BZ34-9 oilfield,which discovered in recent years,is a high quality oilfield in Bohai Sea.During the drilling operation process of the early exploration and development,there are complicated conditions such as pipe sticking,leakage and so on,which increase the operation cost.To reduce complicated conditions and meet the requirements of reservoir protection,we analyzed the main problems in drilling operation process of BZ34-9 oilfield directional well,optimized the drilling fluid system of directional well,an...