Preparation method and application of high-temperature-resistant organic modified bentonite

Abstract

The invention relates to a preparation method and application of high-temperature-resistant organic modified bentonite. According to the method, three organic modifiers of long-chain quaternary ammonium salt, amide and a silane coupling agent are compounded to modify bentonite, and the problem that a single modifier is easy to decompose at high temperature is solved through the synergistic effect of physical intercalation, chemical crosslinking and interface bonding; and secondly, a three-dimensional stable structure is constructed by adding nano silicon dioxide and a composite modifier, so that the high temperature resistance and dispersion stability of the modified bentonite are further enhanced. According to the invention, the requirements of deep well and ultra-deep well drilling fluids on the temperature resistance and rheological property of the treating agent can be met, and the ultra-deep well drilling fluid which can tolerate the high temperature of 250-300 DEG C, and is low in filter loss and good in dispersion stability can be obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil drilling engineering, and particularly relates to a preparation method and application of high-temperature-resistant organically modified bentonite. BACKGROUND

[0002] As the "blood" of drilling engineering, drilling fluid has the key functions of carrying suspended cuttings, balancing formation pressure, lubricating and cooling drilling tools, stabilizing the borehole, protecting the reservoir, and transmitting hydrodynamic force. With the breakthrough of the first million-meter scientific exploration well "Shengdi Ta Ke 1 Well" in China, deep resource exploration has become a "must-win" place to ensure energy independence. The ultra-deep well drilling fluid needs to serve in an extreme environment consisting of high temperature (over 220℃), high pressure (over 100MPa), strongly corrosive geological fluids (containing H2S, CO2 and high salinity formation water), and complex formation lithology (shale, salt and gypsum layers, etc.). Compared with water-based drilling fluid, oil-based drilling fluid has good high-temperature resistance, and also has the abilities of anti-sloughing, lubrication and anti-pollution, and has become the research focus in the field of deep well and ultra-deep well drilling fluid technology. Among them, organic clay is the key factor to determine the high-temperature stability of drilling fluid. Adding organic bentonite to oil-based drilling fluid can well increase viscosity and reduce filtration loss and stabilize the well wall, which directly affects the high-temperature resistance, rheological properties and cuttings carrying efficiency of drilling fluid. For example, Chinese patent CN106542536A discloses a preparation method of high-performance organic bentonite for oil-based drilling fluid, which effectively improves the rheological properties, anti-filtration properties and cuttings carrying capacity of the organic sodium-based bentonite for drilling fluid by quaternary ammonium salt modification, but the high-temperature resistance is not optimized; Chinese patent CN104004503A discloses a high-temperature-resistant organic clay for drilling and a preparation method thereof, which introduces a chelating agent to enhance the binding force between quaternary ammonium salt and clay, and introduces sulfonated polystyrene-based ammonium to change the interlayer structure of the organic clay and improve its temperature resistance. The obtained organic modified bentonite can be used in oil-based drilling fluid with white oil, diesel oil and gas oil as base fluid, and the temperature resistance can reach 220℃, but its high-temperature resistance still needs to be further improved.

[0003] In the prior art, organic modified bentonite improves its lipophilicity by introducing organic groups, but traditional organic modifiers (such as single quaternary ammonium salt) are easily decomposed at high temperature, resulting in limited temperature resistance (usually not more than 150℃) of the modified bentonite. At the same time, the existing preparation methods mostly use single modification process, which is difficult to balance the high-temperature resistance and dispersibility, and is easy to flocculate in high salinity drilling fluid, further limiting its application range. Therefore, developing a preparation method of organic modified bentonite with good high-temperature resistance (above 250℃), low filtration loss and good dispersion stability has become the key to solving the technical problems of deep well drilling fluid. SUMMARY

