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The AAPG/Datapages Combined Publications Database

Indonesian Petroleum Association


Proceedings of an International Conference on Petroleum Systems of SE Asia and Australasia, 1997
Pages 425-447

Exploration in the Savannakhet Basin, Peoples Democratic Republic of Laos

P. J. Cullen, P. L. Birch, S. C. Wright, C. J. Keamey, A. T. Pink


Flexural loading due to the collision of the Indochina Block with the South China Plate in Early Carboniferous times led to the initiation of the Khorat Basin as a foreland basin to the Annamitic fold-belt of northeastern Vietnam. The subsequent Permo-Triassic collision of the Shan-Thai plate from the west trapped the Indochina Block between converging thrust-fold belts. Marine clastic foredeep and carbonate foreland ramp sedimentation gave way to continental foreland basin deposition across the Mesozoic Khorat intermontane basin. Later collision of the Lhasa/Myanmar Block and the Indian Plate from the west rejuvenated earlier compressional structures and progressively propagated the thrust-fold belts into the foreland, resulting in the isolation of a number of sub-basins including the Savannakhet Basin.

The marine to continental syn-orogenic clastic and carbonate sequence exposed around the margins of the Savannakhet Basin records the early tectonic evolution of the area. The thick red-bed sequence of the Khorat Group records post-orogenic sedimentation from Early Jurassic to Mid Cretaceous times, when up to 5 kilometres of continental molasse was deposited. Continuous regional uplift of the Khorat Plateau area since Early Tertiary times has eroded up to 3 kilometres of sediments.

The Savannakhet Basin lies in the south central part of the Peoples Democratic Republic of Laos, between the Mekong River and the eastern border with Vietnam. Oil seeps located in and around the basin were reported prior to the commencement of hydrocarbon exploration in 1989 by a group led by Enterprise Oil Exploration Ltd.

This paper examines the tectonic history of the Savannakhet Basin through a review of recent literature and the interpretation of newly acquired high resolution seismic data. The stratigraphic succession and structural configuration of the basin are interpreted with reference to its tectonic evolution. The application of apatite and zircon fission track analysis, vitrinite reflectance, and spore colouration index to constrain the maximum depth of burial is also demonstrated.

Gravity, aeromagnetic, seismic, geological and geochemical data have been utilised in an integrated interpretation of the geology and hydrocarbon prospectivity of the licence area. Three hydrocarbon plays have been identified, a Palaeozoic carbonate play analogous to the Khorat Plateau play of Thailand, a Triassic clastic play, and a Khorat Group clastic play of Early Jurassic age. The elements comprising these potential hydrocarbon systems are discussed.

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