LAUSR

The wettability of shale oil reservoirs is an important petrophysical property to determine subsurface multiphase flow and residual oil saturation. While a few studies have been undertaken to understand the effect of brine chemistry on shale wettability, the existing research fails to take into account the oil composition in particular the functional groups thereby presenting substantial impediments to predicting shale oil wettability. We thus hypothesized that oil composition particularly the acidic functional group likely affects the in situ physiochemical process and oil–brine–shale wettability. To test the hypothesis, we conducted contact angle measurements using two oils with almost the same base number (1.2 KOH mg/g), but a different acid number (oil A = 1.7 mg KOH/g, and oil B = 3.98 mg KOH/g), in the presence of NaCl and CaCl2 with salinity from 0.01 to 1.0 mol/L at ambient condition. Furthermore, surface complexation modeling was conducted to interpret the contact angle measurements by calculatin...