THE MODIFIED STRETCHED-EXPONENTIAL MODEL FOR CHARACTERIZATION OF NMR RELAXATION IN POROUS-MEDIA

A compact model, the modified stretched exponential (MSE), for charact erization of transverse and longitudinal NMR relaxation of fluid in sa turated porous media is presented. The MSE model exhibits the theoreti cally correct long- and short-time behavior, and its general applicabi lity for representing transverse-relaxation data is demonstrated for a wide range of rock lithologies and saturating fluids at various magne tic field strengths and echo times. The model also provides a reliable and sample-independent method for signal back-extrapolation, which is necessary for quantitative petrophysical NMR measurements, and overco mes the limitations of the well-known stretched-exponential model. (C) 1996 Academic Press, Inc.