Summary
Production was dramatically improved by cavitating (i.e., intentionally
producing sand) an offshore gas well on the Gulf of Mexico shelf. The
cavity completion was conducted over a period of 10 days and involved producing
the well with temporary equipment to safely produce, collect, and dispose of
the produced sand. No hydrocarbon emissions resulted because production
could be routed back through the permanent facilities. Following the
operations, the well was returned to flow through the permanent facilities at a
much higher producing rate, with much lower sand production.
Before the cavity-completion operations, the well had been choked back to a
low gas rate (<1 MMscf/D) because of sand production. The low gas rate
was insufficient to continuously lift liquids, causing the well to become
liquid loaded and/or slug. The well was evaluated for a sand-control
completion, but this type of repair was believed to entail too much economic
risk because of significant reservoir unknowns. Further evaluation
suggested that the well had the attributes for successful cavity
completion.
This paper discusses the cavity-completion evaluation process employed and
the operational results and learnings; a similar process may be applicable to
other wells.
Introduction
A cavity-like completion has been used in other areas to attempt to reduce
the amount of solids produced and improve the productivity of wells.1 For
this offshore-well application, a cavity-like completion was believed to
provide a viable option once it was determined that the well produced too many
solids as originally completed. A conventional repair to install a sand-control
completion was evaluated but was believed to entail too much economic
risk. While there were significant reservoir unknowns, a cavity-type
completion could be attempted at a relatively low cost. Following the
cavity completion, the well was returned to production at a higher rate (four-
to five-fold increase), with minor amounts of sand production, until the
reservoir watered out.
A cavity-like completion involves purposely producing sand with the
intention of creating an enlarged void or enhanced-permeability area around the
wellbore. Sand production can entail risks (discussed below), so this
method may not be appropriate in other situations.
© 2005. Society of Petroleum Engineers
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History
- Original manuscript received:
10 May 2004
- Revised manuscript received:
1 July 2005
- Manuscript approved:
15 July 2005
- Version of record:
15 September 2005
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