The Effect of Bottomhole Assembly Dynamics on the Trajectory of a Bit

The basic mechanisms associated with pipe rotation are explained by showing the predominant paths of motion of five BHA's as a function of rotary speed, and stabilizer-bit, and pipe-friction coefficient values. In a parallel test program, five shallow wells were drilled directionally under controlled conditions. Results of these tests are incorporated to demonstrate that dynamic predictions of the bit's tendencies compared well with numerical results predicted by the program. Two other field examples are cited: one from the Gulf of Mexico, and another from Holland. Data from these wells are used to illustrate how the dynamic results can be applied to explain the bit's trajectory behavior. A final section examines the use of the computer-generated results in predicting the tendencies of the bit for the five assemblies. 17 refs.