CO2 Injection in Carbonates

Abstract

AbstractStarted as an EOR technique to produce oil, injection of carbon dioxide which is essentially a greenhouse gas is becoming more and more important. Although there are a number of mathematical modeling studies, experimental studies are limited and most studies focus on injection into sandstone reservoirs as opposed to carbonate ones. This study presents the results of computerized tomography (CT) monitored laboratory experiments to characterize relevant chemical reactions associated with injection and storage of CO2 in carbonate formations. Porosity changes along the core plugs and the corresponding permeability changes are reported for differing CO2 injection rates and with differing salt concentrations. CT monitored experiments are designed to model fast near wellbore flow and slow reservoir flows. It was observed that permeability initially increased and decreased for slow injection cases. As the salt concentration decreased the porosity and thus the permeability decrease was less pronounced. The experiments were modeled using a commercial simulator where solution and deposition of calcite were considered by means of chemical reactions. The calibrated model was then used to analyze field scale injections. It was observed that solubility storage of CO2 is larger compared to mineral trapping.