The UK North Sea is mature after 30 years of exploration. The application of new technology to continue the discovery and development of smaller reserve base fields is essential. Advances in 3D seismic acquisition have enabled improved subsurface imaging. Ocean Bottom Cable (OBC) seismic can improve imaging of fields overlain by gas chimneys. PreStack Time and Depth Migration have contributed to better definition of steeply dipping prospects underlying diapirs. Amplitude Variation with Offset (AVO) can reduce exploration risk in a proven play. Quantitative interpretation techniques (e.g. seismic inversion) can be used to image reservoir units in mature areas. High resolution geochemistry can also assist intra-reservoir characterisation. New drilling techniques (e.g. multilateral wells) can unlock fault blocks, layered reservoirs or small outstep accumulations. Extended reach drilling from platforms is also effective in mature areas. Long distance subsea tiebacks, for both high pressure/ high temperature and low energy fluids, can make the development of small and remote hydrocarbon accumulations feasible. The Shell Expro multi-discipline organisation has identified new practices for exploration/keeper well design and equipment procurement which reduce the time between field discovery and first production. Innovative engineering designs are unlocking small field development. New commercial practices are also required to facilitate application of technology in mature areas.