ABSTRACT: Fluid/Rock Interface Morphology in Reservoir and Source Rocks as Revealed by a Cryogenic-Scanning Electron Microscope Device with a UTW-EDX Analyzer

MANN, ULRICH, VOLKER HEINEN, and DIETRICH H. WELTE, Research Centre Juelich (KFA), Juelich, Germany, and JENS D. NEISEL and WILLY-G. BURCHARD, Technical University of Aachen, Aachen, Germany

Cryogenic-scanning electron microscopy, coupled with an Ultra Thin Al-Window EDX-analyzer (UTW-EDX) is a powerful tool for investigating fluid-bearing rocks because it provides (1) high resolution SE-micrographs of the configuration of liquid pore substances--i.e., petroleum or water--in contact with mineral surfaces in their undisturbed state; and (2) energy dispersive elemental analysis for low-energy (< 1 keV) X-rays--i.e., carbon and oxygen--for differentiation between petroleum and water. This paper presents details of the CRYO-SEM devices, the cryopreparation techniques and examples of SEM-micrographs of petroleum-bearing as well as water-bearing rocks.

A mobile cryofixation, cryostorage, and cryotransportation device allows sampling without alteration of the natural liquid distribution during transportation of the rock samples to the CRYO-SEM facilities. Shock-freezing, freeze-fracturing, cool sputtering, and cold stage mounting of the frozen samples under vacuum conditions allow an artefact-free simultaneous observation of both the mineral plus the liquid configuration.

Fabrics of petroleum/rock interface morphologies from several case histories are presented. Specific parameters such as the completeness, thickness, or the contact angle of the petroleum coating on and between mineral grains could be determined. The same parameters could also be determined between water and mineral interfaces. Therefore, the CRYO-SEM/UTW-EDX tool provides a completely new perspective not only for research and application in petroleum generation and migration but especially for characterization of the petroleum/reservoir rock interface conditions.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)