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The AAPG/Datapages Combined Publications Database
AAPG Special Volumes
Abstract
Fault
-seal Analysis, Offshore Myanmar: A Case Study
11. Structural Trap and
Fault
-seal Analysis, Offshore Myanmar: A Case Study
R. K. Davies,1 L. An,2 D. A. Medwedeff,3 D. Yarwood4
1Rock Deformation Research USA, Inc., McKinney, Texas, U.S.A.
2Consultant, Flower Mound, Texas, U.S.A.
3Chevron Petroleum Technology Company, San Ramon, California, U.S.A.
4BP, Houston, Texas, U.S.A.
ACKNOWLEDGMENTS
We thank Willam F. Dula Jr. and two anonymous reviewers for edits that improved the manuscript and ARCO for permission to publish the results.
ABSTRACT
The objectives of this study are to (1) describe the prospect trap style in Block M-9 near the continental shelf break offshore Myanmar in the Gulf of Martaban, (2) analyze the geometry and sealing mechanisms and risks for fault
S1, and (3) use these results as a calibration for trap style and
fault
-seal risks on additional prospects in the block.
Fault
S1 is a key trapping component to seven prospective hydrocarbon accumulations of which six are delineated by anomalously bright seismic amplitudes interpreted from 3-D seismic data in the footwall of the
fault
. All six anomalies correlated with mud log gas peaks during the drilling of the exploration well Shwe Pyi Htay-1 (SPH-1) in 1997. Only one anomaly (DHI 6), however, tested recoverable gas reserves.
We analyzed the seal potential of fault
S1 using an ARCO-proprietary, PC-based
fault
-seal analysis program integrated with 3-D visualization techniques.
Fault
-seal potential (FSP) is a parameter determined from the
fault
geometry, the throw distribution, and the reservoir quality adjacent to the
fault
surface that indicates the likelihood of a
fault
to seal hydrocarbons. The results indicate that the
fault
has high seal potential (65%) in the upthrown DHI 6 sand interval and lower seal potentials (30–45%) in the other prospective sand intervals. These results agree with the drilling results from SPH-1 well and might be applied to other prospects in the same area to assess exploration risk. Our analysis suggests that the gas-water contact (GWC) at the depth of 1497 m (4910 ft) in the upthrown DHI 6 interval may result from gas leakage across the
fault
through a window of low seal potential along a region of low throw associated with a connecting
fault
splay. If this is the case, then the threshold FSP for the DHI 6 interval is 60%. Another possibility is that the small faults below seismic resolution that intersect the S1
fault
control the GWC. If this is true, the threshold FSP would be lower than 60% but higher than 45%, which is the lowest seal potential calculated in the remaining reservoir intervals with residual gas.
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