Development patterns and controlling factors of Tertiary carbonate buildups: Insights from high-resolution 3D seismic and well data in the Malampaya gas field (Offshore Palawan, Philippines)

The comprehensive subsurface database of the Malampaya buildup (Late Eocene to Early Miocene, offshore NW Palawan) provides a rare insight into the development of South-East Asian Cenozoic carbonate systems and their controlling factors. The newly acquired high-resolution three-dimensional seismic survey, combined with facies and well-log analysis, allowed a better understanding of the internal architecture of a carbonate platform whose development was largely controlled by tectonic deformation. The Malampaya carbonate system was initiated in the Late Eocene, as an attached shelf influenced by significant clastic input. The Late Eocene-Early Oligocene shelf was subject to syn-depositional extensional tectonics (eastward tilting and block faulting) that favoured the development of small size buildups on structural highs. After a stage of eastward reef progradation, an aggrading carbonate shelf, frequently affected by subaerial exposure, developed from the earliest Late Oligocene to the Early Miocene. During this period, recurrent reactivation of highs along the western and northeastern buildup margins determined the asymmetric morphology and internal architecture of the carbonate system. The final demise of the carbonate buildup occurred in the late Early Miocene. It resulted from an increase in subsidence rate and/or a sharp increase in nutrient input. Additional parameters like eustacy, oceanographic conditions and the type of carbonate producers played a subordinate role in the buildup development and ultimate demise.