Self-excited torsional vibrations of the bottomhole assembly (BHA) at frequencies above 50 Hz, so-called "high-frequency torsional oscillations" (HFTO), can damage drilling tools and can increase non-productive time (NPT). A recently developed HFTO-isolation tool protects the drilling tools above this tool from these harmful vibrations. More than 200 field runs were investigated to evaluate the changes in reliability and benefits.
The concept of the isolation tool works similarly to a two-mass flywheel used in automotive drive trains. The design was simulated, lab-tested and first deployed in a field run in 2018. Since then, the isolation tool was successfully used in various fields and applications in the Middle East. HFTO severity while drilling was measured and recorded below and above the isolation tool to verify functionality and to quantify reduction in torsional loads (torque, tangential acceleration) for the measurement while drilling (MWD), mud pulse telemetry (MPT), and logging while drilling (LWD) tools above the tool. In addition, HFTO-related incidents and other drilling performance indicators with and without the new tool were analyzed.
Analysis of the recorded vibration data from several field runs with an additional high-frequency MWD-tool reveals that the isolation principle works consistently. As predicted by simulation, the measured torsional vibration amplitudes above the tool are significantly lower than without using it, demonstrating the effective protection for MWD-, LWD-, and MPT-tools in the BHA.
The tool has proven consistent performance in more than 16,000 accumulated circulating hours. Tool failures caused by HFTO were eliminated, compared to 22 percent of all failures without the isolation tool. The results of an analysis of individual MWD- and MPT-tools used in runs with and without the isolation tool show a significant increase in distance drilled per tool deployment and re-run decisions. This directly translates to increased asset utilization, fewer trips for failure, and BHA handling operations that results in less non-productive time (NPT) and enables drilling in extremely challenging environments more efficiently.