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ABSTRACT: Integration of Petroleum Geochemical Indicators and Tectonostratigraphy : Implications for Oil Family Groups, Migration Path Mapping, Timing of Migration and Migration Processes in Central Sumatra Basin

Mertani, Bambang1, Tom L. Heidrick1, Srikanti I. Qivayanti1, and R. J. Hwang2
(1) PT Caltex Pacific Indonesia, Pekanbaru, Indonesia 
(2) Chevron Petroleum Technology Company, San Ramon, CA

Over 100 selected oils from fields scattered across the Central Sumatra Basin (CSB) were examined using advanced geochemical analyses including high resolution biomarkers (GCMS), carbazoles (GC-AED), high temperature gas chromatography (HTGC) and stable carbon isotopes (Hwang et al., 1998). Integration of these data with the tectonostratigraphic development of the CSB sheds new light on the: 1) consanguinity of lacustrine oils; 2) kitchen/oil correlation; 3) delineation of discrete migration routes; 4) long vs. short range migration issues; 5) diachronous migration patterns; and 6) oil migration processes.

The combination of HTGC profiling, bulk geochemical properties, biomaker distributions, and carbon isotope data helps subdivide CSB oils into seven diagnostic geochemical groups. Each group is geochemically and tectogenetically linked to its respective Eo-Oligocene half-graben and generative kitchen: South and North Balam (I), Rangau (II); North Aman Central (III); North Aman North (IV), South Aman North and South (V), Tapung (VI) and Bengkalis (VII).

Group II, III, IV, VI and VII oils commenced migration in the Late Miocene (F3E), were westward-directed up-structure toward syntectonic highs and followed dilatant NNW- and WSW-striking F2-3E strike-slip faults (Heidrick & Aulia, 1993). Fractionation of carbazoles along the F3E pathways is high and suggests migration distances of +100 km across adjoining low-relief footwall platforms. With the onset of the Plio-Pleistocene compressional event (F3L,3.8 Ma - Recent), Groups I, III, IV and V oils migrated predominately eastward toward rising Eo-Oligocene hinge margins inverted along WNW-NW-trending axes. Over 75% of the 25BBOI discovered in the CSB resides in F3L inversion traps charged by this youthful generation-migration event.

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