--> --> Quantitative Seismic Stratigraphy and Geomorphology of the Carnarvon Basin, Northwest Australia

AAPG Foundation 2019 Grants-in-Aid Projects

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Quantitative Seismic Stratigraphy and Geomorphology of the Carnarvon Basin, Northwest Australia

Abstract

A significant portion of the worlds hydrocarbon reserves are contained in fluvio-deltaic depositional systems; in order to explore for hydrocarbons, it is of interest to understand how fluvial reservoirs evolve from upstream to downstream. In coastal fluvial strata, backwater hydrodynamics (resulting from a river running into a standing body of water) change channel character by influencing sediment load and channel mobility. This poses a considerable challenge for subsurface prediction because autogenic backwater processes can significantly influence reservoir quality and connectivity; however, it is not clear how to uniquely identify fluvial packages influence primarily by backwater hydrodynamics from those influenced by base-level change. In particular, large erosional surfaces can form in backwater reaches and may be confused with regionally correlatable sequence boundaries and incised valleys. I aim to use 3D seismic data to investigate how erosional surfaces in fluvio-deltaic strata may be attributed to either allogenic processes such as changing sea level, or autogenic backwater dynamics. The Triassic age Mungaroo Formation located in Carnarvon Basin, Northwest Australia has recently been shown to exhibit strong backwater signatures similar to those observed in the Mississippi Delta. This unit provides an opportunity to measure seismically imageable scour surfaces in a backwater-dominated depositional setting and compare them to large scour surfaces and sequence boundaries mapped in other seismic and outcrop datasets. Distinguishing between erosional surfaces with allogenic vs. autogenic origins will significantly influence how buried fluvial deposits are mapped and correlated, as well as how reservoir distribution is predicted.