APPLICATION OF PETROLEUM INDUSTRY DATA TO THE EVALUATION OF THE ARBUCKLE AND SIMPSON AQUIFERS, ARBUCKLE MOUNTAINS, OKLAHOMA

Increasing demands for groundwater supplies in Oklahoma are focusing attention on the “Arbuckle” aquifer of southern Oklahoma as a potential source of supply. The Arbuckle aquifer outcrops and recharges in the Arbuckle Mountains, a large east-west trending anticlinal fold. The aquifer consists primarily of carbonate flow units in the Cambro-Ordovician Arbuckle Group and sandstone flow units in the overlying Ordovician Simpson Group. The thickness of the Arbuckle Group carbonates exceeds 1000 meters; the thickness of the sandstone flow units typically ranges from 30 to 50 meters. Determining aquifer characteristics is difficult, but essential for ground water flow modeling. Few water-supply wells penetrate more than 300 meters of the Arbuckle Group, whereas in the Simpson Group wells are generally <100 meters deep and restricted to areas close to the outcrop. Fortuitously, the limited aquifer data provided by water supply wells are augmented by information collected during the exploration for petroleum. These latter data, which are not part of the traditional hydrogeologic dataset, are essential to aquifer characterization and include: lithologic and wireline logs to determine interval and flow unit thicknesses, cores and bit cuttings to determine lithology, reports from cable-tool-drilled wells, drill stem test and well completions that establish fluid types in flow units, calculations of fluid properties from wireline log curves, pore morphology and rock architecture determined from core, quantified porosity measurements from core and wireline logs, and seismic sections for interpreting structural elements and stratigraphy. In some cases, only legacy 2-D seismic data are available. Generally, these data are poor quality. However, with modern processing techniques, the quality of the stacked seismic can be improved, leading to a better interpretation of the flow units. The seismic and well data acquired for petroleum exploration are essential to determining the thickness, type and spatial distribution of flow units within aquifer-bearing intervals, establishing the structural grain and predicting paths of potentiometric flow, delineating the distribution of fresh, brackish and saline waters within flow units, and quantifying flow unit porosity and thickness for numerical modeling.