Browsing by Author "Alor, Emmanuel"

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Experimental investigation of the thermophysical properties affecting CO₂ enhanced oil recovery
(Heriot-Watt University, 2025-08) Alor, Emmanuel; Chapoy, Professor Antonin; Burgass, Doctor Rod
Understanding fluid properties in relation to pressure and temperature is crucial for reservoir engineers as they evaluate production performance and manage reservoirs for enhanced crude oil recovery. Additionally, in the context of global decarbonization goals, carbon capture, utilization, and storage (CCUS) have emerged as pertinent strategies. Among these, CO2- enhanced oil recovery (CO2-EOR) stands out due to its intrinsic storage of CO2 in geological formations, making it an attractive option given the challenges and costs associated with finding new reservoirs. CO2-EOR involves five key mechanisms: (1) oil volume swelling, (2) reduction in oil and water density, (3) reduction in oil viscosity, (4) reduction in interfacial tension, and (5) vaporization and extraction of portions of oil, particularly the lighter components. Carbon dioxide exhibits high solubility in hydrocarbons, leading to oil swelling and consequent reductions in viscosity and density. As a result, comprehending the impact of pressure, volume, and temperature (PVT) on the behavior of carbon dioxide and hydrocarbon mixtures becomes imperative in this context. This study focuses on examining the impact of CO2 presence in hydrocarbons through an investigation into the thermophysical properties of binary mixtures comprising CO2 and hydrocarbons. Bubble point measurement was carried at mole fraction CO2 of approximately 0.75 and 0.35, and temperature range of 320 to 400 K. The bubble point of the mixtures were measured with a setup which consists of an equilibrium cell, cryostat, rocking/pivot mechanism, and temperature/pressure recording equipment controlled by a PC. The equilibrium cell is a piston-type variable volume (maximum effective volume of 300 ml), titanium cylindrical pressure vessel with mixing ball, mounted on a horizontal pivot with associated stand for pneumatic controlled rocking through 180 degrees. Cell volume, hence, pressure, can be adjusted by injecting/withdrawal of liquid behind the moving piston. The cell was charged with the test sample and set to the desired temperature for the measurement. The sample volume was then reduced by pumping liquid into the cell (behind the moving piston), at the opposite end to the sample. By this means the sample pressure was increased such that the sample was at a pressure significantly higher than the expected bubble point pressure. The cell was then rocked to mix the contents and ensure equilibrium. The sample temperature was then decreased step-wise until the fluid moves from 1-phase region to a 2-phase region. The stabilized equilibrium pressures and temperature were plotted and the bubble point was indicated by a sharp change in the pressure versus temperature plot. The findings reveal that an elevation in pressure leads to a reduction in viscosity at a constant temperature. Similarly, an increase in temperature results in a decrease in viscosity and density at constant pressure. The interfacial tension (IFT) between CO2 and hydrocarbons follows an almost linear decrease with rising pressure and an increase with temperature. Additionally, the bubble point experiences an increase with a rise in temperature at a constant mole fraction. Furthermore, an increase in the mole fraction of CO2 corresponds to an increased bubble point at a constant temperature. Notably, at a constant CO2 fraction, mixtures with higher carbon numbers exhibit higher boiling points. Bubble points using Peng Robinson equation of state were calculated and compared to our measurements at the same temperature, pressure and mole fraction xCO2, It gave a good correlation. Also, the model that showed the best match with literature data for IFT is the density gradient theory (DGT). GERG 2008 and Peng Robinson performed very well for most of the density predictions.