Zwitterionic Surfactants Show Promise for Enhanced Oil Recovery in Carbonate Reservoirs

Strategic Insights -

Research published in the journal Scientific Reports has provided new insights into the adsorption behavior of zwitterionic surfactants on calcite surfaces, which could lead to more effective enhanced oil recovery (EOR) strategies in carbonate reservoirs. The study, conducted by researchers at the Petroleum University of Technology in Ahwaz, Iran, found that the zwitterionic surfactant 3-(N, N-Dimethylmyristylammonio) propane sulfonate (ZW4) exhibited unique physicochemical properties that enhanced oil recovery. The researchers investigated the effects of key variables such as salinity, temperature, pH, and surfactant concentration on the adsorption behavior of ZW4 on calcite surfaces.

Key Takeaways:

  • The zwitterionic surfactant ZW4 exhibited a spontaneous, entropy-driven micellization process with enthalpy-entropy compensation, ensuring thermodynamic favorability across a wide temperature range.
  • Temperature influenced the critical micelle concentration (CMC) non-linearly, decreasing from 10 °C to 30 °C due to reduced hydrophilicity but increasing above 30 °C as hydrophobic interactions disrupted micelle formation.
  • The roles of different electrolytes (MgSO and Na SO ) were compared, showing that Mg² ions significantly reduced the CMC more effectively than Na ions due to stronger electrostatic double-layer compression and higher ion charge density.
  • Surface charge modifications of calcite by ZW4 were quantified using zeta potential measurements, which identified a point of zero charge near pH 6.7 and demonstrated increased surface negativity with rising surfactant concentration up to 2500 ppm.
  • Higher pH levels inhibited adsorption due to electrostatic repulsion between ZW4's sulfonate group and the negatively charged calcite surface.
  • Increasing salinity enhanced adsorption, transitioning from a 'V-shaped' orientation (low packing density) to a more vertical 'I-shaped' configuration (high packing density), with MgSO demonstrating a greater effect than Na SO .

Statistics:

  • Critical micelle concentration (CMC) of ZW4 decreased from 2000 ppm to 1300 ppm at 0.01 M MgSO
  • CMC of ZW4 decreased from 2000 ppm to 1700 ppm at 0.01 M Na SO
  • Sips model provided the best fit for adsorption equilibrium data, highlighting its flexibility in describing complex adsorption phenomena.

Sources:

  • Experimental and theoretical investigation of zwitterionic surfactant adsorption on calcite for enhanced oil recovery. Scientific Reports, 2025;15(1):22730.
  • Petroleum University of Technology, Ahwaz, Iran.