Improved success in finding hydrocarbons and minerals depends on developing geologic models from seismic, gravity, and magnetic data that most closely approximate real-world settings. Although data processing remains the chore of mainframe and minicomputers, interpretations and modeling of geologic and geophysical information now are best accomplished on personal computers because these computers afford the explorationist maximum freedom to shape and fine tune geophysical evaluations. Three case histories use the GEOSIM geophysical modeling systems to delineate exploration targets.

The first example is Silurian Niagaran reef trends in the Michigan basin. Here, differences in seismic reef anomalies result from variations in carbonate-evaporite stratigraphy encasing the reefs, reef geometry, and reef reservoir parameters. These variations which influence real seismic-response differences can be successfully matched using appropriate geologic models in generating synthetic seismic reef anomalies.

The second example applies gravity and magnetic data to seismic modeling of a Wyoming coal field. Detailed seismic stratigraphy helps locate those portions of the field having multiple seams, although it does not resolve individual economic zones. Gravity data do identify pinchout margins of multiseam zones and pinchouts between principal coals. Magnetic data are then used to delineate the burn (clinker) margin.

Seismic modeling of subtle stratigraphic traps is the broader area of exploration interest contained in the first 2 examples. In the third, successfully modeled and tested examples of lateral changes in deltaic facies and of faulted, unconformity-bounded continent-margin sequences are shown to be successful guides to reinterpretation of seismic data.

End_of_Article - Last_Page 481------------