Modified starch-based petroleum drilling aid and preparation method thereof

Abstract

The application discloses a modified starch-based petroleum drilling aid and a preparation method thereof, and comprises the following steps: S1, oxidizing dialdehyde starch into polycarboxyl starch by using sodium chlorite; S2, performing esterification treatment on the polycarboxyl starch, and then performing amidation reaction on the polycarboxyl starch and sodium p-aminobenzenesulfonate; S3, performing reduction treatment on the amide bond by using a reducing agent; and S4, performing lipolysis on the starch after the reduction treatment to obtain the modified starch. The modified starch prepared by the application can greatly improve the temperature resistance and salt resistance by grafting a large number of rigid benzene rings and hydration groups, and has excellent effects of increasing viscosity, improving cutting and reducing filtration loss.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid technology, and in particular to a modified starch-based petroleum drilling additive and its preparation method. Background Technology

[0002] Global oil and gas extraction is trending towards deeper inland formations, leading to increasingly complex geological conditions. This places higher demands on the performance of drilling fluids. Starch, as a natural resource, is widely available, inexpensive, non-toxic, and easily degradable, making it an important oilfield chemical. However, the poor temperature resistance of starch-based filtration reducers greatly limits their application in high-temperature oil wells.

[0003] Patent CN108101999A discloses a sulfonated starch, its preparation method and application. It is prepared by reacting starch and water-soluble haloethanesulfonate under alkaline conditions, so that ethanesulfonic acid groups and hydroxyl groups are grafted onto the starch main chain, which improves the drilling fluid's resistance to salt pollution. However, it does not introduce rigid benzene rings or other temperature-resistant structures that hinder the thermal movement of molecular chain segments, and its temperature resistance needs to be further improved.

[0004] Patent CN106675533A discloses a grafted starch filtration reducer for drilling fluid and its preparation method. The modified starch is obtained by free radical polymerization of starch, acrylic acid, acrylamide and sodium p-styrene sulfonate. This starch has excellent salt and calcium resistance and can withstand temperatures up to 160°C. However, the free radical polymerization process is complex and requires precise control of the raw material ratio. It is not easy to grasp and control the grafting rate, grafting efficiency and monomer conversion rate, which directly affect the quality of the final product. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an oil drilling additive based on modified starch and its preparation method, so as to solve the problems of poor temperature and salt resistance of modified starch and difficulty in controlling product quality during free radical polymerization in the prior art.

[0006] The objective of this invention is achieved through the following technical solution: a modified starch-based petroleum drilling additive, prepared according to the following steps, S1. Oxidize dialdehyde starch to polycarboxylated starch using sodium chlorite; S2. The polycarboxylated starch is esterified and then subjected to an amidation reaction with sodium p-aminobenzenesulfonate; S3. Use a reducing agent to reduce the amide bond; S4. The starch after reduction treatment is obtained by lipohydrolysis.

[0007] Sodium chlorite is used to oxidize the aldehyde group in dialdehyde starch to a carboxyl group. Then, an alcohol is used to react with the carboxyl group to form an ester bond that is not reduced by BH3THF, thus protecting the carboxyl group. The remaining carboxyl group reacts with sodium p-aminobenzenesulfonate to amidate the carboxyl group and amino group, grafting the rigid benzene ring and sulfonic acid group onto the starch chain. Then, BH3THF is used to reduce the amide bond to a secondary amine bond. The secondary amine bond is more resistant to high temperature and acid and alkali than the amide bond, thus maintaining its stability in the complex drilling fluid. Finally, the lipid is hydrolyzed to expose the carboxyl group grafted on the starch chain, which then coordinates with the sulfonic acid group in the drilling fluid.

[0008] Preferably, in step S1, the dialdehyde starch is dispersed in a solvent, the pH is adjusted to acidic, sodium chlorite is added to dissolve it, and the temperature is controlled at 40-50℃ and stirred for 4-6 hours.

[0009] Preferably, in step S2, the polycarboxylated starch is dispersed in anhydrous methanol, a catalyst is added, and the mixture is refluxed and stirred at 60-70°C for 12-16 hours.

