Composite Damage Zones

The cumulative displacement of multiple slip events along faults may generate composite damage zones of increasing width and modification of hydraulic and mechanical properties. The structure of composite damage zones at the subsurface is analyzed here by using seismic attributes of a three-dimensional, seismic reflection survey. We investigate the geometry, internal architecture, and fracture distribution within tight sandstone reservoirs in northeast Sichuan, China. Based on the damage intensity, we identified six composite damage zones with thickness approaching 1 km along faults ranging 3–15 km in length, and up to 600 m of cumulative slip. The recognition of multiple fault cores and associated damage zones inside the composite damage zones revealed three classes of composite damage zones that are defined as banded-shape, box-shape, and dome-shape. The observed mechanical contrasts and distortion of fault cores indicate an evolution path for the growth of composite damage zones. The analyses could extend to complex, brittle crustal faulting, e.g., for earthquake rupture characteristics and hydraulic behavior.