Summary
Drilling and completion fluids based on cesium formate brines were selected
by Statoil for use in the development of the high-pressure/high-temperature
(HP/HT) Kvitebjørn field. CsFo brine was selected primarily to minimize
well-control problems and maximize well productivity. These important benefits
had been recognized by Statoil in previous HP/HT drilling and completion
operations over the past 5 years. The use of the same fluid system for both
drilling and completion gives the additional benefits of simplified operations,
reduced waste, and elimination of fluid-incompatibility problems.
The challenge on the Kvitebjørn field was to drill long, deviated well paths
through significant sequences of shales into reservoirs with pressures as great
as 81 MPa (11,700 psi) and temperatures up to 155°C (311°F). So far, the CsFo
brine has enabled the successful drilling and completion of seven high-angle,
HP/HT production wells on Kvitebjørn, two completed with a cemented/perforated
liner and five with sand screens.
Additionally, an extended-reach exploration well was drilled from the
Kvitebjørn platform to the Valemon structure. The 705-m (2,313-ft) -long
reservoir section of this 7380-m (24,213-ft) -long well with an inclination of
69° was drilled successfully with the same CsFo fluid system.
In all these wells, the CsFo-brine system once again demonstrated clear
performance benefits such as very low equivalent circulating densities (ECDs),
moderate-to-high rates of penetration (ROPs), good hole cleaning, and excellent
wellbore stability while logging. Quick, trouble-free, safe, and robust
completion operations were also accomplished, and the wells that have been put
on production show high production rates with low skin.
Full openhole formation evaluation of the Kvitebjørn reservoir has been
carried out successfully with logging-while-drilling (LWD) tools. The
evaluation has been aided by the development of a novel logging-interpretation
solution for a LWD density tool, in which the extremely high photoelectric
effect of cesium-rich filtrate plays a vital role.
CsFo brine has helped Statoil to achieve a record of zero well-control
incidents in all 15 HP/HT-drilling operations and 20 HP/HT-completion
operations in the Kvitebjørn, Kristin, and Huldra fields over a period of 5
years.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
24 November 2006
- Meeting paper published:
20 February 2007
- Revised manuscript received:
23 July 2008
- Manuscript approved:
21 August 2008
- Published online:
16 March 2009
- Version of record:
1 March 2009
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