Solid-free well killing fluid for oil and gas field and preparation method of solid-free well killing fluid

Abstract

The invention relates to the technical field of well killing fluids, and discloses a solid-free well killing fluid for oil and gas fields and a preparation method of the solid-free well killing fluid. The solid-free well killing fluid for the oil and gas field is obtained by stirring and mixing water, potassium formate, calcium chloride, gemini imidazoline quaternary ammonium salt modified polyacrylamide and pyridine sulfonate modified hydroxyethyl cellulose. Due to the imidazole ring, the benzene ring and the long-chain alkyl with relatively large steric hindrance, the rigidity of the polyacrylamide is enhanced, the curl of a molecular chain is weakened, the movement capability of the molecular chain segment at high temperature is reduced, and the high-temperature resistance of the well killing fluid is improved; the imidazoline quaternary ammonium salt group can be combined with clay mineral particles on the rock surface to form a compact adsorption layer, so that water in the well killing fluid entering the well wall is reduced, and the filtrate loss reduction performance is improved; a pyridine group and a sulfonic acid group which have relatively strong polarity and hydrophilicity are introduced into hydroxyethyl cellulose, so that the hydration dispersity, high temperature resistance and adsorption capacity of cellulose in the well killing fluid are improved, and the filtrate loss reduction performance of the well killing fluid is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of well killing fluid, in particular to a solid-phase-free well killing fluid for oil and gas fields and a preparation method thereof. Background Art

[0002] Well repair operations are usually required in the later stage of oil field development. During the operation, the wellbore usually needs to be filled with well killing fluid. Well killing fluid with excellent performance should not only prevent the formation fluid from flowing into the wellbore and causing accidents such as blowouts, but also prevent the well killing fluid from leaking into the formation. The loss of well killing fluid will cause serious formation damage and reduce the formation permeability, which will in turn lead to a decrease in the production capacity of oil and gas wells. More seriously, it will cause blowouts, causing unsafe operations and environmental pollution. In order to solve the leakage problem, additives such as fluid loss reducers are usually added to the well killing fluid to increase the flow resistance of the well killing fluid and prevent the well killing fluid from flowing to the near-well area. As the drilling depth continues to increase, the temperature of the formation is also getting higher and higher, which puts higher requirements on the performance of the well killing fluid. Among them, fluid loss reducers are one of the important additives that affect the temperature resistance of well killing fluids. Their structure and function play a vital role in the stability of the wellbore wall. In the document "A New Low-cost Anti-scaling Composite Salt High-density Solid-free Well Killing Fluid", a high-efficiency scale inhibition technology was used and a new weighting agent was developed. At the same time, cheap inorganic salts were widely selected to prepare the base fluid. A new low-cost anti-scaling composite salt high-density solid-free well killing fluid system was developed. It has the advantages of low cost, high density, no solid phase and non-toxicity, but the filtration loss reduction performance and high temperature resistance of the well killing fluid have not been improved. Summary of the invention

[0003] 1. Technical issues to be resolved In view of the shortcomings of the prior art, the present invention provides a solid-free well-killing fluid for oil and gas fields and a preparation method thereof. The solid-free well-killing fluid prepared by the present invention has good fluid loss reduction performance and high temperature resistance performance.

