NEW CONCEPT FOR DETERMINING THE TOP TANGENTIAL POINT ON BHA

The tangency point of Bottom Hole Assembly is located at where the drill string just touches the wall of the borehole, and the contact force is zero here.Therefore, the method to determine the position of tangency point should be based on this condition instead of the traditional one which requires the moment is zero here.The formula of this new method was deduced, the different results of the two methods were shown through examples, the rationality of the new method was proved by the result of the examples.