Abstract: Located at the high position of nose-type structure of Jiexie-2 of Linnan depression in Shengli oilfield,Jie- 206 well is a second supdding well in medium depth.It is the first well that adopted polymer sulfonated emulsion drilling fluid,with drilled depth about 3980m.During the process of previous drilling,borebole wall leaking and sidewall collapsing always occurred.In order to meet the requirement of drilling operation,a suitable drilling fluid formulation is optimized through comprehensive analysis in laboratory and its application in Jie-206 well proves to be very successful.