Controls on Geobody Interconnectivity in Upper Jurassic – Lower Cretaceous Reservoirs in the Papuan Foreland, Papua New Guinea.
Alexander Robson - 2013
Bachelor of Science (Petroleum Geology and Geophysics)
Australian School of Petroleum
The University of Adelaide
Exploration and research of the Papuan Basin has primarily been focused on the Papuan Fold Belt, however this thesis gives new insights into geobody interconnectivity in upper Jurassic and lower Cretaceous reservoirs of the Papuan Foreland, namely the Toro Formation and Elevala Sandstone. The purpose of this study is to interpret depositional trends, lateral changes in sandstone quality and connectivity and vertical connectivity of stacking geobodies, with potential implications for reservoir distribution and communication. The focus is primarily within Horizon Oil Limited licences PRL 21 and PRL 4 in the western Papuan Foreland, with regional well data used where possible. Geobody interconnectivity was studied through an analysis involving well correlations, seismic interpretation, isopach mapping, examination of core images and reports, depositional architectural classification and mercury injection capillary pressure (MICP) testing.
Structural analysis of the seismic interpreted basement and lower Cretaceous Toro Formation suggest a dextral strike-slip origin to the fault system through the study area during deposition of the Toro Formation and Elevala Sandstone. This substantially contradicts previous literature and complicates future research and exploration in terms of sandbody geometry and location. This initial dextral shear sense may potentially explain the separation of depocentres during the Toro Formation and Elevala Sandstone deposition and could have a large influence on exploration for potential reservoir quality sandbodies, not just in the study area, but across the entire Papuan Foreland.
Analysis of core and a depositional architectural classification through wells in Horizon Oil’s PRL 4 and PRL 21 licenses suggests embayed tidal and fluvial influenced deltaic deposition through the Stanley region and lobate to straight coastline morphology with wave influenced deposits in the Kiunga area and PRL 21 during the Toro Formation deposition. The Embayment surrounding Stanley appears to have moved further north during the deposition of the Elevala Sandstone, creating lobate and straight coastline morphology with highly tidal and wave influenced deposition throughout PRL 4 and PRL 21. MICP analysis has revealed vertical connectivity of geobodies, with indicated areas of communication, regional seals and intraformational seals. Controls on sandbody geometry have been interpreted to establish the interconnectivity of the Toro Formation and Elevala Sandstone. Moderately compartmentalised sands interpreted through the Kiunga and Stanley regions and east of PRL21 for the Elevala Sandstone will limit prospectivity through these areas. The Toro Formation has been interpreted to display good proximal connectivity through the Stanley and Kiunga regions, with parasequence compartmentalisation increasing to the north of PRL4 and east through PRL21.