OPTIMIZED DESIGN OF THE ANTI-DEFLECT BOTTOM-HOLE ASSEMBLY BY USING ROCK-BIT INTERACTION MODEL

Based on the rock-bit interaction model, and taking into account the influence of anisotropic characteristics of rock and bit, as well as the bit lateral force and bit tilt angle on deviation, a new term named the trend angle of deviation (TAD) was brought forward. In addition, simple and practical formulae aiming to isotropic formation were derived. Conclusions were drawn as follows: (1) When designing the bottom hole assembly (BHA) to deviation control and optimizing drilling parameters (weight-on-bit, rotary speed etc), it was essential to consider the impacts due to all the factors above. (2) Comparing to the single criterions, such as the bit lateral force and bit tilt angle, the TAD criterion was more synthetical, more reliable.