Summary
This paper documents the results of a new stage of development in the
application of coiled-tubing drilling (CTD). Combining CTD technology with a
conventional jointed-pipe workover capability represents the next-step change
in providing low-cost reserves access solutions through selection of the most
efficient tool for the application.
Drilling sidetracks using coiled tubing is an established practice in
Alaska’s North Slope oil fields. During these operations, the use of jointed
pipe was avoided, except for running liners, with the CTD rig. A conventional
workover rig was the preferred approach to prepare the coiled-tubing candidate
well when it required a changeout of production tubing or other workover
activity.
In 2001, a North Slope operator evaluated the opportunity to utilize one rig
to perform both operations. In 2002, a workover rig was modified to fit the
need.
Integrating two established technologies presented many challenges.
Specialized equipment, multidisciplinary personnel, and control of overall well
cost are just a few of the many parts of the operation to be planned. This
paper details the results, problems encountered, solutions, and a
quantification of the real benefits achieved combining CTD with a jointed pipe
workover.
Introduction
CTD began in the North Slope oil fields during the mid 1990s. More
than 400 wells have been sidetracked using this technology during that decade
of operation. Drilling equipment selection evolved significantly during this
time frame. The first wells were sidetracked with a conventional, arctic-style,
coiled-tubing unit (CTU) rigged up over a tree, with external tanks, pits,
pumps, and support equipment scattered around location. This was
sufficient for proof of concept but extremely difficult in the harsh Arctic
environment and posed significant health, safety, and environmental (HSE)
exposure. A small workover rig was added to the operation to enclose all
the fluids handling equipment and provide a proper Arctic-enclosed rig floor
for which to make up drilling assemblies. There still were multiple components,
adding to a lengthy rig up in harsh conditions. The makeup of the CTD
“rigs” continued to evolve as through-tubing sidetracks proved to be an
economical success.
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
4 November 2004
- Revised manuscript received:
13 September 2006
- Manuscript approved:
24 September 2006
- Version of record:
20 December 2006
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