Academics from the University of Southampton, the University of Edinburgh, and the National Oceanography Centre (NOC) worked together to understand more about the hazards involved in the storage of CO2 in depleted oil and gas reservoirs and saline aquifers in the North Sea. Carbon Capture and Storage (CCS) is recognised as an important way of reducing the amount of CO2 added to the atmosphere, and oil and gas reservoirs and saline aquifers are the preferred storage location of most European nations. However, the safety of such storage is dependent on fully exploring the risks of any leakage. The four-year CHIMNEY project developed better techniques to locate these sub-sea floor structures and determine the permeability of the pathways so that they can be better constrained and quantified. The team worked closely with GEOMAR, in Germany; the Lawrence Berkeley National Laboratory, in California; CGG, in the UK; and Applied Acoustics, in the UK. The project was funded by the Natural Environment Research Council (NERC) under grant reference NE/N016130/1. The project is complementary to the EU-funded Horizon 2020 project 'Strategies for Environmental Monitoring of Marine Carbon Capture and Storage' (STEMM-CCS).