A new 3D drillstring model determines the static and dynamic behavior of bottomhole assemblies (BHAs) in realistic wellbores. The modeling approach provides a prediction of the BHA’s mechanical and dynamic behavior and can be used as a planning tool for BHA design, an investigative tool for root-cause analysis, or, potentially, as a real-time optimization tool for avoiding harmful operating conditions.
Introduction
When using any model, engineers cannot forget the limits of calculation. However, they can settle for “good enough” as long as they adhere to the following two rules:
- The results capture the general behavior of the system with respect to the parameters of interest.
- The engineer using the results fully understands the limits of the model used to obtain them.
These rules are particularly important when considering highly nonlinear systems, such as the 3D behavior of BHAs. Nonlinearity arises in these systems from the large, coupled deflection that occurs in the downhole components as they move within the wellbore, and the frictional contact that results from the borehole wall restraining that movement.