[0004] (II) Technical solution To achieve the above object, the present invention provides the following technical solution: a solid-free well-killing fluid for oil and gas fields, comprising the following components by weight: 70-90 parts by weight of water, 15-18 parts by weight of potassium formate, 10-14 parts by weight of calcium chloride, 0.5-0.8 parts by weight of gemini imidazoline quaternary ammonium salt modified polyacrylamide, and 0.3-0.6 parts by weight of pyridine sulfonate modified hydroxyethyl cellulose; Preferably, the preparation method of the gemini imidazoline quaternary ammonium salt modified polyacrylamide comprises the following steps: (1) Add triethylenetetramine to a reactor, raise the temperature to 100-115°C, and drop oleic acid thereinto, the dropping time being controlled at 20-40 min. After the dropping is completed, raise the temperature to 145-155°C, continue the reaction for 1-3 h until no water is generated, then raise the temperature to 220-240°C and react for 7-9 h. After the reaction is completed, perform vacuum distillation to obtain gemini imidazoline; (2) Add 7-11 g of 1-allyl-3-chlorobenzene and 8-14 g of geminimidoline to an acetone solvent, stir to dissolve, heat to 60-65° C., and reflux at 300-500 rpm for 4-6 hours. After the reaction is completed, filter, wash, and dry by rotary evaporation to obtain an alkenyl-containing geminimidoline quaternary ammonium salt; (3) Add 15-18 g of acrylamide, 6-9 g of alkenyl-containing gemini imidazoline quaternary ammonium salt, 4-7 g of N-vinyl pyrrolidone, and 5-10 g of N,N-dimethylacrylamide to deionized water, stir and dissolve, add 3-5 g of 38%-42% sodium hydroxide solution to adjust the pH to neutral, control the temperature at 22-30°C, pass nitrogen for 25-40 min to remove oxygen, add 0.06-0.09 g of benzoyl peroxide oxidant and 0.05-0.07 g of sodium bisulfite reducing agent, heat to reaction temperature and react for 4-8 h. After the reaction is completed, wash and dry to obtain gemini imidazoline quaternary ammonium salt modified polyacrylamide; Preferably, the method for preparing the pyridine sulfonate-modified hydroxyethyl cellulose comprises the following steps: S1. Add 10-14 g of 2,4-diaminopyridine to deionized water, stir to dissolve, heat to 85-95 ° C, take 14-16 g of p-mercaptobenzenesulfonic acid and dissolve it in deionized water, then add it dropwise to the 2,4-diaminopyridine solution, keep warm for 2-2.5 hours, and after the reaction is completed, cool naturally, filter, wash and dry to obtain pyridine sulfonate; S2. Add 8-13 g of 3,4-epoxy-2-methyl-1-butene and 5-7 g of pyridine sulfonate to N,N-dimethylformamide solvent, stir and mix, then add 0.04-0.08 g of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 36-42 ° C. After the reaction is completed, centrifuge, wash and dry to obtain intermediate 1; S3. Dissolve 7-15 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 5-10 g of intermediate 1 thereto, stir and mix, heat to 50-70°C, add 0.07-0.08 g of tin tetrachloride catalyst thereto, reflux for 1-3 h, after the reaction is completed, cool, remove the dimethyl sulfoxide solvent by solvent replacement with ethyl acetate, filter to obtain a solid product, disperse the solid product in distilled water and dialyze for 12-16 h, rotary evaporate, and freeze-dry to obtain pyridine sulfonate modified hydroxyethyl cellulose.

[0005] Preferably, in step (1), the mass ratio of triethylenetetramine to oleic acid is 1.8-2.2:1.

[0006] Preferably, the reaction temperature in step (3) is 45-60°C.

[0007] Preferably, the ultraviolet light irradiation time in S2 is 2.5-3h.

[0008] Preferably, the preparation method of the solid-free well-killing fluid for oil and gas fields is: add water, potassium formate and calcium chloride into a reactor, stir for 2-5 minutes, then add gemini imidazoline quaternary ammonium salt modified polyacrylamide and pyridine sulfonate modified hydroxyethyl cellulose, stir and mix for 8-12 minutes to obtain the solid-free well-killing fluid for oil and gas fields.

[0009] 3. Beneficial technical effects The invention obtains solid-phase-free well-killing fluid for oil and gas fields by stirring and mixing water, potassium formate, calcium chloride, gemini-imidazoline quaternary ammonium salt-modified polyacrylamide and pyridine sulfonate-modified hydroxyethyl cellulose.

[0010] The carboxyl group in oleic acid reacts with triethylenetetramine to undergo amidation and cyclization to obtain gemini imidazoline and introduce long-chain alkyl groups. The chlorine in 1-allyl-3-chlorobenzene reacts with gemini imidazoline to undergo quaternization to obtain alkenyl-containing gemini imidazoline quaternary ammonium salt. Acrylamide, alkenyl-containing gemini imidazoline quaternary ammonium salt, N-vinyl pyrrolidone, and N,N-dimethylacrylamide undergo polymerization to obtain gemini imidazoline quaternary ammonium salt-modified polyacrylamide. The amino group in 2,4-diaminopyridine reacts with the sulfonic acid group in p-mercaptobenzenesulfonic acid to obtain pyridine sulfonate. The mercapto group in pyridine sulfonate reacts with the alkenyl group in 3,4-epoxy-2-methyl-1-butene to introduce epoxy groups to obtain intermediate 1. The epoxy group in intermediate 1 reacts with hydroxyethyl cellulose to obtain pyridine sulfonate-modified hydroxyethyl cellulose.

