Experimental and simulation studies have thus far demonstrated that surfactant-based Enhanced Oil Recovery (EOR) is a feasible method to improve recoveries from initially oil-wet or mixed-wet Unconventional Oil Reservoirs (UORs). The summarized principle is that surfactant triggers spontaneous imbibition by either Interfacial Tension (IFT) reduction or wettability alteration. Several related studies have focused on the effectiveness of different surfactants or their combinations on the final oil recoveries from selected rock/fluid samples. However, the relative significance of each mechanism is not clear yet. In this work, by following both experimental and numerical simulation approach, we attempt to separately investigate the effect of IFT reduction and wettability alteration on the performance of surfactant based EOR in UORs. Further, the relative importance of each function is addressed while determining the dominating mechanism. Both experimental and simulation results showed that achieving a water-wet status is crucial for higher oil recoveries in shale and tight reservoirs. The effects of IFT reduction could be detrimental to the recovery once the wettability is altered to water-wet due to a lower capillary driven force. Therefore, to design a successful surfactant EOR case in UORs, a surfactant must have the capability of altering the wetness to a more water-wet status. Meanwhile, maintaining a relatively high IFT is also significant. Results from this paper will provide a general suggestion on surfactant selection to enhance oil recovery in UORs.
|Number of pages||14|
|Journal||Journal of the Taiwan Institute of Chemical Engineers|
|State||Published - Jan 2020|
- Hydraulic fracturing
- Petroleum engineering