Bottom-Hole Assembly Modeling and Dynamic Response Determination

Understanding bottom-hole assembly (BHA) dynamic phenomena remains a critical drilling systems issue due to the cost of potential failures. Many studies have provided useful insight into drillstring dynamics. This study extends previous efforts by providing a novel BHA model which accounts for several critical response factors and can be augmented to address a variety of other effects; new data from an experimental study regarding damping are presented. The proposed model represents the transfer function of the drillstring in terms of its natural modes and properly incorporates several factors critical to BHA dynamic response prediction, including frequency-dependent fluid added mass, and nonlinear wellbore constraints. Results from pertinent numerical studies are presented.