Abstract: Complicated problems such as borehole instability exist in drilling in Fumin and Yongan area of Jiangsu.Study was conducted on wellbore stability by investigating the drilling case history in Well Yong-23 and Well Fu-X1,which is a deep well,and a collapsing pressure profile of this area is established.Field application of the pressure profile effectively avoided and minimized downhole troubles,and the drilling efficiency was also improved.This study was beneficial for drilling engineering design,field drilling fluid density adjustment and the implementation of fast and safe drilling operation,while provided scientific evidences for performing these work.