Mesoscale numerical investigation of fines detachment, migration, and erosion mechanisms in gas hydrate extraction

Abstract

Fines detachment, migration, and settling leads to internal erosion of the skeleton structure and clogging of pores, which is an intricate process during the extraction of gas hydrate from marine sediments. Particularly, fines cemented around gas hydrate particles may detach during the dissociation process. The intricacy of this process has not been well characterized in current mathematical models or numerical modeling. In this paper, a mesoscale numerical model coupling solid particle and fluid seepage for gas hydrate-bearing sediments is developed and employed to simulate the fines erosion process, revealing three different mechanisms for the erosion of fines. Fines detach from the soil or gas hydrate particles during the hydrate phase transition and are subject to the Stokes drag force, frictional force, buoyancy force, capillary force, and interparticle interactions within pore space. Based on the established model, the pore clogging due to either physical aggregation or bridging can be clearly identified. The numerical model was initially calibrated with microfluidics experiments, followed by a series of sensitivity analyses to assess the impacts of porosity, fines content, gas hydrate saturation, and pressure gradient on gas and sand production. Results indicate that the interparticle forces play a significant role in pore clogging, which is crucial for gas hydrate-bearing silty sands. The sand production or physical pore clogging is a multi-stage process due to the dissociation of gas hydrates.