Fracture Mechanics of Methane Clathrate Hydrates

Journal Tittle: Acta Mechanica Sinica

Article Tittle: Fracture Mechanics of Methane Clathrate Hydrates

Author: Jinjie Liu, Ke Xu, Li Yang, Yanwen Lin, Tong Li, Xuezheng Cao, Zhisen Zhang, Jianyang Wu

Novelty/impact/significance

1.      sI, sII and sH methane hydrates mechanically fail via brittle fracture, but with different fracture toughness that are lower than that of hexagonal water ice.

2.      A modified Griffith criterion was proposed to describe fracture mechanics of pre-cracked sI, sII and sH methane hydrates

3.      Providing a theoretical basis of evaluating geomechanical stability of hydrate-bearing sediments for large-scale exploitation of natural gas hydrates.

Scientific question

Fracture mechanics of unconventional energy-related natural gas hydrates is critical to assess the mechanical stability of hydrate-bearing sediments that are important for petro-activities, but it is largely unexplored yet due to harsh conditions for formation and stabilizing of gas hydrates and insufficient direct experimental techniques.

Key of how

1.      Fracture mechanics of sI, sII and sH methane hydrates that are difficultly accessible from experiments can be systemically investigated using classic molecular dynamics simulations with a reliable coarse-grained forcefield.

2.      To describe the fracture mechanics of nanocrack-contained methane hydrates, classic Griffith criterion was modified.

Major points

1. sI, sII and sH methane hydrates show intrinsic different mechanical properties due to its distinct microstructures in clathrate cages formed by unique hydrogen-bonded water molecules

2. In terms of energy release rate, methane hydrates are sorted as sH > sI > sII

3. As a result of its unique combination of clathrate cages, sH methane hydrate with specific nanocrack defects exhibits slower crack propagation than sI and sII ones.

Funding of the work

1. National Natural Science Foundation of China with grant numbers of 11772278, 11904300 and 12002350

2. The Jiangxi Provincial Outstanding Young Talents Program with grant number of 20192BCBL23029 

Please go to the website to read this article: http://ams.cstam.org.cn/EN/abstract/abstract157437.shtml