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Development Strategy at Statfjord Field

John W. Buza

The Statfjord field is the largest oil field discovered in Europe, with initial recoverable reserves of more than 3 billion bbl of oil and 3 tcf of gas. The field lies 120 mi offshore from Bergen, Norway, in 475 ft of water, and is being developed using three Condeep platforms with a combined production capacity of more than 800,000 bbl/day. To date, approximately 70 of a planned 99 development wells have been drilled.

The main hydrocarbon reservoirs are Mesozoic sandstones of the Brent Group and Statfjord Formation. Both units exhibit excellent reservoir properties, with porosities ranging from 20 to 35% and permeabilities up to several darcys. A sandstone unit within the intervening Dunlin shales is under study for future development. Pressure maintenance is achieved in the Brent Group by water injection and in the Statfjord Formation by high-pressure miscible gas displacement.

Reservoir simulation studies and regular formation-pressure monitoring guide the drilling sequence and, coupled with field geology, dictate the selection of well locations and completion intervals. Placement of updip wells along the eastern flank of the field, where the Brent and Statfjord reservoirs are erosionally and tectonically thinned, is determined by mapping the start of truncation for each reservoir. Total oil recovery is enhanced by initially completing wells in stratigraphic units of less than optimal porosity and permeability to ensure these zones are not bypassed.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.