CO2 Storage Resource and Reservoir Feasibility Assessment of Deep Saline Cambrian-Ordovician Formations in Eastern Ohio

A systematic, multi-scale reservoir feasibility analysis consisting of static and dynamic evaluation methods is a critical component of the site screening and characterization process necessary to advance development of deep geologic resources for potential CO₂ storage in a region. In 2015, approximately 113 Mt of CO₂ was reportedly emitted from stationary industrial sources in Ohio, with nine of the largest emitters being coal-fired power plants located in eastern Ohio. The potential for deep geologic storage of anthropogenic CO₂ in eastern Ohio and the adjacent Appalachian basin area is assessed via static and dynamic modeling approaches, with the intent to develop a widely applicable methodology for evaluating the feasibility and scale of geologic CO₂ storage in the study area. Reservoir feasibility is evaluated with respect to performance metrics of CO₂ storage resource, injectivity, and plume extent in consideration with dynamic operational constraints such as reservoir fracture-pressure gradients and injection well configurations that may affect CO₂storage projects in practice.

A regional three-dimensional (3D) static earth model (SEM) has been constructed to represent the geologic storage framework of nine deep Cambrian-Ordovician saline formations over a 61,236 km²area in eastern Ohio. The regional SEM provides a representative model honoring the regional geology, with sufficient resolution of vertical and lateral formation heterogeneity to facilitate static and dynamic modeling efforts, and illustrate application of a systematic methodology for screening and ranking prospective storage locations based on specific reservoir porosity, permeability, and thickness criteria.

Static (volumetric) CO₂ storage potential of the deep saline formations of interest is quantified in terms of Theoretical Maximum CO₂ Storage Resource, Prospective CO₂ Storage Resource, and CO₂ storage efficiency. Prospective storage resource maps are also generated to provide visual representations of calculated storage estimates and enable geospatial evaluation of favorable locations for potential CO₂ injection in the deep saline formations of interest. Preliminary site-scale dynamic numerical analysis is conducted using different injection scenarios for two systems of interest for large-scale CO₂injection in the study area: (1) single reservoir injection, and (2) vertically stacked reservoir injection.

Of the deep saline formations evaluated in the study area, the Maryville formation, the Upper Copper Ridge dolomite, the basal Cambrian sandstone, and the Lower Copper Ridge dolomite have the highest static storage resource, with each having an estimated 3-4 gigatonnes (Gt) of Prospective CO₂ Storage Resource at the P50 (median) percentile. The potential for stacked storage reservoir systems is suggested by the re-occurrence of local highs in similar locations on static storage resource maps for the formations evaluated. Storage resource values of 50 Mt or greater (P50) are observed in localized areas in northeastern Ohio, east-central Ohio, and south-central Ohio; all within 50-100 km of large CO₂emission sources.

Dynamic modeling examples show approximately 20 Mt of CO₂ injection was attained over 30 years for the single-reservoir injection scenario in the basal Cambrian sandstone, and approximately 15 Mt of CO₂ injection was achieved in the vertically-stacked injection scenario in the Copper Ridge dolomite formations. Sensitivity analyses performed with the dynamic models suggest permeability-thickness product of the injection zones, the number of injection wells, and the associated operational pressure constraints (i.e., fracture pressure) are primary factors controlling the amount of CO₂that can be injected and the storage efficiency that can be achieved during a 30-year injection period at a given site.

Static modeling exercises presented in this work provide important bounds on the amount and geospatial distribution of geologic storage resource potential in the study region. Site-specific dynamic modeling suggests injection and storage may be feasible in practice. The storage estimates presented here are not yet supported by field-scale injection tests or case studies in the study area. Site-specific characterization and engineering design optimization of the injection well layout and injection scheme is essential to achieving a higher, more efficient utilization of the available pore space at a given site. Future work should be aimed toward reducing the current uncertainty involved in many of the key reservoir parameters such as storage efficiency, permeability, and transmissivity.

This work was supported by the Ohio Development Services Agency OCDO Grant OOE-CDO-D-13-22 and the U.S. Department of Energy through the Midwest Regional Carbon Sequestration Partnership (MRCSP) award number DE-FC26-05NT42589.