Drilling Fluid Technology of Horizontal Well S77-5-8in Sulige Gas Field

The problem of borehole instability in Dyas of Sulige region has been kept as a major difficulty in the exploration and development.The key of successful drilling of complex lithological formation is to use drilling fluid with appropriate density.This paper analyzes and researches the labile factor of Sulige region Dyas complex formation and the difficulties to the implementation of drilling fluid technology,improves the compatibility of the drilling fluid and optimized polysulfonate drilling fluid system as the appropriate drilling fluid.The drilling fluid system has good rheological,building capacity,oiliness and rejection capability.Application result shows that the drilling fluid is useful to the easy drilling,underground safety and hydrocarbon reservoir protection.