Surfactant selection and formulation screening for low interfacial tension foam flooding in conditions of high-temperature and high-salinity

UDK: 661.185.1.004.14

DOI: 10.24887/0028-2448-2026-2-17-22

Key words: oil displacement efficiency, chemical enhanced oil recovery (EOR), surfactant, foam, laboratory screening

Authors: A.I. Kolosova (ZN STC LLC, RF, Moscow); V.E. Vakhmistrov (ZN STC LLC, RF, Moscow); E.S. Ivanova (ZN STC LLC, RF, Moscow); A.S. Levchenko (ZN STC LLC, RF, Moscow); D.S. Kruglov (ZN STC LLC, RF, Moscow); D.R. Altynbaeva (ZN STC LLC, RF, Moscow); I.V. Tkachev (ZN STC LLC, RF, Moscow); A.V. Fomkin (Zarubezhneft JSC, RF, Moscow)

The article is devoted to the technology of nitrogen-based foam injection with reduced interfacial tension being a promising combined method for enhanced oil recovery (EOR). The efficient development of carbonate reservoirs, characterized by an extensive fracture network, high temperatures (70 °C) and high salinity (209 g/l), typical for the Central-Khoreiver Uplift fields, is associated with challenges of uneven sweep and a rapid increase in water cut. Under such conditions, the implementation of traditional EOR methods is limited. The presented technology contributes to an increase in oil displacement efficiency by reducing residual oil saturation and to an improvement in sweep efficiency through gas mobility control and lower relative permeability of the injected agents. Selecting a stable and effective surfactant composition for such challenging reservoir conditions constitutes a non-trivial task. This work describes a systematic approach to optimization of the surfactant formulation that combines the properties of an effective foaming agent and an oil-displacing agent. The approach encompasses surfactant solubility evaluation, detailed investigation of foam generation capacity and stability in bulk and during filtration experiments, optimization of the blend composition, and foam injection parameters. Under the conditions considered, it was concluded that the effectiveness of the technology is predominantly attributed to the stability of the foam system rather than the reduction of interfacial tension. The developed composition achieved a 17 % additional oil recovery factor in filtration experiments by demonstrating high oil displacement efficiency.

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