In-situ observation of reactive wettability alteration using algorithm-improved confocal Raman microscopy

Area of Science:

• Surface science
• Colloid and interface science
• Materials chemistry

Background:

• Wettability of complex fluids is governed by interfacial solute adsorption.
• Controlling interfacial processes through phase composition changes allows for smart responsive systems.
• Understanding these dynamics is crucial for applications like enhanced oil recovery.

Purpose of the Study:

• To demonstrate 3D Confocal Raman Microscopy (CRM) for mechanistic insights into interfacial processes.
• To simultaneously monitor contact angle variations and chemical species redistribution.
• To investigate the role of brine salinity on surfactant layer stability and wettability.

Main Methods:

• Studied picolitre oil drops on mineral substrates (mica, silica) coated with deuterated-stearic acid.
• Varied ambient brine salinity to observe surfactant layer response.
• Utilized 3D CRM in a faster 'ai' (algorithm-improved) mode for imaging.

Main Results:

• Surfactant layer stability was salinity-dependent: stable at high salinities (oil wetting), decomposed at low salinities (water wetting).
• Reduced salinity caused surfactant to partly dissolve in oil and partly precipitate at the oil-water interface.
• Mica and silica surfaces showed increased water wettability upon decreasing brine salinity.

Conclusions:

• 3D CRM effectively reveals mechanistic details of salinity-dependent interfacial processes.
• The findings provide insights into reactive wetting phenomena.
• Algorithm-improved 3D CRM is a promising tool for studying complex interfacial systems.