[0011] In the polyacrylamide modified by gemini imidazoline quaternary ammonium salt, the imidazole ring, benzene ring and long-chain alkyl with large steric hindrance enhance the rigidity of polyacrylamide, weaken the curling of the molecular chain, reduce the mobility of the polyacrylamide molecular chain segments in a high-temperature environment, and improve the high-temperature resistance of the well-killing fluid; the imidazoline quaternary ammonium salt group has strong adsorption and can be tightly combined with the clay mineral particles on the surface of the rock to form a dense adsorption layer, reducing the water in the well-killing fluid from entering the well wall, thereby reducing the filtration loss and improving the filtration loss reduction performance of the well-killing fluid; hydroxyethyl cellulose is a natural high molecular polymer filtration loss reducer. By introducing pyridine groups and sulfonic acid groups with strong polarity and hydrophilicity, the hydration dispersibility, high temperature resistance and adsorption capacity of hydroxyethyl cellulose in the well-killing fluid are improved, thereby improving the filtration loss reduction performance of the well-killing fluid. DETAILED DESCRIPTION Example 1

[0012] (1) Add triethylenetetramine to a reactor, heat it to 100°C, and drop oleic acid therein, wherein the mass ratio of triethylenetetramine to oleic acid is 1.8:1, and the dropping time is controlled within 20 min. After the dropping is completed, heat it to 145°C, continue to react for 1 h until no water is generated, then heat it to 220°C and react for 7 h. After the reaction is completed, distill under reduced pressure to obtain gemini imidazoline; (2) Add 7 g of 1-allyl-3-chlorobenzene and 8 g of geminimidoline to acetone solvent, stir to dissolve, heat to 60°C, and reflux at 300 rpm for 4 h. After the reaction is completed, filter, wash and dry by rotary evaporation to obtain an alkenyl-containing geminimidoline quaternary ammonium salt; (3) Add 15 g of acrylamide, 6 g of alkenyl-containing gemini imidazoline quaternary ammonium salt, 4 g of N-vinyl pyrrolidone, and 5 g of N,N-dimethylacrylamide to deionized water, stir and dissolve, add 3 g of 38% sodium hydroxide solution to adjust the pH to neutral, control the temperature at 22°C, pass nitrogen for 25 min to remove oxygen, add 0.06 g of benzoyl peroxide oxidant and 0.05 g of sodium bisulfite reducing agent, heat to 45°C and react for 4 h. After the reaction is completed, wash and dry to obtain gemini imidazoline quaternary ammonium salt modified polyacrylamide; (4) Add 10 g of 2,4-diaminopyridine to deionized water, stir to dissolve, heat to 85°C, take 14 g of p-mercaptobenzenesulfonic acid and dissolve it in deionized water, then add it dropwise to the 2,4-diaminopyridine solution, keep the temperature for 2 h, and after the reaction is completed, cool naturally, filter, wash and dry to obtain pyridine sulfonate; (5) Add 8 g of 3,4-epoxy-2-methyl-1-butene and 5 g of pyridine sulfonate to N,N-dimethylformamide solvent, stir and mix, then add 0.04 g of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 36° C. for 2.5 h. After the reaction is completed, centrifuge, wash and dry to obtain intermediate 1; (6) Dissolve 7 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 5 g of intermediate 1 thereto, stir and mix, heat to 50° C., add 0.07 g of tin tetrachloride catalyst thereto, reflux for 1 h, cool after the reaction, replace the dimethyl sulfoxide solvent with ethyl acetate, filter to obtain a solid product, disperse the solid product in distilled water and dialyze for 12 h, rotary evaporate, and freeze-dry to obtain pyridine sulfonate modified hydroxyethyl cellulose; (7) Add 70 parts by weight of water, 15 parts by weight of potassium formate, and 10 parts by weight of calcium chloride into a reactor, stir for 2 minutes, then add 0.5 parts by weight of gemini imidazoline quaternary ammonium salt-modified polyacrylamide and 0.3 parts by weight of pyridine sulfonate-modified hydroxyethyl cellulose, stir and mix for 8 minutes to obtain a solid-free well-killing fluid for oil and gas fields. Example 2

