Effects of impurities on CO2 storage in chalk reservoirs

The feasibility of a CO2 storage scheme depends on many factors, including the presence of impurities in the CO2 supply. This study investigates the effects of CO2 purity on storage in mature chalk oil reservoirs in late stages of production with geological and petrophysical characteristics favorable to CO2 injection. The presence of minor impurity constituents in the supercritical CO2 stream will affect the phase behavior, viscosity, density and interfacial behavior of the CO2, particularly for the non-compressible impurities N2, Argon and O2. These phase parameters as well as other chemical and physical properties depend on the intermolecular interactions between the CO2 molecules and the available impurities, which may for some polar impurities strongly dominate relative to the self-association forces between CO2 molecules. The approach is a series of quantum chemical calculations and of the interactions between CO2 and all relevant impurities to identify those that interact most significantly with CO2 relative to the self-association forces between CO2 molecules in the pure form. The most important systems are confirmed experimentally, and subsequently core flood experiments with the identified impurity-CO2 systems are conducted to investigate the effects on rock integrity and dissolution during injection and storage.