Structural Basins and Petroleum Resources of Thailand, Malaysia, and Brunei

Keith Robinson

In southeast Asia, most of the sedimentary basins of a size and volume suitable for hydrocarbon generation and accumulation are Tertiary in age and located in offshore areas. However, in northern Thailand, several relatively small deep Tertiary basins occur in grabens that are onshore extensions of the Gulf of Thailand. Jurassic limestones and Permian and Carboniferous rocks underlying the geologically complex Khorat Plateau also have good potential for oil and gas accumulation.

The offshore regions of Thailand, Malaysia, and Brunei encompass most of (1) the Thai, Malay, Penyu, and several smaller basins in the Gulf of Thailand, (2) the Sarawak, Sabah, and the smaller Sandakan and Tarakan basins in eastern Malaysia and Brunei, (3) the Ranong and Mergui basins in the Andaman Sea, and (4) the Malaysian part of the Strait of Malacca. On the basis of structure and stratigraphy, many of these basins have been subdivided into distinct geologic provinces.

Plays include those associated with fault-bounded horst and graben structures, half-graben structures, gently folded anticlines, carbonate shelf and reef complexes, delta systems, and deep marine turbidites. Sediments in the various basins include deep-marine to shallow-marine clastics, deltaic clastics, shelf and reef limestones, coastal-plain clastics, and nonmarine estuarine to complexly interbedded cyclic lacustrine and delta-plain infill clastics. Thickness of sediments in these basins ranges up to 8,000 m.

Major accumulations of Tertiary oil and gas are located in the Thai and Malay basins, and in the Central Luconia and Baram Delta provinces. Estimated mean undiscovered resources (1982) were approximately 1 billion bbl oil and 21 tcf gas for Thailand, and 8 billion bbl oil and 80 tcf gas for Malaysia and Brunei combined.

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