[0004] The present application aims to overcome the defects of insufficient high-temperature resistance and poor dispersion stability in high salinity environment of the existing organically modified bentonite, and provides a preparation method and application of high-temperature resistant organically modified bentonite. The method uses three organic modifiers, long-chain quaternary ammonium salt, amide and silane coupling agent, to modify the bentonite. Through the synergistic effect of "physical intercalation-chemical crosslinking-interface bonding", the problem of easy decomposition of single modifier at high temperature is solved. Secondly, by adding nano-silicon dioxide and composite modifier to build a three-dimensional stable structure, the high-temperature resistance and dispersion stability of the modified bentonite are further enhanced. The present application can meet the requirements of drilling fluid for deep well and ultra-deep well drilling on the temperature resistance and rheological properties of the treating agent, and obtain an ultra-deep well drilling fluid which can withstand high temperature of 250-300 DEG C, has low filtration loss and good dispersion stability.

[0005] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0006] A preparation method and application of high-temperature resistant organically modified bentonite, the method comprising the following steps:

[0007] (1) 60-70 parts by weight of sodium-based bentonite is dispersed in 480-560 parts by weight of deionized water, and after high-speed stirring at a speed of 8000-10000 r / min for 2-3 h, the obtained bentonite slurry is sieved and recorded as A;

[0008] (2) The long-chain quaternary ammonium salt is added to anhydrous ethanol, and then the amide and the silane coupling agent are added respectively. After high-speed stirring at a speed of 8000-10000 r / min for 2-3 h, a composite organic modifier solution is obtained and recorded as B;

[0009] The mass ratio of the long-chain quaternary ammonium salt, the amide and the silane coupling agent is 18-30:6-10:6-10, the mass ratio of the anhydrous ethanol and the long-chain quaternary ammonium salt is 18-30:50-70, and the mass of the composite organic modifier is calculated based on the sum of the masses of the long-chain quaternary ammonium salt, the amide and the silane coupling agent. Preferably, the mass ratio of the long-chain quaternary ammonium salt, the amide and the silane coupling agent is 2-3:1:1;

[0010] The long-chain quaternary ammonium salt is octadecyl trimethyl ammonium chloride or dioctadecyl dimethyl ammonium chloride;

[0011] The amide is N-hydroxymethyl acrylamide or N,N'-methylene bisacrylamide;

[0012] The silane coupling agent is gamma-aminopropyl triethoxysilane or gamma-mercaptopropyl trimethoxysilane.

[0013] (3) The bentonite slurry A is heated to 80-90 DEG C, the pH value is adjusted to 8-9, and the composite organic modifier solution B is added dropwise. After the dropwise addition is completed, the mixture is stirred at a constant temperature of 90-95 DEG C for 4-5 h;

[0014] The mass ratio of the composite organic modifier to bentonite is 1:8-10;

[0015] (4) 1-2% of nano-silica based on the mass of bentonite is added, and stirring is continued for 0.5-2 hours to complete the modification reaction;

[0016] The particle size of the nano-silica is 20-50 nm.

[0017] (5) The reaction product is filtered to form a filter cake, which is dried at 100-120°C, crushed, and sieved to obtain the finished high-temperature resistant organically modified bentonite.

[0018] The high-temperature resistant organically modified bentonite prepared by the method is used as a mud-making agent in oil-based drilling fluid resistant to temperatures above 250°C.

[0019] Specifically includes the following steps:

[0020] (1) 70-85 parts by weight of diesel-based fluid is placed in a high-speed stirring kettle, stirring is started (rotation speed 800-1000 r / min), and the temperature is raised to 40-50°C for constant temperature standby;

[0021] (2) Under stirring, 3-8 parts by weight of the high-temperature resistant organically modified bentonite is added to the base fluid, the rotation speed is increased to 1500-2000 r / min, and shearing dispersion is performed for 30-40 min until the bentonite is completely swollen to form a uniform suspension;

[0022] (3) The rotation speed is maintained at 1500 r / min, 2-5 parts by weight of emulsifier (Span-80 mixed with Tween-80 at a ratio of 3:1) and 1-3 parts by weight of sodium dodecyl benzene sulfonate wetting agent are added in sequence, and stirring is continued for 20-30 min to form a preliminary emulsion system;

