A detailed study has been made of all of the major structural features in the prolific Miocene producing trend of southern Louisiana in order to predict the future of its offshore counterpart. These features have been classified as piercement-type salt domes and deep-seated structures, and the oil and gas reserves and drilling success ratios for each type have been established. The study has been restricted to the major structural features, commonly referred to as grade "A" prospects, as the initial offshore exploration program will be restricted to such structures.

It is predicted that one out of four of 95 major offshore structures will be proved commercially submarginal. However, one out of five of the major offshore structures should contain a giant field with reserves in excess of 100 million barrels of oil or its equivalent, or both. These giant fields will account for more than 50 per cent of the total reserve of the above-marginal fields.

Based on the reserves of the onshore counterpart fields, the minimum reserves for the predicted 71 major commercial structures in the Louisiana offshore province are estimated to be 3 billion barrels of oil, 500 million barrels of condensate, and 21.5 trillion cubic feet of gas. The total reserves, expressed in terms of barrels of oil, are estimated to be 4.6 billion barrels, of which 2.6 billion will be found associated with the deep-seated features. These figures do not include the additional large reserves that will certainly be found during a later generation of exploration of lower relief and interdomal structures.