Abstract
Wettability of two types of sandstone cores, Berea (permeability of the order of 600 md), and a reservoir rock (permeability of 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. A new chemical is used which alters 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, and (3) wettability alteration does not have a measurable effect on the absolute permeability of the rock when a suitable chemical is used. We also found out that the reservoir rock, unlike Berea is not strongly water-wet in the gas-water-rock system.
