Reservoir characterization and basement estimates in the Papuan Fold belt (Papua New Guinea-PNG), from reanalysis of the PNG MT data set

Abstract

The PNG MT data set covering a section of the Papuan Fold Belt (PFB) in Papua New Guinea (PNG), which is known for its extensive hydrocarbon resources, re-analyzed using advanced dimensionality technique and inversion algorithms. Although the phase tensor analysis retrieved a dominant 2D conductivity direction matching the regional tectonic trend, a mild 3D behavior with some local strong 3D effect is apparent. The 3D and 2D inversions carried out yielded resistivity features related to the broad stratigraphic column of the area, but with variations in the depth of occurrence and thicknesses of resistivity structures between the inversion models. The preferred 3D model shows an about 1 km thick resistive Miocene Darai limestone cover, thickening towards northeast of the profile, and supports a thick-skinned thrust model. The 3D resistivity section shows an additional differentiation within the underlying Mesozoic column, a highly conductive (∼1 Ωm) and moderately conductive (10–40 Ωm) layer, sandwiched between the Darai formation and crystalline basement. The upper highly conductive layer can be related to the Cretaceous Ieru shale formation, which acts as the regional cap rock in the PFB, and the below moderately conductive layer represents the stack of Mesozoic strata that possibly comprise of the Neocomian Toro sandstone reservoir rocks and underlying Jurassic source rock formations. Nevertheless, the resolution tests do not fully support the demarcation between the Ieru formation and underlying Mesozoics containing the reservoir and source formations, and demand additional constraints for confirmation.