Print this pageDescription of Geometries in Fault Shadow Pitfall as Result of Geological and Geophysical Properties
The fault shadow zone is called by the interpreters as false structures in the seismic data generated by lateral changes in the velocity among the hangingwall and the footwall of the fault. Some of these false structures are the responsible of the several dry hole and noncommercial Wells.
In this work, it is show using different synthetic depth models the typical responses in the time seismic section because to different geological features. Initially, from a well data in the Catatumbo Basin, Colombia were built a synthetic depth model, later, it is displayed with the fault angle, throw, maximum offset and the velocities. Each depth model is view in time seismic section and compared the pull-up and push-down among the different seismic sections.
The synthetic model has 10 stratigraphic units, the first is the shallowest unit with low velocity, 2.430 m/s, later, ranging from shallow to deeper these are: sandstones at 3.718, sandstones at 3.627 m/s, low-velocity shale at 2.438 m/s, five sandstones units at 3.352, 3.048, 3.048, 3.352 and 3.592 m/s. the horizon deepest have 5.400 m/s and represent the basament. With this depth model were simulated a 2D seismic survey using a ray tracer. With the synthetic illumination results were created synthetic seismograms in seg-y format, later; these seismograms were imported into a seismic processing package and viewed the pitfall in the seismic sections.
In total, 11 changes in the original synthetic model were made, and compared each pitfall generated to show the geometries obtained with each feature. The velocity and de angle fault are features stronger in the shadow effect.
Mayors lateral changes in the velocity or increase in the inverse velocity rise mayor fault shadow effects.
The angle fault cause mayor disruptions with faults dip mayors. In low angle faults, the curvature of the pull-up is smoothed compared with the effect caused by the step fault. The disruptions effect is minor in the low angle faults.
Others geophysical features as maximum offset and throw fault do not have strong impact in the geometry of the pull-up and push-down.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil