Depositional and Diagenetic Variability within the Cambrian Mount Simon Sandstone in the Illinois Basin: Implications for Carbon Dioxide Sequestration

Brenda Beitler Bowen¹, John Rupp², Raul Ochoa¹, and Nick Fischietto^1
1Purdue University, West Lafayette, IN, 47907, [email protected]
²Indiana Geological Survey, Bloomington, IN 47405, [email protected]

The Cambrian Mount Simon Sandstone has been identified as an important potential reservoir for geologic carbon dioxide (CO₂) sequestration in the Illinois Basin. Spatial variations in the estimated potential CO₂ capacity depend upon changes in reservoir character with depth and laterally across the basin. Effective and efficient exploitation of the available pore space within this formation requires a detailed knowledge of the depositional and diagenetic textures and mineralogy, and how these parameters vary spatially. By examining existing cores of the Mount Simon Sandstone from varying depth and thickness across the Illinois Basin, we have refined and expanded the existing depositional models and characterized the reservoir variability for the different depositional facies. We identified tidal, fluvial, and eolian depositional systems from sedimentary textures in cores and tied them to corresponding well log data for regional mapping purposes. Diagenetic facies were identified from petrographic observations of over 130 thin sections that were collected from depth ranges that span over 8,000 feet and include variable zones of compaction, quartz and feldspar overgrowths, and clay mineral and iron oxide cementation. Differences in porosity are commonly related to the development of secondary porosity and diagenetic cements and do not necessarily follow the exponential decrease with depth that has often been assumed. Quantifying and mapping out these differences in a depositional and diagenetic facies context will be important as inputs for calculating CO₂ capacity potential and modeling reactivity, and will provide an important baseline for comparing Mount Simon Sandstone samples after they have been subjected to CO₂ injection.

AAPG Search and Discovery Article #90095©2009 AAPG Eastern Section Meeting, Evansville, Indiana, September 20-22, 2009