Kerogen wettability can significantly affect the preferential movement of fluids in organic-rich mudrocks as kerogen constitutes a significant fraction of mudrock volume. In previous publications, the determination of the wettability of kerogen and organic-rich mudrocks was typically achieved using contact angle measurements through the sessile drop method, which might not be considered as a ground truth quantitative measure of wettability. This method also requires pellets of kerogen to create a surface for the contact angle to be measured. No standardized procedure exists for making pellets under stress and saturating fluid to replicate reservoir conditions. In this paper, we introduced a novel method for quantifying the wettability of kerogen, collected from different organic-rich mudrock formations (i.e., formations A, B, and C), as a function of thermal maturity using adsorption isotherms. We compared the results from the adsorption isotherm experiments with contact angle measurements. Results demonstrated a reduction in water adsorption capacity as thermal maturity increases. The cumulative amount of adsorbed water (within the range of 0 to 60% relative humidity) in the isolated kerogen sample relatively decreased by 75.3% and 91.8% for formations B and C, respectively, compared to formation A. Kerogen from formation A formed a 50° air/water contact angle compared to formation B, forming a 111° air/water contact angle, and formation C, forming a 109° air/water contact angle.
Dash et al. (Fri,) studied this question.