A high-temperature resistant filtration loss reducer and its preparation method

Abstract

This invention relates to the field of petrochemical technology, specifically to a high-temperature resistant filtration loss reducer and its preparation method. The preparation steps include: (1) preparing a bicyclic olefin anhydride, (2) preparing high-pressure homogenized corn starch, (3) modifying the high-pressure homogenized corn starch with the bicyclic olefin anhydride to obtain modified starch, and (4) grafting acrylamide copolymer onto the modified starch. The high-temperature resistant filtration loss reducer prepared by this invention, when used to prepare drilling fluid, can achieve a filtration loss of less than 20 mL in general formations after hot rolling at 220℃ for 16 hours, demonstrating excellent temperature resistance and filtration loss reduction performance.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and in particular to a high-temperature resistant filtration loss reducer and its preparation method. Background Technology

[0002] During drilling, due to pressure differentials, water from the drilling fluid can seep into the formation. Clay in the drilling fluid adheres to the wellbore, forming a filter cake. Adding a filtration reducer improves the structure of this filter cake, making it denser. This not only significantly reduces the risk of water entering the formation but also stabilizes the wellbore. Simultaneously, the filtration reducer increases the viscosity of the drilling fluid, increasing resistance to water entering the formation and indirectly preventing further water ingress. The effectiveness of the filtration reducer directly impacts the performance of the drilling fluid and is crucial for the successful extraction of oil and gas from the well.

[0003] Starch is a polymer of glucose with a structure similar to cellulose. Modified products are generally grafted and etherified, but esterification, carboxymethylation and cross-linking reactions can also be carried out. Starch-based filtration loss reducers are among the earliest filtration loss reducers. After being added, they can adsorb clay particles to form a spatial network structure, thereby improving the aggregation stability of clay particles. This has always been a focus of research at home and abroad.

[0004] Patent document CN201810202132.0 discloses a nano-starch filtration loss reducer for drilling fluids and its preparation method. The preparation steps include: S1, preparing nano-starch; S2, preparing etherified modified nano-starch; S3, preparing a crude nano-starch filtration loss reducer product; S4, purifying to obtain the desired nano-starch filtration loss reducer. This filtration loss reducer can significantly reduce the API filtration loss of the base fluid at room temperature and the filtration loss at high temperature and high pressure. However, starch is easily degraded at high temperatures and has poor temperature resistance. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a high-temperature resistant filtration loss reducer and its preparation method, so as to solve the problem of poor temperature resistance of starch-based filtration loss reducers.

[0006] To achieve the above objectives, the present invention provides a method for preparing a high-temperature resistant filtration loss reducing agent, comprising the following steps:

[0007] (1) Add maleic anhydride to furan, stir for 5-10 min, then purge with nitrogen for 15-20 min, stir at room temperature for 24-28 h, filter, wash, dry in vacuum, and finally dissolve in acetone to obtain a bicyclic olefinic anhydride acetone solution.

[0008] (2) Disperse corn starch in deionized water, heat at 90-95℃ for 30 min, keep warm at 60-65℃ for 30-40 min, then homogenize under high pressure, and finally freeze dry to obtain high pressure homogenized corn starch.

[0009] (3) Disperse high-pressure homogenized corn starch in deionized water, adjust the pH to 9.8-10.2 with sodium hydroxide aqueous solution, and then add bicyclic olefin anhydride acetone solution dropwise over 10-20 min. Stir the reaction and maintain the pH of the reaction system at 9.5-10 with sodium hydroxide aqueous solution during the reaction. Purify and vacuum dry to obtain modified starch.

[0010] (4) Add the reactants sequentially to deionized water, stir to dissolve, adjust the pH to 8.2-8.5 with sodium hydroxide aqueous solution, add modified starch, heat to 60-65℃, purge with nitrogen for 15-20 min, add potassium persulfate aqueous solution, continue stirring for 30-40 min, keep warm for 3-4 h, vacuum dry and pulverize to obtain high temperature resistant filtration loss reducer.

