Fault
Relay Structures and Their Impact on Production
Behavior
Michael R. Hudec
Normal faults have traditionally been mapped as long, continuous features
with throw decreasing steadily from a maximum near the center to zero at the
tips. More recent work has suggested a different view, in which normal faults of
all scales are composed of arrays of shorter segments, with relay zones shifting
displacement between fault
segments that overstep in map view. In some instances
segments are linked across the relay zone, whereas in other cases the faults are
unconnected, leaving a "gap" in the middle of the
fault
system.
Identification and correct mapping of relay zones is essential in any area
where faults play a role in field segmentation. Potential relay zones can be
identified by noting strike bends in the fault
system,
fault
systems that are
too long for their throw, displacement anomalies, and areas where the
fault
system splays into two or more strands.
The most common error in fault
mapping is to interpret faults as longer and
more continuous than they really are. This leads to overestimation of
fault
-dependent
trap
size and incorrect mapping of production compartments. An
inaccurate compartment map can in turn lead to a less effective field
development strategy, increasing the likelihood of dry holes or unnecessary
wells.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California