Green enhanced oil recovery (GEOR)

Abstract

Green enhanced oil recovery (GEOR) is a chemical enhanced oil recovery (EOR) method involving the injection of specific green chemicals (surfactants/alcohols/polymers) that effectively displace oil because of their phase-behaviour properties, which decrease the interfacial tension (IFT) between the displacing liquid and the oil. In this process, the primary displacing liquid slug is a complex chemical system called a micellar solution, containing green surfactants, co-surfactants, oil, electrolytes and water. The surfactant slug is relatively small, typically 10% pore volume (PV). It may be followed by a mobility buffer such as polymer. The total volume of the polymer solution is typically ~1 PV. This study was conducted to examine the effectiveness of the combination of microbial by-products Bacillus subtilise strain JF-2 bio-surfactant and alcohol in recovering residual oil. It also considered whether bio-surfactant capability could be improved by blending it with non-ionic green surfactant. The study consisted of a phase behaviour study, IFT measurement and core-flooding experiments. In the phase behaviour study, it was found that 0.5% alkyl polyglycosides (APG) and 0.5–1.00% of butanol at 2% NaCl gave stable middle phase micro-emulsion. Non-ionic (APG 264) and anionic (bio-surfactant) mixtures are able to form stable middle phase micro-emulsion. Based on IFT reduction, two low concentrations (40 and 60 mg/l) of JF-2 bio-surfactant were identified where IFT values were low. The bio-surfactant and butanol formulation produced a total ~39.3% of oil initially in place (OIIP).