[0010] Preferably, in step S2, the esterified starch is dispersed in a buffer solution, condensing agent EDC is added and stirred for 15 min, N-hydroxysuccinimide is added and stirred for 15 min, the pH is adjusted to 7.5-8.0, and sodium p-aminobenzenesulfonate is added and stirred for 24 h.

[0011] Preferably, in step S3, under nitrogen protection, dry starch is added to anhydrous THF solvent, BH3THF solution is added dropwise, the mixture is heated under reflux for 24 hours, and then quenched with methanol.

[0012] Preferably, in step S4, the reduced starch is added to a sodium hydroxide solution, stirred at 40-60°C for 2 hours, the pH is adjusted to acidic, and the organic phase is extracted and then evaporated and dried to obtain the final product.

[0013] Preferably, the degree of polymerization n of the dialdehyde starch is 40-100.

[0014] Preferably, the mass ratio of the polycarboxylated starch to methanol is (0.9-1.2):1.

[0015] The present invention has the following advantages: 1. This invention provides a method for preparing modified starch for drilling fluids, which is prepared through a four-step process of protection-grafting-reduction-deprotection. First, all aldehyde groups are oxidized to carboxyl groups, providing numerous active reaction sites for subsequent reactions. Since both carboxyl and amide bonds can be converted by BH3... THF reduction is performed, and esterification is used in advance to protect the carboxyl groups, avoiding indiscriminate attack of the reducing agent on the carboxyl groups. The remaining carboxyl groups react with sodium p-aminobenzenesulfonate to introduce benzene rings and sulfonic acid groups into the starch backbone, which greatly improves the high temperature and salt resistance of the modified starch. Then, reduction is performed to convert the amide bond formed between the carboxyl group and the amino group, which is not resistant to acid, alkali and high temperature, into a secondary amine bond, which further improves the stability of the modified starch in complex drilling fluids. Finally, the ester bond formed between the carboxyl group and the alcohol hydroxyl group is hydrolyzed to release the protected carboxyl groups, which achieves the purpose of grafting a large number of carboxyl groups onto the starch backbone. The carboxyl groups have a strong integrative effect on high-valence metal ions such as calcium and magnesium, which can "wrap" them up and reduce the adverse effects of these ions on clay flocculation and polymer molecule coiling. The large number of carboxyl groups can significantly improve the performance stability of the polymer in brine, seawater and even calcium-containing formation water, maintain its filtration loss reduction and thickening effect, and its combination with sulfonic acid groups is suitable for drilling in complex formations. 2. The modified starch prepared by this invention has excellent temperature resistance up to 180℃, and can maintain the viscosity of drilling fluid and reduce filtration loss under high temperature and high salt conditions, making it suitable for oil drilling in complex formations. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Example 1

[0017] A modified starch-based petroleum drilling additive is prepared according to the following steps. S1. Take dialdehyde starch with a degree of polymerization of 42, disperse the dialdehyde starch in pure water to prepare a 10% emulsion, adjust the pH value to 4.0-5.0 with dilute hydrochloric acid, add sodium chlorite in equimolar amounts of aldehyde groups to dissolve, control the temperature to 40-50℃ and stir for 4-6 hours to oxidize the dialdehyde starch to polycarboxylated starch, take samples at regular intervals, and monitor the residual aldehyde group content using the hydrochloric acid hydroxylamine method. When the residual aldehyde group content is less than 5%, the reaction is considered complete. After the reaction is completed, add sodium bisulfite, then adjust the pH value to neutral with alkali, precipitate with ethanol, filter and wash, and vacuum dry to obtain polycarboxylated starch; S2. Weigh polycarboxylated starch and methanol at a mass ratio of 0.9:1. Disperse the polycarboxylated starch in anhydrous methanol, add the catalyst p-toluenesulfonic acid, and reflux and stir at 60-70℃ for 12-16 h. Filter, wash and dry to obtain partially esterified starch. Disperse the esterified starch in a water / DMSO mixed solvent at a concentration of 5%. Add excess condensing agent EDC and stir for 15 min. Add excess N-hydroxysuccinimide and stir for 15 min. Add alkali to adjust the pH to 7.5-8.0. Add excess sodium p-aminobenzenesulfonate according to the remaining 25% of polycarboxylated starch that has not been esterified and stir for 24 h. Use ethanol to precipitate and wash multiple times, and dry. S3. Add amidated starch to the reaction flask, purge with nitrogen, add anhydrous THF solvent to the reaction flask, add BH3 THF solution dropwise under ice bath cooling, heat under reflux for 24 h after the addition is complete, quench with methanol dropwise after the reaction is complete, and evaporate to remove the solvent. S4. Add the reduced starch to sodium hydroxide solution, stir and react at 40-60℃ for 2 hours, adjust the pH value to 2-3 with dilute hydrochloric acid, extract with ethyl acetate organic phase, and then separate and evaporate to dry. Example 2

