Thermodynamics and Structure of Confined Fluids

Prediction of the interaction of complex fluids (e.g. hydrogen-bonding fluids, hydrocarbons, proteins, and polymers) with adsorbing surfaces is essential for the control of many processes of current industrial and scientific interest. In our group, we develop tools in statistical thermodynamics, equations of state, molecular simulations, and density functional theory to predict the thermodynamic properties and structures of components confined near hydrophobic and hydrophilic surfaces. These tools can be useful for solving problems in adsorption, shale gas reservoirs, and other systems with confined fluids.

Thermodynamics and Kinetics of Gas Hydrates

Gas hydrates are structures formed by the cooperative hydrogen bonding of water molecules to form cages that encapsulate small molecules. In terms of methane reservoir, these crystalline structures (clathrates) are extremely important because they trap enormous amounts of natural gas on the ocean floor. The amount of carbon in gas hydrates is estimated to be more than twice the amount of carbon in all other fossil fuel deposits. Gas hydrates have also been proposed as potentially useful in novel gas separation processes and in transport of natural gas. In terms of problems, gas hydrates can form in pipelines and, by agglomeration mechanism, can plug subsea pipelines from offshore platforms causing economic loss and potentially unsafe conditions. For the flow assurance in oil and gas industry and in collaboration with Petrobras, our group studies thermodynamic and kinetic aspects related to hydrate formation and hydrate dissociation. Multiphase equilibria and kinetic studies provide thermodynamic, transport, and kinetic data for hydrate decomposition.

Asphaltene Precipitation and Deposition

The formation of asphaltene plugs in piping represent a significant problem in oil production and refining. Asphaltenes are a collection of polydisperse molecules consisting mostly of polynuclear aromatics with varying proportions of aliphatic and alicyclic and small amounts of heteroatoms (oxygen, sulfur, vanadium, etc.). Problems in recovery and refining operations associated with asphaltenes are due primarily to their molecular size and their self-aggregation. Hence, a better understanding of asphaltene phase behavior and deposition requires a better understanding of how molecular size and aggregation affect phase behavior and deposition. For the flow assurance in oil and gas industry our group, in collaboration with Petrobras, we study thermodynamics and kinetics aspect related to asphaltene precipitation, deposition and agglomeration using both CPA type of equation of state and molecular simulation.

Wax Precipitation

During production, petroleum is submitted to different temperature and pressure conditions, which can lead to precipitation of different solids, such as hydrates, asphaltenes and waxes. Among these flow assurance issues, wax deposition gains importance as the frontiers of oil exploration moves towards hostile environments, like deep water and the Artic. Wax deposition is hard to remediate, as it depends on mechanical removal of the deposits through pigging operations or chemical intervention like solvent soaking. As these different operations lead to production loss, the most cost effective strategy to deal with wax deposition is to avoid it during the design of production installations. Thus, the use of thermodynamic models for the calculation of solid-liquid equilibria (SLE) for mixtures of waxes and oil is very important to the petroleum industry. Therefore, our group studies, in collaboration with Petrobras, the thermodynamic aspects related to wax precipitation using different approaches available in the literature.

Structure-Property Relations of Complex Materials

Our research focuses on the study of materials and their applications by means of microscopic-scale modeling and computer simulation. In this way, we try to understand how the molecular constitution of a material determines its observed thermophysical properties. An exciting possibility is the study of yet undiscovered materials, entailing the prediction of their properties and the search for novel applications. This is the core of the discipline known as Material Design. The computational methods we employ in our investigations include advanced Monte Carlo (MC) methods such as Configurational-Bias MC, Multihistogram Reweighting, Multicanonical and other Non-Boltzmann Sampling methods, Transition-Matrix MC, and so on. Not only have we applied known methods, but also developed new ones and assembled many of them under a useful, generalized framework. For instance, we have being studying the equilibrium adsorption of polymers on solids with heterogeneous distributions of active sites, the effects of molecular topology on the scaling behavior and phase transitions of complex polymers, and the interaction between proteins and electrically charged surfaces of existing nanodevices.

Lattice Boltzmann Methods (LBM)

The research stream of Lattice Boltzmann Methods (LBM) is a relatively new candidate in the family of Computational Fluid Dynamics (CFD) research. Discretizing the Boltzmann’s Transport Equation with finite velocity sets and using the appropriate collision schemes can efficiently solve fluid flow and heat transfer problems. Fluid is considered as fictitious particle and probability distribution functions are characterising the evolution of each particle. Mass, momentum, and energy conservation rules are obliged on suitable lattice models. Navier-Stokes equations can easily be recovered when hydrodynamic limits of the lattice Boltzmann equations are considered. Complex boundary conditions can be incorporated naturally in the LBM thus making LBM the favourite choice for simulations of fluid flows and thermal transport in complex geometry e.g., porous media. It is proven that LBM provides accurate and stable solutions for complex geometry and turbulent flows. We, together with AGH University of science and technology, Poland, recently opened up this new research stream at ATOMS to look for real world solutions to address some genuine problems regarding fluid flow and heat transfer. Our current activities involves development of the theoretical foundations and the in-house software based on cascaded, cumulant and entropic isothermal/thermal LBMs i.e. the state-of-art computational tools, which will be applied to complex fluid flows through porous media that can be of great interest to petroleum industry applications e.g., multiphase flows, phase separation, phase transition, mixing of chemicals, reservoir simulations, etc.