A Review of the New Ireland Basin, Papua New Guinea: Architecture, Sediment History and Petroleum Systems

Abstract

The New Ireland Basin covers a 400 × 180 km area of the Pacific Ocean located adjacent to the island of New Ireland in NE Papua New Guinea. This frontier basin contains two major depocentres with marine sediment thicknesses of up to 7 km. Originally a fore-arc depocentre during the westward subduction of the Pacific Plate below the New Ireland island arc during the Oligocene, the basin underwent inversion and thermal reactivation following the Miocene docking of the Ontong Java Plateau with the outer PNG plate margin. Dredging and coring of seafloor sediments returned Oligocene to Recent sediments including deepwater marine shales, deep- and shallow-water marine carbonates and volcanic sandstones. Biostratigraphy and geochronology studies, supported by regional-scale seismic data, allow stratigraphic reconstruction of the first-order basin architecture. Elevated methane concentrations (up to 1,000 nl/l CH4) in bottom waters south of Lihir Island are linked to fault-bounded hydrocarbon seeps of thermogenic origin (Schmidt et al., 2002). The presence of submarine seeps can be linked directly to the basinal sediments containing bitumen within fracture networks, indicating that hydrocarbons are being generated within and migrating through the stratigraphic column. Petroleum system modeling using vitrinite reflectance data to constrain thermal histories indicates that significant volumes of hydrocarbon charge may have been generated since the Early Pliocene. Seismic surveys show extensive horst-graben structures and related anticlinal features developed during the Miocene that could form structural and stratigraphic traps for migrating hydrocarbons. Ref: Schmidt et al. 2002. Chem Geology 186, 249–264.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015