Controlling factors and research prospect on creeping behaviors of marine natural gas hydrate-bearing-strata

Creeping of HBS is a common behavior of hydrate-bearing strata in the process of gas production and has great impact on the occurrence and development of engineering geohazards. In this paper, we summarized the main failure modes of HBS based on the investigation of a large number of literatures. Then the research thoughts and strategies on strata creeping behaviors during hydrate exploitation are comprehensively discussed, based on the key scientific issues expounded. Afterwards, a multi-scale creeping detection and characterization approach for HBS is put forward, together with its future research trends. It is supposed that creeping behaviors of HBS during gas extraction are the result of combination of hydrate distribution and its dissociation-induced changes in multi-physical fields such as phase transformation, heat exchange, seepage, and stress evolution. The current constitutive models for conventional soils are not effective enough to reflect such a complex dynamic multifield, multiphase and multicomponent coupling effect, which are doubtlessly inadaptable for evaluating the geotechnical issues during hydrate exploitation in the case of northern South China Sea. For this reason, a multi-scale detection and characterization system needs to be established to analyze the dynamic damage behaviors of HBS during hydrate production, which consists of the molecular scale, nano-to-micro scale, core scale, pilot scale, and field scales techniques. Using the sediments collected from the HBS at the northern South China Sea, the control mechanisms of different geological and engineering parameters on hydrate-bearing strata creeping should be quantitatively modeled.