Offshore Giant Fields, 1950-1990

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ABSTRACT OFFSHORE GIANT FIELDS 1950 - 1990 During the past forty years, 125 giant offshore oil and gas fields have been discovered in 28 countries, on five continents. The cumulative reserves discovered in these giant offshore fields is 316 BBOE. A giant field has an ultimate reserve of 500mill ion barrels of oil and/or gas equivalent. Gas is converted to oil equivalent at 6000 cubic feet per barrel. Offshore giant oil and gas fields account for 23 percent of the 540 known giants and for a 22 percent of the 1450 BBOE discovered to date in giant fields. Seventy-eight percent of the total oil and gas discovered occurs in giant fields. Five Middle East countries hold 200 BBOE (62%) of the total offshore reserves in 33 fields, with Saudi Arabia alone holding 105 BBOE (32%). The 28 remaining non-Middle East countries hold 116 BBOE unequally distributed in 95 fields. Norway, UK and Mex1co together account for 65 BBOE in 34 giant offshore fields. During the decade of the 80's, only 22 giant offshore fields were found containing only 20 BBOE. Recognizing that economic and politica1 pressures decreased discoveries of offshore giant fields during the 1980's, there still have been very significant declines in the worldwide combined onshore-offshore giant field finding rates from 1960 to 1990. However, the potential for discovery of offshore giant fields is still good due to the variety of exploration frontiers remaining worldwide. The total world-wide hydrocarbon reserve base from which production is derived may increase into the early 21st Century as additional discoveries and reserve reV1 S1ons are made particularly in the Middle East. Also, eventual crude price increases and/or technology breakthroughs may permit both the aggressive enhanced recovery of conventional oil and the economic development of tar sand and oil shale resources. These techno1ogies will extend "The Age of Oil" through the 21st Century. INTRODUCTION During the past forty years (1950-1990), 125 giant offshore oil and gas fields have been discovered in 28 countries, on five continents. (See Figure 1) The cumulative recoverable reserves discovered in these giant offshore fields is 316 BOE. (See Figure 2) DEFINITIONS A giant field has an ultimate reserve of 500 million barrels of oil and/or gas equivalent. Gas is converted to oil equivalent at 6000 cubic feet per barrel. Reserves are defined as economically recoverable oil or gas. The lists of giant fields published by Halbouty et. al. (1970), Nehring (1978) and St. John (1980) were Combined and pub1i shed in 1983 by Carmalt and St. John. This paper forms the basis of the giant field list from which offshore giant fie1ds were selected for this paper. Some past field discoveries not now credited with 500 BBOE may in the future be proven to contain this minimum reserve amount and become categorized as giant fields. In some cases it has taken some as long as twenty years for fields to be recognized as giants.