Application of Petroleum Geophysical Well Logging and Sampling Techniques for Evaluating Aquifer Characteristics

The Hilton Head Island Test Well #1 was drilled to a depth of 3833 feet to evaluate the upper Cretaceous section as a potential ground‐water source for Hilton Head Island, South Carolina. The initial plan was to analyze continuous conventional cores. The interval to be analyzed extended from the top of the Eocene to the base of the Cretaceous (approximately 3500 feet). However, due to the high cost ($400,000), the decision was made to evaluate aquifer potential using advanced geophysical logs with sidewall cores for calibration. The logging suite consisted of a dual induction resistivity, spontaneous potential, compensated neutron, density log, gamma ray, spectral gamma, multipole array acoustic log, caliper, high resolution dipmeter, and a circumferential borehole imaging log. In addition to the wireline logs, 239 sidewall cores and 12 Formation Multi‐Test samples were obtained. The log, sidewall core, and FMT information were integrated into an interpretive package using computer generated logs and simple spreadsheets to calculate aquifer properties. Porosity, hydraulic conductivity, transmissivity, and lithologic data derived from this integrated analysis were then used to select screen zones. Water quality in relation to drinking water standards exceeded expectations. The information obtained from the integrated program allowed estimates to be made about the well's productivity without the expense of conventional coring, flow testing, and completion of the well.