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Overpressure generating mechanisms in the Peciko Field, Lower Kutai Basin, Indonesia.

Ramdhan, A.M. and Goulty, N.R. (2010) 'Overpressure generating mechanisms in the Peciko Field, Lower Kutai Basin, Indonesia.', Petroleum geoscience., 16 (4). pp. 367-376.


The Peciko Field contains gas in multiple stacked reservoirs within a Miocene deltaic sequence. In the deeper reservoirs, gas is trapped hydrodynamically by high lateral overpressure gradients. We have analysed overpressure and compaction in this field by using wireline log, pressure, temperature, and vitrinite reflectance data. The top of overpressure is located below 3 km burial depth, below the depth range for transformation of discrete smectite to mixed-layer illite/smectite. Density-sonic and density-resistivity crossplots for mudrocks show reversals within the transition zone into hard overpressure below 3.5 km depth. Vitrinite reflectance measurements indicate that the start of unloading coincides with the onset of gas generation. Moreover, mudrock density continues to increase with depth in the overpressured section to values above 2.6 g cm-3. We conclude that gas generation and chemical compaction are responsible for overpressure generation, contradicting previous interpretations that disequilibrium compaction is the principal mechanism for generating overpressure in the Lower Kutai Basin. The particular circumstances which make our radical interpretation plausible are that it is a warm basin with lateral reservoir drainage, so the overpressured mudrocks are probably overcompacted as a result of diagenesis.

Item Type:Article
Keywords:Lower Kutai Basin, Overpressure, Unloading, Gas generation, Compaction.
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Publisher statement:This material has been published in Petroleum Geoscience, 16 (4), 2010, pp. 367-376, the only definitive repository of the content that has been certified and accepted after peer review. Copyright and all rights therein are retained by The Geological Society of London. © 2010 Geological Society of London. The Geological Society's on-line journals at:
Record Created:17 Nov 2010 15:20
Last Modified:13 Dec 2010 14:40

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