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 stuck-pipe hazard event.
Historical pipe cutting or severing has been hindered for decades by high
bottomhole pressures (BHPs) and internal-diameter restrictions. Chemical
cutters and radial cutting torches 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.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
28 September 2010
- Meeting paper published:
1 March 2011
- Revised manuscript received:
13 June 2011
- Manuscript approved:
5 July 2011
- Published online:
5 December 2011
- Version of record:
27 December 2011
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