A reservoir that is located underneath the salt (i.e. it was deposited before (pre) or (earlier) than the salt). These reserves of oil and gas are situated in deep layers bellow the sea which require the development of new technology and processes to explore and develop. Discoveries in the pre-salt layers of the Brazil Santos Basin have been made in 2008 in water depths of 1,500-3,000 meters and sediments of 3,000-4,000 meters deep in pre-salt structures, including a salt layer that obscures traditional seismic imaging. Development of pre-salt reserves is expensive and complicated