Mapping of fluvial sand systems using rock physics analysis and simultaneous inversion for density: Case study from the Gulf of Thailand

摘要

Tertiary rift basins in the Gulf of Thailand are major hydrocarbon-producing areas of Thailand. The reservoirs in these basins are fluvial sands. Imaging these reservoir sands is not always easy using conventional seismic amplitudes because of rapid lateral and vertical lithological variations due to the fluvial depositional environment. We applied rock physics and simultaneous inversion techniques to predict sand distribution within the Pattani Basin, Gulf of Thailand. According to rock physics analysis, P-impedance is most useful down to depths of ～1800 m, but at greater depths, density differentiates sand and shale more effectively. Vp/Vs data alone are not a good discriminator of sand bodies in the study area. However, used in conjunction with the P-impedance, they could be useful for identifying high porosity sands. Density prediction through simultaneous inversion gave a reasonable match with the sand distribution throughout the zone of interest, based on well log correlation, and at depths greater than ～1800 m resolves sands more effectively than the P-impedance volume. Horizon slices of density-inverted sections successfully delineate sand geometries associated with fluvial systems in the area.