With current techniques (hydraulic fracturing and horizontal drilling), the oil recovery factor from the tight formations, e.g. the Bakken Formation is only a few percent of the original oil in place (5% - 10% of OOIP). What can be done to the remaining oil? How to keep the wells flowing? Since 2009, our research group has focused on an idea of using surfactant spontaneous imbibition to enhance the oil recovery from the Bakken Formation, and this idea has been already put in use for a field application test. Our previous work showed that with optimized surfactant formulations, the oil recovery was up to 20 % incremental over brine imbibition alone. However, the slow oil extraction rate from the rock for field application is one of the issues identified in our previous laboratory research. To advance that work, this paper aimed an approach of speed up oil extraction rate by surfactant stimulation with a driving process which enhancing both of fluid penetrating rate and contact area between the fluid and rock matrix.
Semi-preserved Bakken cores with natural fractures were used for aqueous formulation imbibition combined with driving process at reservoir conditions. Also, the effect of initial water saturation, surfactant concentration, and surfactant solution salinity on this process were examined by paired cores.
Based on the laboratory studies, we conclude:
Surfactant flooding by driving process for tight rocks with low permeability (10−3 md) has good potential for oil recovery enhancement at various conditions.
Wettability alteration is also considered as a dominant mechanism for oil recovery enhancement during the driving process from tight rocks, as we observed by spontaneous imbibition process.
Initial water saturation, surfactant concentration, and salinity effect on oil recovery are dominated by permeability, heterogeneity or lithology differences.
Positive oil extraction rate was observed compared to the spontaneous imbibition.