Discrete element simulation of the hydrate-bearing sediments mechanical behaviors under typical hydrate dissociation patterns

The hydrate-bearing sediments (HBS) mechanical properties during hydrate dissociation are important to the safe, efficient and sustainable exploitation of natural gas hydrates (NGH). However, the inhomogeneous hydrate dissociation patterns inherent to HBS may make it difficult to accurately obtain its mechanical properties. In this study, a discrete element method (DEM) model was adopted to simulate the HBS mechanical behavior under various hydrate dissociation patterns. By investigating the simulation results and the corresponding internal mechanism, it is found that the stratified and radial inhomogeneous hydrate dissociation in HBS significantly affects its stress-strain characteristics, and HBS under radial hydrate dissociation has a larger deviation. Moreover, it is suggested that when designing experiments to study the hydrate dissociation effect on the HBS mechanical strength, if the hydrate dissociation homogeneity cannot be guaranteed, a preference for a stratified hydrate dissociation pattern can lead to more desirable results. Finally, a method to judge the HBS hydrate dissociation pattern was also proposed. The results have a guiding significance for the experimental study of HBS mechanisms under hydrate dissociation and ultimately contribute to the realization of accurately predicting reservoir mechanical behavior during NGH exploitation.