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Studying Surfactant Effects on Hydrate Crystallization at Oil-Water Interfaces Using a Low-Cost Integrated Modular Peltier Device
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Dynamic Asphaltene-Stearic Acid Competition at the Oil-Water Interface
Bastian Sauerer1, Mikhail Stukan1, Jan Buiting2
1Schlumberger Dhahran Carbonate Research Center , Dhahran Techno Valley - KFUPM , P.O. Box 39011, Dammam/Doha Camp , Dhahran 31942 , Saudi Arabia.
Langmuir : the ACS Journal of Surfaces and Colloids
|April 19, 2018
Summary
This study reveals how natural surfactants like stearic acid and asphaltenes compete at oil-water interfaces, impacting fluid flow in oil recovery. Stearic acid initially dominates, but asphaltenes adsorb slower and bind stronger, influencing interfacial tension dynamics.
Area of Science:
- Petroleum Engineering
- Surface Chemistry
- Colloid Science
Background:
- Interfacial tension (IFT) is critical for fluid flow in oil production and recovery.
- Natural surfactants in crude oil, such as carboxylic acids and asphaltenes, significantly influence IFT.
- Understanding the competitive adsorption of these surfactants is key to optimizing oil recovery processes.
Purpose of the Study:
- To investigate the interfacial activity and competitive adsorption of carboxylic acids (modeled by stearic acid) and asphaltenes at toluene/water interfaces.
- To analyze the dynamic interfacial tension (IFT) behavior of these components in a water-in-oil system.
- To determine the influence of surfactant concentrations on IFT and adsorption kinetics.
Main Methods:
- Dynamic IFT measurements using water-in-oil pendant drops.
- Utilized stearic acid (SA) as a model for surface-active carboxylic acids.
- Varied concentrations of SA (0.1 to 2 mg KOH/g oil) and asphaltenes (10 to 100 ppm) in model oil-water systems.
- Applied Langmuir isotherm analysis and dynamic surface adsorption models.
Main Results:
- Stearic acid (SA) initially dictates surface pressure, while asphaltenes exhibit slow adsorption over time.
- Asphaltenes show a higher final surface pressure than SA individually, but mixtures result in lower combined pressures.
- Langmuir analysis indicates asphaltenes bind 200-250 times stronger than SA, despite SA dominating at high concentrations.
- Apparent diffusivity of asphaltenes is low, suggesting adsorption is barrier-controlled, possibly due to a dense SA layer repelling asphaltenes.
Conclusions:
- The competitive adsorption between SA and asphaltenes significantly impacts interfacial tension dynamics in oil-water systems.
- Asphaltenes possess stronger binding affinity but slower adsorption kinetics compared to SA.
- The findings provide insights into surfactant behavior in crude oil, relevant for enhanced oil recovery strategies.
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