Diagenesis of a tight gas sand reservoir Upper Cretaceous Mesaverde Group, Piceance Basin, Colorado.pdf

Marine and Petroleum Geology 40 (2013) 48e68
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Marine and Petroleum Geology
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Diagenesis of a tight gas sand reservoir: Upper Cretaceous Mesaverde Group,
Piceance Basin, Colorado
Trevor M. Stroker a,*,1, Nicholas B. Harris c, W. Crawford Elliott b, J. Marion Wampler b
a Department of Geology and Geological Engineering, Colorado School of Mines, Golden, CO 80401, USA
b Department of Geosciences, ia State University, Atlanta, GA 30302-4105, USA
c Department of Earth and Atmospheric Sciences, University of Alberta, Canada T6G 2E3
article info abstract
Article history: The Upper Cretaceous Mesaverde Group in the Piceance Basin, western Colorado, contains thick sections
Received 5 March 2012 of low porosity, low permeability sandstones that are reservoirs for large accumulations of hydrocarbon
Received in revised form gas. The Mesaverde sandstones are lithic arkoses and feldspathic litharenites, containing quartz,
5 July 2012
plagioclase, variable K-feldspar, chert, and volcanic rock fragments. Important ic processes that
Accepted 24 August 2012
have affected the sandstones paction, dissolution of feldspar and/or alteration to clay,
Available online 5 October 2012
precipitation of carbonate and quartz cements, precipitation of illite, and alteration of detrital clays
(mixed-layer illiteesmectite). Porosity is relatively constant; a decrease in primary porosity downward is
Keywords: fi
KeAr approximately balanced by an increase in secondary porosity, with signi cant microporosity in authi-
Diagenesis genic and ic clays. K-feldspar is pletely absent below 5500 feet (1675 m). Fibrous
Fluvial illite is relatively abundant above this depth and variable in abundance below. The KeAr ages of the clays
Tight gas sands increase with depth, from 40 . at the top of the sampled section to 55 . at the base, indicating
Illite illitization of a precursor smectite at appro