[0023] (4) The rotation speed is reduced to 800-1000 r / min, 2-5 parts by weight of sulfonated asphalt fluid loss reducer and 0.5-2 parts by weight of calcium oxide alkalinity regulator are added, and stirring is performed for 15-20 min to disperse the additives;

[0024] (5) 5-15 parts by weight of calcium chloride aqueous solution (20-30% concentration) is added dropwise, the dropwise addition rate is controlled at 1-2 parts by weight / min, and after the dropwise addition is completed, stirring (800-1000 r / min) is maintained for 30-40 min to form a stable water-in-oil emulsion system;

[0025] (6) 1-30 parts by weight of barite weighting agent is added to the system, and stirring (800-1000 r / min) is performed for 60-90 min until complete dispersion to obtain oil-based drilling fluid resistant to temperatures above 250°C.

[0026] The preparation method of the high-temperature resistant organic modified bentonite for drilling fluid, other raw materials, reagents and equipment involved in addition to the bentonite are obtained through a known way, and the operation process can be mastered by the person skilled in the art.

[0027] The substantial features of the present application are:

[0028] The long-chain quaternary ammonium salt, amide and silane coupling agent are innovatively compounded in a mass ratio of 2-3:1:1, the space steric hindrance effect of the long-chain quaternary ammonium salt, the cross-linking network stability of the amide and the covalent bond connection characteristics of the silane coupling agent are utilized, a multiple action mechanism of 'physical intercalation-chemical cross-linking-interface bonding' is formed, the problem of easy decomposition of a single modifier at high temperature is solved. After the modification reaction, nano-silicon dioxide with a specific particle size (20-50 nm) is added, can interact with the organic modifier and the groups on the surface of the bentonite, can also fill the interlayer pores of the bentonite, disperses the local stress at high temperature, and together with the composite modifier, a three-dimensional stable structure is constructed, so that the upper limit of the temperature resistance is increased to 250-300 DEG C, and the filtration loss is controlled to be less than 8 mL.

[0029] The present application has the following outstanding substantial features and significant progress compared with the prior art:

[0030] (1) excellent high-temperature resistance: through the synergistic effect of the composite organic modifier and nano-silicon dioxide, the obtained modified bentonite can withstand high temperature above 250 DEG C, which is significantly higher than the high temperature resistance of 220 DEG C of the traditional organic modified bentonite.

[0031] (2) low filtration loss: under the condition of high temperature above 250 DEG C, the filtration loss is less than or equal to 8 mL (API standard), which is much lower than the filtration loss of 30-40 mL of the traditional organic bentonite.

[0032] (3) good dispersion stability: after composite modification, the bentonite is uniformly dispersed in the drilling fluid, and no obvious stratification occurs after standing for 24 hours, and the stratification volume ratio (clear layer + sediment layer) is less than or equal to 10%.

[0033] (4) good reproducibility: the present application utilizes the synergistic effect of the composite organic modifier and nano-silicon dioxide to modify the bentonite, and the preparation process is relatively simple, and the inclusivity of experimental parameters is relatively high.

[0034] The present application provides a preparation method and application of a high-temperature resistant organic modified bentonite, utilizes the multiple action mechanism of 'physical intercalation-chemical cross-linking-interface bonding' of the composite modifier to solve the problem of easy decomposition of a single modifier at high temperature, and further introduces the nano-silicon dioxide particles with a surface rich in hydroxyl groups to interact with the composite modifier and the groups on the surface of the bentonite, and together with the composite modifier, a three-dimensional stable structure is constructed, so that the high-temperature resistance of the organic modified bentonite is improved. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Figure 1 is a comparison chart of the contact angle measurement results of the samples before and after modification of the bentonite. DETAILED DESCRIPTION

[0036] The application will be described in detail below with specific examples, but the scope of protection of the application is not limited to these examples.