[0018] A modified starch-based petroleum drilling additive is prepared according to the following steps. S1. Take dialdehyde starch with a degree of polymerization of 96, disperse the dialdehyde starch in pure water to prepare a 10% emulsion, adjust the pH value to 4.0-5.0 with dilute hydrochloric acid, add sodium chlorite in equimolar amounts of aldehyde groups to dissolve, control the temperature to 40-50℃ and stir for 4-6 hours to oxidize the dialdehyde starch to polycarboxylated starch, take samples at regular intervals, and monitor the residual aldehyde group content using the hydrochloric acid hydroxylamine method. When the residual aldehyde group content is less than 5%, the reaction is considered complete. After the reaction is completed, add sodium bisulfite, then adjust the pH value to neutral with alkali, precipitate with ethanol, filter and wash, and vacuum dry to obtain polycarboxylated starch; S2. Weigh polycarboxylated starch and methanol in a mass ratio of 1.2:1. Disperse the polycarboxylated starch in anhydrous methanol, add the catalyst p-toluenesulfonic acid, reflux and stir at 60-70℃ for 12-16 h, filter, wash and dry to obtain partially esterified starch. Disperse the esterified starch in a water / DMSO mixed solvent with a concentration of 5%, add excess condensing agent EDC and stir for 15 min, add excess N-hydroxysuccinimide and stir for 15 min, add alkali to adjust the pH to 7.5-8.0, add excess sodium p-aminobenzenesulfonate according to the remaining 35% of polycarboxylated starch that has not been esterified, stir and react for 24 h, precipitate and wash with ethanol multiple times, and dry. S3. Add amidated starch to the reaction flask, purge with nitrogen, add anhydrous THF solvent to the reaction flask, add BH3 THF solution dropwise under ice bath cooling, heat under reflux for 24 h after the addition is complete, quench with methanol dropwise after the reaction is complete, and evaporate to remove the solvent. S4. Add the reduced starch to sodium hydroxide solution, stir and react at 40-60℃ for 2 hours, adjust the pH value to 2-3 with dilute hydrochloric acid, extract with ethyl acetate organic phase, and then separate and evaporate to dry. Example 3

[0019] A modified starch-based petroleum drilling additive is prepared according to the following steps. S1. Take dialdehyde starch with a degree of polymerization of 83, disperse the dialdehyde starch in pure water to prepare a 10% emulsion, adjust the pH value to 4.0-5.0 with dilute hydrochloric acid, add sodium chlorite in equimolar amounts of aldehyde groups to dissolve, control the temperature to 40-50℃ and stir for 4-6 hours to oxidize the dialdehyde starch to polycarboxylated starch, take samples at regular intervals, and monitor the residual aldehyde group content using the hydrochloric acid hydroxylamine method. When the residual aldehyde group content is less than 5%, the reaction is considered complete. After the reaction is completed, add sodium bisulfite, then adjust the pH value to neutral with alkali, precipitate with ethanol, filter and wash, and vacuum dry to obtain polycarboxylated starch; S2. Weigh polycarboxylated starch and methanol at a mass ratio of 0.9:1. Disperse the polycarboxylated starch in anhydrous methanol, add the catalyst p-toluenesulfonic acid, and reflux and stir at 60-70℃ for 12-16 h. Filter, wash and dry to obtain partially esterified starch. Disperse the esterified starch in a water / DMSO mixed solvent at a concentration of 5%. Add excess condensing agent EDC and stir for 15 min. Add excess N-hydroxysuccinimide and stir for 15 min. Add alkali to adjust the pH to 7.5-8.0. Add excess sodium p-aminobenzenesulfonate according to the remaining 25% of polycarboxylated starch that has not been esterified and stir for 24 h. Use ethanol to precipitate and wash multiple times, and dry. S3. Add amidated starch to the reaction flask, purge with nitrogen, add anhydrous THF solvent to the reaction flask, add BH3THF solution dropwise under ice bath cooling, heat under reflux for 24 hours after the addition is complete, quench with methanol dropwise after the reaction is complete, and evaporate to remove the solvent. S4. Add the reduced starch to sodium hydroxide solution, stir and react at 40-60℃ for 2 hours, adjust the pH value to 2-3 with dilute hydrochloric acid, extract with ethyl acetate organic phase, and then separate and evaporate to dry. Example 4

