Numerical simulation of methane hydrate accumulation in subsea sediments based on a partial-equilibrium reaction model

Key words:  gas hydrate  reaction kinetics  numerical simulation  cold vent at seabed  hydrate accumulation

Abstract:

Aiming at subsea gas hydrate reservoirs formed via a seepage-type gas migration, a hydrate formation and accumulation model in subsea sediments was established using a reservoir simulation method. Based on the phase equilibrium and reaction kinetics of methane hydrate in sea water, the process of hydrate formation during methane migrating into the upper hydrate stability zone from a deep gas reservoir was realized, in which a partial-equilibrium setting of the hydrate reaction model and high-pressure and low-temperature of the subsea sediments were considered. The effects of different influence factors on methane migration and hydrate formation are analyzed, and a low-permeability barrier case and a leakage case were considered. The simulation results show that low flux of methane gas, cap rock barrier, large water depth, and small geothermal gradient below the mud line are beneficial to the formation of large and thick hydrate reservoirs with high hydrate saturation. It has been also proved that conventional reservoir simulation method can be used as an effective tool to study the hydrate accumulation mechanisms, which deserve for further development and utilization.