Fault interaction in porous sandstone and implications or reservoir management; examples from southern Utah

Different types of fault interaction are examined and compared to a single fault situation with respect to density, distribution, and orientation of subseismic structures. Fault branch points are found to be considerably more complex than single faults. The damage zone in these areas shows a wider range in orientation of deformation bands and fractures, and the damaged volume extends far into the fault blocks. Overlapping structures develop wide damage zones at early stages, typically with structures that are oblique to the faults and, thus, represent potential flow barriers. The damage associated with relay structures is inherited by later stages, when the fault segments are coalesced and behave as a single fault. At advanced stages, the damage zones are uncommonly wide in breached relay locations. Such locations can be recognized as places where faults make abrupt steps or bends. The extent to which complications associated with both single-tip and double-tip interactions affect reservoir performance depends on the nature of the minor structures in the damage zone. It is thus crucial that the physical nature of minor structures is investigated so that their influence on reservoir performance can be evaluated.