[0011] Preferably, the weight ratio of maleic anhydride to furan in step (1) is 0.98:3.4.

[0012] Preferably, the solvent used for washing in step (1) is diethyl ether.

[0013] Preferably, the concentration of the bicyclic olefin anhydride acetone solution in step (1) is 50 wt%.

[0014] Preferably, the pressure of high-pressure homogenization in step (2) is 150 MPa, and the number of times is 3.

[0015] Preferably, the weight ratio of corn starch to deionized water in step (2) is 1:10.

[0016] Preferably, the concentration of the sodium hydroxide aqueous solution in steps (3) and (4) is 20 wt%.

[0017] Preferably, in step (3), the weight ratio of high-pressure homogenized corn starch, deionized water and bicyclic olefin anhydride acetone solution is 6-18:12-36:0.5-2.

[0018] Preferably, the purification in step (3) is: Soxhlet extraction with acetone for 48-62 hours.

[0019] Preferably, the reactant monomer in step (4) is a mixture of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide and acrylic acid in a weight ratio of 4-6:2-4:1-3.

[0020] More preferably, the reactant monomer in step (4) is a mixture of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide and acrylic acid in a weight ratio of 5:3:2.

[0021] Preferably, the weight ratio of the reactant monomer, deionized water and modified starch in step (4) is 10-20:50-100:5-15.

[0022] Preferably, the concentration of the potassium persulfate aqueous solution in step (4) is 1 wt%.

[0023] Furthermore, the present invention also provides a high-temperature resistant filtration loss reducing agent, which is obtained by a method for preparing a high-temperature resistant filtration loss reducing agent.

[0024] The beneficial effects of this invention are:

[0025] This invention uses bicyclic olefin anhydride-modified high-pressure homogenized corn starch as the matrix, and grafts it with acrylamide copolymers to obtain a high-temperature resistant filtration loss reducer. This results in drilling fluids prepared with fresh water-based slurry and brine-based slurry having a high-temperature and high-pressure filtration loss of 9-12 mL and 12-15 mL respectively after hot rolling at 220℃ for 16 hours. This meets the requirement of filtration loss of less than 20 mL for general formations and has excellent temperature resistance and filtration loss reduction performance.

[0026] This invention modifies high-pressure homogenized corn starch with bicyclic olefin anhydride, introducing a large number of acidic groups, alkenyl groups, and high-temperature resistant cyclic structures into the corn starch, effectively improving the temperature resistance and filtration loss reduction properties of the corn starch.

[0027] This invention employs high-pressure homogenization to treat corn starch. The corn starch treated with high-pressure homogenization exhibits superior temperature resistance, effectively mitigating the dissociation of the filtration loss reducer prepared from it at high temperatures. Furthermore, the corn starch treated with high-pressure homogenization has more reaction sites, which can increase the grafting rate of dicyclic olefin anhydrides, thereby improving temperature resistance and filtration loss reduction performance. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0029] The corn starch used in the embodiments and comparative examples of this invention was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with product number S116030. Example 1

[0030] (1) Add 0.98g maleic anhydride to 3.4g furan, stir for 5min, then purge with nitrogen for 15min, stir at room temperature for 24h, filter, wash with ether, dry in vacuum, and finally dissolve in acetone to obtain a 50wt% dicyclic olefinic anhydride acetone solution.

[0031] (2) Disperse 10g of corn starch in 100g of deionized water, heat at 90℃ for 30 min, then keep warm at 60℃ for 30 min, then perform high-pressure homogenization at 150MPa three times, and finally freeze dry to obtain high-pressure homogenized corn starch.

[0032] (3) Disperse 6g of high-pressure homogenized corn starch in 12g of deionized water, adjust the pH to 9.9 with 20wt% sodium hydroxide aqueous solution, and then add 0.5g of 50wt% dicyclic olefin anhydride acetone solution dropwise over 10min. Stir the reaction and maintain the pH of the reaction system at 9.7 with 20wt% sodium hydroxide aqueous solution during the reaction. Soxhlet extract with acetone for 48h, and vacuum dry to obtain modified starch.

