Vinyltriethoxysilane modified cellulose nanocrystal mud cake reinforcing agent and application thereof in drilling fluid

Abstract

The invention relates to the field of drilling fluid, in particular to a mud cake reinforcing agent of vinyltriethoxysilane modified cellulose nanocrystals and application of the mud cake reinforcing agent to the drilling fluid, the vinyltriethoxysilane modified cellulose nanocrystals are adopted, and the ratio of the adding amount of the vinyltriethoxysilane to the adding amount of the cellulose nanocrystals is (0.5-6) mL: 1 g. Meanwhile, the modification method is provided and then applied to the drilling fluid, the quality of a mud cake is improved, and then the drilling quality, speed and efficiency are improved. The silane provided by the invention is used for modifying the nano cellulose crystal and is formed through chemical reaction, so that the silane modified nano cellulose crystal has good stability and high temperature resistance, and the required raw materials are few; and the method has a wide application prospect and is worthy of popularization.

Description

Technical Field

[0001] The invention relates to the field of drilling fluid, and in particular to a vinyltriethoxysilane modified cellulose nanocrystalline mud cake enhancer and application thereof in drilling fluid. Background Art

[0002] Water-based drilling fluid is a multiphase dispersion system composed of bentonite, water (or brine), various treatment agents, weighting materials and drill cuttings. Water-based drilling fluid is widely used in oil fields at home and abroad due to its advantages of economy, environmental protection and simple process. During the drilling process, when the drill bit drills through the permeable formation, the liquid column pressure of the drilling fluid is generally always greater than the pore pressure of the formation. Under the action of the pressure difference, the liquid of the drilling fluid will penetrate into the formation. This characteristic is often called the filtration property of the drilling fluid. While the liquid is filtering, the solid particles in the drilling fluid will adhere and deposit on the well wall to form a layer of mud cake. The filtration property of the drilling fluid mainly refers to the amount of drilling fluid loss and the quality of the mud cake formed. The mud cake of good quality is generally thin and tough, while the mud cake of poor quality is thick and not tough.

[0003] The mud cake is thick and of poor quality, which has the following hazards: large friction coefficient, which can easily cause mud cake to adhere to the drill and jam; mud can easily pack the drill bit or block the wellbore, causing large fluctuation pressure when drilling; increased friction resistance when drilling, and even jamming; hindering casing installation and affecting cementing quality; electrical measurement encounters resistance and jamming, resulting in inaccurate data. The main reasons for the poor quality of mud cake are as follows: (1) Geological factors: Although the mud shale in the formation is diagenetic, it is easy to hydrate and disperse, which increases the mud or solid content in the wellbore. After mud pollution, the harmful solids in the mud are difficult to remove. The formation permeability is high. Under the action of pressure difference, the harmful solids in the wellbore and the cuttings that are not carried out in time are adsorbed to form a thick mud cake; (2) Drilling factors: The displacement during drilling is small, and the drilling and drill bit cannot be effectively cleaned. At the same time, the return speed is insufficient, the cuttings stay in the well for a long time, and adhere to the well wall to form a thick mud cake; (3) Drilling fluid performance factors: The drilling fluid has poor inhibition and cannot control the hydration and dispersion of mud shale; the solid content and viscosity are too high, the drilling fluid specific gravity is high, and the water loss is large, which is easy to form an overly thick and rough mud cake.

