Nuclear Magnetic Resonance Relaxation Studies in Shale

Abstract

The present work involves a comprehensive experimental study of proton (¹H) nuclear magnetic resonance (NMR) transversal relaxation in shale. The sample studied belongs to the “Vaca Muerta” formation of the Neuquén basin, Argentina. The results show that the relaxation process is governed by anomalous diffusion processes in micro-pores. These processes result from the combination of interactions between the liquid molecules and the pore walls, whose structure is characterized by both large tortuosity and abundance of paramagnetic impurities, giving rise to local strong time-dependent magnetic field gradients. In addition, a simultaneous experimental method of data fitting is presented which allows processing all the relaxation profiles within a single time domain. Thus, yielding results univocally related to the complete set of relaxation data.