--> Abstract: Outcrop Quantification of Flow-Unit and Seal Properties and Geometries, Ferron Sandstone, Utah, by N. Tyler, M. D. Barton, and R. J. Finley; #91004 (1991)

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Outcrop Quantification of Flow-Unit and Seal Properties and Geometries, Ferron Sandstone, Utah

TYLER, NOEL, MARK D. BARTON,* and ROBERT J. FINLEY, Bureau of Economic Geology, Austin, TX

River-dominated deltaic sandstones of the Upper Cretaceous Ferron Member of the Mancos Shale provide the opportunity to quantify the 3-D architecture and permeability structure of fluvial, deltaic, and shorezone sandstones that are analogous to large oil and gas reservoirs of the Gulf Coast. Current investigations, working within a previously established stratigraphic framework, are aimed at quantifying flow-unit character as well as delineating bounding and sealing surfaces that cause inefficient drainage and the abandonment of conventionally recoverable hydrocarbons in reservoir analogs. Measured sections at 1-mi spacings establish the facies framework within which windows are selected for detailed study. In the detailed-study windows, lithofacies and permeability data are collected at three scales. Vertical profiles spaced at 100-ft intervals, supported by permeability measurements taken vertically at 1-ft intervals (or less where potential seals were encountered); a 70- by 70-ft grid where permeabilities are measured every 2 ft; and a detailed grid consisting of measurements taken at 4-in. intervals provide the data for this analysis of between-well, or macroscale, heterogeneity. Average permeabilities are highest in distributary-channel facies. Distributary sandstones are, however, also characterized by the highest degree of permeability heterogeneity. Lateral permeability heterogeneity, a response to lateral accretion and channel-flooring scours, is pronounced. In contrast, associated shoreface sandstones have lower average permeabilities, simple upwardly increa ing permeability profiles, and a high degree of lateral continuity. Vertical heterogeneity, provided by laterally continuous mud layers, is dominant. Communication between distributary channel and associated shoreface sandstones is likely to be hindered by low-permeability (less than 5 md) zones that consistently occur at the base of channel sandstones and along the toesets of lateral accretion surfaces.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)