It has been observed that a continuous, regional-scale transgression has been experienced in the Central Sumatera Basin during lower to middle Miocene era. Having such transgression on a river mouth will most likely yield land-ward stepping sand deposition, especially when sediment supply constant or decrease. Tide current will then redistribute the sediments, thus avoid the development of a delta depocenter, and instead, initiate the formation of an estuarine system with all its associated facies. The investigated area has been identified as having inner to middle neritic marine system during most of the Miocene time based on presence of abundant carbonate, glauconite and specific forams. Furthermore, the presence of silty sand with carbonaceous material, as well as mud-drapes, bioturbations, and various sediment structures has indicated the area had been under wide flooding with tide domination, while the thin sand body geometry suggested low sediment supply. With these conditions, and the fact that no depocenter has been observed or reported, it is not surprising to have the main sand body (amalgamated Rindu 4 & Rindu 5), as having been deposited in an estuarine system.
This study will give an opportunity to a new alternative in correlating other sand bodies in the Duri field. The estuarine model approach could help in better defining the reservoir flow-unit, especially on amalgamated / stacking channel sands. Thus, will improve the efficiency of the steam flooding strategy, in order to increase the heavy oil production in Duri field.
Authors : Nana Yoanita & Batara Simanjuntak