[0037] Example 1

[0038] 60 parts by weight of sodium-based bentonite was dispersed in 480 parts by weight of deionized water, and after high-speed stirring at a speed of 8000 r / min for 2 h, coarse particles were removed through a 200-mesh screen, and the obtained bentonite slurry was recorded as A; 18 parts by weight of octadecyl trimethyl ammonium chloride long-chain quaternary ammonium salt was added to 50 parts by weight of anhydrous ethanol, and then 6 parts by weight of N-hydroxymethyl acrylamide and 6 parts by weight of γ-aminopropyl triethoxysilane were added, respectively, so that the mass ratio of the three was 3:1:1, and after high-speed stirring at a speed of 8000 r / min for 2 h, a composite organic modifier solution was obtained, which was recorded as B (the modifier theoretically contains 18 parts by weight of octadecyl trimethyl ammonium chloride long-chain quaternary ammonium salt, 6 parts by weight of N-hydroxymethyl acrylamide, and 6 parts by weight of γ-aminopropyl triethoxysilane); 20 parts by weight of bentonite slurry A was heated to 80℃, the pH value was adjusted to 8, and the composite organic modifier solution B was slowly added dropwise, with the mass ratio of modifier to bentonite being controlled at 1:8, and after the dropwise addition was completed, constant-temperature stirring was carried out at 90℃ for 4 h; 1% of nano-silicon dioxide (particle size 20 nm) based on the mass of the bentonite was added, and stirring was continued for 1 h to complete the modification reaction; the reaction product was filtered to form a filter cake, which was dried at 100℃, and after being crushed and passed through a 200-mesh screen, an organic modified bentonite with good high-temperature resistance, low filtration loss, and dispersion stability was obtained.

[0039] Example 2

[0040] The 70 parts by weight of sodium bentonite is dispersed in 560 parts by weight of deionized water, and after high-speed stirring at 10000 r / min for 3h, coarse particles are removed through a 200-mesh screen, and the obtained bentonite slurry is recorded as A; 30 parts by weight of dioctadecyl dimethyl ammonium chloride long-chain quaternary ammonium salt is added to 70 parts by weight of anhydrous ethanol, and then 10 parts by weight of N,N'-methylene bisacrylamide and γ-mercaptopropyl trimethoxysilane are added respectively, and the mass ratio of the three is maintained at 2:1:1, and after high-speed stirring at 10000 r / min for 3h, a composite organic modifier solution is obtained, recorded as B; 30 parts by weight of bentonite slurry A is heated to 90°C, the pH value is adjusted to 9, and the composite organic modifier solution B is slowly added dropwise, and the mass ratio of the modifier to bentonite is controlled to be 1:10, and after the dropwise addition is completed, constant temperature stirring is carried out at 95°C for 5h; 2% of nano-silicon dioxide (particle size 50nm) based on the mass of bentonite is added, and stirring is continued for 1h to complete the modification reaction; the reaction product is filtered to form a filter cake, which is dried at 120°C, and after being crushed and passed through a 200-mesh screen, an organic modified bentonite with good high-temperature resistance, low filtration loss and dispersion stability is obtained.

[0041] Comparative Example 1

[0042] The 60 parts by weight of sodium bentonite is dispersed in 480 parts by weight of deionized water, and after high-speed stirring at 8000 r / min for 2h, coarse particles are removed through a 200-mesh screen, and the obtained bentonite slurry is recorded as A; 18 parts by weight of octadecyl trimethyl ammonium chloride long-chain quaternary ammonium salt is added to 50 parts by weight of anhydrous ethanol, and after high-speed stirring at 8000 r / min for 2h, an organic modifier solution is obtained, recorded as B; 20 parts by weight of bentonite slurry A is heated to 80°C, the pH value is adjusted to 8, and the organic modifier solution B is slowly added dropwise, and the mass ratio of the modifier to bentonite is controlled to be 1:8, and after the dropwise addition is completed, constant temperature stirring is carried out at 90°C for 4h; 1% of nano-silicon dioxide (particle size 30nm) based on the mass of bentonite is added, and stirring is continued for 1h to complete the modification reaction; the reaction product is filtered to form a filter cake, which is dried at 120°C, and after being crushed and passed through a 200-mesh screen, an organic modified bentonite is obtained.

