Investigation of the Coupled Effect of IFT Reduction and Wettability Alteration for Oil Recovery: New Insights

Interfacial tension (IFT) reduction and wettability alteration (WA) are both important enhanced oil recovery (EOR) mechanisms. In oil-wet formations, IFT reduction reduces the magnitude of negative capillary pressure, releasing trapped oil. WA changes the negative capillary pressure to positive conditions, helping the entrance of the aqueous phase, and the displacement of the oil phase. In most cases, IFT reduction and WA happen at the same time. However, studies regarding the coupled effect provided different, sometimes conflicting observations. It requires further study and better understanding. In our study, oil-aged Indiana limestone samples were chosen to represent oil-wet carbonate rocks. Static contact angle and spinning drop method were adopted for wettability assessment and IFT measurement, respectively. Spontaneous imbibition was adopted to reflect on the oil recovery mechanisms in different cases. The impact of IFT reduction, WA, and permeability on the coupled effect was discussed by choosing four pairs of comparison tests. Results showed that when the coupled effect took place, both a higher IFT value and a stronger WA performance resulted in faster and higher oil recoveries. The importance of IFT reduction was enhanced in the higher-permeability condition, while the importance of WA was enhanced in the lower-permeability condition.

Automated summary

Interfacial tension (IFT) reduction and wettability alteration (WA) are important mechanisms for enhanced oil recovery (EOR). They work together to release trapped oil in oil-wet formations. However, studies have shown conflicting observations about their coupled effect, necessitating further research. This study used oil-aged Indiana limestone samples to represent oil-wet carbonate rocks and conducted tests to assess wettability and IFT. Results showed that higher IFT values and stronger WA performance led to faster and higher oil recoveries. The importance of IFT reduction was enhanced in higher permeability conditions, while the importance of WA was enhanced in lower permeability conditions.