School of Engineering
The oxidation of fossil fuels produces billions of tons of anthropogenic carbon dioxide (CO2) emissions from stationary and nonstationary sources per annum, contributing to global warming. The natural carbon cycle consumes a portion of CO2 emissions from the atmosphere. In contrast, substantial CO2 emissions accumulate, making it the largest contributor to greenhouse gas emissions and causing a rise in the planet's temperature. The Earth's temperature was estimated to be 1 °C higher in 2017 compared to the mid-twentieth century. A solution to this problem is CO2 storage in underground formations, abundant throughout the world. Millions of tons of CO2 are stored underground into geological formations annually, including deep saline aquifers. However, these geological formations have minute concentrations of organic material, significantly influencing the CO2 containment security, fluid dynamics, and storage potential. Examining the wetting characteristics and influencing parameters of geological formations is pertinent to understanding the supercritical CO2 behavior in rock/brine systems. Wettability is an important parameter governing the ability of injected CO2 to displace formation water and determine the containment security and storage capacity. Previously, many studies have provided comprehensive overviews of CO2-wettability depending on various factors, such as pressure, temperature, salinity, formation type, surfactants, and chemicals. However, mineral surfaces in these wettability studies are chemically cleaned, and natural geological storage conditions are anoxic (containing organic molecules) where reductive conditions ensue. A severe gap exists in the literature to comprehend the effects of organic material for determining the CO2 storage capacities and how this effect can be reversed using nanomaterial for increased CO2 storage potential. Therefore, we conducted a thorough literature review to comprehend the recent advances in rock/CO2/brine and rock/oil/brine systems containing organic material in different geo-storage formations. We also present recent advances in anoxic rock/CO2/brine and rock/oil/brine systems that have employed nanomaterial for wettability reversal to be more water-wet. This comprehensive review is divided into four parts: 1) reviewing CO2 emissions and geological systems, 2) recent advances in direct quantitative experimental procedures in anoxic rock/CO2/brine systems and effects of organic contaminations on experimental methodology and their controls, 3) effects of organics and nanomaterial in rock/CO2/brine and rock/oil/brine systems, and 4) the future outlook of this study.
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