Permeability Damage Due to Fines Migration During CO2 Sequestration

Abstract

Fines migration has not been widely considered during CO2 injection into water-saturated rocks. Mineral dissolution effects are only considered in long-term experiments (weeks to months scale). This study conducts a series of short (few hours) dynamic experiments to study the effect of dissolution and fines migration on CO2 injectivity in cores. Three coreflooding experiments were performed using Berea sandstone at difference salinity brine (0, 10, 30 and 60 g/L NaCl). First, the core plugs were subjected to brine injection. Then, CO2-saturated brine was injected to displace unsaturated brine from the core. Afterward, brine saturated supercritical CO2 (scCO2) was injected into the core. The Pressure drop across the core was monitored and produced water samples were collected continuously during the experiments. To characterize the core sample, X-Ray Powder Diffraction (XRD), X-Ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM) analyses were performed. After the experiment, SEM-EDS analysis was run and registered with the pre-injection images to visualize fines migration. Fines concentration was measured, and ionic chromatography analysis was performed to characterize produced water samples. Numerical simulations were performed to model the experiment geochemical reactions. The permeability of the core sample is significantly reduced after the experiment due to pore blockage. SEM-EDS analysis of the blocked pores and produced fines show blockage is mostly caused by clay, quartz and cement. Numerical simulations showed that the reaction rate; hence, cement dissolution is faster at higher salinity.