Field applications of a new nuclear magnetic resonance fluid characterization method

This paper discusses the application of a new magnetic resonance fluid (MRF) characterization method to field data acquired by a nuclear magnetic resonance (NMR) well-logging tool. The theoretical and experimental foundation underlying the method was discussed in a previous publication.(1) The MRF method provides a detailed formation evaluation of the near-wellbore region investigated by modem NMR logging tools. This information includes total and bound-fluid porosities, hydrocarbon saturations, oil viscosities, and hydrocarbon-corrected permeabilities. This paper presents MRF oil saturation and viscosity estimates in oil-bearing wells. In this paper, we first provide a short review of the main ideas and key equations that make up the MRF method. We discuss the generalization of the MRF method to logging data acquired by the Combinable Magnetic Resonance (CMR)** tool and apply the method to mixture data acquired by a CMR tool on crude-oil and water samples. We also discuss the existing database of MRF results on partially saturated rocks and present new laboratory results that include blind tests on Yates field dolomite rocks measured at initial and residual oil saturation. The sources of uncertainty inherent in NMR diffusion-based viscosity estimation in reservoir rocks are discussed, and we propose a strategy that accounts for the uncertainties and provides reasonable estimates of oil saturations and viscosities. The strategy is applied to the MRF analysis of the field data in this paper. The MRF method is applied to CMR station log data acquired in three wells. Analysis of the MRF data and the results from each of these wells is discussed.