Summary
Drilling in the North Sea is confronted with an ever more challenging
pressure-management issue because of narrow geopressure windows in depleted
reservoirs. Further, the occurrence of packoffs can cause serious damage to the
formation and contribute to nonproductive time. To address these problems,
automation of mud-pump management has been developed over the last 4 years to
minimize the chance of fracturing the formation while starting the mud pumps or
circulating. To account for abnormal flow restrictions in the annulus,
automatic actions are also an integral part of the mud-pump automation
described in this paper.
Since the downhole conditions are continuously changing (e.g., depth,
temperature, flow-rate, gel time, cuttings proportion), the necessary
safeguards to operate the mud pumps need to be updated constantly. Advanced
transient temperature and hydraulic models are used to estimate, in real-time,
the downhole situation. On the basis of the current context, evaluations of
maximum pump rates and acceptable flow accelerations are performed and sent to
the mud-pump control system to be used as an envelope of protection.
Furthermore, to assist the driller during connections, the pump-startup
procedure has been semiautomated to decrease connection time. Finally, an
automatically triggered pump-shutdown procedure is also available to minimize
the consequences of a packoff on formation fracturing.
A first version of the system has been tested during the drilling of one
well in 2008 in the North Sea. Based on the initial experience, a revised
version has been used during the drilling of three wells drilled on the
Norwegian continental shelf in 2009. The feedback from the drillers involved in
the testing has been used to improve the user friendliness of the system. The
automation of the mud-pump management has been well accepted by the drilling
crews. However, the testing has shown that additional instrumentation at the
rigsite is necessary before such automation can be rolled out safely.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
11 February 2010
- Meeting paper published:
2 February 2010
- Revised manuscript received:
1 September 2010
- Manuscript approved:
3 September 2010
- Published online:
1 March 2011
- Version of record:
11 March 2011