[0004] How to improve the strength of the mud cake, improve the quality of the mud cake, and thus improve the quality, speed, and efficiency of drilling is a hot topic of research. Chinese patent CN 201911248970.2 discloses a modified nanocellulose-based cementing additive and its preparation method and application, which uses water-soluble monomers preferably including acrylamide, acrylic acid and its sodium salt, etc. to modify nanocellulose, and react with nanocellulose dispersion and initiator to polymerize, and use it as a cementing additive. Chinese patent CN 202310902256.0 discloses an environmentally friendly high temperature and high salt resistant fluid loss reducer and its preparation method and application, which uses amide monomers and olefin monomers to graft the prepared nanocellulose crystals to form a modified nanocellulose fluid loss reducer. Both of the above patents use amide monomers to modify nanocellulose, and this modification method is already very common. Shi Guang et al. published a paper titled "Research on Surface Modification of Nanocrystalline Cellulose by Silane Coupling Agents" in Functional Materials. However, the surface polarity of the modified nanocellulose was reduced, and the intermolecular forces were weakened, which resulted in the inability of the modified nanocellulose to form a strong network structure and greatly reduced strength. In the master's thesis "Research on Nanocellulose Modified by Silane Coupling Agent KH550 and Its Enhanced Waterborne Acrylic Composite Coatings" by Tan Yao of Northeast Forestry University, cellulose nanofibrils (CNF) were modified by silane coupling agent KH550. According to the morphology of nanocellulose reported in current related research, it is mainly divided into the following four categories: crystalline nanocellulose (cellulose nanocrystals, CNC; canocrystalline cellulose, NCC), microcrystalline nanocellulose (microcrystalline cellulose, MCC), fibrillar nanocellulose (cellulose nanofibrils, CNF), spherical nanocellulose (spherical nano cellulose, SNC) and sheet nanocellulose (cellulose nanosheet, CNS). Compared with amorphous nanocellulose (such as CNF), crystalline nanocellulose (such as CNC, NCC, MCC) is a crystalline form of cellulose with high crystallinity, more ordered structure and less susceptible to modification. Amorphous nanocellulose is a nanoscale particle formed by the polymerization of cellulose particles and is more susceptible to modification. Summary of the invention

[0005] In view of the problems existing in the mud cake enhancers at this stage, the present invention provides a mud cake enhancer of vinyltriethoxysilane-modified cellulose nanocrystals, which adopts vinyltriethoxysilane to modify cellulose nanocrystals, and provides the above-mentioned modification method, which is then applied to the drilling fluid to enhance the strength of the mud cake, thereby improving the drilling quality, speed and efficiency.

[0006] The technical solution of this application is as follows:

[0007] A vinyltriethoxysilane modified cellulose nanocrystal mud cake enhancer comprises a reaction product of vinyltriethoxysilane and cellulose nanocrystals in the presence of an ethanol solvent, wherein the ratio of the vinyltriethoxysilane to the cellulose nanocrystals is (0.5-6) ​​mL:1 g.

[0008] Preferably, the ratio of the added amount of silane to the cellulose nanocrystals is (2.5-5) mL:1 g. As a specific embodiment of the present invention, the ratio of the added amount of silane to the cellulose nanocrystals is 2.5 mL:1 g, 4 mL:1 g, or 5 mL:1 g.

[0009] On the other hand, the preparation method of the above-mentioned vinyltriethoxysilane modified cellulose nanocrystal mud cake enhancer comprises the following steps:

[0010] Vinyl triethoxysilane is dispersed in an ethanol solution to obtain a mixed solution, the pH value of the mixed solution is adjusted to 4-5, the mixed solution is mixed evenly with cellulose nanocrystals, heated and stirred, and centrifuged to obtain the mixed solution.

[0011] Furthermore, the ethanol solution is an aqueous solution with a volume percentage of 80%-90%; and / or, the amount of ethanol solution corresponding to 1g of cellulose nanocrystals is ≥100mL; and / or, an organic acid is used to adjust the pH value of the mixed solution; preferably, the organic acid is formic acid and / or acetic acid.

[0012] Preferably, the heating and stirring conditions are: time: 8-24h, temperature: 60-100°C; and / or, the preparation method further comprises washing the centrifuged product with ethanol before drying to remove unreacted silane.

[0013] As a specific embodiment of the present invention, the preparation method of the cellulose nanocrystals is:

[0014] Disperse microcrystalline cellulose MCC in sulfuric acid solution and stir; add water to obtain a suspension, centrifuge to obtain a white solid precipitate; dialyze the white solid precipitate in water until the eluent is neutral, centrifuge to obtain a white solid, and dry to obtain cellulose nanocrystal NCC powder.

[0015] As a specific embodiment of the present invention, before dialysis, washing is performed with ethanol and water respectively.

[0016] Preferably, the stirring conditions are: the temperature is 40-60° C., the stirring time is controlled at 0.5-1 h; and / or the mass concentration of sulfuric acid in the sulfuric acid solution is 60-70%.

[0017] In another aspect, the mud cake enhancer or the mud cake enhancer prepared by the above preparation method is used in drilling fluid.

[0018] As a specific implementation of the present invention, the drilling fluid is a water-based drilling fluid.

