| CPC C09K 8/16 (2013.01) [C09K 8/206 (2013.01); C09K 8/24 (2013.01); C09K 8/426 (2013.01); C09K 8/44 (2013.01); E21B 33/138 (2013.01)] | 3 Claims |
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1. A silicate water-based drilling fluid for coalbed methane wells, wherein in terms of parts by weight, raw materials of the silicate water-based drilling fluid comprise: 100 parts of water, 1-3 parts of bentonite, 1-5 parts of pH regulator, 3-5 parts of silicate, 2-4 parts of silicate stabilizer, 0.1-0.15 parts of tackifier, 2-4 parts of filtrate reducer, 3-5 parts of auxiliary inhibitor, 1-2 parts of activator, 2-4 parts of plugging agent, and 2-4 parts of lubricant;
wherein in terms of parts by weight, the pH regulator is a mixture of 40-60 parts of sodium hydroxide and 40-60 parts of potassium hydroxide, the silicate is at least one of sodium silicate and potassium silicate, and a modulus of the silicate is in a range of 2.85 to 3.40;
wherein in terms of parts by weight, the silicate stabilizer is a mixture of 40-60 parts of sodium citrate and 40-60 parts of potassium citrate;
wherein in terms of parts by weight, the tackifier is a mixture of 30-40 parts of xanthan gum, 30-40 parts of scleroglucan and 20-40 parts of welan gum;
wherein in terms of parts by weight, the filtrate reducer is a mixture of 10-20 parts of pregelatinized corn starch, 10-20 parts of pregelatinized potato starch, 10-20 parts of pregelatinized cassava starch and 40-70 parts of modified lignin;
wherein a preparation method of the modified lignin comprises the following steps:
step 1, adding 3-aminopropyltriethoxysilane to an ethanol-aqueous solution to perform a hydrolysis reaction, and adding, after completion of the hydrolysis reaction, lignin to perform a reaction to thereby obtain an intermediate product; and
step 2, adding the intermediate product and 1-ethyl-(3-dimethylaminopropyl) carbodiimide to a mixture of adipic anhydride and N,N-dimethylformamide, and reacting under an inert atmosphere to obtain the modified lignin;
wherein in the step 1, a mass ratio of the ethanol-aqueous solution to the 3-aminopropyltriethoxysilane is 200:(1-3), and a mass ratio of the 3-aminopropyltriethoxysilane to the lignin is (1-3):(15-20); a temperature of the hydrolysis reaction is 60° C., and a time of the hydrolysis reaction is 4 hours (h); a temperature of the reaction performed after adding the lignin is in a range of 70° C. to 80° C., and a time of the reaction performed after adding the lignin is 10 h; and
wherein in the step 2, a mass ratio of the lignin to the adipic anhydride is (15-20):(6-9), a mass ratio of the adipic anhydride to the N,N-dimethylformamide is (6-9):150, and a mass ratio of the lignin to the 1-ethyl-(3-dimethylaminopropyl) carbodiimide is (15-20):(0.5-1.0); the inert atmosphere is a nitrogen atmosphere, a temperature of the reacting is in a range of 80° C. to 90° C., and a time of the reacting is 6 h;
wherein in terms of parts by weight, the auxiliary inhibitor is a mixture of 60-80 parts of potassium sulfate and 20-40 parts of sodium sulfate; and
wherein in terms of parts by weight, the activator is a mixture of 40-60 parts of polylactic acid, 20-30 parts of polyhydroxybutyrate and 20-30 parts of polybutylene succinate.
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