Finite element analysis of sea floor subsidence caused by tunnel like dissociation of gas hydrate in the Krishna Godavari (KG) Basin East Coast of India

As a non-conventional promising energy resource, methane hydrates research is gaining momentum globally as alternate resource with low carbon foot print. Many challenges are to be addressed for gas hydrates extraction feasibility approach in deep water marine settings. The reaction of the reservoir soil during methane gas production from the Natural Gas Hydrate (NGH) reservoir is the most important aspect to understand for the sea floor stability. Present study numerically investigates the surface settlement of the sea floor using PLAXIS 3D due to tunnel like structure formation by spherical dissociation front propagation around the well in Krishna Godavari basin of Indian deep water gas hydrate reservoir. In addition, analyses had also brought out the variation in subsidence characteristics due to changing tunnel parameters such as tunnel size and placing depth of tunnel, for optimizing the design parameter for methane hydrate spherical dissociation front. Results show maximum surface soil settlement in the tunnel size of 4m (diameter) while placing the dissociation front depth at 50 meter below sea floor (mbsf) at 1050 m water depth. Results recommend this proposed technique for safe production of methane gas from hydrates.