Summary
Oseberg Sør field, operated by Hydro Oil & Energy, is situated 130 km
west of the Norwegian coast on the eastern flank of the Viking Graben
structure. It comprises a sequence of fault-bounded structural units of varying
geological complexity. Within these units, the reservoir intervals are of
moderate to poor quality and can exhibit strong contrasts in permeability and
formation water composition. Reservoir support is provided by combined
injection of gas and Utsira aquifer water. The wells are a combination of
platform and subsea and comprise extended reach horizontals with complex
geometry and lesser numbers of vertical wells.
Detailed scale predictions have been performed to identify the scaling risk
for each producer. From these, it was identified that the major risk to well
performance and integrity was CaCO3 precipitation in the upper
tubing with potential failure of the downhole safety valve. The risk varied
from negligible to severe and reflected the variable composition of the
produced water and well operating conditions. The scale predictions provided
the basis for a technical and economic evaluation to identify an appropriate
scale-management strategy for Oseberg Sør. For those wells completed with
downhole chemical injection lines, the option to use these for scale inhibition
was considered cost effective. In other wells where this option was not
available, scale inhibitor injection into the gas lift system or squeezing
using a viscosified treatment was considered viable.
The paper will provide the technical and economic reasoning for the
scale-management strategy selected along with field case histories for each
treatment type (i.e., experience with treatment using chemical injection lines,
injection of scale inhibitor into the gas lift system, and squeezing).
© 2007. Society of Petroleum Engineers
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History
- Original manuscript received:
27 February 2006
- Meeting paper published:
30 May 2006
- Revised manuscript received:
18 October 2006
- Manuscript approved:
26 October 2006
- Version of record:
20 August 2007
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