MRI study on CO2 capillary trap and drainage behavior in sandstone cores under geological storage temperature and pressure

Abstract

Capillary pressure is an important parameter to characterize the core properties in CO2 geological storage applications, and it is necessary to study the CO2 drainage behavior to predict the potential and ensure the safety of storage. In this work, we conducted CO2 drainage experiments in two types of sandstone cores (Berea sandstone and synthetic sandstone) under reservoir conditions (800 m underground) and measured the capillary pressure using an MRI system. The drainage experiments were repeated in a capillary number range from 5.22 × 10−9 to 5.5 × 10−7 by varying the injection rate. The entry pressure and pore size distribution index were calculated by fitting a straight line on a log-log curve of the effective saturation versus capillary pressure. Relative permeability curves were plotted using the calculated entry pressure and pore size distribution index. The curves were consistent with the properties of the sandstone cores. The capillary desaturation curves gave the irreducible brine saturations for different permeability, wettability, injection pressure and injection direction conditions as a function of capillary number.