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Scenarios for Potential Impacts from Hypothetical Leakage from Geological Storage Facilities for Carbon Dioxide

RISCS project deliverable
A. Paulley, P. Maul, R. Metcalfe (Quintessa)
Facilities for the geological storage of carbon dioxide (CO2) as part of carbon capture and storage (CCS) schemes will be designed to prevent leakage back to the surface. However, it is important to be able to assess the consequences of any such leakage should it occur, and the RISCS programme is concerned with research into the potential environmental impacts that might be associated with hypothetical leakage in a European context. The importance of assessing the potential for environmental impacts should any leaks occur is recognized by the EC Directive on storage and other sources of guidance such as the OSPAR Framework, USEPA Vulnerability Evaluation Framework and the CO2QUALSTORE Guideline. Research within the RISCS programme is focused on receptor impacts and related monitoring.
A set of reference European receptor environments has been defined as an input to research together with associated high-level impact scenario descriptions. These high-level scenarios provide the basis for mathematical modelling studies that will be undertaken later in the project, and provide input to experimental studies in both terrestrial and marine environments.
This document summarises the output of work undertaken to date in this area for interested parties both inside and outside the RISCS project. Much of the information presented derives from an expert workshop held in Brussels in May 2010.
The baseline ‘most likely’ scenario is for a storage system to evolve as designed, with no leaks occurring. In other words, potential receptors, such as organisms and groundwater resources, will evolve as they would in the absence of any CO2 storage project. It is important to explore this baseline scenario to understand the impacts that could be associated with any leaks. 'Impact' scenarios are therefore potential low likelihood 'alternative evolution' scenarios. Alternative evolution scenarios identified for terrestrial systems include those involving impacts to animals and plants arising from direct releases to the atmosphere following well seal failure, and localized releases of CO2 in the near-surface environment. Localized releases to aquifers that may be exploited as drinking or irrigation water resources are also considered. Impacts to human receptors are considered through the definition of a scenario based upon releases within an urban environment. In each case, relevant release and exposure mechanisms have been described. Equivalent scenarios for marine systems include impacts to marine biota, habitats and other sensitive receptors in both the biologically active sediments and overlying water column caused by different types of release.
Based on simplified scoping calculations and a review of published literature concerning natural CO2 seepages and modelled CO2 behaviour, illustrative CO2 leakage fluxes and areas that would be plausible for the alternative leakage scenarios are presented.
Impact Scenarios.pdf (1162 KB)