Depositional and diagenetic histories of reservoir sandstones in the Jerneh field, central Malay Basin

Mazlan Madon. (1994) Depositional and diagenetic histories of reservoir sandstones in the Jerneh field, central Malay Basin. Bulletin of the Geological Society of Malaysia, 36. pp. 31-53. ISSN 2637-109X

Abstract

The depositional and diagenetic histories of upper Miocene reservoir sandstones in the Jerneh field, Malay Basin, were interpreted from core and log data. The sandstones, at depths of between 1,250 and 2,000 m, were deposited during a middle to late Miocene regressive episode. Sandbodies characterize different facies associations: distributary mouthbar and shoreface sandbodies in the delta front, and channel point bar deposits in the delta plain facies association. Laterally continuous sheet sandstones characterize the shallow marine facies association which was deposited during transgression over the delta. With increasing depth, the reservoir sandstones show a higher degree of compaction and quartz cementation, which resulted in reduced porosities ranging between 10% and 25%. An estimated 15% to 50% of the original depositional porosity was lost by compaction during shallow burial (<1 km). Quartz overgrowths (1-7%) are interpreted to have started forming at depths of about 1,200 m, K-feldspar was selectively dissolved by acidic formation waters, while plagioclase remained relatively stable. The effect of dissolution, however, is thought to be insignificant in terms of porosity enhancement.

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