Numerical simulation of CO2 leakage along fault system for the assessment of environmental impacts at CCS site

This paper examines a hypothetical CO2 seepage by numerical simulations for assessment of potential environmental impacts at geological storage sites. A reasonable but the worst seepage case for geological CO2 storage site in Japan was considered. In order to select the model parameters, papers which reported faults/fractures in mainly Tertiary formations in Japan were reviewed. From this review we considered that undetectable faults could have 1 km length and 5 m width, and the permeability in faults/fractures would be in the range of 1-1000 mD. The migration along a hypothetical fault with 200 mD permeability was studied using TOUGH2 simulator. CO2 seepage rate became the maximum at around 5 years, and then decrease gradually. The total amounts of escaped CO2 and maximum seepage rate were about 1 % and 0.3 %/year of injected CO2, respectively. The sensitivity analysis of the model parameters was carried out. It suggests that the seepage rate is controlled not only the permeability of the fault but also that of the reservoir. (C) 2014 The Authors. Published by Elsevier Ltd.