Influences of hydrate decomposition on submarine landslide

Abstract

Natural gas hydrate reservoirs on the sea floor have characteristics of a shallow overburden depth, weakened rock formation, and easy deformation. Thus, the mining of hydrate may cause geological disasters such as submarine landslides. To clearly learn about the failure process of submarine landslides induced by hydrate decomposition and influence the laws of various factors on submarine slope stability, this study established a thermal-fluid-solid-stress coupling model for hydrate. In combination with a strength reduction method, submarine slope stability in the mining of hydrates was analyzed. By utilizing the orthogonal experimental design method, this study analyzed the influence laws of these factors, including the hydrate decomposition range, submarine slope angle, overburden depth of hydrates, thickness of hydrate layers, seawater depth, and initial hydrate saturation on submarine slope stability, and evaluated the sensitivity to these factors. The result shows that hydrate mining may result in settlement of the seafloor and slippage of submarine sedimentary layers to the mining center, thus probably inducing submarine landslides. According to the significance of influences on submarine slope stability, the factors were ranked in descending order as follows: submarine slope angle, hydrate decomposition scale, thickness of hydrate layer, overburden depth of hydrates, initial saturation of hydrate layer, and seawater depth. Among the above factors, except for the overburden depth of hydrates and the seawater depth, the increases of which promoted submarine slope stability, the increase in the values of the other factors reduced submarine slope stability to different degrees. Therefore, in the mining of hydrates, the effects of each factor on submarine slope stability should be evaluated comprehensively to prevent disasters such as submarine landslides.