Wettability Alteration of Calcite by Nonionic Surfactants

Area of Science:

• Surface Chemistry
• Petroleum Engineering
• Materials Science

Background:

• Wettability alteration is crucial for enhanced oil recovery.
• Surfactant selection is complex, influenced by mineralogy, temperature, salinity, and oil properties.
• Understanding surfactant-rock-oil interactions is key to optimizing wettability.

Purpose of the Study:

• To experimentally investigate the effectiveness of nonionic surfactants for wettability alteration.
• To analyze the impact of surfactant molecular structure (hydrophobic groups, hydrophilic ethylene oxide chain length) on wettability.
• To elucidate the mechanisms of surfactant action in altering rock wettability.

Main Methods:

• Experimental study of nonionic surfactants with varying hydrophobic and hydrophilic components.
• Measurement of contact angle evolution of oil drops on oil-wet surfaces at different temperatures.
• Qualitative experiments on surfactant-induced dewetting of oil films.

Main Results:

• Surfactant effectiveness is influenced by molecular structure and environmental conditions.
• Shorter hydrophilic units and increased temperatures enhance wettability alteration.
• Experimental data can be summarized by thermodynamic and kinetic parameters.
• Proposed coating and sweeping mechanisms explain surfactant action.

Conclusions:

• Nonionic surfactants can effectively alter rock wettability by interacting with water-rock and oil-rock interfaces.
• Surfactant design, particularly hydrophilic chain length, and operational temperature are critical factors for efficient wettability modification.
• The proposed model provides insights into the dynamic mechanisms of surfactant-driven wettability alteration.