Journal of Conference Abstracts

Insights to Temporal and Spatial Variability of a Miocene Platform, Offshore Vietnam, Provided by 3D Visualisation and Computer Modelling

James Owens (jowens@fs1.ge.man.ac.uk), Dave Hunt, Stuart Hardy & Trevor Burchette

Dept. Earth Science, University of Manchester, Manchester, UK

Antecedent topography, tectonic subsidence and oceanographic setting constitute some of the primary controls on carbonate production and the development of landmass-detached carbonate platforms. A high quality, closely spaced (1.5-5 km) 2D seismic grid imaging a Miocene platform, offshore Vietnam, provides an excellent data base from which these controls can be investigated. The platform architecture, facies and rates of aggradation are evaluated against comparable Oligo-Miocene platforms in South East Asia.

Key seismic surfaces have been mapped over a 160 km long, 25 km wide, elongate platform and reveal significant north to south thickening from less than 500 m to over 1 km. The platform initiated along an established regional structural high (related to the Red River and East Vietnam rift systems) and can be divided into three discrete areas of carbonate growth. These are separated by two 10 km wide basement fault controlled palaeo-seaways. Internally, the platform demonstrates pronounced asymmetry and significant along strike variability of stacking patterns and seismic facies as a result of tectonic and oceanographic controls.

Two wells penetrate the platform succession, providing wireline, core and biostratigraphic data. These enable the wireline characterisation of carbonate facies and development of a chronostratigraphic framework for platform growth. Seismic stratigraphic surfaces from the 2D database have been depth converted and manipulated using GoGad workstation software to provide a three dimensional view of changing platform morphology. The incorporation of biostratigraphic control within this framework enables carbonate accumulation rates and sediment volumes to be estimated for individual seismic sequences and for the platform as a whole.

The platform surfaces have also been incorporated into a 3D forward modelling program capable of simulating carbonate growth and deposition. The effects of eustasy, differential subsidence, clastic contamination and windward-leeward energy flux have been investigated. The simulated platform morphologies and stacking patterns have been compared to the subsurface data as a means to understanding spatial and temporal varibility of the controls on isolated platform development and architecture.

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