Fractured shale formations that are depleted of natural gas could be attractive targets for geologic carbon dioxide (CO2) storage. These formations have large capacity and existing infrastructure, which can be repurposed for injection, but they are not as geographically widespread as saline aquifers, a more common repository for CO2 storage. To examine the geospatial and economic viability of CO2 storage in fractured shale formations compared to storage in saline aquifers, estimates were calculated for the storage capacities and costs associated with storing CO2 in depleted shale formations and saline aquifers in Ohio, Pennsylvania, and West Virginia using the Tao and Clarens (2013), NATCARB, and CO2-PENS models. These estimates were then used in the engineering-economic geospatial optimization model for CO2 capture and storage SimCCS (Scalable infrastructure model for CO2 Capture and Storage). The average cost of CO2 storage in shale formations was found to be cheaper than in CO2 storage in saline aquifers by $5-10/tCO2 (10-15%) on average, due, in part, to smaller estimated Areas of Review and assumed repurposing of well infrastructure.
Based on the results of the SimCCS, in this region CO2 storage in shale formations can be more centralized, occur in fewer sites, require less pipeline infrastructure, and have lower system-wide costs than if equivalent amounts of CO2 were stored in saline aquifers. System-wide costs could be reduced another 10-30% by sequestering the entire flue gas in shale formations. Common pipeline routes are deployed for CCS networks using either saline aquifers or fractured shale formations for storage and across various CO2 storage rates or CO2 prices, indicating that a robust network could be built that could serve many different storage scenarios. The results suggest that CO2 storage in fractured shale is attractive in regions with abundant shale gas development for both technical and economic reasons due to the lower storage costs and larger storage capacities.