(85b) Kinetics Study of Asphaltenes Adsorption Onto Hydrophilic Solid Surfaces

Large quantities of crude oil are left behind in some rock reservoirs after waterflooding in enhanced oil recovery processes. Asphaltenes, as the heaviest and most polar indigenous component of crude oils, is believed to have a profound influence on wettability changes of rock reservoir. The physics of how asphaltenes adsorb onto originally water-wet surfaces and alter their wettability is still poorly understood. Quantifying the effect of asphaltenes adsorption on wetting and the interaction between asphaltenes and rock surfaces remains a big challenge.

This study investigates the controlling asphaltenes adsorption mechanisms onto hydrophilic surfaces using the experimental results from quartz crystal microbalance with dissipation (QCM- D), and examines the wetting property changes caused by the adsorbed asphaltenes layer. Within the most common types of hydrophilic rock surfaces, calcium carbonate and silicon dioxide are tested.

The maximum surface coverages obtained from QCM-D experiment at different concentrations indicate a two-step process, which can be successfully interpreted with a multilayer adsorption model, i.e. the so-called Brunauer, Emmet & Teller (BET) model. Both the equation of state and adsorption isotherm for multilayer adsorption can be derived from statistical mechanics theories. Using an optimization method that was developed, it was found that the optimized BET adsorption isotherm curve not only fits the experimental data well at low concentrations like the Langmuir adsorption isotherm does, but also approaches to the experimental data at high coverage where the Langmuir isotherm diverges. The water wettability of the crystal sensors are examined before and after asphaltenes adsorption to investigate the effect of the adsorbed asphaltenes layer, which is found to increase the water to crystal contact angle.