The recovery factor of waterflood operations is constrained by formation geology and pore trapping mechanisms. This is particularly important for unconventional reservoirs such as shale oil with ultra-low permeability and porosity. Surfactant flooding can be used in these reservoirs to reduce oil trapping and increase sweep efficiency due to a reduction in interfacial tension and wettability alteration. On the other hand, a major concern with surfactant flooding is the adsorption of surface-active agents on the reservoir rock leading to loss of chemicals. In this study, the behavior of a non-ionic surfactant was investigated in order to enhance oil recovery from a producing shale oil reservoir using reservoir crude oil and rock samples. In the preliminary experiments, phase behavior tests were performed in the presence of reservoir shale rock to monitor micro-emulsion stability. The critical micelle concentration (CMC) of this surfactant was determined by both surface tension measurements and spectroscopy. Dynamic interfacial tensions (IFT) and contact angles (CA) of the non-ionic surfactant in brine/oil/shale systems were then measured by the rising/captive bubble technique using a state-of-the-art IFT/CA apparatus at reservoir conditions (6840 psi and 116?) for different surfactant concentrations (0.005 to 0.5 wt%). The amount of surfactant adsorption from surfactant-brine solutions onto crushed shale rocks were measured using UV-Vis spectroscopy at different surfactant concentrations. The data could be fit to a Langmuir type adsorption isotherm. The adsorption parameters were determined and results were compared and discussed. This work shows that the non-ionic surfactant is able to reduce the reservoir oil-brine IFT from its original value (27 mN/m) down to 15 mN/m while exhibiting minimal adsorption on the shale surface.

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