环保型弱凝胶护壁护心钻井液研究与应用OA北大核心CSTPCD

When drilling and coring loose sandstone in offshore shallow gas geological survey and salt lake environmental scientific drilling project,we often encounter technical problems such as easy collapse of borehole and low porosity.This work researched the environment-friendly weak gel wall-and-core-protecting drilling fluid technology for loose sandstone formation.Through the structural study of weak gel and the optimization of gelling agent,crosslinking agent,and salt resisting fluid loss reducer,a set of environment-friendly weak gel wall-and-core-protecting drilling fluid was developed.The rheological properties,filtration performance,inhibition,core protection and environmental protective performance of the drilling fluid system were evaluated,and the drilling fluid was applied in a salt lake environmental science drilling site.Laboratory experiments and field application indicate that the developed weak gel wall-and-core-protecting drilling fluid has excellent rheological properties,fluid loss reduction,inhibition(rock debris recovery rate 96.3%),wall-and-core-protecting performance,and environmental protecting performance(BOD5/COD=24.6%,EC50=47950 mg/L).This weak gel wall-and-core-protecting drilling fluid can effectively solve the problems of borehole collapse in loose sandstone and cuttings carrying difficulties,which has broad application prospects in loose formation drilling.