[0043] Comparative Example 2

[0044] 60 parts by weight of sodium bentonite was dispersed in 480 parts by weight of deionized water, after high-speed stirring at 8000 r / min for 2 h, coarse particles were removed by passing through a 200 mesh screen, and the obtained bentonite slurry was recorded as A; 18 parts by weight of octadecyl trimethyl ammonium chloride long-chain quaternary ammonium salt was added to 50 parts by weight of anhydrous ethanol, then 6 parts by weight of N-hydroxymethyl acrylamide and γ-aminopropyl triethoxysilane were added respectively, the mass ratio of octadecyl trimethyl ammonium chloride long-chain quaternary ammonium salt, N-hydroxymethyl acrylamide and γ-aminopropyl triethoxysilane was kept at 3:1:1, after high-speed stirring at 8000 r / min for 2 h, a composite organic modifier solution was obtained and recorded as B; 20 parts by weight of bentonite slurry A was heated to 80℃, the pH value was adjusted to 8, and the composite organic modifier solution B was slowly added, the mass ratio of modifier to bentonite was controlled at 1:8, after the addition was completed, constant temperature stirring was carried out at 90℃ for 4 h; the reaction product was filtered to form a filter cake, which was dried at 120℃, then crushed and passed through a 200 mesh screen, to obtain the organic modified bentonite.

[0045] The surface wettability of the products of the above examples and comparative examples was evaluated.

[0046] The modification effect of the examples and comparative samples was evaluated by measuring the contact angle of the bentonite before and after organic modification, the theoretical basis was the Young equation proposed by Thomas Young, the formula was:

[0047] γ sg = γ sl + γ lg cosθ

[0048] γ sg : surface tension of solid-gas interface (unit: mN / m); γ sl : surface tension of solid-liquid interface (unit: mN / m); γ lg : surface tension of liquid-gas interface (unit: mN / m); θ: contact angle (unit: °), which is the angle between the tangent of the liquid surface and the solid surface.

[0049] The actual measurement calculation used the Young-Laplace equation to fit the droplet profile, the formula was:

[0050]

[0051] ΔP: pressure difference between the inside and outside of the droplet (unit: Pa); R1, R2: principal radii of curvature of the droplet surface (unit: m), corresponding to the "width" and "height" directions of the curvature respectively.

[0052] Take the unmodified bentonite raw ore, grind and pass through a 200-mesh sieve to remove impurities; use the tabletting method to prepare the sample. Weigh 2 g of bentonite powder and place it in a mold. Use a tablet press to compress it at a constant pressure of 20 MPa for 60 seconds to form a round tablet with a smooth surface and a density of about 10 mm in diameter and about 2 mm in thickness. Take the modified bentonite, grind and sieve it, and prepare the sample according to the tabletting method described above to ensure that the compression conditions (pressure, time) are consistent with those of the original soil sample and that the surface state is comparable. Test three different positions (avoiding the influence of surface unevenness), repeat the measurement three times at each position, and take the average value as the final result as shown in Figure 1

[0053] Figure 1 As can be seen, after modification by the composite organic modifier, the contact angles of the sample of the example and the sample of the comparative example are significantly enhanced compared to the unmodified bentonite, showing good hydrophobic and lipophilic properties. Notably, since only one kind of organic modifier, long-chain quaternary ammonium salt, is added in the sample of Comparative Example 1, its contact angle is slightly smaller than that of the sample with composite organic modifier in the example; and no nano-silicon dioxide is added in the sample of Comparative Example 2, which has little effect on the contact angle.

[0054] The temperature resistance of the above-mentioned example and comparative product is evaluated as follows:

[0055] I. Measurement of the slurry-making ability and high temperature resistance of the organic bentonite in diesel oil

[0056] Add 6% (mass ratio) of the organic soil to 0# diesel oil, stir at a speed of 8000 r / min for 1 h, and measure its performance at room temperature. Measure its performance at room temperature after the mixed solution is hot-rolled at 250℃ for 16 h, and the results are shown in Table 1.

