Chapman, Walter G2019-05-172019-11-012019-052019-04-19May 2019Liu, Jinlu. "Thermodynamic Modeling of Fluid Distribution and Phase Behavior in Nanoporous Shale." (2019) Diss., Rice University. <a href="https://hdl.handle.net/1911/105948">https://hdl.handle.net/1911/105948</a>.https://hdl.handle.net/1911/105948Understanding fluid partitioning and phase behavior in unconventional shale is essential for reservoir characterization and production prediction. Unlike in conventional reservoirs where hydrocarbons are stored in pores of micrometers, a large fraction of the hydrocarbons in shale is trapped in nanosized pores and absorbed in organic matter kerogen, which makes the fluid distribution and phase behavior a complex problem. Despite the active research being done using experiments and molecular simulation to understand fluids in shale nanopore systems, a theoretical model that accurately predicts the thermodynamics of complex mixtures is of fundamental and practical value. This thesis aims to improve our understanding of thermodynamics of unconventional reservoir fluids using a theoretical modeling approach that is both verified versus molecular simulations of model systems and provide accurate predictions for real complex mixture systems. The goal is to develop a theory to describe the competitive adsorption of hydrocarbon mixtures in shale nanopores, phase transitions of fluids under nanopore confinement, characterization of different maturity kerogens, equilibrium partitioning of original fluid-in-place between different storage environments, and CO2 sorption selectivity with hydrocarbon mixtures under various conditions. In this work, a molecular density functional theory for associating chain molecules,i.e. interfacial Statistical Associating Fluid Theory, which accounts for molecular size and shape, van der Waals attraction, and hydrogen bonding interactions is used to study the microstructure, equilibrium partitioning, adsorption versus absorption, and phase behavior of fluid mixtures under nanopore confinement. Molecular dynamics and Monte Carlo simulation are used to validate the theoretical model. Key contributions of this thesis include: 1. Screening of methods to describe dispersion interactions in a DFT framework and systematically studying the vapor-liquid and fluid-solid interfaces of a model fluid with comparisons to molecular dynamics simulation; 2. Description of how the phase behavior for pure and mixed fluids changes due to nanopore confinement and the competitive adsorption of mixtures of alkanes molecules of different size and shape; 3. A new molecular modeling approach for nanoporous kerogen by creating a cross-linked network of asphaltene-like molecules, characterizing the solvent swelling response of kerogen and accounting for the dissolution of fluid molecules in kerogen pore walls; 4. Exploring the CO2 selective sorption behavior in a large parameter space including the effect of temperature, pressure, pore size, bulk fluid composition and pore wall properties, i.e. organic matter maturity, moisture level.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.thermodynamicsphase behaviorclassical density functional theoryshaleconfined fluidcompetitive adsorptionabsorptionkerogenThesis2019-05-17