[0020] A modified starch-based petroleum drilling additive is prepared according to the following steps. S1. Take dialdehyde starch with a degree of polymerization of 76, disperse the dialdehyde starch in pure water to prepare a 10% emulsion, adjust the pH value to 4.0-5.0 with dilute hydrochloric acid, add sodium chlorite in equimolar amounts of aldehyde groups to dissolve, control the temperature to 40-50℃ and stir for 4-6 hours to oxidize the dialdehyde starch to polycarboxylated starch, take samples at regular intervals, and monitor the residual aldehyde group content using the hydrochloric acid hydroxylamine method. When the residual aldehyde group content is less than 5%, the reaction is considered complete. After the reaction is completed, add sodium bisulfite, then adjust the pH value to neutral with alkali, precipitate with ethanol, filter and wash, and vacuum dry to obtain polycarboxylated starch; S2. Weigh polycarboxylated starch and methanol in a mass ratio of 1.2:1. Disperse the polycarboxylated starch in anhydrous methanol, add the catalyst p-toluenesulfonic acid, reflux and stir at 60-70℃ for 12-16 h, filter, wash and dry to obtain partially esterified starch. Disperse the esterified starch in a water / DMSO mixed solvent with a concentration of 5%, add excess condensing agent EDC and stir for 15 min, add excess N-hydroxysuccinimide and stir for 15 min, add alkali to adjust the pH to 7.5-8.0, add excess sodium p-aminobenzenesulfonate according to the remaining 35% of polycarboxylated starch that has not been esterified, stir and react for 24 h, precipitate and wash with ethanol multiple times, and dry. S3. Add amidated starch to the reaction flask, purge with nitrogen, add anhydrous THF solvent to the reaction flask, add BH3 THF solution dropwise under ice bath cooling, heat under reflux for 24 h after the addition is complete, quench with methanol dropwise after the reaction is complete, and evaporate to remove the solvent. S4. Add the reduced starch to sodium hydroxide solution, stir and react at 40-60℃ for 2 hours, adjust the pH value to 2-3 with dilute hydrochloric acid, extract with ethyl acetate organic phase, and then separate and evaporate to dry.

[0021] Comparative Example A modified starch-based petroleum drilling additive is prepared according to the following steps. S1. Take dialdehyde starch with a degree of polymerization of 42, disperse the dialdehyde starch in pure water to prepare a 10% emulsion, adjust the pH value to 4.0-5.0 with dilute hydrochloric acid, add sodium chlorite in equimolar amounts of aldehyde groups to dissolve, control the temperature to 40-50℃ and stir for 4-6 hours to oxidize the dialdehyde starch to polycarboxylated starch, take samples at regular intervals, and monitor the residual aldehyde group content using the hydrochloric acid hydroxylamine method. When the residual aldehyde group content is less than 5%, the reaction is considered complete. After the reaction is completed, add sodium bisulfite, then adjust the pH value to neutral with alkali, precipitate with ethanol, filter and wash, and vacuum dry to obtain polycarboxylated starch; S2. Disperse polycarboxylated starch directly in a water / DMSO mixed solvent at a concentration of 5%, add excess condensing agent EDC and stir for 15 min, add excess N-hydroxysuccinimide and stir for 15 min, add alkali to adjust the pH to 7.5-8.0, weigh out sodium p-aminobenzenesulfonate at 25% carboxyl content of polycarboxylated starch and add it to the solution, stir and react for 24 h, remove water by vacuum distillation, precipitate with cold ethanol multiple times, filter and dry; S3. Add amidated starch to a reaction flask, purge with nitrogen, add anhydrous THF solvent to the reaction flask, add BH3 THF solution dropwise under ice bath cooling, heat under reflux for 48 h after the addition is complete, quench with methanol dropwise after the reaction is complete, evaporate to remove the solvent, and obtain starch with hydroxyl and benzenesulfonic acid groups grafted on.

