Effect of water salinity on permeability alteration during CO₂ sequestration

Abstract

Fines migration during CO₂ injection into water-saturated rocks causes mineral dissolution and precipitation. We present a careful experimental study to investigate the effect of water salinity on permeability damage during CO₂ sequestration.Core samples were cut from two Berea sandstone blocks for coreflooding images. The core samples were characterized using X-Ray Powder Diffraction (XRD), X-Ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM) analyses. The coreflooding began by injecting a core sample with water having salinity values of 0, 10, 30, or 60 g/L NaCl. Then, CO₂-saturated water was injected to displace the previously injected water. The resulting fluid was then displaced by the injection of water-saturated supercritical (sc) CO₂. Throughout coreflooding, the pressure difference across the core sample was monitored, and produced water samples were collected. After the coreflooding, SEM and energy dispersive X-ray spectroscopy (EDS) analysis was run to generate images that were then registered with the pre-injection images to reveal fines migration. The produced water samples were subjected to measurement of fines concentration and ionic chromatography analysis.During CO₂-saturated water injection, permeability increased for low-salinity water coreflooding (0 and 10 g/L NaCl) and decreased for high-salinity water coreflooding (30 and 60 g/L NaCl). After water-saturated scCO₂ injection, Permeability decrease ranged from 85% for freshwater (0 g/L NaCl) to 20% for high-salinity water (60 g/L NaCl). Fines migration and its consequent mineral dissolution and precipitation determine the core samples' permeability.