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.