[0013] (1) Add triethylenetetramine to a reactor, heat it to 115°C, and drop oleic acid therein, wherein the mass ratio of triethylenetetramine to oleic acid is 2.2:1, and the dropping time is controlled within 40 min. After the dropping is completed, heat it to 155°C, and continue to react for 3 h until no water is generated, then heat it to 240°C and react for 9 h. After the reaction is completed, distill under reduced pressure to obtain gemini imidazoline; (2) Add 11 g of 1-allyl-3-chlorobenzene and 14 g of geminimidoline to acetone solvent, stir to dissolve, heat to 65°C, and reflux at 500 rpm for 6 h. After the reaction is completed, filter, wash and dry by rotary evaporation to obtain an alkenyl-containing geminimidoline quaternary ammonium salt; (3) Add 18 g of acrylamide, 9 g of alkenyl-containing gemini imidazoline quaternary ammonium salt, 7 g of N-vinyl pyrrolidone, and 10 g of N,N-dimethylacrylamide to deionized water, stir and dissolve, add 5 g of 42% sodium hydroxide solution to adjust the pH to neutral, control the temperature at 30°C, pass nitrogen for 40 min to remove oxygen, add 0.09 g of benzoyl peroxide oxidant and 0.07 g of sodium bisulfite reducing agent, heat to 60°C for reaction for 8 h, wash and dry after the reaction to obtain gemini imidazoline quaternary ammonium salt modified polyacrylamide; (4) Add 14 g of 2,4-diaminopyridine to deionized water, stir to dissolve, heat to 95°C, take 16 g of p-mercaptobenzenesulfonic acid and dissolve it in deionized water, then add it dropwise to the 2,4-diaminopyridine solution, keep the temperature for reaction for 2.5 hours, and after the reaction is completed, cool naturally, filter, wash and dry to obtain pyridine sulfonate; (5) Add 13 g of 3,4-epoxy-2-methyl-1-butene and 7 g of pyridine sulfonate to N,N-dimethylformamide solvent, stir and mix, then add 0.08 g of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 42 ° C for 3 h. After the reaction is completed, centrifuge, wash and dry to obtain intermediate 1; (6) Dissolve 15 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 10 g of intermediate 1 thereto, stir and mix, heat to 70° C., add 0.08 g of tin tetrachloride catalyst thereto, reflux for 3 h, cool after the reaction, replace the dimethyl sulfoxide solvent with ethyl acetate, filter to obtain a solid product, disperse the solid product in distilled water and dialyze for 16 h, rotary evaporate, and freeze-dry to obtain pyridine sulfonate modified hydroxyethyl cellulose; (7) Add 90 parts by weight of water, 18 parts by weight of potassium formate, and 14 parts by weight of calcium chloride into a reactor, stir for 5 minutes, then add 0.8 parts by weight of gemini imidazoline quaternary ammonium salt-modified polyacrylamide and 0.6 parts by weight of pyridine sulfonate-modified hydroxyethyl cellulose, stir and mix for 12 minutes to obtain a solid-free well-killing fluid for oil and gas fields. Example 3

[0014] (1) Add triethylenetetramine to a reactor, heat it to 112°C, and drop oleic acid therein, wherein the mass ratio of triethylenetetramine to oleic acid is 2:1, and the dropping time is controlled within 30 min. After the dropping is completed, heat it to 150°C, continue to react for 2 h until no water is generated, then heat it to 230°C and react for 8 h. After the reaction is completed, distill under reduced pressure to obtain gemini imidazoline; (2) Add 9 g of 1-allyl-3-chlorobenzene and 11 g of geminimidoline to acetone solvent, stir to dissolve, heat to 62°C, and reflux at 400 rpm for 5 h. After the reaction is completed, filter, wash and dry by rotary evaporation to obtain an alkenyl-containing geminimidoline quaternary ammonium salt; (3) Add 16.5 g of acrylamide, 7.5 g of alkenyl-containing gemini imidazoline quaternary ammonium salt, 5.5 g of N-vinyl pyrrolidone, and 7.5 g of N,N-dimethylacrylamide to deionized water, stir and dissolve, add 4 g of 40% sodium hydroxide solution to adjust the pH to neutral, control the temperature at 26°C, pass nitrogen for 32 min to remove oxygen, add 0.08 g of benzoyl peroxide oxidant and 0.06 g of sodium bisulfite reducing agent, heat to 53°C for reaction for 6 h, wash and dry after the reaction to obtain gemini imidazoline quaternary ammonium salt modified polyacrylamide; (4) Add 12 g of 2,4-diaminopyridine to deionized water, stir to dissolve, heat to 90°C, take 15 g of p-mercaptobenzenesulfonic acid and dissolve it in deionized water, then add it dropwise to the 2,4-diaminopyridine solution, keep the temperature for reaction for 2.2 h, and after the reaction is completed, cool naturally, filter, wash and dry to obtain pyridine sulfonate; (5) Add 10.5 g of 3,4-epoxy-2-methyl-1-butene and 6 g of pyridine sulfonate to N,N-dimethylformamide solvent, stir and mix, then add 0.06 g of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 39 ° C for 2.8 h, after the reaction is completed, centrifuge, wash and dry to obtain intermediate 1; (6) Dissolve 11 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 7.5 g of intermediate 1 thereto, stir and mix, heat to 60°C, add 0.075 g of tin tetrachloride catalyst thereto, reflux for 2 h, cool after the reaction, remove the dimethyl sulfoxide solvent by solvent replacement with ethyl acetate, filter to obtain a solid product, disperse the solid product in distilled water and dialyze for 14 h, rotary evaporate, and freeze-dry to obtain pyridine sulfonate modified hydroxyethyl cellulose; (7) Add 80 parts by weight of water, 16.5 parts by weight of potassium formate, and 12 parts by weight of calcium chloride into a reactor, stir for 2-5 minutes, then add 0.6 parts by weight of gemini imidazoline quaternary ammonium salt-modified polyacrylamide and 0.4 parts by weight of pyridine sulfonate-modified hydroxyethyl cellulose, stir and mix for 8-12 minutes to obtain a solid-free well-killing fluid for oil and gas fields. Example 4

