Positioning of horizontal well-bore in the hydrate reservoir using a custom developed coupled THMC solver

Natural gas hydrate sediments are considered as an unconventional source of energy found in deep sea reservoirs and permafrost regions under specific equilibrium conditions. To efficiently extract the gas from these sediments, well-bores need to be installed in these reservoirs followed by adopting an appropriate hydrate dissociation technique. This study presents a custom-developed coupled THMC solver to realistically quantify the gas production and associated sediment deformation. The numerical scheme solves coupled equations describing hydrate phase change kinetics and non-isothermal multiphase flow in porous media. The proposed THMC solver incorporates the HISS-MH constitutive model, enabling it to capture the non-linear geomechanical behavior of gas hydrate sediments, including strain-softening and dilation characteristics. The solver is validated against existing experimental results and a benchmark problem. Finally, the effect of different horizontal well-bore positions on vertical settlement and cumulative gas production is studied. The results indicate that the well-bore in the middle of the reservoir yields the highest cumulative gas production while differential settlement is minimum, thus making it a preferable location for placing the horizontal well-bores. This study contributes towards the development of a custom THMC solver with advanced models in addition to identifying the ideal location of the horizontal well-bore for efficient gas extraction.