[0033] (4) Add 5g of 2-acrylamido-2-methylpropanesulfonic acid, 3g of acrylamide and 2g of acrylic acid to 50g of deionized water in sequence, stir to dissolve, adjust the pH to 8.3 with 20wt% sodium hydroxide aqueous solution, add 5g of modified starch, heat to 60℃, purge with nitrogen for 15min, add 10g of 1wt% potassium persulfate aqueous solution, continue stirring for 30min, then keep warm for 3h, vacuum dry and pulverize to obtain high temperature resistant filtration loss reducer. Example 2

[0034] (1) Add 0.98g of maleic anhydride to 3.4g of furan, stir for 10min, then purge with nitrogen for 20min, stir at room temperature for 28h, filter, wash with ether, dry in vacuum, and finally dissolve in acetone to obtain a 50wt% dicyclic olefinic anhydride acetone solution.

[0035] (2) Disperse 15g of corn starch in 150g of deionized water, heat at 90℃ for 30 min, then keep warm at 65℃ for 40 min, then perform high-pressure homogenization at 150MPa three times, and finally freeze dry to obtain high-pressure homogenized corn starch.

[0036] (3) Disperse 12g of high-pressure homogenized corn starch in 24g of deionized water, adjust the pH to 10.1 with 20wt% sodium hydroxide aqueous solution, and then add 1.2g of 50wt% bicyclic olefin anhydride acetone solution dropwise over 15min. Stir the reaction and maintain the pH of the reaction system at 9.8 with 20wt% sodium hydroxide aqueous solution during the reaction. Soxhlet extract with acetone for 54h, and vacuum dry to obtain modified starch.

[0037] (4) 7.5g of 2-acrylamido-2-methylpropanesulfonic acid, 4.5g of acrylamide and 3g of acrylic acid were added to 75g of deionized water and stirred to dissolve. The pH was adjusted to 8.4 with a 20wt% sodium hydroxide aqueous solution. Then 10g of modified starch was added, the temperature was raised to 65℃, nitrogen gas was passed through for 20min, and then 18g of a 1wt% potassium persulfate aqueous solution was added. The mixture was stirred for 40min and then kept warm for 3h. The mixture was then vacuum dried and pulverized to obtain a high-temperature resistant filtration loss reducer. Example 3

[0038] (1) Add 0.98g of maleic anhydride to 3.4g of furan, stir for 10min, then purge with nitrogen for 20min, stir at room temperature for 28h, filter, wash with ether, dry in vacuum, and finally dissolve in acetone to obtain a 50wt% dicyclic olefinic anhydride acetone solution.

[0039] (2) Disperse 20g of corn starch in 200g of deionized water, heat at 95℃ for 30 min, then keep warm at 65℃ for 40 min, then perform high-pressure homogenization at 150MPa three times, and finally freeze dry to obtain high-pressure homogenized corn starch.

[0040] (3) Disperse 18g of high-pressure homogenized corn starch in 36g of deionized water, adjust the pH to 10.2 with 20wt% sodium hydroxide aqueous solution, and then add 2g of 50wt% dicyclic olefin anhydride acetone solution dropwise over 20min. Stir the reaction and maintain the pH of the reaction system at 9.9 with 20wt% sodium hydroxide aqueous solution during the reaction. Soxhlet extract with acetone for 62h, and vacuum dry to obtain modified starch.

[0041] (4) 10g of 2-acrylamido-2-methylpropanesulfonic acid, 6g of acrylamide and 4g of acrylic acid were added to 100g of deionized water and stirred to dissolve. The pH was adjusted to 8.5 with a 20wt% sodium hydroxide aqueous solution. Then 15g of modified starch was added, the temperature was raised to 65℃, nitrogen gas was passed through for 20min, and then 25g of a 1wt% potassium persulfate aqueous solution was added. The mixture was stirred for 40min and then kept warm for 4h. The mixture was then vacuum dried and pulverized to obtain a high-temperature resistant filtration loss reducer.

