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ABSTRACT: Carbonate Platforms - Modern Analogues in a 3-D World, Examples from the Java Sea

Park, Robert K. , Kodeco Energy Co., Ltd, Jakarta, Indonesia

Modern carbonate platforms provided the foundations to our understanding and rationale for modeling carbonate depositional and diagenetic systems. The Seribu Platform and associated "Thousand Island" chain of reefal build-ups, located 40km north of Jakarta, has proved itself a useful analogue for Tertiary carbonates in the region in terms of facies patterns, controls on distribution and perhaps most strikingly, the scale and geometry of features found.

Many documented examples of early Tertiary carbonate platforms, attached and isolated, exist within Indonesia. NNE-SSW fault defined horsts and grabens, an established feature of the Java-Sumatra back arc basins, commonly provide the structural foundation for their development. The JS-1 Ridge, bisecting the N. Madura contract area, is one such example. Although some build-ups may prove uneconomic in size, it is noteworthy that individual islands atop the platform, display a pronounced ENE-WSW orientation and elongation, suggesting oceanographic controls have changed little since the Miocene. Porosity trends within the structures appear to mimic reef growth patterns, adding to the striking comparison with the modern Seribu Platform.

3-D seismic allows more detailed mapping of surface topography at reservoir depths, while the use of attributes provides additional insights into reservoir architecture by highlighting facies and porosity trends. As resolution capability increases, modern analogues remain essential, for the details as much as the models they provide. Factors of scale, geometry, facies relationships and associated rates of change, as documented in modern analogues, are critical in the evaluation, drilling and development of carbonate reservoirs. The enhanced resolution now available serves as a reminder that, while structural grain may define a play concept, 3-D geometry and internal architecture define the prospect.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia