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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 72 (1988)

Issue: 5. (May)

First Page: 523

Last Page: 535

Title: Porosity Enhancement from Chert Dissolution Beneath Neocomian Unconformity: Ivishak Formation, North Slope, Alaska

Author(s): G. Shanmugam (2), J. B. Higgins (3)

Abstract:

Secondary porosity caused by chert dissolution is common in the hydrocarbon-producing fluvial facies of the Ivishak Formation (Triassic), North Slope, Alaska. Petrographic observations suggest that macroporosity caused by chert dissolution tends to increase toward the Neocomian unconformity. In the Prudhoe Bay field, a lateral increase in core porosity (from 15% at about 30 km from the unconformity to 30% near the unconformity) and in permeability (from 50 md at about 30 km from the unconformity to 800 md near the unconformity) is evident toward the unconformity. This increase occurs within the fluvial facies (zone 4) of nearly uniform grain size and framework composition (chert litharenite). Major chert dissolution probably took place during the Neocomian uplift when the Ivishak Formation was exposed to acidic meteoric waters in the near-surface environment.

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