Figure 4

In-situ changes to the oil-brine-calcite contact angles at 25 °C in a single pore during core flooding (a) after displacement of petroleum by TW1 (with a contact angle of 145°), (b) after the TW1 brine is displaced by TW2 reducing the contact angle to 125° while the three-phase contact point is unchanged. (c) Re-injection of petroleum to move the three-phase contact point and leads to a decrease in the contact angle to 81°. (Here, water and oil are shown as blue and red regions, respectively, while the carbonate matrix is shown in grey).