Effects of RPM and ROP on PDC Bit Steerability

Abstract

Abstract Directional drilling is a critical necessity in many of today's wells. Accurate prediction and awareness of achievable build rates is vital in lowering drilling cost. The science behind controlled wellbore deviation has advanced beyond prediction based solely on BHA geometry. Although BHA configuration is an important factor, interaction between each of the four primary components (bit, BHA, operating parameters and formation) must be evaluated thoroughly. Previous papers have described how changes in bit characteristics, BHA configuration and various formations influence build rates. With regards to operating parameters, weight-on-bit (WOB) is well-known to be beneficial in increasing the desired build rate under certain drilling conditions and yet does not help in other situations. We propose that most of the weight-on-bit effects are actually due to its influence on rate of penetration and bit tilt. However, the influence of operating parameters has not been fully investigated. RPM has been neglected as a significant influence on steerability. In theoretical studies, these properties have been measured and quantified with the use of a full scale drilling laboratory and commercially available PDC bits. This paper investigates the effects of RPM and ROP on build rate and illustrates the importance of these parameters. Practical guidelines for understanding the effect of operating parameters on steerable systems are also provided.