Reservoir wettability has direct impact on the relative movement of reservoir fluids and oil displacement efficiency by EOR techniques. The industry standard wettability laboratory techniques of Amott, USBM and modified Amott/USBM are very time demanding due to its complex experimental setup and procedure.
This paper describes the theory and experimental setup and procedure of a new wettability laboratory technique. Rise In Core, RIC, technique is based on a modified version of the Washburn Equation. The modified equation could be solved for the wettability contact angle by only substituting the slope of a fitted straight line of the square line of the square of core sample mass change with time, resulting from either water imbibition into oil saturated core sample, and/or vice versa. A constant of the equation, that is characteristic of the rock type, needs to be determined prior, however, by conducting an imbibition experiment of a reference liquid into air saturated twin core sample. The reference liquid completely wets the core sample with zero contact-angle.
The new technique was applied to measure the wettability of Berea sandstone core samples. The wettability of natural outcrop cores was found to be weakly water wet. Experiments conducted on neighboring samples, produced similar wettability result, indicating good repeatability. The applicability of the RIC in other wettability regions was also tested, resulting in repeated strong wetness for standards that were artificially treated to be either strongly water wet, and oil wet. The technique was also compared to the existing industry technique and proved to provide equivalent and more consistent wettability measurements for more than ten twins of carbonate core samples.
RIC technique is theoretically sound, and requires simple experimental setup and procedure. Moreover, it determines wettability in terms of contact angles rather than wettability index. It is more consistent and applicable to all wettability regions.