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PSOne
Direct Indicator for Reservoir
in Fractured Carbonate*
By
GuangJun Chen1, Mohamed Redal1, Jianguo Zhu2, and Wei Meng2
Search and Discovery Article #40258 (2007)
Posted September 2, 2007
*Adapted from poster presentation at AAPG Annual Convention, Long Beach, California, April 104, 2007
1Schlumberger, Beijing, China ([email protected])
2Northwest Bureau, SinoPec
The reservoirs in the Tahe
oilfield are fractured carbonates
with extremely severe anisotropy, typically
karsted. The rock is a very tight limestone, with matrix porosity of < 2%. Vugs
and caves connected by natural fractures are the storage. Reservoirs are
developed along with a weathering crust. Some wells produce oil at a relative
high rate, while others have a very quick breakthrough or produce water
initially. Accurate
characterization
of the reservoirs to enable increased oil
and decreased water production is a challenge.
In an attempt to directly
characterize the reservoirs seismic variance was used, which calculates the
direct measurement of dissimilarity of seismic traces and produces much sharper
and more distinct terminations than those observed in normal amplitude data.
Calibrated with core, log, and high-resolution resitivity data, fractures,
caves, and vugs are all shown to result in high variance values, indicating that
a reservoir
can be developed only where variance shows high values. Variance
results are displayed in 3D or in cross-sections, and are used to identify the
geological features in the volume. Based on the variance indicators, caves and
vugs can be directly identified to predict the carbonate reservoirs, which
significantly aids properties modeling and production management.
While seismic
variance does not provide a perfect definition of the reservoir
, it has proven
to be a reliable direct indicator for
reservoir
facies in the fractured
carbonates
of the Tahe field.
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Background and Challenges
Solution and Workflow
While seismic variance does not provide a perfect definition of the
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