Molecular modelling and simulation of fluids, surfaces and their interactions in reservoir settings
File(s)
Author(s)
Zheng, Lingru
Type
Thesis
Abstract
Fluid interactions within porous media are of vital importance in petrol-chemical processes. Problems encountered macroscopically, e.g., contact line tracking, confined fluid, and wetting alternation motivates investigations at a smaller scale. Nanoscale molecular modeling techniques such as molecular dynamics (MD) are a suitable tool; recent development of the Statistical Associating Fluid Theory (SAFT) force fields used in MD makes coarse-grained (CG) representation a viable option to describe large and complex systems. The work starts by assessing the predictive and correlative capability of the SAFT CG force field as applied to pure components and mixtures of CO2 with n-decane and n-hexadecane and 2,2,4-trimethylhexane, a lubricant. By using the principle of corresponding states to obtain the SAFT force field parameters for chemicals of limited experimental measurements and are selected as representative components based on 2D gas chromatography data of three different stock tank crude oils, the density, viscosity and surface tension as functions of temperature are simulated and compared to experimental data, observing good overall agreement. This work also provides a strategy for converting the topography of a natural rock surface measured by atomic force microscopy (AFM) into a series of synthetic surfaces of nanometer-scale amplitudes and wavelengths. The surface chemistry is characterised as calcite by fitting the water-surface interactions to atomistic water density profiles and the oil-surface interactions to experimental contact angle measurements on a smoothly cleaved calcite. The wettability can be examined systematically via the apparent contact angles and curvatures of the droplet at various surface roughness. The dependence of the contact angle with roughness is found to be in qualitative agreement with macroscopic Wenzel and Cassie-Baxter relations. Overall, the flow of this work provides a plausible strategy of assessing nanoscale wetting in reservoir settings; future information on surface adsorption of specific components would facilitate more quantitative evaluations.
Version
Open Access
Date Issued
2020-05
Date Awarded
2020-12
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Muller, Erich
Trusler, John
Bresme, Fernando
Sponsor
Shell International Ltd
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)