Subsea sedimentary rocks favorable for petroleum are confined largely to the continental shelves and adjacent offshore areas. The total world offshore area out to 1,000 feet of water depth is 10,763,000 square miles. This area may be classified as follows.

Table

The foregoing figures are broken down in Tables I, II, and III by 10 continent or major world subdivisions.

The only sound basis for rating sedimentary areas is geologic understanding of the factors that control oil occurrence. Such understanding can be attained only through intensive analysis of the vast quantity of facts concerning oil occurrence that is available from industry experience in thousands of instances worldwide. From these analyses, world averages have been derived for such basic parameters for each category or subcategory of basin or basin area as: the percentage of total area that will prove productive, the yield per unit of productive area, the yield per square mile or per cubic mile of basin sediments. Still other parameters provide various means of cross-checking.

After applying the world averages to the total world offshore basin areas of categories A and B, the following conservative estimates of potential offshore liquid petroleum resources recoverable by primary production methods are derived.

                Barrels
Total A area   168,450,000,000
Total B area   530,240,000,000
               ---------------
Total          698,690,000,000

or, say, 700 billion barrels of petroleum liquids.

Other subsea sources of hydrocarbons are available. Their volumes are similarly estimated. The grand total of all of the offshore hydrocarbon resources of the world (not including the large amounts of additional hydrocarbons which may be derived from coal) is indicated as follows.

Table

For reasons that are explained in the paper, the comparative economic disadvantage of offshore hydrocarbons, which results from the somewhat greater average operating costs, will be more than offset by a greater incidence of oil occurrence and resulting productivities to be expected offshore.

The paper concludes with a review of the principal current happenings in world-wide exploration.