(209g) Experimental Framework for Understanding Intermolecular Interactions in Carbon Dioxide-Water Mixtures for EOR and Storage

The injection of carbon dioxide (CO₂) into reservoirs for enhanced oil recovery (EOR) is a mature technology in the petroleum industry. This work is motivated by the recent interest in using CO₂-EOR to support CO₂ storage, which can retain the benefits to commercial oil producers and also support environmental targets on carbon capture and storage. To ensure the twin goals of oil extraction and underground CO₂ storage, we need to increase the effectiveness and kinetics of at least two trapping mechanisms: (i) Solubility trapping; and (ii) Structural trapping. The first mechanism is enabled by EOR operations that alternate between CO₂ and water flooding, resulting in the dissolution of CO₂ in aqueous phase. In CO₂-EOR, which is a tertiary phase technique, the sequenced CO₂ and water injection operations are designed to mitigate the viscous fingering of low viscosity fluid. However, its effectiveness for both CO₂-EOR and storage crucially depends upon the properties of CO₂-water mixture. Similarly, the second mechanism utilizes the (undamaged) seal of geological reservoirs as trapping sites for CO₂ storage, and again the interaction between CO₂ and water molecules play an important role in the effectiveness of storage. This presentation will discuss our experimental framework for better understanding of CO₂-water intermolecular interactions in the context of above-mentioned trapping mechanisms. Specifically, we utilize two complementary sets of techniques--interfacial tension measurements and Raman spectroscopy---and present our results for a range of temperature and pressure conditions. The key contribution of our research is the study of intermolecular interactions for equilibrated CO₂-water mixtures as opposed to first contact properties. The former is relevant for reservoir flooding since local equilibrium is established fairly quickly compared to displacement time-scales. Our inferences may then be used for reservoir simulation and a systematic evaluation and design of optimal CO₂-EOR and storage operations.