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Geologic Development and Hydrocarbon Potential of Circum-Borneo Region, Southeast Asia

Keith Robinson

Borneo appears to have formed as a result of the southward migration, collision, and accretion of microcontinental blocks rifted from the southern margin of the Asian continent. All significant hydrocarbon accumulations in the circum-Borneo region are contained in Tertiary clastic and carbonate rocks. The thickness of economically productive Tertiary sediments ranges up to 10 km. The thickest sections are generally associated with areas of deltaic sedimentation. Approximately 15 major Tertiary basins and four platform areas lie peripheral to, or straddle, the coastal margins of Borneo. Only one major Tertiary basin is located entirely within the interior of Borneo. Many basins are divided into geologic provinces or subbasins, separated by major structural features. Althou h similarities exist, each area is geologically unique.

Paleocene through early Miocene was a time of major marine transgression in the circum-Borneo region. During this period, an active subduction zone, emergent mountains, marine trenches and basins, rapidly filled marginal troughs, and carbonate platforms developed.

In contrast, middle Miocene through Pliocene was a time of major regression, accompanied by cyclical periods of intense tectonism. It was marked by the development of large delta systems, carbonate platforms and pinnacle reefs, shallow marine environments, and basin infill.

The circum-Borneo region has major hydrocarbon potential. Only six of the sedimentary basins and two platform areas have been intensively explored. Plays include those associated with transgressive to regressive clastics, horst and graben structures, deltaic systems, carbonate platform and reef complexes, turbidite clastics, and possibly with fractured basement. Many clastic-reservoir plays contain both oil and gas, whereas most carbonate-reservoir plays contain only gas.

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