[0015] (1) Add triethylenetetramine to a reactor, heat it to 100°C, and drop oleic acid therein, wherein the mass ratio of triethylenetetramine to oleic acid is 1.8:1, and the dropping time is controlled within 20 min. After the dropping is completed, heat it to 145°C, continue to react for 1 h until no water is generated, then heat it to 220°C and react for 7 h. After the reaction is completed, distill under reduced pressure to obtain gemini imidazoline; (2) Add 7 g of 1-allyl-3-chlorobenzene and 8 g of geminimidoline to acetone solvent, stir to dissolve, heat to 60°C, and reflux at 300 rpm for 4 h. After the reaction is completed, filter, wash and dry by rotary evaporation to obtain an alkenyl-containing geminimidoline quaternary ammonium salt; (3) Add 15 g of acrylamide, 6 g of alkenyl-containing gemini imidazoline quaternary ammonium salt, 4 g of N-vinyl pyrrolidone, and 5 g of N,N-dimethylacrylamide to deionized water, stir and dissolve, add 3 g of 38% sodium hydroxide solution to adjust the pH to neutral, control the temperature at 22°C, pass nitrogen for 25 min to remove oxygen, add 0.06 g of benzoyl peroxide oxidant and 0.05 g of sodium bisulfite reducing agent, heat to 45°C and react for 4 h. After the reaction is completed, wash and dry to obtain gemini imidazoline quaternary ammonium salt modified polyacrylamide; (4) Add 14 g of 2,4-diaminopyridine to deionized water, stir to dissolve, heat to 95°C, take 16 g of p-mercaptobenzenesulfonic acid and dissolve it in deionized water, then add it dropwise to the 2,4-diaminopyridine solution, keep the temperature for reaction for 2.5 hours, and after the reaction is completed, cool naturally, filter, wash and dry to obtain pyridine sulfonate; (5) Add 13 g of 3,4-epoxy-2-methyl-1-butene and 7 g of pyridine sulfonate to N,N-dimethylformamide solvent, stir and mix, then add 0.08 g of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 42 ° C for 3 h. After the reaction is completed, centrifuge, wash and dry to obtain intermediate 1; (6) Dissolve 11 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 7.5 g of intermediate 1 thereto, stir and mix, heat to 60°C, add 0.075 g of tin tetrachloride catalyst thereto, reflux for 2 h, cool after the reaction, remove the dimethyl sulfoxide solvent by solvent replacement with ethyl acetate, filter to obtain a solid product, disperse the solid product in distilled water and dialyze for 14 h, rotary evaporate, and freeze-dry to obtain pyridine sulfonate modified hydroxyethyl cellulose; (7) Add 80 parts by weight of water, 16.5 parts by weight of potassium formate, and 12 parts by weight of calcium chloride into a reactor, stir for 2-5 minutes, then add 0.6 parts by weight of gemini imidazoline quaternary ammonium salt-modified polyacrylamide and 0.4 parts by weight of pyridine sulfonate-modified hydroxyethyl cellulose, stir and mix for 8-12 minutes to obtain a solid-free well-killing fluid for oil and gas fields. Example 5

