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Title: Developing a Comprehensive Risk Assessment Framework for Geological Storage CO2

The operational risks for CCS projects include: risks of capturing, compressing, transporting and injecting CO₂; risks of well blowouts; risk that CO2 will leak into shallow aquifers and contaminate potable water; and risk that sequestered CO2 will leak into the atmosphere. This report examines these risks by using information on the risks associated with analogue activities such as CO2 based enhanced oil recovery (CO2-EOR), natural gas storage and acid gas disposal. We have developed a new analysis of pipeline risk based on Bayesian statistical analysis. Bayesian theory probabilities may describe states of partial knowledge, even perhaps those related to non-repeatable events. The Bayesian approach enables both utilizing existing data and at the same time having the capability to adsorb new information thus to lower uncertainty in our understanding of complex systems. Incident rates for both natural gas and CO2 pipelines have been widely used in papers and reports on risk of CO2 pipelines as proxies for the individual risk created by such pipelines. Published risk studies of CO2 pipelines suggest that the individual risk associated with CO2 pipelines is between 10-3 and 10-4, which reflects risk levels approaching those of mountain climbing, which many would find unacceptably high. This reportmore » concludes, based on a careful analysis of natural gas pipeline failures, suggests that the individual risk of CO2 pipelines is likely in the range of 10-6 to 10-7, a risk range considered in the acceptable to negligible range in most countries. If, as is commonly thought, pipelines represent the highest risk component of CCS outside of the capture plant, then this conclusion suggests that most (if not all) previous quantitative- risk assessments of components of CCS may be orders of magnitude to high. The potential lethality of unexpected CO2 releases from pipelines or wells are arguably the highest risk aspects of CO2 enhanced oil recovery (CO2-EOR), carbon capture, and storage (CCS). Assertions in the CCS literature, that CO2 levels of 10% for ten minutes, or 20 to 30% for a few minutes are lethal to humans, are not supported by the available evidence. The results of published experiments with animals exposed to CO2, from mice to monkeys, at both normal and depleted oxygen levels, suggest that lethal levels of CO2 toxicity are in the range 50 to 60%. These experiments demonstrate that CO2 does not kill by asphyxia, but rather is toxic at high concentrations. It is concluded that quantitative risk assessments of CCS have overestimated the risk of fatalities by using values of lethality a factor two to six lower than the values estimated in this paper. In many dispersion models of CO2 releases from pipelines, no fatalities would be predicted if appropriate levels of lethality for CO2 had been used in the analysis.« less
  1. Univ. of Texas, Austin, TX (United States)
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Technical Report
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Univ. of Texas, Austin, TX (United States)
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United States