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The North Sea covers parts of the intracratonic Northwest European basin. Exploration efforts in onshore parts of this basin peaked in the 1950s and 1960s and resulted in the proving of ultimate recoverable reserves of 2.4 × 109 bbl of oil and 110 Tcf of gas.
Exploration in the North Sea began in the early 1960s. Ultimate technically recoverable reserves in established offshore accumulations are estimated to amount to 24 × 109 bbl of oil and 90 Tcf of gas.
The gas province of the southern North Sea forms a direct extension of the onshore Permian gas play. Onshore oil plays do not extend into the offshore.
The prolific oil and gas province of the central and northern North Sea is closely tied to the Mesozoic North Sea rift. Reservoirs range in age from Devonian to early Tertiary. Upper Jurassic kerogenous shales are the principal source rocks; in large parts of the Viking and Central grabens the source shales reached maturity during the Tertiary by which time the North Sea rift had become inactive and was replaced by regional subsidence which led to the development of the Cenozoic North Sea basin.
Most of the hydrocarbon reserves in the Viking and Central grabens is contained in structural traps. High reserve concentrations in relatively small areas are related to the availability of abundant, mature source rocks, the blanket development of reservoirs, and the close spacing of trap-providing structures. Many of the known oil accumulations are contained in overpressured reservoirs. Long-range migration is apparently of little significance in the oil habitat of the North Sea.
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