[0042] Comparative Example 1:

[0043] (1) Disperse 15g of corn starch in 150g of deionized water, heat at 90℃ for 30 min, then keep warm at 65℃ for 40 min, then perform high pressure homogenization at 150MPa three times, and finally freeze dry to obtain high pressure homogenized corn starch.

[0044] (2) 7.5g of 2-acrylamido-2-methylpropanesulfonic acid, 4.5g of acrylamide and 3g of acrylic acid were added to 75g of deionized water and stirred to dissolve. The pH was adjusted to 8.4 with a 20wt% sodium hydroxide aqueous solution. Then 10g of high-pressure homogenized corn starch was added, the temperature was raised to 65℃, nitrogen gas was passed through for 20min, and then 18g of a 1wt% potassium persulfate aqueous solution was added. The mixture was stirred for 40min and then kept warm for 3h. The mixture was then vacuum dried and pulverized to obtain the filtration loss reducer.

[0045] Comparative Example 2:

[0046] (1) Disperse 15g of corn starch in 150g of deionized water, heat at 90℃ for 30 min, then keep warm at 65℃ for 40 min, then perform high pressure homogenization at 150MPa three times, and finally freeze dry to obtain high pressure homogenized corn starch.

[0047] (2) Disperse 12g of high-pressure homogenized corn starch in 24g of deionized water, adjust the pH to 10.1 with 20wt% sodium hydroxide aqueous solution, and then add 1.2g of 50wt% maleic anhydride acetone solution dropwise over 15min. Stir the reaction and maintain the pH of the reaction system at 9.8 with 20wt% sodium hydroxide aqueous solution during the reaction. Soxhlet extract with acetone for 54h, and vacuum dry to obtain modified starch.

[0048] (3) 7.5g of 2-acrylamido-2-methylpropanesulfonic acid, 4.5g of acrylamide and 3g of acrylic acid were added to 75g of deionized water and stirred to dissolve. The pH was adjusted to 8.4 with a 20wt% sodium hydroxide aqueous solution. Then 10g of modified starch was added, the temperature was raised to 65℃, nitrogen gas was passed through for 20min, and then 18g of a 1wt% potassium persulfate aqueous solution was added. The mixture was stirred for 40min and then kept warm for 3h. The mixture was then vacuum dried and pulverized to obtain the filtration loss reducer.

[0049] Comparative Example 3:

[0050] (1) Add 0.98g of maleic anhydride to 3.4g of furan, stir for 10min, then purge with nitrogen for 20min, stir at room temperature for 28h, filter, wash with ether, dry in vacuum, and finally dissolve in acetone to obtain a 50wt% dicyclic olefinic anhydride acetone solution.

[0051] (2) Disperse 12g of corn starch in 24g of deionized water, adjust the pH to 10.1 with 20wt% sodium hydroxide aqueous solution, and then add 1.2g of 50wt% dicyclic olefin anhydride acetone solution dropwise over 15min. Stir the reaction and maintain the pH of the reaction system at 9.8 with 20wt% sodium hydroxide aqueous solution during the reaction. Soxhlet extract with acetone for 54h, and vacuum dry to obtain modified starch.

[0052] (3) 7.5g of 2-acrylamido-2-methylpropanesulfonic acid, 4.5g of acrylamide and 3g of acrylic acid were added to 75g of deionized water and stirred to dissolve. The pH was adjusted to 8.4 with a 20wt% sodium hydroxide aqueous solution. Then 10g of modified starch was added, the temperature was raised to 65℃, nitrogen gas was passed through for 20min, and then 18g of a 1wt% potassium persulfate aqueous solution was added. The mixture was stirred for 40min and then kept warm for 3h. The mixture was then vacuum dried and pulverized to obtain the filtration loss reducer.

