Engineering Cost Analysis of Synthetic and Natural Surfactants for Surfactant Flooding

In this research, extract from Hibiscus calyx is introduced as a novel natural surfactant for sandstone reservoirs. Recent studies have reported the ability of some natural materials in recovering oil under near-surface conditions owing to their phytochemical composition. To ascertain their effectiveness in enhancing oil recovery at reservoir conditions, the oil displacement efficiency of Hibiscus calyx extract in the presence of divalent ions was determined with the aim of comparing its recoverability with that of commonly used, synthetic surfactant, sodium dodecyl sulphate (SDS) under similar conditions. An upscaling from laboratory to field scale and a comparative cost analysis was performed thereafter. To determine the efficiency of these surfactants in extracting residual oil at high temperature and pressure of 80°C and 8000 psi, respectively, phase behavior and sandstone core analyses were performed. Results indicated high compatibility for both surfactants in brine containing divalent ions with an improved solubility between the natural surfactant-hard brine system. The absence of Type III micro emulsion for both surfactants was indicative of a high interfacial tension. An additional oil recovery factor of 24% OOIP and 19% OOIP was obtained for Hibiscus calyx extract and SDS, respectively in the presence of divalent as opposed to 21% OOIP and 20% OOIP when flooding with soft brine. A chemical injection rate of roughly 5 barrels per day was achieved using an upscaling factor to field scale. An investigation of comparative costs revealed that the natural surfactant is more economical. This study supports the use of natural surfactants even in harsh oilfield conditions, eliminating processes of brine softening with economic advantages of reusing produced water to prepare chemical slugs for EOR treatments. However, chemical modification of these natural surfactants will further improve their performance.