Sedimentology, Depositional Environment and Reservoir Quality of the Miri Formation and the Lambir Formation in Miri, Sarawak

In Miri, shallow marine rock formations represent important analogues to the age equivalent, hydrocarbon-bearing offshore in Baram Province. Based on the sedimentological data gathered from all of the outcrops, the depositional environment or paleoenvironment of the rock formations was studied to relate them to the reservoir quality. This work presents the detailed facies analysis of the Miri Formation and Lambir Formation exposed around Miri, Sarawak, East Malaysia. Outcrops of the Miri Formation and Lambir Formation around Airport Road, Canada Hill, Lambir Hill, and Miri-Bintulu Road were studied.
Eight (8) lithofacies recognized in the Miri Formation include hummocky sandstone, interbedded sandstone-mudstone, herringbone cross-bedded sandstone, lenticular-bedded facies, bioturbated sandstone, trough and tabular cross-bedded sandstone, massive sandstone, and flaser to wavy-bedded facies. Facies analysis conducted in the Lambir Formation had identified five (5) main lithofacies which are massive sandstone, trough cross-bedded sandstone, flaser to wavy-bedded facies, lenticular-bedded facies, and interbedded sandstone-mudstone.
The depositional environments for the Miri Formation are interpreted as a wave-dominated shoreface and a tide-dominated estuary based on the abundance of hummocky structures and the presence of herringbone structure in the outcrop respectively. On the other hand, the Lambir Formation is interpreted as an estuarine and tidal-dominated environment due to the dominance of tidal flat associations and heterolithic bedding.