--> --> Abstract: Controls on Porosity and Permeability Within the Carmel Formation: Implications for Carbon Sequestration, by William G. Payne, Peter S. Mozley, Douglas A. Sprinkel, and Andrew R. Campbell; #90124 (2011)

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Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Controls on Porosity and Permeability Within the Carmel Formation: Implications for Carbon Sequestration

William G. Payne1; Peter S. Mozley1; Douglas A. Sprinkel2; Andrew R. Campbell1

(1) Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM.

(2) Geologic Mapping Program, Utah Geological Survey, Salt Lake City, UT.

Having quality data on reservoir and seal properties for proposed CO2 injection sites is vital for predicting and modeling how CO2 will behave in the subsurface. For a proposed sequestration site at the Gordon Creek field (Carbon County, Utah), the reservoir for the proposed injection unit is the Navajo Sandstone, with the Carmel Formation acting as the primary seal. We are investigating the controls on porosity and permeability in both units, with a specific interest in the sealing behavior of the Carmel Formation using a regional outcrop analog study.

The Carmel is a near-shore assemblage of limestone, siltstone, mudstone, sandstone, and gypsum. It changes laterally across Utah, from more carbonate-dominated lithofacies in the west, to more clastic-dominated lithofacies in the east. Because of the lateral changes in lithology, it was necessary to examine outcrops of the Carmel at Mt. Carmel Junction and on the San Rafael Swell; equivalent beds of the Twin Creek-Arapien were also examined at Thistle. The Mt. Carmel Junction site is thought to best represent what is at Gordon Creek field.

Samples collected from the three outcrop locations, as well as subsurface samples from the proposed injection site, were analyzed using a combination of petrography, stable isotope geochemistry, and scanning electron microprobe. From preliminary data, quartz overgrowths and pore-filling calcite cements account for most of the porosity loss in the Carmel. Relatively high IGVs and a dominance of tangential contacts indicate that compaction was not of great importance in reducing porosity. Porosity in the limestone beds in the Carmel is low, because they are dominantly carbonate muds. Some detrital quartz grains in both the limestone and sandstone beds were partially replaced by calcite. In the shale and mudstone beds, the only macroscopic porosity is fracture related. There are multiple mineralized fractures throughout the Carmel (gypsum, calcite) that may be preserved at depth. The fractures are mainly developed in limestone and, to a lesser extent, sandstone beds. In a few places they can be seen to extend into adjacent mudstone beds.

The underlying Navajo Sandstone is an eolian cross-bedded sandstone that has relatively high porosity and permeability. In all study localities, the Navajo is cut by prominent deformation bands that would clearly influence flow in potential reservoirs.