Locally Produced Sustainable and Resilient Surfactants for Enhanced Oil Recovery

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 24518, “Locally Produced Sustainable and Resilient Surfactants for Enhanced Oil Recovery,” by Syed Muhammad Shakil Hussain, SPE, Muhammad Shahzad Kamal, SPE, and Afeez Gbadamosi, King Fahd University of Petroleum and Minerals, et al. The paper has not been peer reviewed. Copyright 2024 International Petroleum Technology Conference. _ Chemical flooding is a major enhanced oil recovery (EOR) method for recovering residual oil within rock pores. Injected chemicals such as surfactant, however, must be soluble in low- and high-salinity brine, compatible with reservoir ions, and stable at elevated temperatures. The main objective of the study described in the complete paper is to explore the potential of locally produced surfactants for EOR in high-temperature and high-salinity reservoir environments. Design and synthesis of the new surfactants were achieved using green or no solvents. Importance of Chemical EOR Because only 15–20% of hydrocarbons can be extracted in the primary recovery stage, the waterflooding or gas-injection techniques usually are applied in the secondary recovery stage to extract 15–20% more oil and maintain the oilfield’s original pressure. After the application of these two techniques, however, a large amount of oil remains, the extraction of which requires the use of EOR, which can include thermal, gas, or chemical techniques. In thermal EOR, hot water or steamflooding are usually used to recover heavy oil. Currently, other thermal EOR methods such as in-situ combustion or steam-assisted gravity drainage receive considerable attention, especially in reservoirs containing heavy to extra-heavy crude oil. Gas methods normally are used in reservoirs featuring light and volatile oil. CO2 flooding is perhaps the most extensively applied gas EOR method for light oil extraction. Other gases such as nitrogen, hydrocarbon gas, acid gas, and air also are used for oil recovery. Chemical EOR involves the injection of chemicals including surfactants, polymers, alkali, and mixtures thereof. The polymer tends to increase the viscosity of the aqueous phase and lower the permeability of reservoir rocks. Surfactants minimize the interfacial tension (IFT), cause emulsification, and alter the wettability of the reservoir rocks. Alkali flooding generates in-situ surfactant by reacting with organic acid and ultimately reducing the IFT. Surfactants are organic compounds having both lipophilic and lipophobic parts. The lipophilic part is called a nonpolar compound and is soluble in the oil phase. The lipophobic part is termed a polar group and is soluble in the aqueous phase. Because of the availability of both lipophilic and lipophobic compounds in the same chemical structure, the surfactant stays on the interface ­of the water and oil phase and reduces the IFT. Based on the charge of the lipophobic head, the surfactants can be classified as nonionic, cationic, anionic, and zwitterionic (Fig. 1). Each class of surfactants possesses unique properties. For example, anionic surfactants are the material of choice in sandstone reservoirs because of their low adsorption into reservoir rocks. Similarly, the cationic surfactants exhibit minimum adsorption in carbonate rocks because of charge repulsion. Zwitterionic surfactants (ZS) show high heat-stability and salt-tolerance properties, and nonionic surfactants are known for their use as cosurfactants or solvents.