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ABSTRACT: Multiple inversion of the Khorat Plateau Basin, NE Thailand, with the formation and preservation of a productive gas play

Booth, John1, and Nares Sattayarak2
(1) Amerada Hess, Bangkok, Thailand 
(2) Department of Mineral Resources, Bangkok, Thailand

The Khorat Plateau Basin of NE Thailand contains a proven hydrocarbon system, with commercial gas production from the Nam Phong field (peak 115 mmscfgd) and 3 other significant gas discoveries. A further 17 prospects have been drilled, of which all but 1 are now known to have been based on invalid play concepts. The basin was deformed and inverted by at least three major events during the Indosinian Orogeny (Late Permian - Late Triassic), when the trapping structures were formed, with the gas generated during the Late Jurassic and Early Cretaceous. In the Late Cretaceous and the Tertiary the basin was again inverted, uplifted and folded by at least 2 major events, during which some 2 km of section was eroded. Thus, the gas charged structures, which are in some cases overpressured, have apparently retained their hydrocarbons for some 60-90 million years. Individual structures have complex deformational histories, related to repeated basin inversion. These commonly include repeated normal, reverse, compressional strike-slip and shallow angle thrust faulting, with multiple episodes of folding. The key to understanding the hydrocarbon system has been the modern understanding of the nature of structures formed during basin inversion, combined with a revised plate-tectonic model, which explains the driving mechanisms and the relative timing of the separate inversion events.

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