[0057] Table 1 Slurry-making ability and high temperature effect of the organic soil in diesel oil

[0058]

[0059] Note: AV refers to apparent viscosity, unit: millipascal seconds (mPa·s); PV refers to plastic viscosity, unit: millipascal seconds (mPa·s); YP refers to yield point, unit: pascal (Pa); API refers to API filtration loss, unit: milliliters (mL). The above data measurement standards refer to the national standard GBT 16783.2-2012 "Oil and gas industry Drilling fluid field testing Part 2: Oil-based drilling fluid".

[0060] As can be seen from Table 1, after adding 6% of the organic modified bentonite, the apparent viscosity and yield point of the mixed solution are basically stable, and the filtration loss increases slightly; after being hot-rolled at 250℃ for 16 h, the slurry-making ability of the organic modified bentonite of the present application is significantly better than that of the commercially available organic soil. ​​

[0061] II. Effect of organic clay on emulsion stability

[0062] Take 300 mL of 0# diesel oil, add 10 g of emulsifier SP-80 and 30 mL of a solution containing 5 g of CaCl2, stir at a speed of 8000 r / min for 1 h; add 10 g of high-temperature resistant organically modified bentonite to the above base fluid, ultrasonic dispersion for 10 min, then stir at a speed of 8000 r / min for 1 h, then heat roll at 250°C for 16 h, measure its performance at room temperature, and the results are shown in Table 2:

[0063] Table 2 Effect of organic clay on emulsion stability

[0064]

[0065] Note: AV refers to apparent viscosity, unit: millipascal seconds (mPa·s); PV refers to plastic viscosity, unit: millipascal seconds (mPa·s); YP refers to yield point, unit: pascal (Pa); Es refers to emulsion stability voltage, the above data measurement standard refers to GB / T16782-1997 "Oil-based drilling fluid field test procedure" national standard.

[0066] Further, the dispersion stability of bentonite in drilling fluid is evaluated by calculating the layered volume ratio (volume ratio of clear layer + sediment layer). Slowly pour the uniformly dispersed emulsion sample into a 100 mL graduated cylinder, record the initial volume. After covering, place the graduated cylinder in a constant temperature static device (such as room temperature or simulated downhole temperature) for 24 h, avoid shaking or drastic temperature changes during this period. After the static state ends, observe the layered state of the system, and read the clear layer volume (V 清 ) and sediment layer volume (V 渣 ) respectively, and calculate the layered volume ratio according to the following formula:

[0067]

[0068] Take 3 parallel experiments, and take the average value as the final result. The results show that the layered volume ratio of the emulsion with the addition of commercially available organic clay reaches 15%, while the layered volume ratio of the emulsion with the addition of Example 1 and Example 2 is 7% and 7.5% respectively, and the layered volume ratio of the emulsion with the addition of Comparative Example 1 and Comparative Example 2 is 8.5% and 8% respectively. It can be seen that the dispersion stability of the emulsion is improved after organic modification, and the addition of a single modifier and the absence of nano-silicon dioxide are not conducive to the dispersion stability of the emulsion.

[0069] It can be seen from the above examples and comparative examples that the application solves the problem of easy decomposition of a single modifier at high temperature by using the steric hindrance effect of long-chain quaternary ammonium salt, the cross-linking network stability of amide modifier and the covalent bond connection characteristics of silane coupling agent. Then, nano-silica is introduced into the interlayer and pores of bentonite to enhance the structural stability, and interact with the groups on the surface of the organic modifier and bentonite to enhance the adsorption firmness of the organic modifier on the surface of bentonite. The preparation process of the application is simple, and through the synergistic effect of the composite organic modifier and nano-silica, the organic modified bentonite with good high-temperature resistance, low filtration loss and good dispersion stability can be obtained.

[0070] The above display description shows the basic principles and main features of the application and the advantages of the application. It should be understood by those skilled in the art that the application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the application. Without departing from the spirit and scope of the application, various changes and improvements can be made to the application, and these changes and improvements all fall within the scope of the claimed application. The scope of protection of the application is defined by the appended claims and their equivalents.

[0071] The details of the application are known to those skilled in the art.

