Screening considerations for caprock properties in regards to commercial-scale carbon-sequestration operations

Risk management of commercial-scale sequestration operations involves comprehensive site characterization of reservoirs, especially with the long-term integrity of low-permeability seals. Even though storage costs are significantly less than those of carbon capture, the variable costs of pipeline transport can have a significant impact in the overall deployment budget for carbon capture and storage (CCS) technologies. This is especially valid with existing electrical generating units (EGUs) where CO2 source-geologic sink matching may not have been considered in siting. It is therefore important to understand all options with source-sink matching, including storage reservoirs nearby EGUs with potentially sub-optimal confining zones. As such, a finely tuned comprehension of the effects of the most relevant caprock characteristics on its integrity during injection and storage will be paramount to ensuring the safety of future operations. This study supports an understanding toward this end first by summarizing the current regulatory framework and industry practices for assessing caprock integrity. After which it defines how pertinent caprock parameters, most notably the thickness of the primary seal layer, affect the principal sealing and leakage mechanisms involved in typical CO2 injection and storage scenarios. Lastly, all of these analyses are synthesized into a back-of-the-envelope initial screening protocol.