Recalibration of CO2 storage in shale: prospective and contingent storage resources, and capacity.

Storing CO 2 in shale formations is an essential complement to the resources of geological CO 2 sequestration and the achievement of carbon neutrality. However, previous estimations have reported significant discrepancies in estimating CO 2 storage resources. To rationalize and address the broad range of these resource estimates, we introduce a categorization framework inspired by the SRMS (CO 2 Storage Resources Management System). Thus, we reclassify estimates according to the categories of prospective storage resources, contingen t storage resources, and capacity estimates for CO 2 storage in shales, in rank order considering the decreasing challenge associated with their attainment (such as energy/pressure requirements and time-consumed in injection). Classical volumetric and production-based methods are employed for assessing prospective and contingent storage resources, respectively. The capacity is estimated by analyzing the historical records of hydraulic fracturing, focusing on the dominant role of fractures in the storage process. A significant disparity (two to three orders of magnitude) is revealed between capacity and contingent or prospective storage resources, which aligns with known challenges encountered during field injections. This disparity highlights the importance of further efforts and advanced techniques to secure CO 2 injection in fields and recalibrate the geological CO 2 inventories to achieve carbon neutrality. • CO 2 storage in shales is reclassified into prospective , contingent and capacity. • Volumetric and production-based methods are used for prospective and contingent. • Capacity is estimated by analyzing fracturing records using a data-driven method. • Contingent or prospective far exceed capacity by two to three orders of magnitude. • Notable disparity is revealed between theoretical capacity and practical limits. [ABSTRACT FROM AUTHOR]