[1] Hydraulic conductivity (K) is one of the most important parameters of interest in groundwater applications because it quantifies the ease with which water can flow through an aquifer material. Hydraulic conductivity is typically measured by conducting aquifer tests or wellbore flow (WBF) logging. Of interest in our research is the use of proton nuclear magnetic resonance (NMR) logging to obtain information about water-filled porosity and pore space geometry, the combination of which can be used to estimate K. In this study, we acquired a suite of advanced geophysical logs, aquifer tests, WBF logs, and sidewall cores at the field site in Lexington, Nebraska, which is underlain by the High Plains aquifer. We first used two empirical equations developed for petroleum applications to predict K from NMR logging data: the Schlumberger Doll Research equation (K SDR ) and the Timur-Coates equation (K T-C ), with the standard empirical constants determined for consolidated materials. We upscaled our NMR-derived K estimates to the scale of the WBF-logging K(K WBF-logging ) estimates for comparison. All the upscaled K T-C estimates were within an order of magnitude of K WBF-logging and all of the upscaled K SDR estimates were within 2 orders of magnitude of K WBF-logging . We optimized the fit between the upscaled NMR-derived K and K WBF-logging estimates to determine a set of site-specific empirical constants for the unconsolidated materials at our field site. We conclude that reliable estimates of K can be obtained from NMR logging data, thus providing an alternate method for obtaining estimates of K at high levels of vertical resolution.

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TA-GOGD is thermally assisted gas-oil gravity drainage suited for heavy oil in highly fractured formations. Steam is injected into the fractures to serve two purposes: to apply a gas gradient across the matrix blocks so that the oil in the matrix drops down by gravity and to heat the carbonate matrix blocks so that the reduced viscosity oil drips out faster. The reservoir has two fluid systems, which are gas/oil/water levels in the fractures and gas/oil/water contacts in the matrix blocks that are separated by the fractures. Reservoir surveillance requires logs of the remaining oil saturation to confirm the recovery, which is dependent upon the heterogeneities of fracture intensity and vertical permeability. The changing fluid saturations in the matrix are primarily oil replaced by hydrocarbon gas, but six fluids could be present and change: methane and steam, hot low-viscosity and cold high-viscosity oil, formation water, and condensed steam. The important zone is above the fracture gas/oil contact, where drained oil is replaced by the secondary gas cap or steam. Time-lapse pulsed neutron capture logs during the pilot phase did not provide the required matrix fluid saturations due to interference from variable annular fluids in the poorly cemented casing that masked the reservoir response. There is no logging tool available that is capable of measuring the matrix oil saturation change without being influenced by the other fluids in the matrix or the fracture-controlled fluid levels in the casing annulus, or characterized for an open gas-filled borehole, and built to withstand 247°C. The physics of nuclear magnetic resonance (NMR) provides the best chance to fulfill this reservoir surveillance requirement. This paper recounts the decision process that preceded this conclusion, and suggests a method of building a high-temperature non-metallic and non¬magnetic flask to facilitate NMR time-lapse logging in dedicated openhole observation wells in TA-GOGD developments.

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