A resolved CFD-DEM investigation of near-wellbore fine sand migration and production during methane hydrate extraction

Methane hydrate extraction from unconsolidated reservoirs can face challenges due to excessive sand production in the wellbore. Sand production has long been a concern in petroleum engineering and has been extensively studied by researchers. This study investigates sand production in gas-water two-phase flow through numerical simulations. The simulations incorporate the discrete element method (DEM) and resolved computational fluid dynamics (CFD) to model the solid-fluid interaction，which allows for simulating the particle movements and capturing the variations in hydraulic properties of the granular sample at a particle scale. Additionally, a volume of fluid (VOF) method is employed to simulate the two-phase flow. The numerical model provides insights into the gas movement process within the granular matrix and visually depicts the microscopic mechanisms of particle migration during methane hydrate extraction. The results of the study demonstrate that the model incorporating gas injection, which involves injecting a predetermined volume of gas at the inlet to the fluid model, yields a higher mass of produced sand compared to the model without gas injection. Furthermore, as the volume of gas injection increases, the produced mass initially rises and then declines. In addition, parameter analysis shows that the pattern of sand production differs between the model with a higher fines content and the model with a lower fines content. With the increase of hydraulic gradient, the produced mass increase.