Geologic estimates of undiscovered oil and gas resources in the United States were published in 1975 in the U.S. Geological Survey Circular 725, and the ranges for offshore United States were 10 to 49 billion bbl of oil, and 42 to 181 Tcf of gas. The offshore area included 28 separate provinces within the regions of Alaska, Pacific coastal states, Gulf of Mexico, and Atlantic coastal states.

Assessments were limited to the shelf areas in water depths of 0 to 200 m. Important exploration wells have been drilled in five of the 28 provinces since the publication of Circular 725, and a comparison of the results of these exploratory efforts with the resource appraisals is the object of this study.

Resource assessments for the Gulf of Alaska were 0 to 4.4 billion bbl of oil and 0 to 13 Tcf of gas. Industry leased 76 tracts (409,057 acres; 163,623 ha.) for $560 million in April 1976, and has drilled 11 tests on nine structures without success. There has been no activity in the area since July 1978.

The Southern California Borderland includes two provinces: (1) inner basins and (2) outer basins and ridges. Resource assessments for the inner basins were 0.4 to 2.0 billion bbl of oil and 0.4 to 2.0 Tcf of gas. Outer province assessments were 0 to 0.2 billion bbl of oil, and 0 to 0.2 Tcf of gas.

A federal lease sale that was held in December 1975 included 56 tracts (310,049 acres; 124,000 ha.) in both the inner and outer areas. Subsequent drilling has resulted in at least one oil discovery in the inner area, and activity continues. Six tests in the outer area have been negative, and there is no activity in this area at present.

Resource assessments for the Florida Gulf platform (Gulf of Mexico), were 0 to 2.8 billion bbl of oil, and 0 to 2.8 Tcf of gas. The Mafla sale of December 1973, in which 87 tracts (485,397 acres; 354,159 ha.) were leased, preceded this estimate; some wells had been drilled in

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these tracts at the time of the estimate, but the information from these wells was unavailable. Nearly $1.5 billion was spent for the leases, and since the sale 18 dry holes have been drilled. Almost half of the tracts leased have now been dropped.

The resource appraisal ranges for the Baltimore Canyon (Central Atlantic Shelf) were 0 to 4.6 billion bbl of oil and 0 to 14.2 Tcf of gas. A sale was held in August 1976, and more than $1 billion was spent for 93 leases (529,466 acres; 211,786 ha.). Several exploratory tests have been drilled with one reported gas discovery.

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