Summary
BZ25-1s field in Bohai Bay, China, is characterized as a complex channelized
fluvial reservoir in which small meandering channels were deposited at
different geological times stacking and cross cutting each other. There are
many isolated small reservoir systems following channel distributions. Early
production showed steep pressure and production decline. Quick implementation
of water injection was needed to arrest the fast production decline and to
stabilize reservoir pressure.
While designing the water-injection plan, we faced a number of challenges,
such as high oil viscosity (≈200 cp), strong heterogeneity, poor reservoir
connectivity, complex channel geometry, and irregular well patterns. A workflow
integrating geological, well-log, seismic, and dynamic production data was
developed to optimize a water injection plan for this field after a short
production history. Focuses of this workflow are the selection of injection
wells (converted from existing producers), timing of water injection, and the
optimization of injection rates.
Following the workflow, the optimal water-injection design for the areas
around Platforms D and E was developed and quickly implemented within the first
year of production. We started with a relatively small water-injection rate and
gradually increased the injection rate to avoid the fast water breakthrough and
yet to limit the pressure-decline rate.
The responses from the water injection were very positive and resulted in
stable reservoir pressure and increase of oil production. Before water
injection, the production-decline rates were 26 and 47% in Platforms D and E,
respectively. After 1 year of water injection, oil-production-decline rates in
these two platforms were reduced to 19 and 14%, respectively. The responses of
water injection for different well groups were analyzed in a timely fashion and
adjustments to injection/production strategies were implemented accordingly.
New information revealed from the water-injection response analysis was used to
update the geological model to reduce the model uncertainty, as well as to
adjust the water-injection strategies for better sweep efficiency. Our
experiences showed that such dynamic adjustment of injection and production
schedule is very important to achieve better water-injection efficiency for
this heavy-oil reservoir with complex channel geometry.
© 2009. Society of Petroleum Engineers
View full textPDF
(
3,641 KB
)
History
- Original manuscript received:
2 August 2007
- Meeting paper published:
11 November 2007
- Revised manuscript received:
28 January 2009
- Manuscript approved:
1 February 2009
- Published online:
24 November 2009
- Version of record:
31 December 2009
View Cart
