SEISMIC RAY-TRACE MODELING AS A TOOL FOR INTERPRETING COMPLEX SUBSURFACE STRUCTURES IN THE WICHITA MOUNTAINS FRONTAL ZONE, SOUTHERN OKLAHOMA

The Wichita Mountains Frontal Zone (WMFZ) is part of the linear trend in southern Oklahoma that extends from the Arbuckle Mountains in south central Oklahoma through the Wichita Mountains to the buried Amarillo Mountains in the Texas Panhandle. Intense subsurface deformation exists along the WMFZ, including overturned beds and crystalline basement rocks thrust over Paleozoic sedimentary rocks. Correct migrations of seismic data are vital to accurate interpretations; but they cannot be achieved without well defined velocity models. Velocity models are in turn based on interpretations of the data. Seismic ray-tracing can confirm or condemn an interpretation.

A synthetic zero offset seismic data set paralleling an actual seismic line was created with ray-tracing software by building a valid cross section using all available data, including well data and seismic data. Ray paths were calculated and analyzed to determine where reflections occurred in the subsurface and their corresponding CMP location. Arrival times and reflection amplitudes were used to produce synthetic traces for comparison to actual seismic data.

Two alternate velocity models were constructed to demonstrate that a lack of data, or an inaccurate interpretation produce ambiguous results. The synthetic data set was time migrated with the exact velocity grid used to create the data; then the data set was migrated with the alternate velocity models. Comparing the three resulting migrations to the actual seismic data confirmed that the more accurate migration velocity model produced the clearest result. The most accurate migration, however, does not accurately position all reflection events. A reflection from the overturned limb of an anticline is not placed in the correct horizontal location.