The data consists of a poster presented at 'The Fourth International Conference on Fault and Top Seals', Almeria, Spain, 20-24th September 2015. The abstract describes work carried-out on behalf of the 'Fault seal controls on CO2 storage capacity in aquifers' project funded by the UKCCS Research Centre, grant number UKCCSRC-C1-14. Shallow gas accumulations in the Netherlands sector of the Southern North Sea provide an opportunity to study their coincidence with faulting. Although difficult to attribute the occurrence of shallow gas to leakage of thermogenic fluids from depth (indeed shallow-sourced biogenic gas is common in the North Sea), evidence suggests a relationship, and the common attributes of the faults provide indications of the conditions under which faults in the region may leak, providing a useful indications of factors that should be avoided during CO2 storage operations.