Synthesis of alkyl phosphates and investigation of their surface-active properties in an alkaline surfactant polymer system for enhanced oil recovery

Chemical flooding is a technique of enhanced oil recovery (CEOR) using formulations containing alkaline components, surfactants and polymers (ASP technology). The development and synthesis of novel highly efficient industrial surfactants take this technology to a new level, allowing the chemical composition of reagents to be tailored to the reservoir conditions of fields in Western Siberia. Alkyl phosphates with various structures are one type of the surfactants that can be used in ASP technology. This work aimed to synthesize and examine the properties of commercial (semi-industrial) alkyl phosphates and alkoxylated alkyl phosphates of mixed composition that meet the requirements of an efficient surfactant component of an ASP-flooding formulation. The synthesis was carried out using industrial fatty alcohols by the phosphating reaction with phosphorus pentoxide. A mixture of monoand disubstituted phosphoric acid esters of a defined ratio can be obtained by target tailoring of the feedstock properties (structural changes, molecular weight distribution in alcohols) and the synthesis conditions. This mixture, requiring no addition of cosurfactants, is an effective multi-component surfactant for an ASP-system. In this work, three effective alkyl phosphates and alkoxylated alkyl phosphates blends were synthesized. The composition of the synthesized phosphoric esters was evaluated by high-resolution mass spectrometry (HRMS), infrared (IR) spectroscopy and potentiometric titration. At reservoir temperature, the obtained samples provided sufficient solubility in an oil-displacing aqueous solution in the technologically required salinity interval, compatibility with other components, low interfacial tension (IFT) values at the interface between ASP solution and oil from Western Siberia fields, and the formation of the sufficient volume of the emulsion phase in a phase experiment. The primary laboratory research data proved the efficiency of the synthesized surfactants in ASP technology in the fields of Western Siberia.