Evaluation method of parameters design for bottom hole assembly

Considering the design parameters effect on the drilling tendency,the conception of drilling tendency angle was proposed as an evaluation index for the bottom hole assembly(BHA) design.Based on the rock-bit interaction model and the mechanical analysis of BHA,an evaluation method of the parameters design for BHA was established.The effects of parameters including mechanical characteristics of BHA,operation parameters,the borehole geometry on drilling tendency were analyzed by the method.The proper design parameters and operation parameters for the BHA to meet the demands of different wellbore conditions on well trajectory control can be obtained.The results of basic and application research show that the drilling tendency doesn't change at the site where the value of the lateral force on the bit is zero.The drilling tendency can be changed by weight on bit in certain range when the positions of stabilizers are properly selected.The roller cone bits can work better than polycrystalline diamond compact(PDC) bits in the process of vertical well drilling.