Summary
Wettability of two types of sandstone cores, Berea (permeability on the order of 600 md), and a reservoir rock (permeability on the order of 10 md), is altered from liquid-wetting to intermediate gas-wetting at a high temperature of 140°C. Previous work on wettability alteration to intermediate gas-wetting has been limited to 90°C. In this work, chemicals previously used at 90°C for wettability alteration are found to be ineffective at 140°C. New chemicals are used that alter wettability at high temperatures. The results show that: (1) wettability could be permanently altered from liquid-wetting to intermediate gas-wetting at high reservoir temperatures, (2) wettability alteration has a substantial effect on increasing liquid mobility at reservoir conditions, (3) wettability alteration results in improved gas productivity, and (4) wettability alteration does not have a measurable effect on the absolute permeability of the rock for some chemicals. We also find the reservoir rock, unlike Berea, is not strongly water-wet in the gas/water/ rock system.
