--> ABSTRACT: Aspects of Reservoir Geology and Production Behavior of Sirikit Oil Field, Thailand: and Integrated Study, by S. Flint, D. J. Stewart, T. Hyde, E. C. A. Gevers, O. Dubrule, and E. D. Van Riessen; #91030 (2010)

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Aspects of Reservoir Geology and Production Behavior of Sirikit Oil Field, Thailand: and Integrated Study

S. Flint, D. J. Stewart, T. Hyde, E. C. A. Gevers, O. Dubrule, E. D. Van Riessen

The Sirikit oil field, onshore Thailand, lies within an intracratonic, half-graben basin that was subsequently deformed by sinistral strike-slip movement. The 8-km thick Tertiary basin-fill includes the fluvial-deltaic Lan Krabu Formation, which contains two main oil reservoirs (K and L sands). This formation intertongues with lacustrine claystones (Chum Saeng Formation) that form stratigraphic seals to both reservoirs.

The geology of the Sirikit field, based on cores and wireline log suites from 45 wells, is characterized by coarsening-upward sequences, up to 15 m thick. These regressive cycles reflect cyclic progradation of fluvial-dominated deltas into a large, relatively shallow tropical lake. Individual mouth-bar reservoir sandstones form complex, sheetlike bodies that have little inferred geometrical similarity to contemporary barfinger models postulated for river-dominated lacustrine deltas. Geostatistical analyses demonstrate a high variability in cumulative sheet-sand thickness over reservoir intervals. Hence, interpolation between wells is unreliable.

Production decline rates are highly variable in Sirikit wells. However, combined petrophysical and geological analysis has established a relationship between sandstone geometry and well behavior, supported by pressure data. Wells perforated in thin sheet sands commonly have lower decline rates than those completed in thicker, but isolated, channel sands. Seismic attribute maps show discontinuities of gross reservoir packages, which may relate to variations in drainage areas.

Interpretation of horizon seiscrops near mapped seismic markers has refined the understanding of local reservoir structure; the resolution of small dislocations and flexures by seiscrop has applications in well targeting.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.