This project aims to develop technologies of aqueous nanobubble (NB) dispersion of CO2 for geological carbon sequestration, primarily for CO2 mineralization in (ultra)mafic rock formations. We aim to substantially reduce the amount of water required to sequester a given amount of CO2 (e.g., by a factor of 2), leading to a reduced cost (capital and operational) of CO2 mineralization. Aqueous nanobubble dispersion also enables supersaturation of brine by CO2 beyond the inherent solubility and enhances the kinetics and extent of mineral dissolution and CO2 mineralization. In addition to fundamental studies of aqueous NB dispersion, we are developing suitable methods of aqueous CO2 NB generation for continuous operation at elevated pressure for CO2 mineralization. Primary collaborators on this topic include “44.01” and “Japan Petroleum Exploration”.

Wettability alteration has been studied as a potential way to enhance oil recovery from tight formations. One of the commonly used wettability modifiers is surfactant, which is expected to make rock surfaces less oil-wet and lower the oil/water interfacial tension (IFT). Shortcomings of using surfactants include i) it unlikely affects fluid flow in tight matrices where the molecular size is greater than pore sizes even as a surfactant monomer, ii) the lowered oil/water IFT tends to reduce the water imbibition, iii) many surfactants are unstable at high-temperature high-salinity conditions (e.g., carbonate reservoirs in the Middle East), and iv) the total cost for an effective surfactant formulation can be high. This project aims to develop ketone EOR technologies for enhanced oil recovery from conventional and unconventional reservoirs. The central hypothesis in this project is that aqueous ketone solution can alter the wettability of rock surfaces to more water-wet by rapidly penetrating matrices through oil and water phases in small pores without affecting the oil/water IFT. We found that 3-pentanone or diethyl ketone is the most effective ketone for EOR in shales and carbonates, as also confirmed by other academic and industrial research groups. The molecular size of 3-pentanone was reported to be 0.4-0.79 nm and stable under high-salinity and high-temperature conditions. The cost is approximately $2/lb. The solubility of 3-pentanone in brine is usually below 3 wt% and decreases with increasing salinity. Primary collaborators on this topic include OXY for shale reservoirs, and INPEX and Cosmo Energy for carbonates.

The energy transition requires managing the global carbon balance with a large throughput of CO2 while shifting to less carbon intensive energy sources, such as hydrogen, in economically feasible, publicly acceptable ways. Many issues with processing CO2 and H2 come from their physical properties, their compression, transportation, and storage [e.g., H2 embrittlement]. Also, geological CO2 sequestration has various issues associated with the properties of CO2, such as low carbon density at low to moderate pressure, low mass density, low viscosity, immiscibility with water, and corrosivity [e.g., low pH near a CO2 plume]. In particular, CO2 injection often results in inefficient use of pore space in the formation under geophysical heterogeneities.

This project aims to develop technologies for aqueous CO2 nanobubble (NB) dispersion for enhanced oil recovery from conventional and unconventional reservoirs. The central hypothesis in this project is that the CO2-rich phase generated near the fronts of oil displacement in CO2 NB injection can greatly enhance oil recovery. Previous studies on carbonated water injection (CWI) showed a markedly increased oil recovery factor upon breakthrough (RFBT) in comparison to the control experiment with brine with no CO2 when the CO2-rich phase was generated near the displacement fronts. CO2 NB is expected to promote this new mechanism of oil recovery by substantially increasing the CO2 concentration in water beyond the inherent solubility. Aqueous CO2 NB injection is also expected to be much simpler and less expensive than CO2 injection because a small amount of CO2 is injected as an effectively homogeneous aqueous fluid (e.g., 1 tonne of CO2 in 15 tonnes of brine).