Summary
Good well- and reservoir-management practices demand that new gas wells be
tested to expected potentials at the onset of production and buildup surveys be
conducted at specified intervals during the life of the well. This will help to
determine the deliverability of the wells, obtain base reservoir parameters,
and improve reservoir surveillance in monitoring abandonment conditions. It was
the pursuit of these data gatherings that lead to the multirate buildup survey
that resulted in stuck temperature and pressure memory gauges at RN® No-Go
nipple.
The gas-production capability of this well was estimated at 150 MMscf/D.
After the installation of the memory gauges, multirate and 10-hour buildup
tests were conducted. During the retrieval of the bottomhole-pressure (BHP)
gauges, several incidents led to three fish getting stuck successively in the
wellbore. The operator was faced with many options, each with a limitation:
Continue the well in an unsafe manner at 50% potential, attempt a workover, or
attempt a coiled-tubing (CT) rigless intervention.
During the planning stage of the remedial operation, success in retrieving
the multiple fish was identified to be dependent upon the ability to kill the
high-pressure gas well with a time-dependent and acid-degradable
crosslinked-gel system with a high-rate bullhead pumping technique and
appropriate wireline/CT fishing tools. These tools would locate and grab the
wire rope simultaneously, minimizing run time in a cost-effective manner. The
kill fluid needed to have low damage potential to the formation and be capable
of preventing the migration and fingering of formation gas to the surface
throughout the fishing operation, which lasted approximately 1 month. Key
success was identified in the ability of the CT to compress the wire rope in
bunches and withstand the extra overpull required to free the stuck fish.
At the end of the operation, in which some challenges were encountered, five
stuck fish (two additional fish became stuck during the attempt to free the
first three) were retrieved successfully and prefishing conduit potential was
retained, thus indicating that the crosslinked gel degraded completely at the
end of the fishing operation, leaving the near-wellbore region undamaged.
The gain from the operation includes leaving the formation in an undamaged
state, cost savings, high net present value, and meeting the gas-supply
obligation. More than USD 2.0 million was saved operationally with the choice
of rigless activity when compared to the rig re-entry alternative. The well is
still producing satisfactorily 5 years after this activity.
This paper presents the engineering design and field application of, as well
as lessons learned from, fishing operations.
© 2008. Society of Petroleum Engineers
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History
- Original manuscript received:
27 June 2006
- Meeting paper published:
24 September 2006
- Revised manuscript received:
5 February 2008
- Manuscript approved:
21 February 2008
- Version of record:
15 November 2008
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