Oil-source rock correlation in the North Viking Graben

Abstract

Based on evaluation of geochemical properties of nearly 100 oils from the North Viking Graben, we have identified three hydrocarbon populations. One population is derived from marine shales of the Draupne Fm, one from marine shales of the Heather Fm, that are rich in land-plant detritus, and one from a mixture of the two. While the Draupne Fm is the dominant source rock, the Heather Fm (lower Callovian) is an important source on the northern Horda Platform. Furthermore, on the northern Horda Platform Heather Fm shales play a major role in controlling migration. Oil from the Draupne Fm migrates only into Upper Jurassic reservoirs, as no large titled fault blocks permit juxtaposition of Draupne Fm and Brent Gp sands, and the Heather Fm shales are thick and extensive. Oil from the Heather Fm migrates into both Upper and Middle Jurassic reservoirs. Variations in properties of the hydrocarbons in the North Viking Graben Petroleum System are due to a complex interplay of organic source, maturity, migration, pressure distribution and biodegradation. Integration of geochemical and geological data on a regional scale has enhanced our ability to evaluate prospects in this important hydrocarbon system.