Electricity generation and industrial processing typically produce large quantities of carbon dioxide (CO2). These CO2 streams may vary, sometimes substantially, in terms of both composition and mass flow rate. The impact of varying composition and flow rate on injection infrastructure and geologic formations during enhanced oil recovery and/or storage activities is not well known.
Literature searches were conducted by researchers at the University of North Dakota Energy & Environmental Research Center (EERC) to identify some of the effects of CO2 stream variability on the operability of CO2 injection infrastructure (e.g., in-field distribution pipeline system, wells) as well as on the geologic formation in which enhanced oil recovery or geologic storage is occurring. Fatigue and corrosion are considered to be the most likely effects of intermittent flow on wellbore integrity. Injectivity of a reservoir can be diminished or project infrastructure damaged as a result of pressure and temperature changes related to intermittent CO2 supplies. Salt precipitation and hydrate formation, which can be formed as a result of these types of pressure and temperature changes, can significantly impact injectivity in a geologic formation.
The impacts of CO2 stream impurities on enhanced oil recovery or geologic storage are reservoir-specific and depend on both the mineralogical composition and the type and amount of the impurities. Noncondensable impurities in a CO2 stream reduce the density of the gas, leading to a drop in total storage capacity for a reservoir. Fractures and pore spaces can be blocked by mineral precipitation. The formation of acids because of the presence of water and SO2 or H2S can reduce the pH of the geologic formation water. This can form a zone in which mineral dissolution of carbonate and silicate minerals takes place, altering the porosity of the formation.
This paper provides a broad overview of the potential challenges to enhanced oil recovery and CO2 utilization that could arise from variability in CO2 streams. Opportunities for research that could reduce the cost and improve the value of the carbon capture, utilization, and storage chain will be identified.