The Structurally Trapped Matoa Field and Porosity Distribution, Salawati Basin, Irian Jaya



The Matoa field is the only field in the Salawati Basin which produces oil in commercial quantities from a structural trap and from non-reefal Miocene Kais platform carbonates. The Kais Formation in the Matoa field was deposited in a restricted marine environment as a carbonate platform, inner shelf facies during Middle to Late Miocene time. Other fields in the basin are commonly faulted but the primary trapping mechanism is that of shale seal around reefal carbonate build-ups. Structural closure is formed by juxtaposition of porous Kais carbonates against overlying Klasafet shales along the Line “6” fault. Porosity distribution is complex and thought to be controlled by erosional events from nearby carbonate highs. Biostratigraphic and petrographic analysis indicate that the Kais section comprises of shallow water carbonates deposited in a restricted environment and interbedded with tight deeper marine carbonates. Currently, 14 wells have been drilled in the field and produce about 10,000 BOPD from three main porosity zones.


Authors : I Nyoman Suta & Landong Silalahi