An oil and gas field solid-free kill fluid and its preparation method

Abstract

The present invention relates to the technical field of kill fluids, and discloses a solid-free kill fluid for oil and gas fields and a preparation method thereof. In the present invention, water, potassium formate, calcium chloride, Gemini imidazoline quaternary ammonium salt modified polyacrylamide, and pyridine sulfonate modified hydroxyethyl cellulose are stirred and mixed to obtain a solid-free kill fluid for oil and gas fields. The imidazole ring, benzene ring, and long-chain alkyl groups with large steric hindrance enhance the rigidity of polyacrylamide, weaken the curling of molecular chains, reduce the movement ability of molecular chain segments at high temperatures, and improve the high-temperature resistance of the kill fluid; the imidazoline quaternary ammonium salt group can combine with clay mineral particles on the rock surface to form a dense adsorption layer, reduce the entry of water in the kill fluid into the wellbore, and improve the fluid loss reduction performance; by introducing pyridine groups and sulfonic acid groups with strong polarity and hydrophilicity into hydroxyethyl cellulose, the hydration dispersibility, high-temperature resistance, and adsorption capacity of cellulose in the kill fluid are improved, thereby improving the fluid loss reduction performance of the kill fluid.

Description

Technical Field

[0001] The present invention relates to the technical field of kill fluids, and particularly to a solids-free kill fluid for oil and gas fields and a preparation method thereof. Background Art

[0002] During the late stage of oilfield development, workover operations are usually required. When conducting operations, the wellbore usually needs to be filled with kill fluid. A kill fluid with excellent performance should not only prevent formation fluids from flowing into the wellbore and causing blowout and other accidents, but also prevent the kill fluid from leaking into the formation. After the kill fluid leaks, it will cause serious formation damage, reduce the formation permeability, and then lead to a decrease in the productivity of oil and gas wells. More seriously, it will cause blowout, resulting in unsafe operations and environmental pollution problems. To solve the leakage problem, additives such as fluid loss control agents are usually added to the kill fluid to increase the flow resistance of the kill fluid and prevent the kill fluid from flowing into the near-wellbore zone. As the drilling depth continues to increase, the formation temperature is also getting higher and higher, putting higher requirements on the performance of the kill fluid. Among them, the fluid loss control agent is one of the important additives affecting the temperature resistance of the kill fluid, and its structure and function play a crucial role in wellbore stability. In the literature "A New Type of Low-Cost Scale-Inhibiting Composite Salt High-Density Solids-Free Kill Fluid", an efficient scale-inhibiting technology was adopted and a new type of weighting agent was developed. At the same time, inexpensive inorganic salts were widely selected to prepare the base fluid, and a new type of low-cost scale-inhibiting composite salt high-density solids-free kill fluid system was developed, which has the advantages of low cost, high density, solids-free, and non-toxicity. However, the fluid loss reduction performance and high-temperature resistance performance of its kill fluid have not been improved. Summary of the Invention

[0003] (I) Technical Problems to be Solved

[0004] Aiming at the deficiencies of the prior art, the present invention provides a solids-free kill fluid for oil and gas fields and a preparation method thereof. The solids-free kill fluid prepared by the present invention has good fluid loss reduction performance and high-temperature resistance performance.

[0005] (II) Technical Solutions

[0006] To achieve the above object, the present invention provides the following technical solutions: A solids-free kill fluid for oil and gas fields, comprising the following weight components: 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 bis-imidazoline quaternary ammonium salt modified polyacrylamide, and 0.3-0.6 parts by weight of pyridine sulfonate modified hydroxyethyl cellulose;

[0007] Preferably, the preparation method of the bis-imidazoline quaternary ammonium salt modified polyacrylamide, wherein, comprises the following steps:

[0008] (1)Add triethylenetetramine to the reactor, heat up to 100 - 115 °C, and dropwise add oleic acid thereto. The dropping time is controlled within 20 - 40 min. After the dropping is completed, heat up to 145 - 155 °C and continue the reaction for 1 - 3 h until no water is generated. Then heat up to 220 - 240 °C and react for 7 - 9 h. After the reaction is completed, perform vacuum distillation to obtain gemini imidazoline;

