Defining Geobody Geometries and Architectural Elements within Fluvio-Deltaic Depositional Systems: a Quantitative Analysis of the Mixed Continental / Marine Mungaroo Fm, NW Australia

Heldreich, Georgina; Redfern, Jonathan; Hodgetts, David

The stratigraphically complex Triassic fluvio-deltaic Mungaroo Formation is the main reservoir in the multi-TCF gas play offshore Northern Carnarvon Basin, NW Shelf, W. Australia. To characterise the Mungaroo Formation depositional system, reservoir architecture and geobody geometries, this research utilises a high resolution 3-D seismic volume, covering approximately 17,500Km2, located NW of the Exmouth and Barrow sub-basins on the broad NW shelf of Australia, integrated with a full suite of well log data from 21 wells and conventional core from 8 wells.

The dominant facies and facies associations deposited on the Triassic continental shelf include; within channel sandstones, overbank and floodplain lake muds, silts and clays, swampy coal intervals and lagoon/ restricted embayment facies. Core and wireline log analysis has been integrated to produce well correlations across the basin and develop a sequence stratigraphic model for the Mungaroo Formation. The results allow the spatial and temporal characterisation of the depositional environment; defining alternating periods of transgression and regression, within an overall transgressive system, that coincide with zones of low and high N:G respectively.

Various channel morphologies can be identified from seismic attribute analysis, which when integrated with core-wireline log studies, allow the generation of seismic facies GDE maps of the Mungaroo Formation through time, and the development of refined depositional and sequence stratigraphic models.

The paper also examines the control and influence of climate and base-level changes on the observed sedimentary architecture through time, and the significance for reservoir development.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013