Numerical Simulation Of Hydrate Plugging In Water-based System

The problem of natural gas hydrate generation and blockage is not only a flow assurance problem in deep water oil and gas development system,but also a flow assurance problem that is easy to occur in the deep water ’combustible ice’ development system.The problem of hydrate re-generation and blockage in the deepwater’combustible ice’ development and extraction system easily occurs when the gas produced in the water-based system flows near the subsea mudline,which becomes a key problem that needs to be solved for the efficient and safe development of’combustible ice’.Combining with the experimental data of hydrate blockage in water-based system of high-pressure loop,this paper systematically investigates the flow and blockage law of hydrate slurry in straight and bent pipes in water-based system with the help of numerical simulation method combining computational fluid dynamics(CFD)and discrete unit method(DEM),and applies Fluent and EDEM software to reveal the microscopic blockage mechanism.Firstly,we constructed straight and bent pipe structures in equal proportion to the laboratory loops,combined with the experimental data of hydrate slurry flow in aqueous-based system,determined the key mechanical parameters to be set in the simulation software(mechanical models of liquid phase and particle phase in hydrate slurry,etc.),calibrated the key parameters of the model,and ensured that the pressure drop in the simulated pipe section was within ± 20% of the experimental data.Subsequently,simulations of different hydrate slurry flow rates,particle volume fractions and particle sizes are carried out to investigate their effects on hydrate slurry particle deposition in the straight pipe section,to reveal the evolution of hydrate slurry solid-liquid flow pattern in water-based system,and to identify the aggregation characteristics of hydrate particle formation and fragmentation in the straight pipe.Finally,we focus on the flow characteristics of hydrate particles in the bend,propose the analysis method of particle flow and deposition in the bend,analyze the flow law of hydrate slurry particles in the bend,and explore the influence law of hydrate slurry flow rate,particle volume fraction and particle size on the deposition characteristics of hydrate particles in the bend,and investigate the intuition of hydrate particle aggregate formation,aggregation and fragmentation in the bend.The evolutionary process of hydrate aggregates formation,aggregation and fragmentation in the bend is investigated.This study strongly complements the shortcomings of macroscopic invisible loop experiments in studying hydrate particle deposition characteristics,and reveals the microscopic flow,aggregation and deposition patterns and mechanisms of hydrate particles in hydrate slurry of water-based system,which provides theoretical support for the solution and control of hydrate plugging in water-based system of ’combustible ice’development and extraction system.