Reservoir damage around faults: outcrop examples from the Suez rift

Field observations in western Sinai show that damage zones around faults are characterized by (a) a decrease in the frequency of small-scale structures with increasing distance from the master fault, (b) clustering of these structures across damage zones, and (c) a positive relationship between damage zone width and master fault throw in logarithmic space, up to maximum width of about 80 m. This relationship allows damage zone width to be estimated from fault throw, a parameter obtainable from seismic data. Preliminary data on the interconnectivity of structures within damage zones indicate that granulation seams are more likely to intersect than tip out. The thicknesses of small-scale structures were measured, and the cumulative thicknesses 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 of faults on fluid flow may occur not only at fault planes, but throughout their damage zones.