[0009] (2)Add 7 - 11 g of 1 - allyl - 3 - chlorobenzene and 8 - 14 g of gemini imidazoline to the acetone solvent, stir to dissolve, heat up to 60 - 65 °C, and reflux and heat at 300 - 500 rpm for 4 - 6 h. After the reaction is completed, perform suction filtration, washing, and rotary evaporation drying to obtain alkenyl - containing gemini imidazoline quaternary ammonium salt;

[0010] (3)Add 15 - 18 g of acrylamide, 6 - 9 g of alkenyl - containing gemini imidazoline quaternary ammonium salt, 4 - 7 g of N - vinylpyrrolidone, and 5 - 10 g of N,N - dimethylacrylamide to deionized water, stir to dissolve, add 3 - 5 g of sodium hydroxide solution with a mass fraction of 38% - 42% to adjust the pH to neutral, control the temperature at 22 - 30 °C, introduce 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 reductant, heat up to the reaction temperature and react for 4 - 8 h. After the reaction is completed, perform washing and drying to obtain gemini imidazoline quaternary ammonium salt - modified polyacrylamide;

[0011] Preferably, the preparation method of the pyridine sulfonate - modified hydroxyethyl cellulose includes the following steps:

[0012] S1. Add 10 - 14 g of 2,4 - diamino pyridine to deionized water, stir to dissolve, heat up to 85 - 95 °C. Take 14 - 16 g of p - mercaptobenzenesulfonic acid and dissolve it in deionized water, then drop it into the 2,4 - diamino pyridine solution, keep the temperature for reaction for 2 - 2.5 h. After the reaction is completed, cool naturally, perform suction filtration, washing, and drying to obtain pyridine sulfonate;

[0013] S2. Add 8 - 13 g of 3,4 - epoxy - 2 - methyl - 1 - butene and 5 - 7 g of pyridine sulfonate to the N,N - dimethylformamide solvent, stir and mix, then add 0.04 - 0.08 g of benzoin dimethyl ether photo - initiator, irradiate with ultraviolet light of 365 nm at 36 - 42 °C. After the reaction is completed, perform centrifugal separation, washing, and drying to obtain intermediate 1;

[0014] S3. Dissolve 7 - 15 g of hydroxyethyl cellulose in the dehydrated dimethyl sulfoxide solvent, add 5 - 10 g of Intermediate 1 thereto, stir and mix, heat up to 50 - 70 °C, then add 0.07 - 0.08 g of stannic chloride catalyst thereto, reflux and react for 1 - 3 h. After the reaction is completed, cool, replace the dimethyl sulfoxide solvent with ethyl acetate by solvent displacement, filter by suction to obtain a solid product, disperse the solid product in distilled water and dialyze for 12 - 16 h, perform rotary evaporation, and freeze - dry to obtain pyridine sulfonate - modified hydroxyethyl cellulose.

[0015] Preferably, in the step (1), the mass ratio of triethylenetetramine to oleic acid is 1.8 - 2.2:1.

[0016] Preferably, in the step (3), the reaction temperature is 45 - 60 °C.

[0017] Preferably, in S2, the ultraviolet light irradiation time is 2.5 - 3 h.

[0018] Preferably, the preparation method of the solid - free kill fluid for oil and gas fields is as follows: Add water, potassium formate, and calcium chloride to a reactor, stir for 2 - 5 min, then add gemini imidazoline quaternary ammonium salt - modified polyacrylamide and pyridine sulfonate - modified hydroxyethyl cellulose, and stir and mix for 8 - 12 min to obtain the solid - free kill fluid for oil and gas fields.

[0019] (III) Beneficial technical effects

[0020] In the present invention, by stirring and mixing water, potassium formate, calcium chloride, gemini imidazoline quaternary ammonium salt - modified polyacrylamide, and pyridine sulfonate - modified hydroxyethyl cellulose, a solid - free kill fluid for oil and gas fields is obtained.

