Polymeric surfactants as alternative to improve waterflooding oil recovery efficiency

Abstract

Chemical formulations, including surfactants, polymers, alkalis, or their combinations, are widely used in different oil recovery processes to improve water injection performance. However, based on challenging profit margins in most mature waterfloods in Colombia and overseas, it is necessary to explore alternatives that could offer better performance and greater operational flexibility than the conventional technologies used for enhanced oil recovery (EOR) processes. Polymeric surfactants are compounds widely used in the manufacture of domestic and industrial cleaning, pharmaceutical, cosmetic, and food products. These compounds represent an interesting alternative as they can simultaneously increase the viscosity in water solution and reduce the interfacial tension (IFT) in the water/oil system, which would increase the efficiency of EOR processes. This article shows a methodological evaluation through laboratory studies, numerical reservoir simulation, and conceptual engineering design to apply polymeric surfactants (Block Copolymer Polymeric Surfactants or BCPS) as additives to improve efficiency in water injection processes. Block copolymer type products of ethylene oxide (EO) - propylene oxide (PO) - ethylene oxide (EO) in aqueous solution were studied to determine their rheological and surfactant behavior under the operating conditions of a Colombian field. In the conditions studied, these products allow to reduce the interfacial tension up to 2x10-1 mN/m values and also cause a shear-thinning rheological behavior following the power law at very low shear rates (0.1 s-1– 1 s-1), which corresponds to an increase up to four orders of magnitude in the capillary number (Nc). The IFT and the viscosity reached are maintained in wide ranges of salinity, BCPS concentration, and shear rates, making it a robust performance formulation.  In a model porous medium, BCPS tested have moderate adsorption, less than conventional surfactants but higher than HPAM polymers, in any way allowing a favorable wettability condition. Additionally, it was observed that they offer a resistance factor up to 16 times, causing greater displacement efficiency than water injection, allowing better sweeping in low permeability areas without injectivity restrictions. Numerical simulation shows that it is possible to reach incremental production up to 238,5 TBO by injecting a continuous slug of 0.15 pore volumes of BCPS and HPAM, each with 2,000 ppm concentration and a flow rate of 2,500 BPD. As BCPS  are simple handling and dilution products, these could be injected directly in water injection flow using a high precision dosing pump with high pressure and flow rate operational variables.