关键词: 气体钻井, 坍塌井眼, 下部钻具, 偏转角, 有限元分析

Abstract: The research on the influence of abnormal well bore on bottom hole assembly(BHA) in gas drilling with bore hole collapse is carried out，according to the shape of the collapse，the abnormal well bore is simplified into the collapsed hole with ellipse-shaped section，the mechanical model of finite element analysis for bottom hole is set up and the ANSYS-APDL programe is developed which can be used for analyzing finite mechanics of the assembly conveniently.The BHA stress is studied under the conditions of four types of abnormal well bores，the deformation displacement of the assembly adjacent the collapsed bore，assembly moment，the stress distribution inside the assembly and the deflexion angle of the bit are obtained，which provides the theoretical evidence for the well deviation mechanism of collapsed bore，preventing deviation and increasing drilling rate.

Key words: gas drilling, collapse wellbore, bottom hole assembly, deflexion angle, finite element analysis