Summary
Naturally fractured reservoirs (NFRs) represent more than 20% of the world's
oil and gas reserves. However, their characterization is complex and presents
unique challenges in comparison with conventional reservoirs. It is immensely
difficult to achieve the best results in the secondary-recovery process for
NFRs.
This paper presents a successful development of waterflooding to overcome
the complex geological characterization of the White Tiger field, the largest
fractured basement reservoir to date on the continental shelf of Vietnam. This
reservoir has a complicated geological structure, with high heterogeneity, high
temperature, and high closure stress. The total oil initially in place (OIIP)
of this field reached nearly 4 billion bbl from 2000 m of oil-bearing
thickness, and the field has been produced by more than 100 wells, 10 of which
have flowed at the rate of approximately 1,000 B/D.
The geological study and fractured model have been carefully investigated in
both micro- and macroscale to improve waterflooding performance. The authors
have analyzed the advantages and disadvantages of injection systems in this
basement reservoir during 20 years of production history, and an artificial
water buffer solution has been proposed to improve the waterflooding process.
The authors have described the establishment and association of local
artificial water buffer in the basement reservoir. An effective method to
optimize the injected-water volume has also been discussed. Promising results
from the White Tiger field have shown that the average reservoir pressure and
total oil recovery have increased significantly in comparison with previous
injection schemes.
This paper presents useful guidelines to solve some typical problems of
waterflooding in fractured basement reservoirs:
- What can be applied in waterflooding for a fractured basement
reservoir?
- What is the optimal injection rate and injected volume for the fractured
basement reservoir?
- How do we evaluate the probability of high water cut in production wells
during the waterflooding process?
- How do we predict the rise of an artificial water/oil contact (AWOC)?
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
24 September 2010
- Meeting paper published:
20 October 2010
- Revised manuscript received:
31 January 2011
- Manuscript approved:
5 February 2011
- Version of record:
13 September 2011
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