The Internal Structure and Properties of Fault Damage Zones and the Impact on Sealing and Reservoir Behaviour
R. J. Knipe, G. Jones, Q. J. Fisher, A. F. Farmer, E.
Mcallister, J. R. Porter, M. B. Clennell, B. Kidd, and E. White
The concentration of sub-seismic deformation adjacent to larger faults forms a complex deformation volume or damage zone which is important to hydrocarbon migration, trapping and reservoir management. The results of a combined study of structural logging of cores, microstructural characterisation and physical property measurement of deformation features preserved in cores, with analysis of fault populations from seismic and outcrop studies, are used to evaluate the properties and evolution of damage zones. The detailed internal structure of fault zones is dependant on the conditions of deformation, the lithological architecture present and the position in the fault array. Clusters of deformation within the damage zone are also surrounded by relatively undeformed volumes. uantification of the geometry of the these zones is critical to understanding the fluid-flow and sealing properties of the fault zone. Complete evaluation of the impact of the damage zone on reservoir properties requires knowledge of the petro-physical properties and spatial distributions of the fault rocks present. These range from quartz-rich cataclasites, developed from pure sandstones, to phyllosilicate smears developed from shales. An important class of intermediate fault rock is generated from impure sandstones. Localisation of cement precipitation within the damage zone will remove the applicability of simple seal analysis based only on the host-rock lithology and displacement. Realistic prediction of the impact of faults on reservoir behaviour requires integration of the detailed geometry with the petro-physical characterisation of the fault rocks.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California