Brent Sandstone Research Articles

Statvik Field of Norwegian North Sea--Exploration Study of Unconformity Trap: ABSTRACT

The Statvik field is situated in block 34/10 in the Norwegian sector of the North Sea approximately 20 km east of the Statfjord field. The main reservoir is the Middle Jurassic Brent sandstone which is truncated by the late Kimmerian unconformity. the unconformity is overlain by Upper Cretaceous shales. The delta structure is one of the biggest structures at the late Kimmerian unconformity level in this part of the North Sea. In the early exploration phase the crucial question was whether the Jurassic reservoir rocks had been eroded during the late Kimmerian orogenic event. Early generation seismic showed no reflectors below the unconformity. A square km seismic reflection survey was shot in 1974 and interpretation of this data gave indications of a thick Jurassic sequence below the unconformity. The first well was drilled during the summer of 1978. It showed a 165-m thick hydrocarbon column in sandstones of Middle Jurassic age. The predrilling interpretation was largely correct. An active period with continuous drilling followed; by August 1979, 8 wells had been drilled on the structure. During End_Page 906------------------------------ the summer of 1979 a 3-D seismic survey covering 190 km2 was shot. Interpretation and drilling were simultaneous. Before drilling, probable recoverable reserves were calculated to be 1,600 million bbl. After drilling the estimate was revised to 1,200 million bbl. The field has now been declared commercial and a successful exploration period has been terminated. This discovery has opened new possibilities in an area under active exploration. End_of_Article - Last_Page 907------------