ABSTRACT

The objective of this work is to qualitatively describe the primary nucleation of gas hydrates from water on a molecular "level. At the present time, no such hypothesis exists in the literature. The onset of hydrate formation cannot be predicted because hydrates are complex solids that go through a metastable region upon cooling; thus, it is important to come to a qualitative understanding of hydrate formation on a microscopic level. I It is postulated that the concept of metastability, for which hydrates I are infamous, is directly determined by primary nucleation phenomena. To better understand the cause for metastability involved in this process, it is useful to review I what is known about the structure of water. Thus the work serves to consider hydrates at one end of the spectrum of water structures. The theoretical basis for the hypothesis and some experimental data are provided in support. Confirmation or falsification of the hypothesis will b:e the topic of future work.

INTRODUCTION

The goal of determining hydrate kinetics is to predict hydrate formation in order to prevent the plugging Of flow channels (e.g. deepwater pipelines, well choke and kill lines, etc.) by hydrate masses. Thermodynamic work performed in the past indicates when hydrates might form, but due to the metastable nature of gas hydrates, thermodynamics cannot predict the time when hydrates actually will start forming under the appropriate conditions. Thus kinetic studies are crucial to understanding what causes gas hydrates to be metastable compounds. Gas hydrate formation is a crystallization process which is characterized by two distinct regions, namely primary nucleation and the growth stage. The primary nucleation region is the process wherein a subcritically sized crystal may either grow or shrink before becoming a stable crystal.

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