Downhole acceleration detection of poor drilling performance related to bit damage

Scott Hess, Roman Shor, Alex Vetsak, Kristopher A. Innanen

Improving drilling performance continues to be an active topic of research, not only for the oil and gas industry, but also for emerging industries such as geothermal. Real-time drilling monitoring enables operational decisions that can save significant drilling costs. Monitoring strategies generally utilize surface measurements to detect drilling dysfunctions that degrade drilling performance, but deep or highly deviated wells often require downhole sensors to monitor drill string dynamics effectively. Downhole data does have limitations related to telemetry and sensor operating limits, specifically temperature in the context of geothermal. A potential alternative monitoring solution is bit-source seismic-while-drilling (BSWD), where surface sensors are utilized to detect drilling dysfunctions. The goal of the research presented here is to use the downhole accelerometer data to understand the source characteristics of the bit for future utilization of BSWD. Accelerometer data from 2 different drilling intervals are evaluated along with drilling performance to establish acceleration attributes that could be relevant for understanding the bit as a seismic source. Cross plots of acceleration attributes for the 2 drilling intervals show similar trends even though they have several physical and operational differences. High tangential maximum acceleration values for both datasets correspond to the end of the bit run, approximately the last 10feet of drilling prior to the decision to pull the bit. While both bits incurred significant damage, increased axial vibrations are observed for the bit with more severe damage. In the context of BSWD, the increase in tangential and axial vibrations are expected to result in higher wavefield energy propagating to the surface. Understanding of the various wavefield amplitudes on the BSWD data could be a potential tool to identify drilling events that result in significant bit damage.