[0021] The carboxyl group in oleic acid undergoes an amidation reaction and a cyclization reaction with triethylenetetramine to obtain gemini imidazoline and introduce a long - chain alkyl group. The chlorine in 1 - allyl - 3 - chlorobenzene undergoes a quaternization reaction with gemini imidazoline to obtain an allyl - containing gemini imidazoline quaternary ammonium salt. Acrylamide, the allyl - containing gemini imidazoline quaternary ammonium salt, N - vinylpyrrolidone, and N,N - dimethylacrylamide undergo a polymerization reaction to obtain gemini imidazoline quaternary ammonium salt - modified polyacrylamide. The amino group in 2,4 - diamino pyridine reacts with the sulfonic acid group in p - mercaptobenzenesulfonic acid to obtain pyridine sulfonate. The mercapto group in pyridine sulfonate undergoes a click reaction with the alkenyl group in 3,4 - epoxy - 2 - methyl - 1 - butene to introduce an epoxy group and obtain Intermediate 1. The epoxy group in Intermediate 1 undergoes a ring - opening addition reaction with hydroxyethyl cellulose to obtain pyridine sulfonate - modified hydroxyethyl cellulose.

[0022] In the gemini imidazoline quaternary ammonium salt modified polyacrylamide, the imidazole ring, benzene ring and long-chain alkyl groups with large steric hindrance enhance the rigidity of polyacrylamide, weaken the curling of molecular chains, reduce the movement ability of polyacrylamide molecular segments in high-temperature environments, and improve the high-temperature resistance of the kill fluid; the imidazoline quaternary ammonium salt group has strong adsorption ability, can tightly combine with clay mineral particles on the rock surface to form a dense adsorption layer, reduce the water in the kill fluid from entering the wellbore, thereby reducing the filtration loss and improving the fluid loss reduction performance of the kill fluid; hydroxyethyl cellulose is a natural polymer fluid loss reducer. By introducing strongly polar and hydrophilic pyridine groups and sulfonic acid groups, the hydration dispersibility, high-temperature resistance and adsorption ability of hydroxyethyl cellulose in the kill fluid are improved, and further the fluid loss reduction performance of the kill fluid is improved. Detailed implementation mode Example 1

[0023] (1) Add triethylenetetramine to the reactor, heat up to 100 °C, and drip oleic acid into it. The mass ratio of triethylenetetramine to oleic acid is 1.8:1, and the dripping time is controlled within 20 min. After the dripping is completed, heat up to 145 °C and continue to react for 1 h until no water is generated, and then heat up to 220 °C and react for 7 h. After the reaction is completed, carry out vacuum distillation to obtain gemini imidazoline;

[0024] (2) Add 7 g of 1-allyl-3-chlorobenzene and 8 g of gemini imidazoline to the acetone solvent, stir to dissolve, heat up to 60 °C, and reflux and heat at 300 rpm for 4 h. After the reaction is completed, carry out suction filtration, washing and rotary evaporation drying to obtain the alkenyl-containing gemini imidazoline quaternary ammonium salt;

[0025] (3) Add 15 g of acrylamide, 6 g of the alkenyl-containing gemini imidazoline quaternary ammonium salt, 4 g of N-vinylpyrrolidone, and 5 g of N,N-dimethylacrylamide to deionized water, stir to dissolve, add 3 g of a sodium hydroxide solution with a mass fraction of 38% to adjust the pH to neutral, control the temperature at 22 °C, introduce nitrogen for 25 min to remove oxygen, add 0.06 g of benzoyl peroxide oxidant and 0.05 g of sodium bisulfite reductant, heat up to 45 °C and react for 4 h. After the reaction is completed, carry out washing and drying to obtain the gemini imidazoline quaternary ammonium salt modified polyacrylamide;

[0026] (4) Add 10 g of 2,4-diaminopyridine to deionized water, stir to dissolve, heat up to 85 °C, dissolve 14 g of p-mercaptobenzenesulfonic acid in deionized water, and then drip it into the 2,4-diaminopyridine solution, keep the temperature for reaction for 2 h. After the reaction is completed, naturally cool, carry out suction filtration, washing and drying to obtain pyridine sulfonate;

[0027] (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 thereto, irradiate with ultraviolet light at 365 nm at 36 °C for 2.5 h, after the reaction is completed, centrifuge, wash and dry to obtain intermediate 1;

