A technical review of chemical reactions during CCUS-EOR in different reservoirs

Geochemical reactions play a vital role in determining the efficiency of carbon capture, utilization, and storage combined with enhanced oil recovery (CCUS-EOR), particularly through their influence on reservoir properties. To deepen the understanding of these mechanisms, this review investigates the interactions among injected CO₂, formation fluids, and rock minerals and evaluates their implications for CCUS-EOR performance. The main results are summarized as follows. First, temperature, pressure, pH, and fluid composition are identified as key factors influencing mineral dissolution and precipitation, which in turn affect porosity, permeability, and CO₂ storage. Second, carbonate minerals, such as calcite and dolomite, show high reactivity under lower temperature conditions, enhancing dissolution and permeability, while silicate minerals, including illite, kaolinite, quartz, and K-feldspar, are comparatively inert. Third, the formation of carbonic acid during CO₂ injection promotes dissolution, whereas secondary precipitation, especially of clay minerals, can reduce pore connectivity and limit flow paths. Fourth, mineral transformation and salt precipitation can further modify reservoir characteristics, influencing both oil recovery and long-term CO₂ trapping. Fifth, advanced experimental tools, such as Computed Tomography (CT) and Nuclear Magnetic Resonance (NMR) imaging, combined with geochemical modeling and reservoir simulation, are essential to predict petrophysical changes across scales. This review provides a theoretical foundation for integrating geochemical processes into CCUS-EOR design, offering technical support for field application and guiding sustainable CO₂ management in oil reservoirs.