[0016] (1) Add triethylenetetramine to a reactor, heat it to 112°C, and drop oleic acid therein, wherein the mass ratio of triethylenetetramine to oleic acid is 2:1, and the dropping time is controlled within 30 min. After the dropping is completed, heat it to 150°C, continue to react for 2 h until no water is generated, then heat it to 230°C and react for 8 h. After the reaction is completed, distill under reduced pressure to obtain gemini imidazoline; (2) Add 9 g of 1-allyl-3-chlorobenzene and 11 g of geminimidoline to acetone solvent, stir to dissolve, heat to 62°C, and reflux at 400 rpm for 5 h. After the reaction is completed, filter, wash and dry by rotary evaporation to obtain an alkenyl-containing geminimidoline quaternary ammonium salt; (3) Add 16.5 g of acrylamide, 7.5 g of alkenyl-containing gemini imidazoline quaternary ammonium salt, 5.5 g of N-vinyl pyrrolidone, and 7.5 g of N,N-dimethylacrylamide to deionized water, stir and dissolve, add 4 g of 40% sodium hydroxide solution to adjust the pH to neutral, control the temperature at 26°C, pass nitrogen for 32 min to remove oxygen, add 0.08 g of benzoyl peroxide oxidant and 0.06 g of sodium bisulfite reducing agent, heat to 53°C for reaction for 6 h, wash and dry after the reaction to obtain gemini imidazoline quaternary ammonium salt modified polyacrylamide; (4) Add 10 g of 2,4-diaminopyridine to deionized water, stir to dissolve, heat to 85°C, take 14 g of p-mercaptobenzenesulfonic acid and dissolve it in deionized water, then add it dropwise to the 2,4-diaminopyridine solution, keep the temperature for 2 h, and after the reaction is completed, cool naturally, filter, wash and dry to obtain pyridine sulfonate; (5) Add 8 g of 3,4-epoxy-2-methyl-1-butene and 5 g of pyridine sulfonate to N,N-dimethylformamide solvent, stir and mix, then add 0.04 g of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 36° C. for 2.5 h. After the reaction is completed, centrifuge, wash and dry to obtain intermediate 1; (6) Dissolve 15 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 10 g of intermediate 1 thereto, stir and mix, heat to 70° C., add 0.08 g of tin tetrachloride catalyst thereto, reflux for 3 h, cool after the reaction, replace the dimethyl sulfoxide solvent with ethyl acetate, filter to obtain a solid product, disperse the solid product in distilled water and dialyze for 16 h, rotary evaporate, and freeze-dry to obtain pyridine sulfonate modified hydroxyethyl cellulose; (7) Add 90 parts by weight of water, 18 parts by weight of potassium formate, and 14 parts by weight of calcium chloride into a reactor, stir for 5 minutes, then add 0.8 parts by weight of gemini imidazoline quaternary ammonium salt-modified polyacrylamide and 0.6 parts by weight of pyridine sulfonate-modified hydroxyethyl cellulose, stir and mix for 12 minutes to obtain a solid-free well-killing fluid for oil and gas fields.

[0017] Comparative Example 1 The difference between this comparative example and Example 1 is that no gemini imidazoline quaternary ammonium salt-modified polyacrylamide is added in step (7).

[0018] Comparative Example 2 The difference between this comparative example and Example 1 is that no pyridine sulfonate-modified hydroxyethyl cellulose is added in step (7).

[0019] The filtration loss of the solid-free well-killing fluid for oil and gas fields in Examples 1-5 and Comparative Examples 1-2 after aging at 20°C and 200°C for 16 hours was measured using a water loss meter, and the apparent viscosity was measured using a rotational viscometer. The test results are shown in Table 1.

[0020] Table 1: Fluid loss reduction performance test.

[0021]

[0022] As can be seen from Table 1, compared with Comparative Examples 1-2, the solid-free well killing fluid for oil and gas fields in Examples 1-5 still has lower fluid loss and higher apparent viscosity after high-temperature aging, indicating that it has good fluid loss reduction performance and high temperature resistance.

