(1) ChevronTexaco, San Ramon, CA
ABSTRACT: Recognizing Strike-Slip Indicators on Seismic Data and Why it Matters
It is generally challenging to spot strike-slip on seismic data because geological markers tend to be nearly horizontal, especially near the large, gently dipping structural traps we are commonly exploring. Strike-slip components thus are often overlooked and unreasonable structural models are applied. This may have severe consequences for assumptions about fault-seal, timing of trap formation, charge models, field geometry, reservoir quality, stress directions during deformation, interpretation consistency, modeling of subseismic faults and fractures, as well as for exploration strategies in regions with poor data density.
Even while lacking visibly offset markers, many strike-slip systems change their geometry in characteristic ways in vertical and especially horizontal dimensions. Some of the seismically imageable telltales include en-echelon fault systems, bow-tie geometries, flower structures, restraining and releasing bends. Salt or shale horizons often vertically separate seemingly unrelated structures like en-echelon normal faults above and single, through-going faults or flower structures below.
Whereas a single, clearly identifying feature may be lacking, the entire three-dimensional geometry of a fault system is often characteristic. Strike-slip faults in compressional or extensional regions usually become apparent as such when the directions of the various structures are analyzed on maps or horizontal slices.
All these points are illustrated by comparing a number of seismic examples from North America, South America, the Caspian, and the Middle East to schematic diagrams and exposed examples.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.