The Rousse CO2 storage project has consisted in injecting over a 3-year period (from 2010 to 2013) about 50 000 tons of CO2 into a depleted gas field located near the city of Pau. This project has been a unique opportunity to investigate various scientific and technological issues related to CO2 storage, with scopes/applicabilities exceeding those of this particular projet. University of Pau & Pays de l'Adour has been involved in these investigations along with other academic or research institutions including BRGM, IFPEN, IPGP and University of Nancy. The topics examined by UPPA are seal and fault response to CO2. The methodologies devised and implemented for assessing top seal integrity and the evolution of rock joint roughness and shear behaviour in presence of CO2 have made use of samples from the overburden of the Rousse reservoir.