High Frequency Downhole Dynamic Measurements Provide Greater Understanding of Drilling Vibration in Performance Motor Assemblies

Abstract

Abstract The use of downhole mud motors to improve drilling performance in vertical wells is becoming more common throughout the oil and gas industry. The additional torque provided by a downhole mud motor allows for a more aggressive drill bit design to be selected, and achieve a greater ROP. This paper will present a series of case studies where a near bit dynamics recorder has been used to determine the dynamic conditions below a motor. In several cases a dynamics recorder was also located above the motor, providing two discrete points of measurement. In the first case, near bit dynamic measurements allowed for BHA stick-slip to be identified as the cause for severe bit damage rather than difficult formation as was suspected. In the second case study, a near bit recorder coupled with a recorder above the mud motor identified that a significant level of vibration was generated by the motor. A different motor design was used on the following well and a reduction in vibration severity allowed for the section to be drilled in a shorter time. In the third case study, frequency analysis of near bit dynamic data conclusively identified backwards bit whirl as the cause for severe bit damage. In conclusion, the use of a near bit dynamics recorder has allowed for a greater understanding of the dynamics involved in performance motor assemblies. The application of this knowledge has helped to address the root cause of previously misunderstood vibration problems and improve drilling performance.