Summary
A technological breakthrough within the application of wireline technology
has been achieved. In August 2008 on an offshore platform on the Norwegian
continental shelf, a wireline tractor and a new wireline milling system were
used to mill and remove a permanent bridge plug at 4,147 ft measured depth
(MD).
The operator decided to mill out the plug on electric wireline and worked
closely with the service company to develop this novel solution. Having
developed and tested several bits and milling tools, results showed that by
combining the wireline miller with hydraulically provided weight on bit (WOB),
it would be possible to mill out the retaining rings of the plug, which would
cause the plug to collapse. The milling-control unit allows the WOB to be
adjusted for each application and also controls the reactive torque--the force
generated when the milling bit engages the plug.
The service company was able to develop the solution within the client's
parameters and in accordance with the timeline set out for this project. The
offshore operation was completed in 3 days, to the operator's satisfaction.
In another platform well, a permanent bridge plug had been set in 2003 in
the sealbore between two screen sections [3-ft sealbore, 67° well angle,
4.75-in. inner diameter (ID)]. The plug was set in order to isolate the
somewhat higher water cut in the lower reservoir zone to prolong oil production
from the well. In 2006, the well drowned after a 2-week-maintenance period. Two
years later, a coiled-tubing (CT) gas lift operation was carried out with good
results. It was then decided to remove the permanent bridge plug to reopen for
production before another CT gas lift operation was carried out. A method for
milling the permanent bridge plug was developed on the basis of lessons learned
from the other plug-milling operation and by extensive testing at the service
company's facilities. The operation was completed successfully in 13 days.
This new application for milling completion hardware and other wellbore
obstructions offers a cost-efficient alternative to existing methods. The
success of the milling operation is a significant achievement and has pushed
the limits for what is possible on electric wireline.
This paper will examine two cases of milling bridge plugs on electric
wireline and the technical challenges that had to be overcome in offshore
operations.The first case used the well stroker as WOB, and the second cased
used the well tractor as WOB.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
4 August 2009
- Meeting paper published:
9 September 2009
- Revised manuscript received:
22 January 2010
- Manuscript approved:
27 January 2010
- Published online:
19 May 2010
- Version of record:
11 August 2010
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