ABSTRACT
Using a slightly modified version of the Lopatin method of determining the level of thermal maturation of source rocks, it is found that major hydrocarbon generation from the Kimmeridge Clay began in the Late Cretaceous/early Paleocene along the deeper parts of the Viking and Central grabens. Throughout the Tertiary, maturation progressed as subsidence and deposition continued. As the maturation in the deep graben areas passed from the oil generation stage into wet-gas and/or condensate generation and finally into the dry-gas stage, the areas of strong active oil generation migrated from the graben areas into shallower areas toward the continental craton.
Applying the results of the maturity calculations in conjunction with chemical analyses of the Kimmeridge Clay allows computations of the original generative capacity, hydrogen index, total organic carbon, kerogen type, and the volume of hydrocarbons generated. The Kimmeridge Clay is mainly characterized by Type II kerogen, with Type I kerogen occurring in the deeper graben areas, and Type III in the platform areas. It is heterogeneous as a source, with original generative capacities ranging from essentially zero to over 35,000 ppm, and averaging about 13,300 ppm.