Claims

1. A method for preparing high-temperature resistant organic modified bentonite, characterized in that, The method includes the following steps: (1) Disperse 60-70 parts by weight of sodium-based bentonite in 480-560 parts by weight of deionized water, stir at high speed of 8000-10000 r / min for 2-3 hours, and then sieve. The resulting bentonite slurry is denoted as A. (2) Add long-chain quaternary ammonium salt to anhydrous ethanol, then add amide and silane coupling agent respectively, and stir at high speed for 2-3 hours at 8000-10000 r / min to obtain a composite organic modifier solution, denoted as B. The mass ratio of long-chain quaternary ammonium salt: amide: silane coupling agent is 18-30: 6-10: 6-10; the mass ratio of anhydrous ethanol to long-chain quaternary ammonium salt is 18-30: 50-70. (3) Heat the bentonite slurry A to 80-90℃, adjust the pH value to 8-9, add the composite organic modifier solution B dropwise, control the temperature, and stir at 90-95℃ for 4-5 hours after the addition is completed; The mass ratio of the composite organic modifier to bentonite is 1:8 to 10. (4) Add 1-2% nano-silica by weight of bentonite, and continue stirring for 0.5-2 hours to complete the modification reaction; (5) The reaction product is filtered to form a filter cake, dried at 100-120°C, pulverized and sieved to obtain the high-temperature resistant organic modified bentonite product.

2. The preparation method of high-temperature resistant organic modified bentonite as described in claim 1, characterized in that, In step (2), the mass ratio of long-chain quaternary ammonium salt, amide and silane coupling agent is 2 to 3:1:

1.

3. The preparation method of high-temperature resistant organic modified bentonite as described in claim 1, characterized in that, In step (2), the long-chain quaternary ammonium salt is octadecyltrimethylammonium chloride or dioctadecyldimethylammonium chloride; The amide is N-hydroxymethylacrylamide or N,N′-methylenebisacrylamide; The silane coupling agent is γ-aminopropyltriethoxysilane or γ-mercaptopropyltrimethoxysilane.

4. The preparation method of high-temperature resistant organic modified bentonite as described in claim 1, characterized in that, In step (4), the particle size of the nano-silica is 20-50 nm.

5. The application of the high-temperature resistant organic-modified bentonite prepared by the method described in claim 1, characterized in that, It is used as a mud-forming agent in oil-based drilling fluids that can withstand temperatures above 250°C.

6. The application as described in claim 5, characterized in that, Includes the following steps: (1) Take 70-85 parts by weight of diesel base liquid and place it in a high-speed stirring tank. Turn on the stirring (speed 800-1000 r / min), heat it to 40-50℃, and keep it at a constant temperature for later use. (2) Under stirring, add 3 to 8 parts by weight of the high-temperature resistant organic modified bentonite to the base liquid, increase the rotation speed to 1500 to 2000 r / min, and shear and disperse for 30 to 40 min until the bentonite is completely swollen and forms a uniform suspension; (3) Keep the speed at 1500 r / min, add 2 to 5 parts by weight of emulsifier (Span-80 and Tween-80 mixed in a 3:1 ratio) and 1 to 3 parts by weight of sodium dodecylbenzenesulfonate wetting agent, and continue stirring for 20 to 30 min to form a preliminary emulsion system; (4) Reduce the rotation speed to 800-1000 r / min, add 2-5 parts by weight of sulfonated asphalt filtration loss reducer and 0.5-2 parts by weight of calcium oxide alkalinity adjuster, stir for 15-20 min to disperse the additives; (5) Add 5-15 parts by weight of calcium chloride aqueous solution (20-30% concentration) dropwise, controlling the dropping rate to 1-2 parts by weight / min. After the addition is complete, keep stirring (800-1000 r / min) for 30-40 min to form a stable water-in-oil emulsion system. (6) Add 1 to 30 parts by weight of barite weighting agent to the system and stir (800 to 1000 r / min) for 60 to 90 min until completely dispersed to obtain oil-based drilling fluid resistant to temperatures above 250°C.

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