AAPG Studies in Geology No. 50, (Section Title: General Geology of the Ferron Sandstone) Chapter 9: Petrophysics of the Cretaceous Ferron Sandstone, Central Utah, by Richard D. Jarrard, Carl H. Sondergeld, Marjorie A. Chan, and Stephanie N. Erickson, Pages 226 - 250
from:
AAPG Studies in Geology No. 50: Regional to Wellbore Analog for Fluvial-Deltaic Reservoir Modeling: The Ferron Sandstone of Utah, Edited by Thomas C. Chidsey, Jr., Roy D. Adams, and Thomas H. Morris
Copyright © 2004 by The American Association of Petroleum Geologists and the Society of Exploration Geophysicists. All rights reserved.

General Geology of the Ferron Sandstone

Chapter 9:
Petrophysics of the Cretaceous Ferron Sandstone, Central Utah

Richard D. Jarrard¹, Carl H. Sondergeld², Marjorie A. Chan¹, and Stephanie N. Erickson^3
1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah
²Mewbourne School of Petroleum and Geological Engineering, University of Oklahoma, Tulsa, Oklahoma
³ConocoPhillips Alaska, Inc., Anchorage, Alaska

"Wild men armed," Charles T. Lupton second from the left, circa 1910. Photograph courtesy of the family of C. T. Lupton.

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ABSTRACT

The fluvial-deltaic sandstones of the Cretaceous Ferron Sandstone, Utah, provide an opportunity to document and compare petrophysical properties of outcrop and subsurface rocks. We find that the processes that generate outcrop exposures -- uplift, erosion, and exhumation -- can overprint patterns of velocity, porosity, and permeability developed in the subsurface. Burial to depths of 3000-3400 m (9800-11,100 ft), with associated compaction and carbonate cementation, was followed by uplift, which exhumed different portions of the Ferron Sandstone by 0 to >3400 m. Acomplex diagenetic history culminated with the development of secondary intergranular porosity by carbonate dissolution during exhumation, because of increasing groundwater flux at depths shallower than ~2 km (7000 ft) subsurface. Velocity logs show velocity decreases larger than expected from porosity increase; we attribute the excess to presence of microcracks. Outcrop plugs exhibit even higher porosity and lower velocity than shallow logs, probably because of enhanced leaching of carbonate cement. Ferron coreplug and log velocity responses to this secondary porosity are comparable to that of primary intergranular porosity, but these samples lack permeability anisotropy and sensitivity of velocity and permeability to clay content, both of which are typical of primary porosity. Ferron Sandstone permeability is very closely related to porosity, and therefore exhumation increases permeability by porosity enhancement. The influence of grain size on porosity and permeability persists after both initial compaction/cementation, and subsequent exhumation and secondary porosity development. Consequently, Ferron outcrop stratigraphy can provide useful clues to fluid-flow patterns in other deltaic formations, despite its complex diagenetic history.