(18g) Thermodynamic Properties and Transport of Fluids in Presence of Cross-Linked Polymers and Confinement: Modeling, Simulations and Experiments

Teaching Interests:  Thermodynamics, Fluid Dynamics, Reservoir Characterization and Engineering, Molecular Simulations

Thermodynamic properties of fluids change in presence of cross linked polymers and in confined spaces. Correct prediction of deviation in these properties is valuable to many industries including the oil and gas industry. In last decade, the shale play resources have played a key role in increasing oil production in the United States. However, the average hydrocarbon recovery factors from many of these formations are usually less than 10%. There is a considerable interest in understanding the production of liquids from shale rock plays such as the Eagle Ford Play in Texas. The sizes of pores in shales holding the oil are believed to be of the order of nano meters. The fluids present in such small nano pores have different properties compared to properties measured in bulk. Fluid saturation pressures at given temperatures â?? bubble points for oils and dew points for condensates in the nano pores are affected by the influence of pore walls in the vicinity of the fluid molecules. Moreover, kerogen, a cross linked polymer like organic matter present in the shale rocks, absorbs a part of oil present in these rocks. Such interactions with kerogen changes the pressure-volume-temperature (PVT) properties of oil in association with kerogen. Approach to bubble point or dew point influences the proportion of liquid or gas produced from a given well, and thus impacts the economic viability. Hence an accurate measure of saturation pressures is important. The traditional equation of state fails to add the complexity of pore wall interaction in calculating thermodynamics properties of confined fluids. It is important to understand how liquids are produced from ultra-low permeability rocks so that production rates and recovery can be optimized. Apart from the fluid properties, the understanding of transport of fluids through the organic and inorganic matrix in rocks is valuable for economic exploitation of oil and gas from shales.

Current research includes study of thermodynamics of solvent (oil) â?? kerogen (polymer) interaction, Molecular Dynamics simulations for assessment of hydrocarbon storage in kerogen, Monte Carlo simulations in Gibbs and Grand Canonical ensemble for understanding of flow and phase behavior of confined fluids, experiments conducted on isolated kerogen using Differential Scanning Calorimetry (DSC) to understand swelling of kerogen and associated affect on pressure-volume-properties of oil and fabrication of nano fluidics channels for the study of fluid flow in nano channels of tight rocks. In this paper we describe thermodynamic models, molecular simulations and experiments using DSC and in well characterized fabricated nano channels to understand effect of presence of cross linked polymer and confinement on flow and phase behavior of fluids. The results from Molecular Dynamics Simulations show that the kerogen interacts with hydrocarbons. The subsequent thermodynamic modeling demonstrate that kerogen-oil interaction suppresses the bubble point of oil in shales when compared to the bubble point of oil in the bulk. It was observed that for a type II kerogen with hydrogen index (HI) in range of 450-500 mg/g TOC, a suppression of over 1700 Psia in bubble point pressure (at 400 ^oF) was observed for in-situ oil from the original bubble point of 3950 Psia (at 400 ^oF) of produced â??freeâ?? oil in Eagle Ford Shale oil play.

The possibility of enhanced oil recovery through CO2 sequestration is also studied in this research. The self diffusivities of CO₂ were found to be in order of 10^-9 m²/s in kerogen. The research demonstrates that CO₂ has more affinity for adsorption in kerogen like organic macromolecules compared to CH₄. The skill sets developed during this research include but are not limited to thermodynamic modeling, molecular simulations of cross-linked polymers and protein like complex macromolecules with different fluids and fabrication of nano â?? microfluidics devices. Such skills are easily transferrable to the fields of bio-medical engineering, polymer science, material engineering and semi-conductors.