Summary
Brine displacements were one of several areas of focus in a continuous
process to optimize completion methodology in Amerada Hess’s Ceiba project
wells, located in deepwater offshore Equatorial Guinea. The time between
making up the cleaning string and laying it down, after displacement and
filtration operations are completed, can exceed two days and cost U.S.
$500,000. It is imperative that wellbore-cleaning operations are performed
efficiently and correctly the first time. Amerada Hess and its brine
suppliers, working together in a joint task force, have taken specific steps to
minimize the time required for displacement and filtration operations.
Introduction
The Ceiba field in deepwater Equatorial Guinea was discovered in mid-1999 by
Triton Energy Ltd., now Amerada Hess. To date, 20 wells have been
completed, and three wells have been recompleted. Ongoing development of the
field still continues at this time. Five of the wells were completed as
openhole gravel-packed producers. The others were cased-hole producers or
injectors. The initial average pore pressure in the field was 8.7
lbm/gal, and the majority of wells in the field were completed in a 9.0 to
9.2-lbm/gal CaCl2 brine. This fluid was selected because of its minimal
damage effect during core tests and its ready availability at stock points in
the west Africa operating area. All wells were drilled through the pay
interval by use of mineral-oil-based mud.
The Ceiba field lies in approximately 800 m of water. The wells flow
through individual subsea flowlines for 8 to 11 km to a floating-production,
storage, and offloading unit that was positioned to receive first oil in the
late fall of 2000.1 The semisubmersible Sedco 700 has been on location in the
field since the spring of 2000 and has drilled the majority, and completed all,
of the Ceiba development wells.
As part of a continuing improvement program used throughout the development
of Ceiba, a critical review of brine-displacement practices was performed to
optimize this process. A review of cased-hole completions by the task
force indicated room for improvement in our displacement process and chemical
usage. At the time the task force was formed, the average displacement took 25
or more hours, with up to 4,000 bbl of completion brine discarded because of
poor quality and filtration problems. This paper examines the stages of
mud-to-brine displacement used in the cased-hole completions of the Ceiba
deepwater development and demonstrates how these stages were adjusted in their
relationship to one another to make a more efficient displacement. Data
are presented to show simplification of procedures, improved mud-solids
removal, shorter filtration time, reduced loss of brine, and shorter rig time
over the course of the development. These modifications and changes had a
major impact on time and cleaning efficiency. Please note, Ceiba
openhole-completion displacements are not addressed in this paper.
© 2005. Society of Petroleum Engineers
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History
- Original manuscript received:
10 May 2004
- Revised manuscript received:
9 December 2004
- Manuscript approved:
23 December 2004
- Version of record:
15 March 2005
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