Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Torabi, A. Articles by Fossen, H. GeoRef GeoRef Citation

Spatial variation of microstructure and petrophysical properties along deformation bands in reservoir sandstones

¹ Centre for Integrated Petroleum Research, Unifob Petroleum, University of Bergen, Post Box 7800, 5020 Bergen, Norway; anita.torabi{at}cipr.uib.no
² Centre for Integrated Petroleum Research/Department of Earth Science, University of Bergen, Post Box 7800, 5020 Bergen, Norway; Haakon.Fossen{at}geo.uib.no

Anita Torabi received her B.S. degree in geology from the University of Tehran (1993) and her Ph.D. in petroleum structural geology from the University of Bergen (2008). She joined the Center for Integrated Petroleum Research at the University of Bergen in 2004 and is currently a senior researcher. Her scientific interests include the analysis of faulted and fractured reservoirs in different stress regimes, fault-related folding and its role in hydrocarbon entrapment, and the effect of faulting on the petrophysical properties of rocks and fluid flow.

Haakon Fossen received his Candidatus Scientiarum (M.S. degree equivalent) degree from the University of Bergen (1986) and his Ph.D. in structural geology from the University of Minnesota (1992). He joined Statoil in 1986 and, since 1996, has been a professor in structural geology at the University of Bergen. His scientific interests cover the evolution and collapse of mountain ranges, the structure of rift basins, and petroleum-related deformation structures at various scales.

ABSTRACT

A series of deformation bands from various reservoir sandstones deformed at different burial depths have been studied with respect to microstructural and petrophysical variations. In many of the examples explored, the internal microstructure, porosity, and permeability vary along the bands at the centimeter or even millimeter scale, changing and in most cases reducing the ability of the bands to act as barriers to fluid flow. Porosity varies by up to 18% and permeability by up to two orders of magnitude. Such petrophysical variations are found along different types of deformation bands, but the range depends upon the deformation mechanisms, in particular on the degree of cataclasis and dissolution in cataclastic and dissolution bands, and on the phyllosilicate content in disaggregation bands. For cataclastic bands, the grain-size distribution changes along the bands with regard to the degree of cataclasis. Furthermore, the increased specific surface area of the pore-grain interface as a result of cataclasis causes higher permeability reduction in cataclastic bands than in other types of deformation bands. Phyllosilicate content can influence the thickness of phyllosilicate bands. However, no apparent correlation between thickness and intensity of cataclasis in the studied cataclastic deformation bands is observed.