The Structural and Tectonic Evolution of the Andaman Sea During the Cenozoic, and Implications for Petroleum Systems

Abstract

The Andaman Sea is a large region with some major gas discoveries (Arun Field, North Sumatra Basin, Indonesia; Yadana and Yetagun fields, Myanmar), together with many smaller discoveries. Yet it remains a relatively poorly understood area in the region. The tectonic setting is that of a sheared back-arc passive margin. During the Oligocene the margin underwent more E-W oriented extension, which evolved to more NNW-SSE transtensional deformation in the Early Miocene. Currently the basin is opening as a dextral pull-apart between the Sagaing Fault in Myanmar to the NE, and the West Andaman-Sumatra fault systems to the SW. The largest undrilled basin is the East Andaman basin, which in the deepwater area is some 500 km long and up to 100 km wide. Hence the petroleum system of the basin is speculative, with a postulated Late Eocene-Middle Miocene syn-rift section, and a Middle Miocene-Recent post-rift section. Fault patterns in the basin include an unusual mix of ENE-WSW trending normal fault cut by NNW-SSE trending strike-slip faults. Considerable doubt remains about the exact extent of oceanic and continental crust under the East Andaman Basin, and the Alcock and Sewell rises to the west of the basin. The timing of seafloor spreading remains controversial: is it predominantly Miocene in age, or Pliocene-Recent? These major questions about the tectonics of the Andaman Sea not only impact our understanding of basin development and petroleum systems within the Andaman Sea, but also impact understanding of the tectonics of onshore Myanmar.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015