Facies Analysis and Reservoir Characterization of the Cambrian Mount Simon Formation in the Illinois Basin: Implications for CO2 Sequestration and Storage
Deep saline reservoirs are a target of increased study with the growing development of geological carbon dioxide sequestration. Within the Illinois Basin, the Upper Cambrian Mount Simon Sandstone is being evaluated as an important potential reservoir for storage of CO2. Depth and limited economic interest in the Mount Simon have left it minimally investigated with previous detailed depositional facies analysis only performed at local scales or at localities outside of the Illinois Basin, where the Mount Simon is much thinner and exposed at the surface. Using a suite of cores and geophysical well logs across the Illinois Basin, we evaluate sedimentological evidence for the depositional history and present a revised regional depositional model for the Mount Simon and the resulting implications for its use as a reservoir for CO2. The Mount Simon is a sub-quartz to quartz arenite that unconformably overlies the crystalline basement in some parts of the interior North American craton. Within the Illinois basin, the thickness of the Mount Simon ranges from a few hundred to over 2000 feet thick and structurally from 2,000 to over 14,000 feet below sea level. The upper contact of the Mount Simon Formation is gradational with the overlying Eau Clair Formation. Core analysis has led to the identification of several distinct facies within the Mount Simon. Coarse, bioturbated, nearshore marine sands dominate the unit while locally present eolian sands, identified by steeply dipping avalanche tongues, lack of bioturbation, and interdunal muds, indicate exposure in some areas of the basin. Tidal facies are prominent in the Upper Mount Simon and consist primarily of wavy and flaser bedded fine to medium grained sandstones with interbedded shales. Determination of the depositional facies within this unit and their associated petrophysical characteristics has direct bearing on the ability to predict reservoir performance of the Mount Simon for carbon sequestration.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009