Introducing a New, Low-Cost Biosurfactant for EOR Applications: A Mechanistic Study

Abstract

Biosurfactants attract attentions in recent years due to their low-cost and environmental friendly nature. The potential of biosurfactants in improve oil recovery has been addressed previously, yet there are concerns about their performance at high salinity/high temperature conditions. This paper introduces a new biosurfactant named SUTBS which is extracted from the leaves of one of Iranian plants growing in the southern part of the country. It aims to study the EOR potential of SUTBS via IFT reduction and wettability alteration in sandstone core samples containing asphaltenic crude oil. Results showed that SUTBS solution at critical micelle concentration (CMC) and ten-time dilution of sea water (0.1SW) decreased IFT of oil/water from 36 to 5.5 mN/m. Such IFT reduction is comparable with the SDS solution leading to an IFT of 2.16 mN/m at the similar conditions. Dynamic contact angle were also conducted on a series of oil-wet sandstone thin sections at 80˚C at different salinity. Results showed that SUTBS solution has a good potential to alter rock wettability from oil wet to more water wetness such that at salinity of 0.1SW, SUTBS solution caused a significant reduction in contact angle from 155 (initial value) to 60 degrees. Moreover, SUTBS exhibited a good thermal stability as compared to SDS after 480 hours aging at 80oC: the surface tension of SUTBS increased only from 50 to 58 mN/m, while SDS provided a high surface tension of 70 mN/m indicating a significant thermal degradation. Also, to quantify the oil recovery performance of SUTBS solution, a series of spontaneous imbibition tests were conducted using oil-wet sandstone core plugs at 80˚C. The ultimate oil recovery of the SUTBS solution was 14.02% of the OOIP as compared to 8.5% and 8% for 0.1SW and SDS solutions, respectively. It was found that the incremental oil recovery caused by SUTBS was mainly due to wettability alteration to more water wetness coupled by a modest IFT reduction. This was in line with the SEM analysis indicating a rather homogenous adsorption of SUTBS on the grain surface. Results of this study support the potential of the SUTBS biosurfactant as a low-cost chemical agent for IOR/EOR applications.