Iranian Journal of Oil and Gas Science and Technology

Abstract Oil recovery from oil-wet carbonate rock is a significant challenge in the oil industry. The present study investigates the influence of the natural surfactant Hawthorn leaves extract (HLE) on oil recovery from carbonate rock. Two chemical surfactants, sodium dodecyl sulfate (SDS) and dodecyl tri methyl ammonium bromide (DTAB), were used to validate and compare oil recovery with the new natural surfactant HLE. A wettability alteration test using the contact angle method, an interfacial test (IFT) using pendant drop, and core flooding were employed to investigate the behavior of the surfactants on oil recovery. The experimental results show that the critical micellar concentration (CMC) point of different concentrations of HLE, SDS, and DTAB solution occurs at 3.25, 3.00, and 4.06 wt %, respectively. In wettability alteration, the natural surfactant HLE is more effective than other chemical surfactants (SDS and DTAB) at the CMC point. As observed, the contact angle of the carbonate pellet and the HLE at the CMC point is 86°, and this angle for SDS and DTAB is 112° and 92°, respectively. The core flooding results show that the oil recovery factor improves from 37% with water flooding to 47.6% with SDS, 56.2% with DTAB, and 54.7% with HLE. The results prove that this new natural surfactant (HLE) can be used as a novel surfactant for the chemically enhanced oil recovery process in carbonate oil reservoirs. HLE has beneficial effects in oil recovery because of its environment friendly compared to SDS and DTAB.

Abstract The chemical surfactant flooding can mobilize the trapped oil by lowering the interfacial tension between oil and brine and in some cases altering the reservoir rock wettability. In this work, the effect of surfactants on oil/brine interfacial tension was experimentally investigated. First, the effect of surfactants concentration was surveyed. Afterwards, the effect of salinity on surfactant behavior was studied. The experiments were carried out at ambient and reservoir temperatures (all at reservoir pressure) to clarify that we cannot generalize the ambient experimental results to reservoir ones and the experiments must be done in reservoir conditions to attain more certainty. Sodium dodecyl sulfonate, cetyl trimethyl ammonium bromide and Triton X-100 were used as the surfactants. The oil and brine samples of the Iranian Asmari reservoir were used. Pendant drop method was used to measure oil/brine interfacial tension. Based on the results, it is concluded that the anionic surfactant (SDS) has a better performance at reservoir and ambient temperatures. The superiority of SDS is more emphatic at reservoir temperature than ambient temperature. At reservoir temperature, the SDS solution lowers the interfacial tension significantly (0.4 mN/m) even when a very low concentration of SDS (0.04 wt.%) is added to brine.