Geometrical Characterization of Normal Fault Damage Zones in Siliciclastic Reservoirs

Sylvie Schueller¹, Alvar Braathen², and Haakon Fossen^3
1Centre for Integrated Petroleum Research, Bergen, Norway
²Center for Integrated Petroleum Research, Unifob, University of Bergen, N-5007 Bergen, Norway
³University of Bergen, Bergen, Norway

Fault zones are commonly described by a fault core, accommodating most of the displacement, and a surrounding damage zone. In siliciclastic porous rocks, the fault damage zones contain small-scale structures, mainly deformation bands that can be effective hydrocarbon and water seals. The impact of faults on fluid flow may hence occur not only at fault cores but also throughout their damage zones.
This study aims to characterize statistically the geometry of damage zones using an outcrop-based database. The trends thus derived can then be implemented in reservoir modelling and simulation testing in order to evaluate reservoir performance in fault damage zones.
A large dataset of more than 100 scan-lines of damage zones in sandstones has been used to establish sound empirical trends. The bulk of these analogue data are gathered in Egypt and Utah. The processing of the database deals mainly with the characterization of the deformation bands distribution around the fault, showing a logarithmic decrease of the deformation band number away from the fault core. The influence of damage zone width, fault throw, folding, and degree of lithification is also tested. The results show a non-linear relationship between the damage zone width and the throw. The average density of deformation bands in the damage zone seems to depend on the degree of lithification and mechanical layering. The clustering of deformations bands is quantified using the spacing distribution between the deformation bands.
This database reveals several statistical trends that better characterize damage zones of extensional faults in siliciclastic sedimentary rocks.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece