Depositional environment and reservoir quality of Miocene sediments in the central part of the Nam Con Son Basin, southern Vietnam shelf

The Miocene sandstones comprise mostly fine to very fine-grained, feldspathic litharenite to lithic arkose. Deep marine turbidite sandstones of the Upper Miocene succession exhibit the best reservoir qualities (both porosity and permeability) of all the sedimentary facies examined. Paralic sandstones of the Lower Miocene succession and footwall-derived turbidite sandstones of the Middle Miocene succession have similar reservoir qualities. Relatively good reservoir quality sandstones of the Middle and Upper Miocene successions were deposited as thick massive turbidites. However, parallel-laminated turbidites and slumps/debris flows often show poor to moderate reservoir qualities. Precipitation of carbonate cement during burial diagenesis has destroyed the reservoir quality of the Miocene sandstones.