Test research progress on mechanical and physical properties of hydrate-bearing sediments

The formation and decomposition process of natural gas hydrate (NGH) involves many disciplines and theories. Comprehensively evaluating the mechanical and physical properties of hydrate-bearing sediments (HBS) and clarifying the influence law of hydrate decomposition on reservoir structure. It is of great significance to realize the safe exploitation of NGH. At present, the test research on HBS shows the characteristics of diversification, multi-scale and multi-discipline. In order to enhance the comparison of test conclusions and promote the correlation of science and technology. In this study, based on different experimental test methods, the existing test methods are categorized into two types: direct test methods and indirect test methods. By summarizing and analyzing the triaxial test and direct shear test of hydrates, the commonalities and differences of different types of hydrates are pointed out. Meanwhile, the mechanical behavior of hydrate under different influencing factors is reviewed in particular to guide practical works. Then, by combing the visualization techniques of hydrate laboratory tests. The applications of X-ray computed tomography (X-CT) and nuclear magnetic resonance (NMR) in microstructure, pore space, and morphology observation are emphasized. Additionally, an overview of the acoustic and electrical characterization of hydrates in geophysical methods is presented. The correlation of acoustic wave detection and resistivity test with hydrate distribution morphology and saturation estimation is discussed. Finally, the problems existing in the current HBS experimental research are analyzed and targeted suggestions are given. The future development trend of HBS experimental research is discussed, with a view to providing ideas and references for HBS experimental research.