Smart Water flooding of carbonate reservoirs: Core flooding tests using a new approach for designing Smart Water

In recent years "Smart Water flooding" or "Low Salinity (LS)" water flooding has emerged in the petroleum industry as a new method to improve oil recovery from conventional reservoir by 8 to 17% incremental oil recovery after the conventional seawater flooding. Even though "Low Salinity" water flooding has been found to be successful to some extent in some sandstone and carbonate oil reservoirs, the mechanisms leading to the incremental oil recovery by this process from these sandstone and carbonate reservoirs is not fully understood and still debated. Furthermore, most of the presented results were based on either straight sequential dilution of the seawater or increasing/decreasing the concentrations of Ca²⁺, Mg²⁺, and SO₄^2-. In this study, we present a new approach using the method of analysis of variance, ANOVA, to understand first the interactions of Ca²⁺, Mg²⁺, SO₄^2-, and Cl present in the Arabian Gulf seawater with Middle East carbonate reservoir rock in the presence of crude oil. The objective of this study is to test the effectiveness of the smart water designed using the method of analysis of variance, ANOVA and carbonate reservoir rock samples in recovering additional oil at the tertiary flooding mode. Core flooding tests were conducted using carbonate rock samples from the Middle East at reservoir condition to test the effectiveness of the designed smart waters in recovering additional oil after seawater flooding. Among the smart waters, we also used 10 times dilution Arabian Gulf seawater. Different injection sequences with different smart waters were investigated to test the effectiveness of the designed smart waters along with the 10 times dilution seawater at the tertiary mode in recovering incremental oil. The cumulative incremental oil recovery obtained from the coreflooding tests conducted in this study is in the rage of 10.7 to 23.35 % OOIP. Furthermore, the results of these tests show that the incremental oil recovery obtained by smart water is dependent on the sequence of injection of these different waters and not necessarily due to the sequential dilution of seawater.