10. Advances in Estimating the Geologic CO2 Storage Capacity of the Madison Limestone and Weber Sandstone on the Rock Springs Uplift by Utilizing Detailed 3-D Reservoir Characterization and Geologic Uncertainty Reduction

In order to implement CO₂ storage in deep saline aquifers a diverse set of geologic, geophysical, and geochemical parameters must be characterized in both the targeted reservoir intervals and at the storage site.

All observational, experimental and theoretical information and laboratory measurements are integrated into a comprehensive geologic model in order to obtain an accurate characterization of a specific set of potential storage reservoirs and a targeted storage site. The integration is achieved through a series of performance assessments for a diverse set of storage scenarios utilizing numerical simulation techniques. Two of the important fluid-flow parameters that are investigated with the numerical simulations are CO₂ storage capacity and CO₂ injectivity. Reliable estimates of these two parameters are essential to both governments making energy policies and environmental regulations, and to industry trying to make quality business decisions.

Three analytical techniques are utilized to evaluate CO₂ storage capacity in both the Madison Limestone and Weber Sandstone on the Rock Springs Uplift: (1) a static volumetric approach, (2) a dynamic fluid-flow simulation approach using a homogenous reservoir model, and (3) a dynamic fluid-flow simulation approach using a more realistic 3-D heterogeneous reservoir model. The results from these three approaches demonstrate how as the descriptive characterization of the spatial distribution of the determinative reservoir parameters become more realistic, the uncertainties of the CO₂ storage performance assessments are substantially reduced.

Using comprehensive regional geologic, structural, geochemical, log suite, core, and seismic data, we present field-scale heterogeneous reservoir models for the Madison Limestone and Weber Sandstone on the Rock Springs Uplift (RSU). These models were used to evaluate uncertainty in critical geologic carbon storage (GCS) performance metrics: storage capacity and well injectivity. The geologic setting of the RSU is presented first and is followed by a description of the techniques used to determine porosity and permeability heterogeneity based on analytic results from log suites, cores, and 3-D seismic data. Random realizations of permeability and porosity (i.e., extrapolations of reservoir properties away from the stratigraphic well into the 3-D seismic volume) are then generated for each of the geologic units including the storage targets (the Weber Sandstone and the Madison Limestone) and sealing formations (the Amsden, Dinwoody, and Chugwater, among others). These heterogeneous property fields then are used to simulate non-isothermal CO₂ injection over a 50-year period.