Permeability Profiling of Rock Cores Using a Novel Spatially Resolved NMR Relaxometry Method: Preliminary Results From Sandstone and Limestone

Permeability characterizes how saturating fluids penetrate and flow through porous rocks. It is an important quantity that can be used to model the behavior of reservoir rocks and to optimize underground resource exploration. Permeability can be characterized via nuclear magnetic resonance (NMR) relaxometry techniques by utilizing the yielded pore volume and pore length scales. However, for heterogeneous rocks a simple estimation of a permeability value based on the existing models may be inadequate. In this work, a new relaxation technique is applied to rock cores in conjunction with magnetic resonance imaging schemes. This allows the interior structures of studied rock cores to be recorded along a chosen sample axis. Based on the spatially resolved relaxation maps obtained, a factor of local connectivity was introduced for the first time and calculated by using the correlation degree between adjacent relaxation time distributions originating from neighboring image slices. Consequently, a permeability profile was estimated by consecutively considering the local porosity, the spatially resolved relaxation time distribution, and the connectivity factor. Experimental results prove that permeability profiles trace the heterogeneity of rock samples. Furthermore, averaged permeabilities of rock cores were calculated while taking into account local connectivity. The values obtained approach better to brine‐permeability measurements as compared to data processing disregarding connectivity. Key Points A rapid, nondestructive method was proposed to estimate rock permeability Rock heterogeneity can be visualized by using obtained permeability profiles The obtained permeability values from the proposed technique were comparable to conventional approach