Wettability in chalk, effect of temperature on the adsorption of the acidic components in crude oil

Abstract

The initial wetting of carbonate reservoirs will affect the overall oil recovery and the potential of EOR methods linked to wettability alteration by the generation of positive capillary pressure. Polar acids in oil also effect the wettability alteration in carbonates. Adsorption of polar acidic materials from oil onto a chalk surface at different tem- peratures is the main essence of this work. The role of only temperature, beside acid number, to wettability alteration of chalk is also presented. Crude oil with an AN of 0.35 mgKOH/g is flooded into three cores with 10 % initial water saturation at three different temperatures (50, 90 and 130 0C). Acid number of the effluent is observed to decrease to a low value for a short time, then increase slowly to the original acid number. The adsorption of acid is more or less equal at 90 and 500C and slightly lower at 130 0C. Wettability of the flooded cores were evaluated by spontaneous imbibition and ion-chromatography analysis, and the results show that the cores were more oil-wet. Our experimental results minimizes the effect of temperature on wettability alteration in chalk. Theoretical understanding of enhanced oil recovery, carbonates and wettability is introduced in chapter 1, and discussed more in chapter 2. In chapter 3 different materials and methods for the experiments are explained. The results of the experi- ments are presented in chapter 4 and discussed in chapter 5. Finally, the conclusion of the experiments is presented in chapter 6.