Summary
Waterflood thief zones in communication with the rest of the reservoir are a
severe and previously challenging problem. This paper gives an introduction to
the nature of a novel, heat-activated polymer particulate. Details are
presented of a trial of this in-depth diversion system, resulting in
commercially significant incremental oil from a BP Alaskan field. The system of
one injector and two producers was selected because of a high water/oil ratio
and low recovery factor, which was recognized as an indicator of the presence
of an injection-water thief zone and was confirmed by study of a previous
injection survey. The area around the wells is bounded by faults, so the system
can be considered to be isolated from surrounding wells and operations. The
position of the thermal front in the reservoir, tracer transit times, injection
rates, and inter-well separations indicated that the slowest reacting of the
three commercial grades available was most appropriate for the trial.
The treatment was designed using laboratory tests and numerical simulation
informed by pressure and chemical-tracer tests. Long-sandpack tests indicated
permeability-reduction factors of 11 to 350 for concentrations of 1,500 to
3,500 ppm active particles in sand of 560- to 670-md permeability at 149°F.
15,587 gal of particulate product was dispersed using 8,060 gallons of
dispersing surfactant, into 38,000 bbl of injected water, and was pumped over a
period of 3 weeks at a concentration of 3,300 ppm active particles.
Placement deep in the reservoir between injector and producer was confirmed
by pressure-falloff analysis and injectivity tests. The incremental oil
predicted from the simulation was 50,000 to 250,000 bbl over 10 years. In fact,
more than 60,000 bbl of oil was recovered in the first 4 years at a cost
comparable with that of traditional well work and less than that of
sidetracking.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
19 February 2009
- Meeting paper published:
21 April 2009
- Revised manuscript received:
3 December 2009
- Manuscript approved:
15 January 2010
- Published online:
13 May 2010
- Version of record:
11 August 2010
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