The Effect of Calcium and Magnesium Ions on a Crude Oil-Brine-Carbonate Rock System for Enhanced Oil Recovery by Sophorolipid Solution

Authors

  • Indah Widiyaningsih Institut Teknologi Bandung
  • Ivan Kurnia Institut Teknologi Bandung
  • Harry Budiharjo Sulistyarso Universitas Pembangunan Nasional Veteran Yogyakarta
  • Tutuka Ariadji Institut Teknologi Bandung
  • Taufan Marhaendrajana Institut Teknologi Bandung

DOI:

https://doi.org/10.17794/rgn.2026.2.6

Keywords:

Sophorolipids, divalent ions, carbonate, salinity conditions, enhanced oil recovery

Abstract

The interaction between crude oil, brine and carbonate rock systems is critical for implementing enhanced oil recovery (EOR). Surfactants, such as sophorolipid biosurfactants, incorporated in the displacing fluid are able to reduce the interfacial tension (IFT) and alter the wettability in these systems. However, the presence of divalent ions, especially calcium (Ca²⁺) and magnesium (Mg²⁺), complicates this interaction, affecting the effectiveness of EOR techniques. This study examines the influence of divalent ions on crude oil–brine–carbonate rock systems with the introduction of sophorolipids through experimental work. Interfacial tension and emulsion viscosity experiments evaluate the fluid-to-fluid interactions, while contact angle and static adsorption measurements characterize the interaction between the fluids and the rock, which are highly pertinent to the EOR mechanism. The Ca²⁺ and Mg²⁺ ions (2000 ppm) to sodium chloride (NaCl) solutions (10,000–15,000 ppm) with a 0.5 wt.% sophorolipid concentration at Critical Micelle Concentration (CMC) increased the water-wetness of the carbonate rock surface. In addition, while the ions reduced the interfacial tension (IFT), they did not significantly affect the viscosity of the oil–water emulsion of the NaCl solution with 0.5 wt.% sophorolipid. At low salinity (5000 ppm NaCl solution), these ions decreased the adsorption rate of the sophorolipid solutions on Indiana Limestone samples. The addition of these divalent ions to the injection solution significantly reduced the oil recovery efficiency, by about 28% for light oil and 32% for medium oil, during the biosurfactant flooding process.

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Published

2026-03-13

Issue

Vol. 41 No. 2 (2026): No. 78

Section

Petroleum Engineering and Energetics

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Copyright (c) 2026 Indah Widiyaningsih, Ivan Kurnia, Harry Budiharjo Sulistyarso, Tutuka Ariadji, Taufan Marhaendrajana

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How to Cite

Widiyaningsih, I., Kurnia, I., Sulistyarso, H. B. ., Ariadji, T., & Marhaendrajana, T. . (2026). The Effect of Calcium and Magnesium Ions on a Crude Oil-Brine-Carbonate Rock System for Enhanced Oil Recovery by Sophorolipid Solution. Rudarsko-geološko-Naftni Zbornik, 41(2), 85-95. https://doi.org/10.17794/rgn.2026.2.6