Synthesis And Application Of Drilling Thermostable Modified Starch

Starch is widely distributed in nature, which is named as renewable energy. Modifiedstarch is biodegradable and will not cause environmental pollution. They are widely used invarious areas of industries. As the drilling fluid filtrate reducer, with a strong salt and calciumresistance, fluid loss properties. It can effectively reduce the pollution to the reservoir.At thepresent, the modified starches in domestic decomposited at the temperature between110to120°C, which greatly limits the application of modified starch in the oil field.In this paper, worked out a way to improve the temperature resistance of modified starchand synthesize one kind of modified starches which can anti-130°C high temperature. Andevaluated it’s drilling fluid performance. Explored oyoutiut one clay free drilling fluid cankeep stable up to130°C.In this paper, corn starch in the alkaline environment with some methanol solvent, somecrosslinking agent, before gelatinized, reacts with etherification. Designed an orthogonal tableon base of five influence factors. Through that, has got the best synthesis conditions: a certainamount of crosslinking agent, under the conditions of the reaction temperature40°C, thereaction time was3hours, the alkaline catalyst etherification agent molar ratio increment was2:1, the amount of molar ratio of etherification agent and the original starch was1:2, andmoisture content in the system is15%.Analysed degree of substitution, the degree of crosslinking,IR of the modified starch.Gotthe following conclusions: compared with native starch, modified starch had a different peakin the infrared, showing the grafting success; in a certain degree of substitution, degree ofcrosslinking, modified starch, was easily to soluble in water, and the temperature resistanceup to130°C.Has designed one kind of drilling fluids which can protect the reservoir. After aging130°C, the filter loss is5.2mL at room temperature and under the medium-pressure; the filterloss is15mL at the congditiong of the high temperature and high pressure.The drilling fluidiis:350mLwater+82gNaCl+1gCMC+7gMs+0.5g NaHCO₃+50gCaCO₃.