--> Insights on Porosity and Pore Size Distribution Using Multiple Analytical Tools: Implications for Reservoir Characterization in Geologic Storage of CO2

AAPG Eastern Section Meeting

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Insights on Porosity and Pore Size Distribution Using Multiple Analytical Tools: Implications for Reservoir Characterization in Geologic Storage of CO2

Abstract

The geologic description and quantification of the physical properties that define a viable reservoir are fundamental for assessing the feasibility of a reservoir to receive and store injected CO2 in the deep subsurface. Two petrophysical properties, porosity and permeability, constrain the reservoir in terms of its storage potential and injectivity. The analytical tools that are useful for measuring these properties vary and are optimally employed at various scales.

We analyzed 52 rock samples from the Cambrian-Ordovician Knox Supergroup spanning a significant area of the midwestern United States. These samples represent a wide range in both the scale and magnitude of the porosity present in this prospective storage reservoir. The samples were analyzed for total porosity and pore size distribution, using petrographic image analysis, helium porosimetry, gas adsorption, mercury porosimetry, and (ultra) small-angle neutron scattering. These analytical techniques were collectively used to understand the relationship between porosity, permeability, and pore size distribution they offer a unique opportunity to study a wide range of pore sizes and to understand the validity of employing these techniques collaboratively.

Results from nitrogen and carbon dioxide adsorption and from mercury injection capillary pressure are important in that they provide insights on small pore size that otherwise cannot be resolved by standard low-pressure helium porosimetry or by image analysis software. Additionally, results from analyses of these carbonate reservoir rocks suggest that microporosity does not have a considerable impact on permeability, but larger pores control this key petrophysical parameter for constraining fluid flow through the pore system.