[0028] (6) Dissolve 7 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 5 g of intermediate 1 thereto, stir and mix, heat up to 50 °C, then add 0.07 g of tin tetrachloride catalyst thereto, reflux and react for 1 h, after the reaction is completed, cool, replace the dimethyl sulfoxide solvent with ethyl acetate by solvent replacement, 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;

[0029] (7) Add 70 parts by weight of water, 15 parts by weight of potassium formate, and 10 parts by weight of calcium chloride to the reactor, stir for 2 min, then add 0.5 part by weight of gemini imidazoline quaternary ammonium salt-modified polyacrylamide and 0.3 part by weight of pyridine sulfonate-modified hydroxyethyl cellulose, stir and mix for 8 min to obtain a solid-free kill fluid for oil and gas fields. Example 2

[0030] (1) Add triethylenetetramine to the reactor, heat up to 115 °C, dropwise add oleic acid thereto, wherein the mass ratio of triethylenetetramine to oleic acid is 2.2:1, control the dropping time within 40 min, after the dropping is completed, heat up to 155 °C, continue to react for 3 h until no water is generated, then heat up to 240 °C and react for 9 h, after the reaction is completed, carry out vacuum distillation to obtain gemini imidazoline;

[0031] (2) Add 11 g of 1-allyl-3-chlorobenzene and 14 g of gemini imidazoline to acetone solvent, stir and dissolve, heat up to 65 °C, reflux and heat at 500 rpm for 6 h, after the reaction is completed, filter, wash and rotary evaporate to dryness to obtain alkenyl-containing gemini imidazoline quaternary ammonium salt;

[0032] (3) Add 18 g of acrylamide, 9 g of alkenyl-containing gemini imidazoline quaternary ammonium salt, 7 g of N-vinylpyrrolidone, and 10 g of N,N-dimethylacrylamide to deionized water, stir and dissolve, add 5 g of sodium hydroxide solution with a mass fraction of 42% 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 reductant, heat up to 60 °C and react for 8 h, after the reaction is completed, wash and dry to obtain gemini imidazoline quaternary ammonium salt-modified polyacrylamide;

[0033] (4) Add 14 g of 2,4-diaminopyridine to deionized water, stir to dissolve, heat up to 95 °C. Take 16 g of p-mercaptobenzenesulfonic acid and dissolve it in deionized water, then drop it into the 2,4-diaminopyridine solution, keep the temperature for reaction for 2.5 h. After the reaction is completed, cool naturally, filter by suction, wash and dry to obtain pyridine sulfonate;

[0034] (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 thereto, irradiate with ultraviolet light of 365 nm at 42 °C for 3 h. After the reaction is completed, perform centrifugal separation, wash and dry to obtain intermediate 1;

[0035] (6) Dissolve 15 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 10 g of intermediate 1 thereto, stir and mix. Heat up to 70 °C, then add 0.08 g of tin tetrachloride catalyst thereto, reflux and react for 3 h. After the reaction is completed, cool, perform solvent replacement with ethyl acetate to remove the dimethyl sulfoxide solvent, filter by suction to obtain a solid product. Disperse the solid product in distilled water and dialyze for 16 h, perform rotary evaporation and freeze-dry to obtain pyridine sulfonate-modified hydroxyethyl cellulose;

[0036] (7) Add 90 parts by weight of water, 18 parts by weight of potassium formate, and 14 parts by weight of calcium chloride to the reactor. After stirring for 5 min, add 0.8 part by weight of gemini imidazoline quaternary ammonium salt-modified polyacrylamide and 0.6 part by weight of pyridine sulfonate-modified hydroxyethyl cellulose, stir and mix for 12 min to obtain a solid-free well killing fluid for oil and gas fields. Example 3

[0037] (1) Add triethylenetetramine to the reactor, heat up to 112 °C, and drop oleic acid into it, where 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 up to 150 °C and continue to react for 2 h until no water is generated, then heat up to 230 °C and react for 8 h. After the reaction is completed, perform vacuum distillation to obtain gemini imidazoline;

