DETERMINATION OF SATURATION PROFILES VIA LOW-FIELD NMR IMAGING

摘要

One-dimensional oil-water saturation profiles can be determined with a low-field Maran Ultra spectrometer by implementing nuclear magnetic resonance(NMR) imaging techniques.Frequency encoding gradients impart spatial resolution to the measurements and allow for the creation of T2 and D-T2 profiles without having to perform multiple slice selective measurements.The first technique,denoted as RARE, relies solely on resolving transverse relaxation,T2,as a function of height.The second method,D-T2 profiling,allows for the determination of both the diffusion coefficient,D, and T2 as a function of height.The ability to resolve D in addition to T2 allows fluids with overlapping relaxation times to be distinguished,and therefore it is not necessary to use D2O in order to differentiate the water signal from the oil signal.Implementation of these two methods allows for the determination of saturation profiles.Experiments were performed with a sandpack in order to demonstrate the applicability of these two techniques.The saturation profile of a sandpack was determined before and after 0.5 PV waterflood.