High Resolution Characterization of Lithological Heterogeneity of the Paaratte Formation, Otway Basin (Australia), a Coastal to Shallow-Marine Deposit

Abstract

Coastal to shallow-marine deposits are inherently highly heterogeneous in sediment composition due to variable depositional conditions. Representation of heterogeneity at sub-seismic scales is required for understanding flow and geochemical processes and poses two challenges: Firstly, the representation of different rock types in geological models requires high resolution sampling vertically and laterally. Secondly, the heterogeneity in petrophysical, flow and mineralogical properties within each rock type needs to be sufficiently characterized in order to support (multiphase) flow and reactive transport simulations. This study addresses these challenges for the Paaratte Formation, Otway Basin (Australia), at the CO2CRC’s Otway Research Facility to enable detailed simulations of CO2 flow and reactions. Based on the analysis of wireline logs, hyperspectral core logs and discrete samples from wells CRC-2 and CRC-3, five rock types are defined and characterized for two coastal to shallow-marine parasequences comprising four depositional facies. A combination of wireline logs is used to derive rock type logs for the wells CRC-2 and CRC-3 at 10 cm vertical resolution and allows high resolution cross-well correlation providing insights into the lateral extent of deposits. Findings of this study will inform future desktop and field studies at the CO2CRC’s Otway Research Facility requiring information on sub-seismic lithological heterogeneity.