Reservoir damage around faults: outcrop examples from the Suez rift

Field observations in western Sinai show that damage zones around faults ar e characterized by (a) a decrease in the frequency of small-scale structure s with increasing distance from the master fault, (b) clustering of these s tructures across damage zones, and (c) a positive relationship between dama ge zone width and master fault throw in logarithmic space, up to maximum wi dth of about 80 m. This relationship allows damage zone width to be estimat ed from fault throw, a parameter obtainable from seismic data. Preliminary data on the interconnectivity of structures within damage zones indicate th at granulation seams are more likely to intersect than tip out. The thickne sses of small-scale structures were measured, and the cumulative thicknesse s of all small-scale structures within individual damage zones calculated. In the examples given, these cumulative thicknesses are up to 1 m within 10 -30 m wide damage zones, implying that as much as Im of deformed rock, most Likely with reduced porosity and permeability, occurs across damage zones. This, together with the interconnectivity data, suggests that the impact o f faults on fluid flow may occur not only at fault planes, but throughout t heir damage zones.