--> Abstract: Evaluation of Petroleum Heterogeneities in the Eldfisk Chalk Reservoir Using Thermal Extraction and Pyrolysis GC and Thermal Extraction GC-MS, by P. B. Hall, M. Bjory, D. Stoddart, S. R. Larter, and J. E. Brasher; #90990 (1993).

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HALL, P. B., and MALVIN BJORY*, Geolab Nor A/S, Trondheim, Norway, D. STODDART and S. R. LARTER, University of Newcastle, Newcastle upon Tyne, England, and J. E. BRASHER, Phillips Petroleum, Tananger, Norway

ABSTRACT: Evaluation of Petroleum Heterogeneities in the Eldfisk Chalk Reservoir Using Thermal Extraction and Pyrolysis GC and Thermal Extraction GC-MS

Petroleum geochemical research is being applied more and more to production-oriented problems such as improving recovery of oil from existing fields and identifying satellite fields. Recent studies by ourselves and others have suggested that compositional heterogeneities within the petroleum column of reservoirs can provide information relevant to these objectives.

Some of the best data for distinguishing petroleum "populations" in reservoirs comes from conventional geochemical techniques, some of which are very time consuming (e.g., solvent extraction, EOM fractionation, and GC and GC-MS of saturated and aromatic hydrocarbon fractions). Furthermore, a large number of samples need to be analyzed to detect the often slight heterogeneities present in a reservoir. The techniques employed in this study (particularly thermal extraction and pyrolysis GC and thermal extraction GC-MS) can be used to generate large amounts of relevant data quickly.

In this study, data were acquired on core samples (~750) from the Paleocene/Cretaceous Eldfisk Chalk reservoir (2/7 block Norwegian North Sea). The acquired data reveal distinct maturity gradients and also small, but still significant, variations in source of the oil within the different Eldfisk oil pools (Alpha, Bravo, and East). This indicates incomplete mixing of the hydrocarbons. These variations have been used to delineate lateral and vertical barriers to petroleum mixing. These observations, when integrated with geological data, can lead to an improved understanding of the possible field filling directions and the intrareservoir compartmentalization. The conclusions from this may also aid in exploration for satellite fields as well as influencing the production plan for the Eldf sk field.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.