Gas Hydrates: Formation, Structures, and Properties

In this chapter, the characteristics of clathrate hydrates of natural gases, generally called gas hydrates, will be presented. After an introduction to hydrate structures, which have been verified in nature as well as the associated hydrate formers, the p

  • PDF / 548,222 Bytes
  • 15 Pages / 439.37 x 666.142 pts Page_size
  • 0 Downloads / 193 Views

DOWNLOAD

REPORT


Gas Hydrates: Formation, Structures, and Properties Judith Maria Schicks

Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Structure and Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Hydrate Formation Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Hypothesis of the Nucleation at the Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Labile Cluster Nucleation Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Local Structuring Nucleation Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Hydrate Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Hydrate Formation in Nature: Effects of Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Thermodynamic Properties of Simple and Mixed Hydrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Research Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

82 83 85 85 85 87 87 89 90 92 93

Abstract

In this chapter, the characteristics of clathrate hydrates of natural gases, generally called gas hydrates, will be presented. After an introduction to hydrate structures, which have been verified in nature as well as the associated hydrate formers, the phase diagrams exhibiting the stability fields and thermodynamic properties of these natural systems depending on their composition will be discussed. Natural gas hydrates are methane-rich but may also contain CO2, H2S, and other hydrocarbons and hence vary in their thermodynamic properties. Different models regarding the formation and growth processes, including kinetics with respect to heat and mass transfer effects, experimental observations

J. M. Schicks (*) GFZ German Research Centre for Geosciences, Potsdam, Germany e-mail: [email protected]; [email protected] © Springer Nature Switzerland AG 2020 H. Wilkes (ed.), Hydrocarbons, Oils and Lipids: Diversity, Origin, Chemistry and Fate, Handbook of Hydrocarbon and Lipid Microbiology, https://doi.org/10.1007/978-3-319-90569-3_2

81

82

J. M. Schicks

regarding the cage occupancy during the formation process as well as the influence of sediments and pore water salinity will be presented and discussed.

1

Introduction

Gas hyd