[0023] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A solid-free well-killing fluid for oil and gas fields, characterized in that: The invention comprises the following components by weight: 70-90 parts by weight of water, 15-18 parts by weight of potassium formate, 10-14 parts by weight of calcium chloride, 0.5-0.8 parts by weight of polyacrylamide modified by gemini imidazoline quaternary ammonium salt, and 0.3-0.6 parts by weight of hydroxyethyl cellulose modified by pyridine sulfonate; The preparation method of the gemini imidazoline quaternary ammonium salt modified polyacrylamide comprises the following steps: (1) Add triethylenetetramine to a reactor, raise the temperature to 100-115°C, and drop oleic acid thereinto, the dropping time being controlled at 20-40 min. After the dropping is completed, raise the temperature to 145-155°C, continue the reaction for 1-3 h until no water is generated, then raise the temperature to 220-240°C and react for 7-9 h. After the reaction is completed, perform vacuum distillation to obtain gemini imidazoline; (2) Add 7-11 g of 1-allyl-3-chlorobenzene and 8-14 g of geminimidoline to an acetone solvent, stir to dissolve, heat to 60-65° C., and reflux at 300-500 rpm for 4-6 hours. After the reaction is completed, filter, wash, and dry by rotary evaporation to obtain an alkenyl-containing geminimidoline quaternary ammonium salt; (3) Add 15-18 g of acrylamide, 6-9 g of alkenyl-containing gemini imidazoline quaternary ammonium salt, 4-7 g of N-vinyl pyrrolidone, and 5-10 g of N,N-dimethylacrylamide to deionized water, stir and dissolve, add 3-5 g of 38%-42% sodium hydroxide solution to adjust the pH to neutral, control the temperature at 22-30°C, pass nitrogen for 25-40 min to remove oxygen, add 0.06-0.09 g of benzoyl peroxide oxidant and 0.05-0.07 g of sodium bisulfite reducing agent, heat to reaction temperature and react for 4-8 h. After the reaction is completed, wash and dry to obtain gemini imidazoline quaternary ammonium salt modified polyacrylamide; The preparation method of pyridine sulfonate modified hydroxyethyl cellulose comprises the following steps: S1. Add 10-14 g of 2,4-diaminopyridine to deionized water, stir to dissolve, heat to 85-95 ° C, take 14-16 g of p-mercaptobenzenesulfonic acid and dissolve it in deionized water, then add it dropwise to the 2,4-diaminopyridine solution, keep warm for 2-2.5 hours, and after the reaction is completed, cool naturally, filter, wash and dry to obtain pyridine sulfonate; S2. Add 8-13 g of 3,4-epoxy-2-methyl-1-butene and 5-7 g of pyridine sulfonate to N,N-dimethylformamide solvent, stir and mix, then add 0.04-0.08 g of benzoin dimethyl ether photoinitiator, irradiate with 365 nm ultraviolet light at 36-42 ° C. After the reaction is completed, centrifuge, wash and dry to obtain intermediate 1; S3. Dissolve 7-15 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 5-10 g of intermediate 1 thereto, stir and mix, heat to 50-70°C, add 0.07-0.08 g of tin tetrachloride catalyst thereto, reflux for 1-3 h, after the reaction is completed, cool, remove the dimethyl sulfoxide solvent by solvent replacement with ethyl acetate, filter to obtain a solid product, disperse the solid product in distilled water and dialyze for 12-16 h, rotary evaporate, and freeze-dry to obtain pyridine sulfonate modified hydroxyethyl cellulose.

2. The solid-free well killing fluid for oil and gas fields according to claim 1, characterized in that: In the step (1), the mass ratio of triethylenetetramine to oleic acid is 1.8-2.2:

1.

3. The solid-free well killing fluid for oil and gas fields according to claim 1, characterized in that: The reaction temperature in step (3) is 45-60°C.

4. The solid-free well killing fluid for oil and gas fields according to claim 1, characterized in that: The ultraviolet light irradiation time in S2 is 2.5-3h.

5. A method for preparing a solid-free well killing fluid for oil and gas fields as claimed in any one of claims 1 to 4, characterized in that: The preparation method of the solid-free well-killing fluid for oil and gas fields comprises the following steps: adding water, potassium formate and calcium chloride into a reactor, stirring for 2-5 minutes, adding polyacrylamide modified with gemini imidazoline quaternary ammonium salt and hydroxyethyl cellulose modified with pyridine sulfonate, stirring and mixing for 8-12 minutes, and obtaining the solid-free well-killing fluid for oil and gas fields.

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