DETECTION OF PETROLEUM HETEROGENEITY IN ELDFISK AND SATELLITE FIELDS USING THERMAL EXTRACTION, PYROLYSIS GC, GC-MS AND ISOTOPE TECHNIQUES

Eldfisk Field is one of several oil-producing chalk fields of the Nort h Sea. Analysis was performed on core samples from 11 wells from the P alaeocene/Cretaceous Chalk reservoir. Analyses performed on cores incl uded various pyrolysis techniques. Conventional CC-MS, was performed o n 27 oils from the 2/7 block. Stable carbon isotope analysis was perfo rmed on bulk and n-alkane fractions of the oils. Pyrolysis data could be used to detect the main producing section of the reservoir and show that there appear to be sections of the reservoir rich in waxes. Biom arker and pyrolysis data indicate that there are differences in maturi ty of the petroleum of Eldfisk Alpha and Brave structures and that the re are lateral and vertical variations in composition within each stru cture. Based on both biomarker and isotopic data, there is evidence fo r at least two phases of reservoir filling.