Drill string safety valve reliability: experimental measurements of actuating torque

Drill String Safety Valves (DSSV's) are used to prevent blowouts through the drill pipe during underground events in drilling. Several case history reviews of well control events have recently shown evidence of poor reliability with DSSV's. Of the problems reported, valve lock up was most significant, resulting in failure to open or close due to high actuation torque. This paper describes an experimental apparatus and experimental procedures used to quantify the actuating torque of DSSV's under a variety of common operating conditions. Experimentally obtained torque curves are presented for both commercially available and prototype DSSV's, and the results are discussed. Results show the benefit of using special low torque DSSV designs under certain operating conditions.