Seismic Velocity Analysis in Shallow Evaporites from 3D Seismic Data: Northwestern Kansas

Steve Reed and Hendratta Ali

Exploration in central and northwestern Kansas has known problems with near surface velocities. Seismic data does not always accurately tie correctly with well log data through evaporite formations. The evaporite effects on seismic exploration have been well studied in other areas like the Gulf of Mexico, due to the importance of velocity for subsurface analysis. When interpreting seismic data, determining the correct depth to drill is extremely important. Missing a potential reservoir because the data is off can be a costly error. Although numerous models have been developed to correct depth readings for wave velocities altered by evaporite deposits around the world, few studies have examined these effects in parts of central and northwestern Kansas. Two well- known shallow evaporite formations in Kansas; the Stone Corral anhydrite and the Hutchinson salt Formations are potential sources of velocity problems in well to seismic ties in this area. The Hutchinson Salt formation is mostly known as the cause of numerous dissolution sinkholes throughout Kansas. The goal of this project is to investigate velocity variations in shallow salt zones in parts of central and northwestern Kansas with active oil exploration. We use 3D seismic and well log data to compare velocity models. We mapped major formation tops, from well log data and seismic data from known marker beds. Velocity is modeled using sonic and density logs and modeled from drill times to known formations. A comparison analysis of well and seismic data was conducted to correct discrepancies observed in shallow zones. These results will be useful in furthering our understanding of velocity variations in shallow formations of central and northwestern Kansas. 

AAPG Search and Discovery Article #90176©AAPG Mid-Continent Meeting, Wichita, Kansas, October 12-15, 2013