Postgraduate Profiles

Rosine Riera

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Thesis: Stratigraphic architectures of an Oligo-Miocene subtropical carbonate system: impact for the petrophysical properties of the overburden (Northern Carnarvon Basin, Western Australia)

The Northern Carnarvon Basin (NCB) on the North West Shelf of Australia is a premier hydrocarbon province. Reservoir rocks are overlaid by two Oligo-Miocene carbonate sequences which cause drilling risks and velocity anomalies:

• The Oligocene-Early Miocene sequence formed along a distally steepened ramp dominated by the shallow foraminiferal packstone deposits of the Tulki Limestone and the finer-grained, deeper water deposits of the Mandu calcarenite

• The Middle Miocene sequence formed along a potentially rimmed platform associated with patch reefs and dominated by the shallow foraminiferal wackestone of the Trealla Limestone

Past studies of this formations have focused on either the lithostratigraphy and large benthic foraminiferal assemblages onshore or the seismic stratigraphy and planktic foraminifera offshore. No onshore-offshore correlation was attempted and basin-scale sedimentary and stratigraphic models of the deposits are lacking.

This PhD project aims to create a stratigraphic, diagenetic and petrophysical model of this deposits using outcrop, well and seismic data. This model will be the first one correlating onshore and offshore data and predicting rock properties of the overburden at the basin scale. The project is based on the integration of field work data, thin sections and acetate peels, Strontium isotope dating, biostratigraphy and 3D seismic interpretation. It will be realized in two steps:

• The analysis of the stratigraphic, sedimentological and diagenetic evolution of the Oligocene-Miocene Supersequence observed in the onshore and offshore North Carnarvon Basin

• The creation of a 3D model predicting the spatial evolution of the petro-acoustic properties (Vp, Vs, density) based on the diagenetic-facies changes observed in onshore and offshore data

Why my research is important

A better understanding of the geological, petrophysical and geophysical properties of the carbonate sequences and associated deposits in the overburden of the North West Shelf will have a direct impact on the future exploration and production of hydrocarbon resources in offshore Western Australia as it will:

• Refine our understanding of the Oligo-Miocene history of the North West Shelf

• Analyse the combined effects of eustatic, tectonic, biologic and oceanic controls on carbonate platform morphology to improve facies prediction

• Bring new insights for seismic data reprocessing

• Help locate geohazards for drilling de-risking

Funding

Mar 2016

Mar 2019

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