[0022] Performance testing 144.0 g of NaCl was added to 400 g of drilling fluid from the examples and comparative examples, respectively, to prepare soil-free saturated brine-based drilling fluids. The drilling fluids were then placed in a stainless steel aging tank and continuously rolled at 180°C for 16 hours. After aging, the fluids were cooled to room temperature and then stirred at 6000 rpm for 20 minutes. The apparent viscosity (AV), plastic viscosity (PV), dynamic shear force (YP), and API filtration loss (FL) of the drilling fluids before and after high-temperature aging were determined according to the petroleum and natural gas industry standard GB / T29170-2012 "Petroleum and Natural Gas Industry - Drilling Fluid Laboratory Testing". API and high temperature and high pressure filtration loss FL HTHP (180℃, 3.5MPa).

[0023] The above results show that the modified starch prepared in Examples 1-4 and the comparative examples all exhibit excellent rheological and anti-filtration effects after aging at 180°C, proving that grafting rigid benzene rings onto the starch chain can improve the starch's temperature tolerance. After reduction of the polycarboxylated starch by BH3 THF, the carboxyl groups are converted into hydroxyl groups. The numerical results of Examples 1 and the comparative examples show that the large number of carboxyl groups grafted onto the modified starch can improve the hydration effect of the drilling fluid compared to hydroxyl groups, and has excellent thickening, shearing, and anti-collapse properties.

[0024] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an oil drilling additive based on modified starch, characterized in that, Includes the following steps, S1. Oxidize dialdehyde starch to polycarboxylated starch using sodium chlorite; S2. The polycarboxylated starch is esterified and then subjected to an amidation reaction with sodium p-aminobenzenesulfonate; S3. Use a reducing agent to reduce the amide bond; S4. The starch after reduction treatment is obtained by lipohydrolysis.

2. The method for preparing a modified starch-based petroleum drilling additive according to claim 1, characterized in that, In step S1, the dialdehyde starch is dispersed in a solvent, the pH is adjusted to acidic, sodium chlorite is added to dissolve it, and the temperature is controlled at 40-50℃ and stirred for 4-6 hours.

3. The method for preparing a modified starch-based petroleum drilling additive according to claim 1, characterized in that, In step S2, polycarboxylated starch is dispersed in anhydrous methanol, a catalyst is added, and the mixture is refluxed and stirred at 60-70°C for 12-16 hours.

4. The method for preparing a modified starch-based petroleum drilling additive according to claim 1, characterized in that, In step S2, the esterified starch is dispersed in a buffer solution, condensing agent EDC is added and stirred for 15 min, N-hydroxysuccinimide is added and stirred for 15 min, the pH is adjusted to 7.5-8.0, sodium p-aminobenzenesulfonate is added and stirred for 24 h.

5. The method for preparing a modified starch-based petroleum drilling additive according to claim 1, characterized in that, In step S3, under nitrogen protection, dry starch is added to anhydrous THF solvent, BH3 THF solution is added dropwise, the mixture is heated under reflux for 24 hours, and then quenched with methanol.

6. The method for preparing a modified starch-based petroleum drilling additive according to claim 1, characterized in that, In step S4, the reduced starch is added to a sodium hydroxide solution and stirred at 40-60℃ for 2 hours. The pH is adjusted to acidic, and the organic phase is extracted and then evaporated and dried to obtain the final product.

7. The method for preparing a modified starch-based petroleum drilling additive according to claim 1, characterized in that, The degree of polymerization n of the dialdehyde starch is 40-100.

8. The method for preparing a modified starch-based petroleum drilling additive according to claim 3, characterized in that, The mass ratio of the polycarboxylated starch to methanol is (0.9-1.2):

1.

9. A modified starch-based petroleum drilling additive, characterized in that, Prepared by any of the methods described in claims 1-8.

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