oa Enhanced oil recovery through wettability alteration of heterogeneous carbonate rocks

Wettability of a carbonate reservoir is one of the key points concerning oil recovery. Most carbonate reservoirs tend to be oil-wet. An oil-wet wettability generates significant problems in oil recovery since the formation has a stronger ability to keep oil attached in its pores, and it also decreases the efficiency of water flooding leading to faster water breakthrough. Wettability alteration in oil wet carbonate reservoirs have demonstrated to be a successful method in enhancing oil recovery through chemical water flooding of such formations. Wettability, IFT (Interfacial tension), and temperature, are all parameters that have a significant effect on the recovery process. Different processes and chemicals have been tested to study the alteration of wettability through contact angle and its effect on oil recovery. It is essential to understand the correlation between the IFT value of the brine injected with the degree of wettability alteration, in order to assemble an optimized brine solution for enhancing oil recovery by finding an optimized contact angle and an IFT value. In this paper, carbonate outcrop samples from Jabal Fuwayrit in Qatar (considered to be a similar and representative to the North Field formation) were used to make a comparative study of wettability alteration effect followed by recovery. Spontaneous imbibition and flooding of brine with different chemical composition were employed. We also studied the effect of non-ionic and cationic surfactants in sea water from Qatar to further enhance oil recovery. Comparison of the results obtained leads to a better understanding of wettability alteration and the appropriate selection of injection brine for optimal recovery. The significance of such study can be easily demonstrated. Wettability understanding and alteration at will is of a great importance and can be expanded in all type of reservoirs, giving a cost-effective, fast and functional process.