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Miocene Carbonate Reservoirs Related to Tectonic and Thermal Evolution of Southeast Asian Marginal Basins

C. S. Fulthorpe, J. P. Brodholt, D. M. Jurdy, S. O. Schlanger

The early Miocene global sea level rise and oceanic warming period allowed the tropical reef growth belt to expand and fostered the development of major carbonate buildups throughout southeast Asia. A regional paleogeographic reconstruction for 18 m.y. places reefal, shelf, and basinal facies in a tectonic setting of island arcs, subduction zones, and marginal basins. For typical basins, such as the Sulu, Celebes, and South China Sea basins, basin formation and sedimentation models have been developed based on ages inferred from identified marine magnetic anomalies and heat flow data. These basins have many of the attributes needed for hydrocarbon development and maturation. They accumulated sediment from pelagic sources and surrounding island arcs and landmasses fringed y reefs. During the early Miocene, limited water circulation in restricted basins, such as the Sulu and Celebes basins, may have induced dysaerobic conditions that enhanced organic carbon preservation.

Models of marginal basin formation provide the basis for studying the time-dependent thermal histories of their sediment sequences. Our models show that, for example, lower Miocene sediments deposited at a rate of 100 m/m.y. on 20-m.y.-old crust in a typical basin have just entered the oil-generation window. Lower sedimentation rates require deposition on younger crust in order for the sediments to reach an equivalent maturation stage. Estimates of the hydrocarbon potential of such marginal basins should be based on a sequential time-slice analysis of each basin in terms of sediment type, sedimentation rate, sea floor age and thermal regime, and the presence of reservoirs.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.