Petrophysical Changes of Sandstone Due to Salt Precipitation and Fines Migration During Carbon Dioxide Injection

摘要

Sequestration of Carbon Dioxide (CO_2) in sandstone formation filled by brine aquifers is widely considered a promising option to reduce the CO_2 concentration in the atmosphere. However, the injection of reactive CO_2 into sandstone rock creates injectivity problems because of CO_2-brine-rock interactions. The injection flow rate and CO_2-fluid-rock exposure conditions are important factors that control the intensity of the reactions. The focus of this research was therefore on evaluating the petrophysical modifications in sandstone core samples at distinct flow rates using different CO_2 injection schemes. In this research, the porosity and permeability of Berea sandstone samples were measured using PoroPerm equipment. The core samples were initially saturated with dead brine (30 g/l NaCI) followed by injection either by supercritical CO_2 (scCO_2) only, CO_2-saturated brine only and CO_2-saturated brine together with scCO_2 at different flow rates. During injection, the differential pressure between the core inlet face and outlet face were recorded. Fines from the produced effluent were separated and collected for characterization using Field Emission Scanning Electron Microscope and Energy Dispersive X-ray Spectroscopy (FESEM-EDX). Post-injection porosity and permeability of the core samples were measured and compared with the pre-injection data to monitor changes. All sandstone core specimens showed favorable storage capability features in the form of capillary residual trapping with residual CO_2 saturation ranging from 40% to 48%. In addition, all samples experienced important changes in their petrophysical characteristics, which were more pronounced in the event of absolute porosity and permeability, which decreased from 20%-51% to 4%-32%. The suggested harm mechanism is primarily owing to salt precipitation and fines migration. Supported by FESEM images, the proposed damage mechanism is mainly due to salt precipitation and fines migration.