# Dynamic in-situ imaging of methane hydrate formation and self-preservation

## TL;DR

This study uses advanced 3D X-ray imaging to observe methane hydrate formation and decomposition in sand, revealing water movement patterns and two hydrate formation types, with implications for hydrate stability and extraction.

## Contribution

It introduces high-resolution in-situ 3D imaging to distinguish hydrate formation mechanisms and their impact on stability during self-preservation.

## Key findings

- Water movement caused by cryogenic suction during formation.
- Identification of hydrate formation into gas pockets and inside water volumes.
- Greater stability of hydrate inside water volumes during decomposition.

## Abstract

We present the results of dynamic in-situ 3D X-ray imaging of methane hydrates microstructure during methane hydrate formation and decomposition in sand samples. Short scanning times and high resolution provided by synchrotron X-rays allowed for better understanding of water movement and different types of gas-hydrate formation. Complementing previous observations, we conclude that the process of gas-hydrate formation is accompanied by the water movements caused by cryogenic water suction that happens in short sequences with longer equilibrium states in between (when the water is immobile). Based on the 3D microstructure we identified two types of gas-hydrate formation: (i) into the gas pockets and (ii) inside water volumes. During the decomposition in the self-preservation mode (pressure drop at negative temperatures) the latter remains more stable compared to the hydrate formed as growing into the gas pocket. This means that the history of the gas-hydrate formation influences its behaviour at the decomposition stage (e.g. gas-hydrate production).