Development of Storage Coefficients for Determining the Effective CO2 Storage Resource in Deep Saline Formations

Abstract

Abstract The development of broadly applicable storage coefficients for determining CO2 storage resource/capacity estimates has been identified as a critical component for stakeholders to make informed decisions regarding the potential implementation of large-scale CO2 storage. While several evaluations have been conducted to determine CO2 storage resource/capacity estimates, they are the result of different methodologies, and a comparison of the results is often difficult and/or misleading. Thus the development of approaches and methods for developing CO2 storage estimates that can be applied to assessments at a wide range of scales has been identified as crucial to the advancement of broadly applicable and comparable "storage coefficients." At the heart of the matter is the fact that only a fraction of the pore space within any given geological formation will be available or amenable to CO2 storage. The purpose of a storage coefficient is to assign a value to that fraction of a given pore volume in which CO2 can be effectively stored. In order to develop broadly applicable storage coefficients, three methodologies for determining storage resource/capacity in deep saline formations were evaluated: two that can be applied to open systems and one for application in closed systems. In the end, effective storage coefficients were developed for application to deep saline formations at scales ranging from site-specific evaluations to entire formations. Real-world data sets and numerical modeling simulations were used to calculate storage coefficients at the site-specific scale for three lithologies, ten depositional environments, and five structural settings. These results can then be modified and translated into effective storage coefficients that can be applied at the formation scale for the three main lithologies. To develop estimates of effective storage resources for entire basins, estimates for each formation within the basin must be summed. This same methodology can be applied for estimating effective storage resources within state/provincial and national boundaries. In this way, the application of the broadly applicable effective storage coefficients developed by this project can be used to estimate the effective storage resource at levels ranging from site-specific to formation-level, ultimately spanning large sedimentary basins and even entire nations and continents. Introduction In recent years, the concept of mitigating global climate change through large-scale carbon capture and storage (CCS) into geologic media (saline formations, depleted hydrocarbon reservoirs, and unminable coal seams) has gained worldwide attention. Identifying potential geologic sinks for carbon dioxide (CO2) storage and developing reliable estimates of their storage resource/capacity is a critical component of determining the efficacy of CCS. While numerous evaluations have been conducted to develop storage resource/capacity estimates for geologic formations throughout the world, they are the product of several different methodologies, and comparison of the results of one evaluation to another is often difficult and misleading. The IEA Greenhouse Gas Research & Development (R&D) Programme (IEA-GHG) has been working closely with a wide variety of international organizations, including the U. S. Department of Energy (DOE) to develop approaches and methods for developing CO2 storage resource/capacity estimates that can be applied to assessments at the site-specific, local, regional, basin, and country scales. Recently, IEA-GHG and DOE have identified the development of technically robust storage coefficients as being crucial to the advancement of broadly applicable and comparable storage resource/capacity estimates at all scales.