[0038] (2) Add 9 g of 1-allyl-3-chlorobenzene and 11 g of gemini imidazoline to acetone solvent, stir to dissolve, heat up to 62 °C, reflux and heat at 400 rpm for 5 h. After the reaction is completed, filter by suction, wash and rotary evaporate to dry to obtain allyl-containing gemini imidazoline quaternary ammonium salt;

[0039] (3) Add 16.5 g of acrylamide, 7.5 g of alkenyl-based gemini imidazoline quaternary ammonium salt, 5.5 g of N-vinylpyrrolidone, and 7.5 g of N,N-dimethylacrylamide to deionized water, stir to dissolve, add 4 g of sodium hydroxide solution with a mass fraction of 40% 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 reductant, raise the temperature to 53 °C and react for 6 h. After the reaction, wash and dry to obtain gemini imidazoline quaternary ammonium salt modified polyacrylamide;

[0040] (4) Add 12 g of 2,4-diaminopyridine to deionized water, stir to dissolve, raise the temperature to 90 °C, dissolve 15 g of p-mercaptobenzenesulfonic acid in deionized water, and then drop it into the 2,4-diaminopyridine solution, keep the temperature for reaction for 2.2 h. After the reaction, cool naturally, filter by suction, wash and dry to obtain pyridine sulfonate;

[0041] (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 ultraviolet light of 365 nm at 39 °C for 2.8 h. After the reaction, centrifuge, wash and dry to obtain intermediate 1;

[0042] (6) Dissolve 11 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 7.5 g of intermediate 1 to it, stir and mix, raise the temperature to 60 °C, then add 0.075 g of tin tetrachloride catalyst, reflux and react for 2 h. After the reaction, cool, replace the dimethyl sulfoxide solvent with ethyl acetate by solvent displacement, filter by suction 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;

[0043] (7) Add 80 parts by weight of water, 16.5 parts by weight of potassium formate, and 12 parts by weight of calcium chloride to the reactor, stir for 2 - 5 min, then add 0.6 part by weight of gemini imidazoline quaternary ammonium salt modified polyacrylamide and 0.4 part by weight of pyridine sulfonate modified hydroxyethyl cellulose, stir and mix for 8 - 12 min to obtain a solid-free kill fluid for oil and gas fields. Example 4

[0044] (1) Add triethylenetetramine to the reactor, raise the temperature to 100 °C, and drop oleic acid into it, where the mass ratio of triethylenetetramine to oleic acid is 1.8:1, control the dropping time at 20 min. After the dropping is completed, raise the temperature to 145 °C and continue to react for 1 h until no water is generated, then raise the temperature to 220 °C and react for 7 h. After the reaction, perform vacuum distillation to obtain gemini imidazoline;

[0045] (2) Add 7 g of 1-allyl-3-chlorobenzene and 8 g of gemini imidazoline to acetone solvent, stir to dissolve, heat up to 60 °C, reflux and heat at 300 rpm for 4 h. After the reaction is completed, filter by suction, wash and rotary evaporate to dryness to obtain alkenyl gemini imidazoline quaternary ammonium salt;

[0046] (3) Add 15 g of acrylamide, 6 g of alkenyl gemini imidazoline quaternary ammonium salt, 4 g of N-vinyl pyrrolidone, and 5 g of N,N-dimethylacrylamide to deionized water, stir to dissolve, add 3 g of sodium hydroxide solution with a mass fraction of 38% to adjust the pH to neutral, control the temperature at 22 °C, introduce nitrogen for 25 min to remove oxygen, add 0.06 g of benzoyl peroxide oxidant and 0.05 g of sodium bisulfite reductant, heat up 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;

[0047] (4) Add 14 g of 2,4-diaminopyridine to deionized water, stir to dissolve, heat up to 95 °C, dissolve 16 g of p-mercaptobenzenesulfonic acid in deionized water, and then drop it into the 2,4-diaminopyridine solution, keep the temperature for reaction for 2.5 h. After the reaction is completed, cool naturally, filter by suction, wash and dry to obtain pyridine sulfonate;

[0048] (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 ultraviolet light of 365 nm at 42 °C for 3 h. After the reaction is completed, centrifuge, wash and dry to obtain intermediate 1;

