Mathematical Models for 3D Analysis of Rotary Steering BHA Under Small Deflection.

A new type of rotary steering stabilizer used in a common rotary bottom hole assembly (BHA) to control well path was developed. In order for design and use of this kind of BHA, mathematical models were proposed for 3D mechanical analysis of rotary steering BHA with small deflection. The mathematical models include (1) differential equations; (2) boundary conditions of drill bit, stabilizer diameter change, tangent point, and bore hole wall; (3) methods for calculating lateral forces and deflection angles of the bit; and (4) models for determining navigation ability and navigation parameters. As an example, a given rotary steering BHA was studied. [ABSTRACT FROM AUTHOR]