Summary
Gullfaks has been in production since 1986 and produces approximately 11 500
std m3/d of oil from three Condeep platforms. The average water cut
is approximately 75 to 80% and gas/oil ratio (GOR) is approximately 200 std
m3/std m3. It has been estimated that between 50 and 100
t of sand is produced yearly per platform, with approximately 60 to 70% of the
wells in active production (approximately 90) limited by sand production. The
typical well completion is cased hole with selective production through
perforated liners. Rock-mechanics studies have shown that sand will be produced
irrespective of well inclination and perforation design.
On Gullfaks, the sand-management strategy used has been to produce wells at
"maximum" or "acceptable" sand rates. This strategy has led to significant
gains in production, although there are challenges with this approach that
include choke erosion, sand removal from the separators, and oil-in-water
quality associated with discharge to sea. In response to this, Statoil has
investigated different methods of retaining sand downhole by chemical sand
consolidation, of which in-situ calcium carbonate (CaCO3)
precipitation will form the basis for this paper. This technology involves
squeezing into the near-wellbore formation predefined concentrations of urea
and calcium nitrate along with the enzyme urease. After application, the well
is shut in, during which the enzyme catalyzes the decomposition of urea to
bicarbonate that reacts with calcium to form calcium carbonate.
This paper will provide details of the laboratory evaluation and, in
particular, will focus on the field results from the first-ever application of
this type. A low-risk candidate well was selected that had a short perforated
interval (19 m) and produced 88 std m3/d oil with a water cut of
94%. Results of the operation design and planning, logistics examination,
thorough risk evaluation, and post-operation results with lessons learned will
be presented.
© 2012. Society of Petroleum Engineers
View full textPDF
(
3,685 KB
)
History
- Original manuscript received:
31 March 2011
- Meeting paper published:
8 June 2011
- Revised manuscript received:
2 July 2011
- Manuscript approved:
10 August 2011
- Published online:
15 March 2012
- Version of record:
1 May 2012
View Cart
