Abstract: To address the common problem of well leakage during drilling in weak formations in Bohai Oilfield,this paper analyzes the mechanism of the well leakage,and carries out the research of the pressure plugging technology. Through geological analysis,drilling fluid characteristic evaluation and well wall stability study,the internal causes of leakage are revealed. On this basis,a leakage prevention technology suitable for the weak strata in the Bohai Sea is developed,and its effectiveness is verified through field tests. The results show that this technology can effectively block the leakage channel,improve the formation bearing capacity,and provide strong support for safe drilling in Bohai Oilfield.

Key words: Bohai Oilfield, weak formation, loss mechanism, pressure plugging technology