Combined with actual air drilling practices and data in western China, mechanical behavior of three different BHA used in actual air drilling was investigated. Bit side force and bit tilt angle of those three BHA both in air drilling and mud drilling were calculated and compared. Analysis results indicated that the bit side force and the bit tilt angle in air drilling is greater than that of in mud drilling due to more deformation of BHA. The fundamental reason of difficulty to control well deviation is because of the great formation anisotropic index and formation dip in air drilling. Some deviation control measures are recommended including the combination of air percussion hammer or air motor and pendulum assembly.

Keywords:
drilling fluids and materials, bit tilt angle, trajectory design, deformation, pendulum assembly, formation anisotropic index, drilling, bit side force, mud drilling, drilling operation
Subjects:
Well Planning, Drilling Operations, Drilling Fluids and Materials, Trajectory design
Copyright 2010, Society of Petroleum Engineers
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