THREE-DIMENSIONAL GEOHYDROLOGIC MODELING OF THE HUNTON ANTICLINE, ARBUCKLE MOUNTAINS, SOUTH-CENTRAL OKLAHOMA

The Arbuckle-Simpson aquifer of south-central Oklahoma encompasses more than 500 square miles and is the principal water resource for south-central Oklahoma. The subsurface geologic framework and ground-water reservoir capacities of this fractured and karstic carbonate aquifer are largely undetermined. Rock units comprising the aquifer are characterized by limestone, dolomite, and sandstones assigned to two lower Paleozoic units: the Arbuckle and Simpson Groups. Also considered to be part of the aquifer is the underlying Cambrian-age Timbered Hills Group that contains limestone and sandstone. The highly faulted and fractured nature of the Arbuckle-Simpson units and the variable thickness (2,000 to 9,000 feet) increases the complexity in determining the subsurface geologic framework of the aquifer.

We have constructed a three-dimensional (3-D) EarthVision™ (EV) geologic framework model that characterizes the geometric relationships of the Arbuckle-Simpson aquifer within the Hunton anticline area. The model helps to visualize the hydrologic connectedness of the water bearing units across fault zones. The 3-D modeling also allows the exploration of the inner geometries of fault blocks and their fault-zone juxtapositions in the subsurface. Smaller-scale structures included in the model area are, from northeast to southwest, the Sulphur syncline, Belton anticline, and Mill Creek syncline.

This preliminary model contains six geologic layers, more than 40 major and minor faults, and accurately depicts the shape and form of the aquifer. The construction of the 3-D EV model involved integrating field studies that include outcrop geology, available geologic and geophysical data from existing maps, data from over 300 drill-holes, and various geologic and hydrogeologic reports. Over 30 surface geologic contacts were extrapolated into the subsurface in areas lacking well control. Other methodologies being developed include techniques for extrapolating GIS geologic map and down-hole well data directly into 3-D EV datasets for discretization into related, ongoing MODFLOW ground-water modeling efforts.