Real time prediction and detection of drilling bit issues during drilling with the focus on bit status evaluation using along string measurement (ASM)

Abstract

Real-time drilling optimization requires online knowledge about drilling bit status, and a novel bit–rock interaction model coupled with extensive drilling data lays the groundwork for bit evaluation. Furthermore, as part of the dynamic modeling of drill strings, forces at the bit must also be calculated. At present, the bit selection protocol is based on the post-drilling bit assessment, although some drilling penetration rate models that are calibrated for a specific field can also be used to estimate bit condition in some cases. This research presents a bit status simulator that overcomes the limitations of existing techniques by making use of a delicate and intelligent application of along-string measurement (ASM) data to predict issues related to drilling bits and mitigate them in real time. This research follows two main lines. The polycrystalline compact (PDC) bit is first reshaped into an equivalent blade bit that incorporates all the design criteria of the PDC bit. Each equivalent blade, however, is composed of some equivalent cutters. Utilizing the ASM data, a novel cutter–rock interaction model is used to estimate normal and contact forces on cutters. Cutter–rock interaction equations and the mechanical specific energy of the bit cutters are used to assess the condition of the bit in real time. Two bits are evaluated in a section of a well on the Norwegian continental shelf using the proposed algorithm. The drilling data, including weight and torque on the bit, are reformulated into normal and cutting forces utilizing a cutter–rock interaction model and recursive least squares method. Consequently, the final simulated values are well in line with the final dull grading reports.