Modeling Heat Transport in Systems of Hydrate-Filled Sediments Using Residual Thermodynamics and Classical Nucleation Theory

Mojdeh Zarifi,Tatiana Kuznetsova,Bjørn Kvamme

doi:10.3390/app11094124

Abstract

As in any other phase transition, hydrate phase transition kinetics involves an implicit coupling of phase transition thermodynamic control and the associated dynamics of mass and heat transport. This work provides a brief overview of certain selected hydrate film growth models with an emphasis on analyzing the hydrate phase transition dynamics. Our analysis is based on the fundamental properties of hydrate and hydrate/liquid water interfaces derived from molecular modeling. We demonstrate that hydrate phase transitions involving water-dominated phases are characterized by heat transport several orders of magnitude faster than mass transport, strongly suggesting that any hydrate phase transition kinetic models based on heat transport will be entirely incorrect as far as thermodynamics is concerned. We therefore propose that theoretical studies focusing on hydrate nucleation and growth should be based on concepts that incorporate all the relevant transport properties. We also illustrate this point using the example of a fairly simplistic kinetic model, that of classical nucleation theory (CNT), modified to incorporate new models for mass transport across water/hydrate interfaces. A novel and consistent model suitable for the calculation of enthalpies is also discussed and appropriate calculations for pure components and relevant mixtures of carbon dioxide, methane, and nitrogen are demonstrated. This residual thermodynamic model for hydrate is consistent with the free energy model for hydrate and ensures that our revised CNT model is thermodynamically harmonious.

Highlights

Gas clathrate hydrate has long been a subject of many studies in the oil and gasrelated industries, with hydrates as a flow hazard historically being both the focus and the main funding source for hydrate research
Kinetic models found in the literature aiming to describe the kinetics of heterogeneous hydrate film formation and growth are frequently incomplete and lack a fundamental connection to physics-based theoretical platforms
We propose and demonstrate a theoretical approach able to derive fairly rigorous kinetic models that include im

Summary

Introduction

Gas clathrate hydrate has long been a subject of many studies in the oil and gasrelated industries, with hydrates as a flow hazard historically being both the focus and the main funding source for hydrate research. A fairly recent innovative approach to hydrate production calls for exchanging carbon dioxide for methane in natural gas hydrate reservoirs, providing a win–win scenario of methane production combined with simultaneous safe CO2 storage in the form of hydrate. This concept has often been envisaged as occurring at pressures needed for the CO2 hydrate formation, which will be significantly lower than those of CH4 hydrate at the same temperature. These circumstances will give rise to a very fast mechanism for formation of new CO2 hydrate from the injected CO2

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