[0049] (6) Dissolve 11 g of hydroxyethyl cellulose in dehydrated dimethyl sulfoxide solvent, add 7.5 g of intermediate 1 thereto, stir and mix, heat up to 60 °C, then add 0.075 g of stannic chloride catalyst, reflux and react for 2 h. After the reaction is completed, cool, replace the dimethyl sulfoxide solvent with ethyl acetate by solvent displacement, filter by suction 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;

[0050] (7) Add 80 parts by weight of water, 16.5 parts by weight of potassium formate, and 12 parts by weight of calcium chloride to the reactor, stir for 2 - 5 min, then add 0.6 part by weight of gemini imidazoline quaternary ammonium salt modified polyacrylamide and 0.4 part by weight of pyridine sulfonate modified hydroxyethyl cellulose, stir and mix for 8 - 12 min to obtain a solid-free kill fluid for oil and gas fields. Example 5

[0051] (1) Triethylenetetramine was added to the reactor, and the temperature was raised to 112 °C. Oleic acid was added dropwise thereto, where the mass ratio of triethylenetetramine to oleic acid was 2:1, and the dropping time was controlled within 30 min. After the dropping was completed, the temperature was raised to 150 °C, and the reaction was continued for 2 h until no water was generated. Then, the temperature was raised to 230 °C and reacted for 8 h. After the reaction was completed, reduced pressure distillation was performed to obtain gemini imidazoline;

[0052] (2) 9 g of 1-allyl-3-chlorobenzene and 11 g of gemini imidazoline were added to acetone solvent, stirred and dissolved, and the temperature was raised to 62 °C. It was refluxed and heated at 400 rpm for 5 h. After the reaction was completed, suction filtration was performed, washed and rotary evaporated to dryness to obtain alkenyl gemini imidazoline quaternary ammonium salt;

[0053] (3) 16.5 g of acrylamide, 7.5 g of alkenyl gemini imidazoline quaternary ammonium salt, 5.5 g of N-vinylpyrrolidone, and 7.5 g of N,N-dimethylacrylamide were added to deionized water, stirred and dissolved. 4 g of a 40% sodium hydroxide solution was added to adjust the pH to neutral, the temperature was controlled at 26 °C, nitrogen was introduced for 32 min to remove oxygen, 0.08 g of benzoyl peroxide oxidant and 0.06 g of sodium bisulfite reductant were added, and the temperature was raised to 53 °C and reacted for 6 h. After the reaction was completed, it was washed and dried to obtain gemini imidazoline quaternary ammonium salt modified polyacrylamide;

[0054] (4) 10 g of 2,4-diaminopyridine was added to deionized water, stirred and dissolved, and the temperature was raised to 85 °C. 14 g of p-mercaptobenzenesulfonic acid was dissolved in deionized water, and then it was added dropwise to the 2,4-diaminopyridine solution, and the reaction was kept warm for 2 h. After the reaction was completed, it was naturally cooled, suction filtered, washed and dried to obtain pyridine sulfonate;

[0055] (5) 8 g of 3,4-epoxy-2-methyl-1-butene and 5 g of pyridine sulfonate were added to N,N-dimethylformamide solvent, stirred and mixed, and then 0.04 g of benzoin dimethyl ether photoinitiator was added thereto. It was irradiated with ultraviolet light of 365 nm at 36 °C for 2.5 h. After the reaction was completed, centrifugal separation was performed, washed and dried to obtain intermediate 1;

[0056] (6) 15 g of hydroxyethyl cellulose was dissolved in dehydrated dimethyl sulfoxide solvent, 10 g of intermediate 1 was added thereto, stirred and mixed, and the temperature was raised to 70 °C. Then, 0.08 g of stannic chloride catalyst was added thereto, and the reaction was refluxed for 3 h. After the reaction was completed, it was cooled, and dimethyl sulfoxide solvent was removed by solvent replacement with ethyl acetate. The solid product was obtained by suction filtration, and the solid product was dialyzed in distilled water for 16 h, rotary evaporated, and freeze-dried to obtain pyridine sulfonate modified hydroxyethyl cellulose;

[0057] (7) Add 90 parts by weight of water, 18 parts by weight of potassium formate, and 14 parts by weight of calcium chloride to the reactor. After stirring for 5 min, 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, and stir and mix for 12 min to obtain a solid-free kill fluid for oil and gas fields.

