Abstract: Miocene Carbonate Buildups in the Nam Con Son Basin, Offshore Socialist Republic of Vietnam

Mike J. Mayall, Alistair Bent, Dave M. Roberts

In the Nam Con Son basin, offshore Vietnam a number of different types of carbonate accumulations can be recognised.

Platform carbonates. Basin-wide units of carbonate which are characterised by strong, continuous parallel seismic reflectors. Small buildups are locally present. The carbonates were deposited during a mostly passive tectonic phase. However in places they are succeeded by local syn-rift carbonates which show thickening into the developing grabens.

Pinnacles. Typically 2-5km across, 300m+ thick with chaotic or mounded internal seismic facies.

Large isolated buildups. The large buildups, typically 5-10km across, developed as isolated features on fault-bounded structures following an uplift phase. They unconformably overlie the platform carbonate facies which are extensively karstified. The isolated carbonate buildups are characterised by steep sided slopes with talus cones, reef-margin rims usually developed around only part of the buildup, and a prominent back-stepping geometry. Fades in the centre of the buildups is dominated by fine to coarse grained coralgal packstones. Fine grained carbonates are associated with deeper water events and multiple karst surfaces can also be identified. Potential reservoir heterogeneities include vertical shallowing upwards facies cycles, the wide-spread fine grained deeper water facies and cementation associated with the karstic surfaces.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France