Drilling practice and cognition of exploration wells in JZ 25-1 block

JZ 25-1 oilfield is a great oilfield in Bohai Bay. There are over ten wells were drilled in JZ 25-1 block in recent years, and many downhole problems such as top wellbore expansion, irregular well caliper, borehole collapse, tight pull, logging tool troubles, hole bottom sands, and circulation loss. Problems in exploration wells were analyzed and the formation pressure profile of JZ 25-1 block was researched on, problems had been tackled and top wellbore expansion rate was small in the following drilling wells, no borehole collapse, logging tool reached to the bottom easily, and working time of drilling procedure increased significantly which provided experience for the production well drilling in JZ 25-1 oilfield.