Summary
A 52-well heavy-oil field development that targeted shallow--a 3,400- to
4,000-ft true vertical depth (TVD)--sands on the North Slope of Alaska was
initiated in 2008. Horizontal wells of 11,000- to 13,000-ft measured depth (MD)
were drilled early in the program. These initial wells served as
"data-gathering and technology-proving" opportunities leading up to the
eventual 23,000-ft-MD wells. Key technical challenges include
equivalentcirculating- density (ECD) and drag management. ECD management became
essential in the 8 1/2-in. productionhole section of the longer wells. A
relatively narrow (less than 600 psi) mud-weight (MW) window necessitated
changes to casing, drillstring, drilling fluids, and operational parameters.
Lighter-weight production casing allowed the drilling of a larger production
hole (8 3/4-in. vs. 8 1/2-in.). A tapered drillstring, reduced mud rheology,
and reduced flow rate all became a necessary part of the ECD management
solution. Advanced drag-management techniques are required to install the 9
5/8-in. production casing, 5 1/2-in. production liner, and 4 1/2- x 3/1/2-in.
intelligent inner-string completion. The 9 5/8-in. casing is installed by use
of the "buoyancy assist" method (i.e., "flotation") so it may be "pushed" and
reamed in the hole beyond the point of negative weight. The lower completion
consists of a 5 1/2-in. slotted liner with swell packers. Centralizers on the
liner were changed from nonrotating to fixed, which allowed breaking axial drag
while reaming the liners to depth. Extensive torque-and-drag modeling was used
to plan intelligent inner-string completions on the injector wells, which
included injection control devices, swell packers, and a fiber-optic
distributed temperature sensor (DTS) to monitor injectivity. This full-length
paper discusses the technical challenges, welldesign solutions, and operational
practices that were trialed and implemented to enable extended-reach wells to
be successfully drilled on the edge of the industry-experience envelope, with
all wells meeting targeted objectives.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
14 December 2011
- Meeting paper published:
6 March 2012
- Revised manuscript received:
24 May 2012
- Manuscript approved:
6 August 2012
- Published online:
6 December 2012
- Version of record:
11 December 2012
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