Browsing by Author "Johnston, Keith P."

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    Evaluating the Transport Behavior of CO2ﾠFoam in the Presence of Crude Oil under High-Temperature and High-Salinity Conditions for Carbonate Reservoirs
    (American Chemical Society, 2019) Jian, Guoqing; Zhang, Leilei; Da, Chang; Puerto, Maura; Johnston, Keith P.; Biswal, Sibani L.; Hirasaki, George J.
    An amine-based surfactant, Duomeen TTM, was evaluated for foam flooding in carbonate rock at high temperature (120 °C), high salinity (22% total dissolved solids), and CO2–oil miscible conditions. We demonstrate enhanced oil recovery by utilizing CO2 foam under miscible conditions in the presence of crude oil. The foam was generated in situ by both co-injection and surfactant alternating gas injection modes. Foam transport and propagation were characterized as a function of the foam quality, shear rate, permeability, surfactant concentration, and method of injection. Finally, we utilize the experimental results to obtain the parameters for the STARS foam model by optimizing multiple variables related to the dry out, shear thinning, and surfactant concentration effects on foam transport. Enhanced oil recovery utilizing CO2 foam under miscible conditions in the presence of SMY crude oil was able to decrease oil saturation to 3.0%. It was also determined that significantly more injected pore volumes were required for the foam to reach the steady state in the presence of SMY crude oil. A foam simulation process in a heterogeneous reservoir is conducted applying the parameters obtained. The TTM CO2 foam generated significantly reduces the mobility of CO2 in the high permeability layers, which results in an improved swept volume in the low permeability zone that significantly improves oil recovery when epoil = 1 and fmoil = 0.5. Oil saturation parameters play important roles in the effectiveness of CO2 foam: large epoil and small fmoil will reduce the efficiency for TTM CO2 foam.
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    Switchable Diamine Surfactants for CO2 Mobility Control in Enhanced Oil Recovery and Sequestration
    (Elsevier, 2014) Elhag, Amro S.; Chen, Yunshen; Reddy, Prathima P.; Noguera, Jose A.; Ou, Anne Marie; Hirasaki, George J.; Nguyen, Quoc P.; Biswal, Sibani L.; Johnston, Keith P.
    The design of switchable amine surfactants for CO2 EOR in carbonate reservoirs at high temperatures is challenging because of the increase in the pH due to dissolution of calcium carbonate at acidic conditions. The increased pH hinders the protonation of the surfactant and its aqueous solubility. In this work, the addition of a second amine headgroup ensured that C16-18 N(EO) C3N(EO)2 is soluble in 22%TDS brine at neutral pH conditions. Also, captive bubble tensiometry measurements confirmed the activity of the surfactant at the C-W interface by large reduction in the interfacial tension coupled with high adsorption. Also, the surfactant generated viscous foam that can stabilize the displacement front in CO2 EOR processes and decrease the mobility of CO2 for enhanced CO2 sequestration.