Pore-scale numerical simulation of mud erosion in the subsea sand-mud alternate layer using lattice Boltzmann method

Commercial-scale extraction of methane gas from subsea methane hydrate is difficult. A major challenge is mud erosion at the interfaces of sand-mud alternate layers in the subsea strata. Without a clear understanding of the various parameters associated with mud erosion, there may be complications in developing methane hydrate deposits, such as reservoir clogging due to mud particles. This study aims to develop a numerical simulation method to predict mud erosion caused by water flow in pore-scale computational domain. Microscopic sand beds were generated numerically in the computational domain while the water flow through the pores of various-shaped sand grains was numerically simulated using the lattice Boltzmann method. Mud was treated as a continuum and eroded at its surface via the shear stress of water flow using the critical shear stress and erosion rate constant, which were estimated by fitting calculated erosion rates with those of a laboratory-scale experiment. Using this numerical model, simulations of long-term mud erosion were conducted. The simulation showed that when the average velocity of water in the pore space is larger than the critical value and smaller than ten times that value, the erosion rate is almost zero after about 10 days.