No abstract

The Balder Field is located on the northwestern margin of the Utsira High in Norwegian Blocks 25/10 and 25/11. The oil is trapped in thick massive submarine-fan sandstones of the Paleocene Heimdal and Hermod Formations and the Early Eocene Balder Formation. These sandstones which were deposited from high-density turbidity currents originating from the East Shetland Platform, are located close to the Paleocene sandstone pinch-out and form thick mounded reservoirs in the field. High-relief mounded geometries are believed to have been caused by a complex interaction between deposition and syn-and post-depositional soft-sediment deformation processes. Slumping, sliding and sand remobilization were the dominant deformational processes. Associated sand injections into overlying shales occurred during the soft-sediment deformation processes which dominantly occurred during Early Eocene. The sandstones which have excellent reservoir properties, appear to be in pressure communication and have a common oil-water contact which is probably related to the soft-sediment deformation processes with associated sand injections.

Organic geochemical correlations between fluid inclusions and associated oils and oil-shows in Mesozoic reservoirs in the Sleipner area demonstrate generation from the same source rock organic facies (type II) for inclusions in wells 15/9-1 and 15/9-19. For well 15/9-9 the oil show is from a mixed type II/III source rock, whereas the fluid inclusion is from a type II source. All fluid inclusions are less thermally mature than the associated free oils and are thought to represent the earliest hydrocarbon yield from the source rocks. GC/MS/MS analyses of the fluid inclusions proved essential for resolving biomarker compounds and correlating them to reservoired fluids. Among the biomarkers, bisnorhopane contents in the fluid inclusions are consistently lower than in the associated reservoired oil. The expected dilution effect of bisnorhopane as progressively more hydrocarbons are generated from kerogen maturation is not observed. The difference in bisnorhopane amounts in fluid inclusions and oils is primarily due to varying relative hydrocarbon yields, through time, from different source rocks.