Mechanisms and experimental research of ion-matched waterflooding to enhance oil recovery in carbonate reservoirs: A case of Cretaceous limestone reservoirs in Halfaya Oilfield, Middle East

PENG Yingfeng,LI Yiqiang,ZHU Guangya,PAN Deng,XU Shanzhi,WANG Xiuyu

Table 2 Formula of activity coefficient and application range.

Name Formula Range of application Guntelberg appro- ximation formula $\lg {{\gamma }_{i}}=-A{{z}_{i}}^{2}\frac{{{I}_{\text{S}}}^{1/2}}{1+{{I}_{\text{S}}}^{1/2}}$ IS≤0.1 mol/L Davies formula $\lg {{\gamma }_{i}}=-A{{z}_{i}}^{2}\left( \frac{{{I}_{\text{S}}}^{1/2}}{1+{{I}_{\text{S}}}^{1/2}}-\text{0}\text{.3}{{I}_{\text{S}}} \right)$ 0.1 mol/L<IS≤ 0.5 mol/L.