Case Study of North Kuwait Field Development with the Introduction of Axial Excitation in a Directional Drilling Motor Bottomhole Assembly

Abstract The drilling process in a 12.25-in. directional section with motor bottomhole assembly (BHA) in one North Kuwait field was impacted by elevated levels of vibrations, which limited weight transfer to the bit and rate of penetration (ROP), thereby affecting overall drilling efficiency. This paper analyzes the effect of introducing an axially operating friction reduction system (FRS) in the BHA while maintaining the dynamic drilling metrics, and the resulting efficiency. The approach comprises quantitative comparison of average ROP required to drill the 12.25-in. section, between well (A) with an FRS in the drillstring and those offset wells (B and C) without the FRS. The wells selected for comparison had identical well trajectory, BHA, and drilling metrics. The FRS consists of two major components – One that generates pressure pulses, and the other that converts these pressure pulses into axial excitations. The excitation keeps the drillstring in a state of constant axial oscillation, which reduces the static friction from interaction with the wellbore, especially in the directional section. Placement analysis to determine the position of the FRS in the drillstring for optimal friction reduction was executed, taking into account the well trajectory, outer diameter (OD) and inner diameter (ID) of BHA components, torque and drag (T&D), weight on bit (WOB), flow rate, and mud weight (MW). The result of the data analysis indicated that, for the same drilling metrics, the addition of an FRS in the drillstring of well A had enhanced the drilling efficiency compared to the offset wells B and C. This was evidenced by the increase in the sliding ROP by 56%, rotating ROP by 38%, overall section ROP by 34%, and reduction in on-bottom drilling hours by 35%. No interference of frequency with the measurement-while-drilling (MWD) tool was observed, and logging-while-drilling (LWD) real-time data was successfully decoded throughout the run. The FRS did not show any compatibility issues with the remainder of the BHA components. The consistent oscillatory excitation of the FRS notably reduced static and dynamic friction. As a result, it successfully assisted in mitigating vibrations and stick-slip (SS), enabling efficient transfer of WOB in the directional section that resulted in performance improvements. The overall study shows that the first FRS run on this field was significant in reducing friction and its resulting vibration in the directional section, the benefits of which include enhanced drilling performance, lower mechanical specific energy (MSE), reduced nonproductive time (NPT) and better tool reliability and maintenance. The result of this initial run has become a benchmark to expand the utilization of the FRS more widely in this field.