[0019] The reaction mechanism of this application is:

[0020]

[0021] Silane hydrolysis reaction

[0022]

[0023] Silanol self-condensation reaction

[0024]

[0025] Silane-modified nanocellulose reaction

[0026] The Si-ethoxy group of the present application can be hydrolyzed to form Si-OH, and react with the active hydroxyl groups on the surface of the inorganic material. The positive reaction is a hydrolysis reaction, and the side reaction is a silanol self-condensation reaction. Therefore, the solution used in the preparation of the silane solution is water and ethanol. Water promotes the hydrolysis of the Si-ethoxy group, and ethanol has a dissolving effect, which can reduce the self-condensation of silanol and stabilize the silanol. Formic acid or acetic acid is used as a catalyst to promote the hydrolysis of the silane group while adjusting the pH value of the solution. It can accelerate the hydrolysis and inhibit the self-condensation reaction of silanol under acidic conditions. The by-products of the self-condensation reaction will promote the reaction of silane-modified nanocellulose under a small amount of conditions, and improve the overall performance; while the by-products are excessive, they will inhibit and hinder the modification reaction. Therefore, to prepare a silane solution, the pH value of the solution must be alkaline first; and then the pH value is adjusted to be acidic in order to accelerate the hydrolysis and inhibit the self-condensation reaction of silanol.

[0027] Beneficial effects of the present invention

[0028] Cellulose nanocrystals are first prepared through microcrystalline cellulose, and silanization grafting modification is performed on the basis of the cellulose nanocrystals. The mud cake enhancer prepared by the grafting modification method has a large number of hydroxyl groups adsorbed on the mud cake on the surface to form a network structure, which improves the performance of the mud cake. After the silane described in the present application is grafted, it is formed through chemical reaction and has good stability and high temperature resistance, and less raw materials are required; it is not easy to deteriorate, has broad application prospects, and is worthy of promotion. DETAILED DESCRIPTION

[0029] Embodiment 1:

[0030] Weigh 3g MCC and disperse it in 65% sulfuric acid solution. Stir magnetically at 40℃ for 1h, and add a large amount of deionized water. Centrifuge the obtained suspension at 10000r / min for 10 minutes, pour off the turbid upper liquid to obtain a white solid precipitate. After washing with ethanol and deionized water three times respectively, dialyze it in deionized water until the eluent is neutral, centrifuge to obtain a white solid, and freeze-dry it to make cellulose nanocrystal (NCC) powder.

[0031] Weigh 0.5 ml of silane and disperse it in 100 mL of ethanol / water solution (volume ratio 90 / 10) to obtain a mixed solution. Add a small amount of formic acid or acetic acid to adjust the pH value of the mixed solution to 4-5 and keep it constant. Stir the solution magnetically at room temperature for 3 hours to obtain a mixed solution. Add 1.0 g of NCC to the above mixed solution, and continue stirring and heating at 60°C for 8 hours to prepare grafted modified cellulose. Centrifuge the silane-grafted modified cellulose at 10,000 r / min for 5 minutes, and wash it with anhydrous ethanol at least three times to remove the unreacted silane coupling agent. Place the silanized modified cellulose in a vacuum drying oven at 60°C and dry it for 24 hours.

[0032] Embodiment 2:

[0033] Weigh 4g MCC and disperse it in 60% sulfuric acid solution. Stir magnetically at 50℃ for 1h, and add a large amount of deionized water. Centrifuge the obtained suspension at 10000r / min for 10 minutes, pour off the turbid upper liquid to obtain a white solid precipitate. After washing with ethanol and deionized water three times respectively, dialyze it in deionized water until the eluent is neutral, centrifuge to obtain a white solid, and freeze-dry it to make cellulose nanocrystal (NCC) powder.

[0034] Weigh 2.5 ml of silane and disperse it in 100 mL of ethanol / water solution (volume ratio 80 / 20) to obtain a mixed solution. Add a small amount of formic acid or acetic acid to adjust the pH value of the mixed solution to 4-5 and keep it constant. Stir the solution magnetically at room temperature for 2 hours to obtain a mixed solution. Add 1.0 g of NCC to the above mixed solution, and continue stirring and heating at 80°C for 16 hours to prepare grafted modified cellulose. Centrifuge the silane-grafted modified cellulose at 15,000 r / min for 10 minutes, and wash it with anhydrous ethanol at least three times to remove the unreacted silane coupling agent. Place the silanized modified cellulose in a vacuum drying oven at 70°C and dry it for 36 hours.

