Chances and Risks of Geologic CO₂ Storage

Abstract

Hardly any other technology in Germany has been as controversial right from the start as CO₂ storage in underground geological formations, often referred to as CCS (carbon capture and storage or sequestration). Opponents and proponents of the technology appear seemingly irreconcilable; many discussions become emotional while some scientific principles have not even been sufficiently investigated. This applies both to the risks as well as the opportunities of underground CO₂ storage.

The use of CO₂ has been common in the international E&P industry and the chemical industry for many decades. However, up to this point neither a secondary process to increase yields, nor the process itself has ever been the focus of public interest.

As a consequence of the CO₂ storage process, CO₂ will become the main process substance and much larger amounts will be handled. In this framework, risk assessments are needed for handling the CO₂ move into the foreground and, ultimately, into the focus of public interest.

This paper focuses particularly on the systematic risk analysis of contact with CO₂ during CO₂ storage. The potential risks are systematized and examples of impact calculations are illustrated. The focus lies in the consideration of impact scenarios for the release of CO₂ into groundwater and into the atmosphere, including the resulting hazards. There are no hazard scenarios thus far and practically no reliable predictive models or risk assessments. At times, this results in potential dangers being dealt with irrationally. Existing risks of CCS and enhanced gas recovery (EGR) will be presented and strategies to systematically reduce risk and deal with disruptions in normal operations will be discussed. Current research findings on the release and dispersal of CO₂ in aquifers and in the atmosphere as well as risk management are incorporated into the depictions.