Drillpipe Cutting at Ultrahigh Pressure Proven for Remediating Deepwater Stuck-Pipe Hazards

Abstract

Summary Efficient separation of stuck drillstrings with proven results is a must for deepwater wells where depths can reach 35,000 ft and daily rates often exceed USD 1,000,000. Operators want proven results instead of theoretical calculations or critical-path experimentation during a stuckpipe hazard event. Historical pipe cutting or severing has been hindered for decades by high bottomhole pressures (BHPs) and internal-diameter restrictions. Chemical cutters and plasma cutters are most affected by the effect of hydrostatic pressure on their method of pipe separation, while jet cutters and severing tools’ explosive charges could overcome more BHP. After leaping the 20,000-psi hurdle, we were still limited to 25,000 psi or less and had unproven products until now. From conceptual development to laboratory data, this paper will describe the need for and development, testing, and results of jet cutters and severing tools for use in ultrahigh-pressure environments up to 30,000 psi for today's deepwater, ultradeep-well market. Designing and building of a new, first-of-its-kind test vessel allowed for visualization and verification of actual separation of drillstring components at BHPs with zero tension applied. Extrapolation of data from previous cutter designs at lower pressure ratings allowed us to tailor each cutter size and charge quantity for the pipe thicknesses and test pressures desired. The material component of the cutter housing and the timing of explosive initiation are critical for the cutters to withstand the descent through the drillstring components and the constantly increasing wellbore pressure and still provide an accurate, efficient detonation for separating the thick metal wall of the pipe. Laboratory testing proved that jet cutting and severing drillstring tubular components are achievable at pressures up to 30,000 psi in drillpipe and heavyweight-drillpipe (HWDP) bottomhole drilling assemblies. Substantial cost and critical-path time savings for deepwater operators can be realized during stuck-pipe incidents by using tested technology proven to separate drillstring components at BHPs up to 30,000 psi.