[0053] Comparative Example 4:

[0054] 7.5g of 2-acrylamido-2-methylpropanesulfonic acid, 4.5g of acrylamide and 3g of acrylic acid were added sequentially to 75g of deionized water and stirred to dissolve. The pH was adjusted to 8.4 with a 20wt% sodium hydroxide aqueous solution, and then 10g of corn starch was added. The mixture was heated to 65℃ and purged with nitrogen for 20min. Then, 18g of a 1wt% potassium persulfate aqueous solution was added and stirred for another 40min. The mixture was then kept at this temperature for 3h, vacuum dried and pulverized to obtain a high-temperature resistant filtration loss reducer.

[0055] Performance testing:

[0056] Preparation of freshwater-based slurry: Add 40g of sodium bentonite and 4g of sodium carbonate to 1000ml of water, stir for 30min, and hydrate and cure at room temperature for 24h.

[0057] Preparation of brine-based slurry: Add 200g sodium chloride, 40g sodium bentonite and 4g sodium carbonate to 1000ml of water, stir for 30min, and hydrate and cure at room temperature for 24h.

[0058] For drilling fluid preparation, the filtration loss reducer prepared according to the examples and comparative proportions is added to different base slurries. The addition amount is 20g of filtration loss reducer per 1000ml of base slurry. Stir for 20min, and pause at least once in the middle to scrape off the filtration loss reducer adhering to the cup wall. Cure at room temperature for 2h.

[0059] Rheology: The rheology of drilling fluid prepared with fresh water-based slurry was measured using a six-speed viscometer. After the measurement, the drilling fluid was placed in an aging tank and heated and rolled at 220°C for 16 hours in a high-temperature roller heating furnace. After cooling, the sample was stirred evenly and its apparent viscosity (AV) and plastic viscosity (PV) were measured. The results are shown in Table 1.

[0060] Filtration reduction: The filtration reduction of drilling fluid was measured using a high-temperature and high-pressure filtration tester. The high-temperature and high-pressure filtration loss (HTHP) was measured after hot rolling at 220℃ for 16 hours. The results are shown in Table 1.

[0061]

[0062] Data Analysis:

[0063] As can be seen from the rheological properties of Examples 1-3 in Table 1, the high-temperature resistant filtration loss reducing agents prepared in this invention all enhance the rheological properties of bentonite. This is because the SO₂ on the molecular chain of the high-temperature resistant filtration loss reducing agents... 3- The positive charges on the radical groups and bentonite end faces interact, thus increasing the viscosity of the drilling fluid after the addition of the filtration loss reducer. After hot rolling at 220℃ for 16 hours, the apparent viscosity and plastic viscosity of the freshwater-based slurry containing the filtration loss reducer showed a slight decrease. This is because the high temperature affected the adsorption of the long chain of the filtration loss reducer to bentonite, causing the bentonite to detach from the polymer long chain. As can be seen from the high-temperature and high-pressure filtration loss of Examples 1-3 in Table 1, the high-temperature resistant filtration loss reducer prepared in this invention results in high-temperature and high-pressure filtration losses of 9-12 mL and 12-15 mL for drilling fluids prepared with freshwater-based and brine-based slurries after hot rolling at 220℃ for 16 hours, respectively. This meets the requirement of less than 20 mL filtration loss in general formations, indicating that it has excellent temperature resistance and filtration loss reduction performance.

[0064] As can be seen from the data in Example 2 and Comparative Examples 1-2 in Table 1, modifying corn starch with bicyclic olefin anhydride can effectively improve the temperature resistance and filtration loss reduction performance of the prepared filtration loss reducer. This is because bicyclic olefin anhydride introduces a large number of acidic groups, alkenyl groups and high-temperature resistant cyclic structures on the surface of corn starch. The acidic groups help to improve the interaction between the filtration loss reducer and bentonite, the alkenyl groups help to form chain structures with the reactants, and the high-temperature resistant cyclic structures help to improve the temperature resistance.