[0058] Comparative Example 1

[0059] Compared with Example 1, the difference in this comparative example is that the gemini imidazoline quaternary ammonium salt modified polyacrylamide was not added in step (7).

[0060] Comparative Example 2

[0061] Compared with Example 1, the difference in this comparative example is that the pyridine sulfonate modified hydroxyethyl cellulose was not added in step (7).

[0062] Use a fluid loss apparatus to measure the fluid loss of the solid-free kill 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 h, and use a rotational viscometer to measure its apparent viscosity. The test results are shown in Table 1.

[0063] Table 1: Fluid loss reduction performance test.

[0064]

[0065] As can be seen from Table 1, compared with Comparative Examples 1-2, the solid-free kill fluid for oil and gas fields in Examples 1-5 still has a lower fluid loss and a higher apparent viscosity after high-temperature aging, indicating good fluid loss reduction performance and high-temperature resistance.

[0066] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention.

Claims

1. An oil and gas field solid-free kill fluid, characterized in that, It includes the following weight components: 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; The preparation method of the gemini imidazoline quaternary ammonium salt modified polyacrylamide, which includes the following steps: (1) Add triethylenetetramine into a reactor, heat up to 100 - 115 °C, dropwise add oleic acid into it, control the dropping time within 20 - 40 min. After the dropping is completed, heat up to 145 - 155 °C and continue to react for 1 - 3 h until no water is generated. Then heat up 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 gemini imidazoline into an acetone solvent, stir to dissolve, heat up to 60 - 65 °C, and reflux and heat at 300 - 500 rpm for 4 - 6 h. After the reaction is completed, perform suction filtration, wash and rotary evaporate to dryness to obtain alkenyl - containing gemini imidazoline 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 - vinylpyrrolidone, and 5 - 10 g of N,N - dimethylacrylamide into deionized water, stir to dissolve, add 3 - 5 g of sodium hydroxide solution with a mass fraction of 38% - 42% to adjust the pH to neutral, control the temperature at 22 - 30 °C, introduce 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 reductant, heat up to the 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 the pyridine sulfonate modified hydroxyethyl cellulose, which includes the following steps: S1. Add 10 - 14 g of 2,4 - diamino pyridine into deionized water, stir to dissolve, heat up to 85 - 95 °C. Take 14 - 16 g of p - mercaptobenzenesulfonic acid and dissolve it in deionized water, then drop it into the 2,4 - diamino pyridine solution, keep the temperature for reaction for 2 - 2.5 h. After the reaction is completed, cool naturally, perform suction filtration, 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 into an N,N - dimethylformamide solvent, stir and mix. Then add 0.04 - 0.08 g of benzoin dimethyl ether photoinitiator, irradiate with ultraviolet light of 365 nm at 36 - 42 °C. After the reaction is completed, perform centrifugal separation, wash and dry to obtain intermediate 1; S3. Dissolve 7 - 15 g of hydroxyethyl cellulose in the dehydrated dimethyl sulfoxide solvent, add 5 - 10 g of intermediate 1 thereto, stir and mix, heat up to 50 - 70 °C, then add 0.07 - 0.08 g of tin tetrachloride catalyst thereto, reflux and react for 1 - 3 h. After the reaction is completed, cool, replace the dimethyl sulfoxide solvent with ethyl acetate by solvent displacement, filter by suction 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, wherein 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, wherein In the step (3), the reaction temperature is 45 - 60 °C.

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

5. A preparation method of the solid-free well-killing fluid for oil and gas fields according to any one of claims 1-4, characterized in that, The preparation method of the solid-free well-killing fluid for oil and gas fields is as follows: add water, formate, and calcium chloride to a reactor, stir for 2 - 5 min, then add gemini imidazoline quaternary ammonium salt-modified polyacrylamide and pyridine sulfonate-modified hydroxyethyl cellulose, stir and mix for 8 - 12 min to obtain the solid-free well-killing fluid for oil and gas fields.

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