Introducing Population Balance in Hydrate Modeling for Guest Gas Swapping: Validation and Optimization

The gas swapping phenomenon in naturally occurring hydrates is primarily characterized by phase transformations, molecular interactions, and the morphological evolution of hydrate particles. To elucidate a deeper understanding of the underlying process, theoretical modeling is indispensable. With this in view, a robust thermokinetic framework integrating the population balance model is proposed in this work to simulate the swapping dynamics in natural gas hydrates. The population balance model is numerically solved using a high-resolution, infinite-volume scheme to evaluate the particle size distribution and corresponding surface area of hydrates. Further, the formulation addresses several practically significant issues arising during the process in hydrate-bearing geologic reservoirs, such as porosity, permeability, and water saturation of distributed and irregularly shaped porous particles, effect of salts and minerals, and nonunity or the nth reaction order kinetics. In addition, a crystallography theory-based stochastic thermodynamic formulation is implemented within the theoretical framework to deparameterize the hydrate phase description. Determining the kinetic parameters of the formulated model by articulating a global optimization technique, it is widely investigated with experimental and field data sets in the presence of porous sediments and saline environment. In all of the cases, the developed hydrate-based gas swapping formulation shows a promising performance (quantified by the absolute average relative deviation) and provides better predictions of data than the available models.