An experimental study on steering response of PDC drill bits

Abstract

This paper presents the findings from an experimental study conducted to understand the steering response of PDC (polycrystalline diamond compact) bits. Various tests are carried out by drilling large limestone blocks with an actual size PDC bit and a highly sophisticated drilling machine. High resolution data acquired during the drilling process and 3D laser scans of the drilled holes are analyzed to assess the effect of drilling parameters and bit dynamics on steering response. The hole deviations measured during experiments are compared to a quasi-static FE (finite element) model, which utilizes a simplified bit-rock interaction formulated via a single bit steerability parameter. It is shown that, although this approach has its merits due to its computational efficiency, it can produce inaccurate prediction when the bit dynamics change. The experiments showed that the WOB (weight on bit) is a crucial parameter in this regard, dictating the stability of the drilling process, which in return affects the influence of the remaining parameters such as RPM (revolutions per minute) and side force.