Common Themes in Risk Evaluation Among Eight Geosequestration Projects

Abstract

Risk-evaluation workshops were held during early stages of eight carbon dioxide (CO2) geosequestration (GS) projects. For all projects, the primary entities evaluated were Features, Events, and Processes (FEPs), which are broad concepts pre-selected for their relevance to GS and to each project. Scenarios were later evaluated in some projects, but this paper addresses only the FEPs data.Design features for all risk workshops included information sharing, participation of 15 to 30 project experts and stakeholders, defined risk receptors (project values), categorical five-point scales of Severity and Likelihood (whose product is the quantity “risk”), and personal expertise ratings. Project values included health and safety of workers, public, and the environment, and usually include budget and schedule, contribution to research goals, and contribution to creating a successful GS industry. A fundamental result for each project was a FEPs ranking in terms of risk to project values.Workshops are not laboratories, and their characteristics may contain important variables. Nevertheless, their quantitative data enable comparing projects on a risk basis, comparing evaluations from experts and non-experts, and seeking commonalities among higher-risk areas in multiple projects. Data subsets are compared based on (1) the density of (Severity, Likelihood) value pairs among the 25 grid cells of a risk matrix, and (2) a cumulative plot of risk from the lowest-risk to the highest-risk FEPs.Data subsets from experts, non-experts, and each separate project show a concentration of risk values at low to moderate levels. Relative to experts, non-experts’ evaluations are slightly concentrated toward medium likelihood and away from medium severity. Among the eight projects, some show a greater incidence of low- to moderate-risk FEPs among their total FEPs lists. While it is these apparently lower- risk projects that have been more successful so far, this paper does not attempt to account for the potential effect of risk-evaluation thoroughness.In each project, some of the highest risks relate to managing a complex of activities and organizations, and to obtaining legal permissions and social license. This suggests that the ability of a GS industry to abate greenhouse gases most depends on addressing programmatic risks. Among physical hazards, those typically judged highest are related to driving, construction, and well drilling, rather than to CO2 itself. Regarding storage characteristics, for the eight selected project sites (evaluated from regional geology and prior to injection-well drilling) the adequacy of injectivity has been judged to pose greater risk than adequacy of capacity.