Sea-level changes, shoreline journeys, and the seismic stratigraphy of Central Luconia, Miocene-present, offshore Sarawak, NW Borneo

• Clastics over carbonate build-ups are interpreted as stacked low-relief deltas.
• Palaeo-coastlines have migrated over 100s of km in response to sea-level movements.
• Deltas frequently prograded basinward of carbonate province.
• Deltaic topsets onlap the sides of carbonate build-ups, leaking hydrocarbons.
• Carbonate reservoir units and events can be correlated via clastic stratigraphy.

Central Luconia is a geological province of the Sarawak Basin, offshore NW Borneo, characterised by extensive development of Miocene to Recent carbonate build-ups. In the subsurface, many of these build-ups are reservoirs for hydrocarbons. This study focuses on shelf-wide stratigraphic architecture, from which implications are drawn for the stratigraphic-sealing potential of the deltaic clastics. A stratigraphic model is proposed whereby clastic sediments surrounding the carbonate build-ups are interpreted as stacked low-relief deltas deposited in response to high-frequency oscillation of the sea level. The deltas are shown to have frequently prograded beyond carbonate build-ups. As a result of interaction between eustacy and deposition, deltaic topsets are juxtaposed against carbonate build-ups, providing migration routes for hydrocarbons. Most of the carbonate reservoirs are consequently underfilled, with hydrocarbon columns limited to the youngest onlapping stratigraphic sequence.