Estimating the likelihood of pipeline failure in CO2 transmission pipelines: New insights on risks of carbon capture and storage

Abstract

Previous studies of risks associated with CO2 pipelines for future carbon capture and storage (CCS) activities have used either the frequency of incidents associated with existing CO2 pipelines or from natural gas pipelines as a proxy. Risks of CO2 pipeline failure have been estimated as in the range of 1.2×10−4 to 6.1×10−4km–1yr. This paper demonstrates that for U.S. natural gas pipeline data, incident/failure metrics are not correlated with fatality rates. Both CO2 and natural gas pipelines are fabricated from the same grades of carbon steel, and both are installed using the same equipment and practices. However, natural gas is lighter than air and explosive in air, whereas CO2 is nonflammable but toxic (and heavier than air). Their risk profiles are therefore not identical, and the differences in hazard certainly impact the nature of individual and societal risk. This study focuses on the likelihood of events that could result in fatalities or injuries. The average fatality rate for natural gas transmission pipelines constructed over the last 3 decades is 1.0×10−6km–1yr. This value can be viewed as an upper bound for estimating individual risks associated with CO2 transmission pipelines. Use of incident rates to model individual risks for CO2 pipelines, has overestimated these risks by 2–3 orders of magnitude. When pipelines are designed with factors of safety required by regulators for populated areas, analysis of natural gas pipeline data demonstrates that risks of significant accidental releases are extremely low. These results require a significant rethinking of previous notions of the risks associated with CO2 pipelines.