Carbon capture and storage is a promising strategy for mitigating the CO2 contribution to global climate change. The large scale implementation of the technology mandates better understanding of the risks associated with CO2 injection into geologic formations and the subsequent interactions with groundwater resources. The injected supercritical CO2 (sc-CO2) is a nonpolar solvent that can potentially mobilize organic compounds that exist at residual saturation in the formation. Here, we review the partitioning behavior of selected organic compounds typically found in depleted oil reservoirs in the residual oil-brine-sc-CO 2 system under carbon storage conditions. The solubility of pure phase organic compounds in sc-CO2 and partitioning of organic compounds between water and sc-CO2 follow trends predicted based on thermodynamics. Compounds with high volatility and low aqueous solubility have the highest potential to partition to sc-CO2. The partitioning of low volatility compounds to sc-CO2 can be enhanced by cosolvency due to the presence of higher volatility compounds in the sc-CO2. The effect of temperature, pressure, salinity, pH, and dissolution of water molecules into sc-CO2 on the partitioning behavior of organic compounds in the residual oil-brine-sc-CO2 system is discussed. Data gaps and research needs for models to predict the partitioning of organic compounds in brines and from complex mixtures of oils are presented. Models need to be able to better incorporate the effect of salinity and cosolvency, which will require more experimental data from key classes of organic compounds.
All Science Journal Classification (ASJC) codes
- Environmental Chemistry