Numerical Simulation of Flow and Deposition Characteristics of Gas-Controlled Hydrate Slurry Based on Computational Fluid Dynamics-Population Balance Model Coupling

Summary The ongoing exploration and development of offshore oil, gas, and hydrate reservoirs require a thorough understanding of the multiphase flow behavior of hydrate slurries in subsea pipelines, which operate under low-temperature and high-pressure conditions. To investigate the flow, deposition, and particle evolution characteristics of these slurries, we develop a gas/liquid/solid three-phase flow model for a horizontal pipe using the population balance model (PBM). The effects of inlet velocity, inlet hydration fraction, initial particle size, and sand concentration on particle distribution and flow deposition behavior are investigated. The simulations show that hydrate particles settle and accumulate at the pipe bottom, forming a deposition bed that locally elevates effective viscosity and turbulent kinetic energy (TKE). Effective slurry viscosity is reduced by higher inlet velocities and lower hydrate volume fractions, initial particle sizes, or sand concentrations. Meanwhile, a transition point is observed when the hydrate volume fraction reaches 15–20%. Grey relational analysis identifies the hydrate volume fraction as the most significant factor influencing slurry viscosity, followed by initial particle size, sand concentration, and flow velocity. This study provides guidance for ensuring the safe transportation of pipelines in natural gas gathering systems and hydrate exploitation processes.