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Eocene and Oligocene Source Rock Distribution and Quality in the South China Sea Region: Inferences from Plate Tectonic Modelling and Play Mapping

Jacques, John M.; Stone, Vaughan C.; Hoult, Ruth J.
Oil and Gas Consultancy, JMJ Petroleum, Singapore, Singapore.

Unresolved problems and alternative models for the tectonic evolution of the South China Sea have been reviewed in an attempt to identify what is known and evaluate what is presumed about the infrastructural framework of the region. Using potential fields data (gravity and magnetics) integrated with seismic, well, and other complimentary datasets, the first phase of the study programme has been designed to define: original (pretectonic) continental block outlines; first-order tectonic elements and predominant structural basement fabrics; distribution of different crustal types (continental, oceanic and heterogeneous) and their boundaries; and the extent of igneous intrusives and volcanics. Placed in a plate tectonic context, we will demonstrate that this information can be confidently used to create a regional "palaeotemplate" that can be ultimately used to create a series of palinspastic base maps for plate tectonic and basin dynamic modelling purposes.

The resultant composite palaeotectonic model has been further assessed and modified by using potential fields and seismic data to define original pre-rift and pre-drift continental block outlines. A particular focus has been to establish the original configuration of the rift systems on both conjugate margins of the South China Sea, with regards to the distribution and quality of both Eocene and Oligocene potential source rocks in terms of their distribution and quality. This, in turn, has been used to produce a series of palaeotectonic and depositional reconstructions for key reservoir intervals. The mapped distribution of different crustal types and intensity of Tertiary extensional activity will be a principal constraint for predicting palaeoheat flow gradients for determining basin subsidence and source rock maturation histories.

Using ESRI's ArcView and ARC/INFO GIS formats this has created a complete attributed digital structural and geological coverage for the South China Sea region, which includes the Pearl River Mouth, Qiongdongnan, Beibu Gulf, Song Hong, Phu Khanh, Sabah, Read Bank and Palawan basin systems. Integrated with field and well data, the structure, stratigraphy and deformational state of each basin provides a very powerful means for identifying important spatial and temporal relationships of the region's essential play elements; and, in turn, a predictive tool for the assessment of their future prospectivity and the identification of regional play fairway trends.


AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012