[0065] As can be seen from the data in Example 2 and Comparative Example 3 in Table 1, high-pressure homogenization of corn starch helps to improve the temperature resistance and filtration loss reduction performance of the prepared filtration loss reduction agent. This is mainly because the unstable chemical bonds in the corn starch after high-pressure homogenization are destroyed, thereby avoiding the dissociation of the prepared filtration loss reduction agent at high temperature. In addition, the corn starch after high-pressure homogenization has more reaction sites, which can increase the grafting rate of bicyclic olefin anhydrides, thereby improving the temperature resistance and filtration loss reduction performance.

[0066] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing a high-temperature resistant fluid loss additive, characterized in that, The method comprises the following steps: (1) adding maleic anhydride into furan, stirring for 5-10 min, then passing nitrogen for 15-20 min, stirring at room temperature for 24-28 h, filtering, washing, drying in vacuum, and finally dissolving in acetone to obtain a dicyclic olefin anhydride acetone solution; (2) dispersing corn starch in deionized water, heating at 90-95 ℃ for 30 min, then keeping at 60-65 ℃ for 30-40 min, high-pressure homogenizing, and finally freeze-drying to obtain high-pressure homogenized corn starch; (3) dispersing the high-pressure homogenized corn starch in deionized water, adjusting the pH to 9.8-10.2 with sodium hydroxide solution, then adding the dicyclic olefin anhydride acetone solution dropwise, completing the dropwise addition within 10-20 min, stirring and reacting, keeping the pH of the reaction system at 9.5-10 with sodium hydroxide solution during the reaction, purifying, drying in vacuum, and obtaining modified starch; (4) adding reaction monomers into deionized water in sequence, stirring and dissolving, adjusting the pH to 8.2-8.5 with sodium hydroxide solution, then adding the modified starch, heating to 60-65 ℃, passing nitrogen for 15-20 min, adding potassium persulfate solution, continuing to stir for 30-40 min, then keeping for 3-4 h, drying in vacuum and crushing to obtain a high-temperature resistant filtrate loss reducer; In the step (3), the weight ratio of the high-pressure homogenized corn starch, deionized water and dicyclic olefin anhydride acetone solution is 6-18:12-36:0.5-2; In the step (4), the reaction monomers are a mixture of 2-acrylamido-2-methylpropane sulfonic acid, acrylamide and acrylic acid in a weight ratio of 5:3:2; In the step (4), the weight ratio of the reaction monomers, deionized water and modified starch is 10-20:50-100:5-15; In the step (1), the concentration of the dicyclic olefin anhydride acetone solution is 50 wt%.

2. The method for preparing the high-temperature-resistant fluid loss additive according to claim 1, characterized in that, In the step (1), the weight ratio of maleic anhydride and furan is 0.98:3.

4.

3. The method for preparing the high-temperature-resistant fluid loss additive according to claim 1, characterized in that, In the step (1), the solvent for washing is diethyl ether.

4. The method for preparing the high-temperature-resistant fluid loss additive according to claim 1, characterized in that, In the step (2), the pressure for high-pressure homogenization is 150 MPa, and the number of times is 3.

5. The method for preparing the high-temperature-resistant fluid loss additive according to claim 1, characterized in that, In the step (2), the weight ratio of corn starch and deionized water is 1:

10.

6. The method for preparing the high-temperature-resistant fluid loss additive according to claim 1, characterized in that, In the steps (3) and (4), the concentration of the sodium hydroxide solution is 20 wt%.

7. The method for preparing the high-temperature resistant filtration loss reducing agent according to claim 1, characterized in that, In the step (3), the purification is Soxhlet extraction with acetone for 48-62 h.

8. The method for preparing the high-temperature-resistant fluid loss additive according to claim 1, characterized in that, In the step (4), the concentration of the potassium persulfate solution is 1 wt%.

9. A high temperature resistant fluid loss additive characterized in that, The high-temperature resistant filtrate loss reducer is prepared by the method of any one of claims 1-8.

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