[0035] Embodiment 3:

[0036] Weigh 5g MCC and disperse it in 65% sulfuric acid solution, stir it magnetically at 60℃ for 1h, and add a large amount of deionized water. Centrifuge the obtained suspension at 10000r / min for ten minutes, pour off the turbid upper liquid to obtain a white solid precipitate. After washing it with ethanol and deionized water three times respectively, dialyze it in deionized water until the eluent is neutral, centrifuge to obtain a white solid, and freeze-dry it to make cellulose nanocrystal (NCC) powder.

[0037] Weigh 6.0 ml of silane and disperse it in 100 mL of ethanol / water solution (volume ratio 85 / 15) to obtain a mixed solution. Add a small amount of formic acid or acetic acid to adjust the pH value of the mixed solution to 4-5 and keep it constant. Stir the solution magnetically at room temperature for 3 hours to obtain a mixed solution. Add 1.0 g of NCC to the above mixed solution, and continue stirring and heating at 100°C for 24 hours to prepare grafted modified cellulose. Centrifuge the silane-grafted modified cellulose at 20,000 r / min for 15 minutes, and wash it with anhydrous ethanol at least three times to remove unreacted silane. Place the silanized modified cellulose in a vacuum drying oven at 80°C and dry it for 48 hours.

[0038] Comparative Example 1:

[0039] Comparative Example 1 is the cellulose nanocrystal (NCC) powder prepared in Example 1 without being grafted and modified.

[0040] Comparative Example 2:

[0041] Comparative Example 2 is CMC, carboxymethyl cellulose.

[0042] Comparative Example 3:

[0043] Comparative Example 3 is a product obtained by modifying nanocellulose CNF with KH550. Silane coupling agent KH550 is also called γ-aminopropyltriethoxysilane, and its structural formula is shown below:

[0044]

[0045] Comparative Example 4:

[0046] Comparative Example 3 is a product in which nanocellulose CNF is modified by KH560. Silane coupling agent KH560 is also called γ-glycidyloxypropyltrimethoxysilane, and its structural formula is as follows:

[0047]

[0048] The mud cake enhancers were prepared according to the methods of Examples 1-3 and Comparative Examples 1-4, and the effects of the mud cake enhancers were evaluated by mud cake performance tests such as mud cake thickness, mud cake strength, shear strength, and mud cake friction coefficient. The data of each group of experiments are recorded in Table 1.

[0049] Performance test: Add the embodiment and comparative example to the polymer drilling fluid (or any water-based drilling fluid, polymer drilling fluid is used as an example here) in a certain amount (0.5% to 1.5%), and stir at a high speed of 11000r / min or 12000r / min for 20 minutes. According to GB / T 16783.1-2014, Field Test of Drilling Fluids in the Petroleum and Natural Gas Industry Part 1: Water-Based Drilling Fluids, the density, medium-pressure filtration loss, and plastic viscosity of the drilling fluid before and after aging are tested. Add mud cake enhancer to the polymer drilling fluid, and use a mud cake thickness and strength automatic measuring instrument to measure the mud cake strength and mud cake thickness, and use a mud cake viscosity coefficient measuring instrument to measure the mud cake viscosity coefficient.

[0050] Table 1 Mud cake performance evaluation

[0051]

[0052] As can be seen from Table 1, after adding Examples 1-3, the thickness of the mud cake becomes thinner, the strength of the mud cake increases, and the viscosity coefficient of the mud cake decreases, indicating that the friction force decreases and the lubricity of the mud cake improves. The mud cake enhancer Example 2 prepared by the present invention has the best conditions and the best effect, wherein the mud cake thickness is only 0.4 mm and the mud cake strength is as high as 280 MPa.

[0053] The mud cake enhancer was prepared according to the methods of Examples 1-3 and Comparative Examples 1-4, and the mud cake enhancer was added to the polymer drilling fluid. The drilling fluid was aged and rolled at 160° C. for 16 hours, and the performance changes of the drilling fluid before and after aging were measured. The relevant data are shown in Table 2.

[0054] Table 2 Performance changes of drilling fluid before and after aging

[0055]

[0056] It can be concluded from Table 2 that the addition of the embodiment improves the performance of the drilling fluid and has good compatibility with the drilling fluid. Among them, the condition of embodiment 2 is the best, the effect is the best, and the lowest filtration loss is only 3.4 ml, and after aging, it is only 3.6 ml.

