The Alba Field: A Middle Eocene Deep Water Channel System in the UK North Sea
The end of the appraisal stage of the Alba field has opened the way for the first development of a middle Eocene reservoir in the North Sea.
The Alba field is located in the Witch Ground graben between the Fladen Ground spur to the north and the Renee ridge to the south, entirely in UKCS (U.K. continental shelf) Block 16/26. In 1984, oil was discovered in a sand within the middle Eocene Alba Formation at a depth of 6100 ft (1860 m) subsea. Seventeen subsequent wells, including sidetracks, have been drilled to appraise the discovery. This drilling indicates that the Alba field is a stratigraphic trap covering an area of approximately 3400 ac (1375 ha).
The sands represent a brief interruption in the hemipelagic sedimentation that dominated this part of the Witch Ground graben during the middle Eocene. Sediment was supplied intermittently from a shelf area to the northwest, into a deep-water environment. Well correlations, seismic mapping, and core analyses indicate that these sands were deposited from turbidity flows as part of a constructional channel/levee complex, within a mud-rich, shelf-sourced, submarine channel system. The cap, updip, and lateral seals of the reservoir are shale.
The reservoir is predominantly a homogeneous, very fine to fine-grained, unconsolidated sand. The average reservoir porosity is 35% and the average permeability is 2.8 darcys. Oil in place is estimated to be 1.1 billion bbl of 20° API biodegraded crude oil.
Figures & Tables
The success of Memoir 14 and the worldwide interest shown for data on giant fields prompted AAPG to schedule a symposium on giant fields at the end of each subsequent decade. The 1968-78 symposium was held in Houston, Texas, April 1-4, 1979, and the papers were published in AAPG Memoir 30, December 1980.
The Stavanger Conference "Giant Oil and Gas Fields of the Decade: 1978-1988" was held in Stavanger, Norway, September 9-12, 1990, and is a continuation of the Giants of the Decade series.
Scientific studies and projections of future world energy demand indicate that although alternative-energy fuel sources must be actively pursued and developed, there also must be adequate petroleum supplies to bridge the gap. For the international petroleum industry, the years covered by this conference, 1978-88, were complex. They were years of boom and bust. The world's energy consciousness was boosted sharply by the effects of the 1979 Iranian revolution and the resulting embargo, which sent world oil prices to record heights. Global petroleum exploration soon surged, leading to the industry's all-time drilling high in 1981. Then came the oil price collapse in 1985, and the following years were characterized by falling oil prices and drastic budget cuts for exploration and development.
Although exploration dropped sharply during the latter part of the decade, there was a steady flow of giant oil and gas field discoveries. Using the giant field designation criteria of 500 million bbl of oil recoverable for fields in Asiatic Russia, North Africa, and the Middle East,