Natural gas hydrate is one of the highest potential energy resources in the future. However, large-scale commercial exploitation of natural gas hydrates may affect the bearing capacity of the surrounding deepwater infrastructure and in turn induce engineering concerns and environmental risks. This paper numerically investigates the uplift bearing capacity of a plate anchor near a hydrate production well. We developed a code in Python to communicate with TOUGH+HYDRATE, a well-established hydrogeology code for simulating multi-phase flow in porous media with hydrates, and ABAQUS, a widely-used commercial finite element code. The thermo-hydro-mechanical-chemical (THMC) one-way sequentially coupled analysis is achieved and adopted to simulate the uplift response of the plate anchor during gas production from a hydrate reservoir configured according to drilling data from the South China Sea. The results show that the uplift bearing capacity of the plate anchor is mainly affected by two mechanisms: 1) the process of depressurization, which improves the bearing capacity of the plate anchor by increasing frictional strength of the surrounding soils; 2) the dissociation of hydrate, which leads to a decrease in cohesion of the surrounding soils and therefore reduces the bearing capacity of the plate anchor. When the anchor plate is close to the well, these two mechanisms dominate in turn, and the uplift bearing capacity of the anchor first increases and then decreases. When the anchor plate is far from the well, the effect of depressurization is insignificant, and the bearing capacity of the anchor decreases over time. After production ends and the pore pressure in the reservoir recovers to the hydrostatic conditions, the bearing capacity of the plate anchor decreases by about 20% of the original value before production.
HUANG Xiang, LIU Fang, JU Xin. Impact of oceanic hydrate production on the uplift bearing capacity of a nearby plate anchor: THMC coupled simulation. Petroleum Science Bulletin, 2020, 02: 229-238.
