high-temperature resistant oil-based drilling fluid also contains barite, and the mass percentage of barite in the high-temperature resistant oil-based drilling fluid does not exceed 25%.

5. The high-temperature resistant oil-based drilling fluid according to claim 3, characterized in that, The volume ratio of white oil to brine in the high-temperature resistant oil-based drilling fluid is 8:

2. The mass ratio of titanate coupling agent, aluminate coupling agent and aluminum zirconium coupling agent in the mixed coupling agent is 1:2.5:0.

75.

6. The high-temperature resistant oil-based drilling fluid according to claim 1, characterized in that, The preparation of the modified bentonite includes the following steps: Titanate coupling agent, aluminate coupling agent and aluminum zirconium coupling agent are added to solvent and stirred evenly. Then bentonite is added and heated and stirred. The solid is separated, washed and dried to obtain the modified bentonite. The heating and stirring treatment is performed at a temperature of 50-70℃ for a time of not less than 4 hours. The ratio of the total mass of the titanate coupling agent, aluminate coupling agent, and alumina-zirconium coupling agent to the mass of the bentonite is 1:100-1:

10.

7. The high-temperature resistant oil-based drilling fluid according to claim 1, characterized in that, The high-temperature resistant oil-based drilling fluid meets the following conditions: after aging at 232℃ for 16 hours, the emulsion, after standing at 25±5℃ for 5 days, has a stability rate of not less than 95%, a sedimentation factor of not more than 0.51, and a demulsification voltage of not less than 1000V.

8. A method for preparing a high-temperature resistant oil-based drilling fluid according to any one of claims 1-7, characterized in that, Includes the following steps: S1. According to the formula amount, mix the white oil and emulsifier evenly, then add modified bentonite, calcium hydroxide, barite and brine for the first stirring treatment to obtain an emulsion. S2. The emulsion is subjected to constant temperature rolling under a protective atmosphere and aging temperature, and after cooling to room temperature, it is subjected to a second stirring treatment to obtain the high temperature resistant oil-based drilling fluid.

9. The preparation method according to claim 8, characterized in that, In step S1, the first stirring process is carried out at a speed of 8000-15000 rpm for a time of 20-60 min.

10. The preparation method according to claim 8, characterized in that, In step S2, the aging temperature is 60-232℃ and the rolling time is 8-16h; The second stirring process is carried out at a speed of 8000-15000 rpm for 20-60 minutes.

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