D3.3 Risk Assessment, UK site

Site characterisation activities to address risks to the secure containment of CO₂ in a multi-store site are presented. The effects of increased pressure from CO₂ injection are assessed to obtain the maximum acceptable pressure as a constraint to the design of the storage site, ensure no slippage on existing faults and whether or not there is likely to be a fracture network. The results of modelling geochemical effects from the interaction of the storage site rocks with CO₂,  indicate mineral reactions are very slow, there is not likely to be clogging of the storage space by mineral growth and there are very minor changes in the available storage space over hundreds, thousands and a million years. The changes are similar whether CO₂ is present or not.  A review of geological features in the shallow subsurface around the multi-store site indicates there is evidence of existing features showing natural fluid flow through the sea bed. A detailed survey of the multi-store site is recommended to establish a baseline prior to operation of a future storage site.  A plan is presented of measures to prevent adverse effects to the containment of CO₂ in the subsurface prior to operation of a storage site.