Novel Ester Based Surfactant to Enhance Oil Recovery in Tight Oil Reservoirs

Abstract Hydraulic fracturing is commonly applied to enhance oil recovery from tight reservoirs, such as shale formations. However, oil production remains primarily limited by several factors, including high capillary forces between the injected fluid and the rock matrix, the interfacial tension of the oil trapped in the rock pores and the fluid media, as well as the reservoir rock wettability. Stimulating oil recovery is achieved by altering the wettability of shale reservoirs using surfactants. The latter promotes the spontaneous imbibition of the fracturing fluids into the shale pores resulting in the mobilization of the oil phase. The challenge lies in developing surfactants that remain effective under specific temperature and salinity conditions, depending on the shale reservoir targeted. A novel ester-based surfactant (S1) was evaluated at 80°C, into a freshwater – Wolfcamp formation brine mixture. The surfactant exhibits an excellent compatibility (clear and homogeneous solution at 0.1 wt%) and stability (degradation < 10 % after 14 days) in brine media. The mixture prevents oil emulsification into the brine, reduces interfacial tensions (< 2 mN/m), altering Wolfcamp rock wettability from oil-wet to water-wet (contact angle ≤ 75°) and significantly improves oil recovery through spontaneous imbibition (oil recovery almost tripled compared to the blank after surfactant treatment). This surfactant outperforms an ethoxylated alcohol.