Evaporation Process and Pore Size Distribution in Tight Sandstones: A Study using NMR and MICP

Abstract

The phenomenon of evaporation is widely observed in a variety of processes and draws attentions from researchers. In the petrophysical study of sandstone, the knowledge of evaporation is necessary to understand the fluids distribution in the rock. Besides, evaporation method was used in the determination of irreducible saturation in lab and removing water blocking in gas well. In this study, Nuclear Magnetic Resonance (NMR) T2 distribution was used to determine the water distribution and migration during evaporation. Mercury Injection Capillary Pressure (MICP) was used to calibrate the T2 distribution produced by NMR. Based on the NMR data and MICP data, the absolute pore radius distribution was obtained and the whole evaporation process of tight sandstones can be divided into three stages. In the tight sandstone samples, the threshold pore radius for the initial evaporation is larger than 0.8 um.