[0057] Among them, Comparative Examples 1 and 2 are common cellulose products, which have poor high temperature resistance and are easily deactivated and unstable under high temperature conditions. Common environmental protection treatment agents, especially cellulose products, can resist temperatures of up to 120°C, and few can resist temperatures of 140°C. Comparative Examples 3 and 4 use common silanes to modify nanocellulose fibers CNF. The silane coupling agent KH550 (γ-aminopropyltriethoxysilane) used in Comparative Example 3 has single bonds that can rotate freely, but double bonds cannot. In terms of spatial structural stability, double bonds are greater than single bonds; the silane coupling agent KH560 (γ-glycidyloxypropyltrimethoxysilane) used in Comparative Example 4 has epoxy groups. Due to the tension of the ring, epoxy groups are much more active than general ethers and can undergo ring-opening reactions with a variety of reagents. Epoxy groups can undergo ring-opening reactions with nucleophilic reagents such as primary amines, thiols or hydroxyls under mild conditions to form secondary amines, thioethers or ether bonds, respectively. Drilling fluid is alkaline, and silane coupling agents with epoxy groups are too active and easily undergo ring-opening reactions under alkaline conditions. It is inappropriate to use silane coupling agents with epoxy groups to modify nanocellulose crystals for use in the field of drilling fluid. Therefore, this patent prefers a vinyl triethoxysilane to modify cellulose nanocrystals as a mud cake enhancer for use in drilling fluid.

[0058] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. Vinyl triethoxysilane modified cellulose nanocrystal mud cake enhancer, It is characterized in that The reinforcing agent includes a reaction product of vinyl triethoxysilane and cellulose nanocrystals in the presence of an ethanol solvent, wherein the ratio of the vinyl triethoxysilane to the cellulose nanocrystals is (0.5-6) ​​mL:1 g.

2. The silane-modified cellulose nanocrystal mud cake enhancer according to claim 1, It is characterized in that The ratio of the vinyl triethoxysilane to the cellulose nanocrystals is (2.5-5) mL:1 g.

3. The method for preparing the vinyltriethoxysilane modified cellulose nanocrystal mud cake enhancer according to claim 1 or 2, It is characterized in that The following steps are involved: Vinyl triethoxysilane is dispersed in an ethanol solution to obtain a mixed solution, the pH value of the mixed solution is adjusted to 4-5, the mixed solution is mixed evenly with cellulose nanocrystals, heated and stirred, and centrifuged to obtain the mixed solution.

4. The preparation method according to claim 3, It is characterized in that The ethanol solution is an aqueous solution with a volume percentage of 80%-90%; and / or, the amount of ethanol solution corresponding to 1g of cellulose nanocrystals is ≥100mL; and / or, an organic acid is used to adjust the pH value of the mixed solution; preferably, the organic acid is formic acid and / or acetic acid.

5. The preparation method according to claim 3 or 4, It is characterized in that The heating and stirring conditions are: time: 8-24h, temperature: 60-100°C; and / or, the preparation method further comprises washing the centrifuged product with ethanol before drying to remove unreacted silane.

6. The preparation method according to any one of claims 3 to 5, It is characterized in that The preparation method of the cellulose nanocrystals comprises: Disperse microcrystalline cellulose MCC in sulfuric acid solution and stir; add water to obtain a suspension, centrifuge to obtain a white solid precipitate; dialyze the white solid precipitate in water until the eluent is neutral, centrifuge to obtain a white solid, and dry to obtain cellulose nanocrystal NCC powder.

7. The preparation method according to claim 6, It is characterized in that Before dialysis, the cells were washed with ethanol and water, respectively.

8. The preparation method according to claim 6 or 7, It is characterized in that The stirring conditions are: the temperature is 40-60° C., the stirring time is controlled at 0.5-1 h; and / or the mass concentration of sulfuric acid in the sulfuric acid solution is 60-70%.

9. Use of the mud cake enhancer according to claim 1 or 2 or the mud cake enhancer prepared by the preparation method according to any one of claims 3 to 8 in drilling fluid.

10. The use according to claim 9, It is characterized in that The drilling fluid is water-based drilling fluid.

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