Numerical Simulation And Risk Assessment Of Hydrate Blockage In Solid-liquid Mixed Pipeline

In the development of oil and gas fields,gas hydrate formation in the oil and gas pipeline is one of the most concerned problems in the field of flow assurance.The formation,growth,aggregation,bonding and deposition of hydrates are likely to lead to blockage of pipes and shut-down of equipment.Blockage can bring great economic losses,and serious safety accidents can also occur.Therefore,understanding the blockage mechanism of hydrate particles,analyzing its critical blockage risk and establishing a theoretical system for risk assessment of hydrate pipeline operation is essential for ensuring the safe and economic operation of oil and gas production industry.The hydrate slurry is a solid-liquid multiphase flow of the hydrate,in this paper,the computational fluid dynamics and discrete element method(CFD-DEM)coupling were applied by using Fluent and EDEM commercial software coupling,the mechanism of blockage of multi-phase mixed pipelines was studied,and combined with reliability theory,the calculation of blockage probability and risk assessment of multi-phase mixed pipelines were carried out.For the first time the particle-particle aggregation and particle-wall adhesion were considered,and based on the experimental data,a reasonable mechanical model was selected to describe the particle adhesion and the reliability of the pipeline simulation model was verified.The influence of hydrate particles on the flow field of the pipeline and its distribution in the horizontal and undulating tubes were studied.Influencing factors related to particle deposition clogging in hydrate solid-liquid mixed pipeline: particle critical deposition flow rate and moving layer height were studied combined with classical solid-liquid three-layer model.In addition,the paper analyzes the impact of the collision of upstream hydrates and downstream hydrates on the pressure drop of pipeline under a certain hydrate volume fraction.And the critical state of hydrate pipe blockage is preliminarily defined from the hydrate volume fraction and the pipe pressure drop.Finally,based on the calculation method of the probability of blockage probability of natural gas condensate pipeline proposed by the research group,the safety operation grade was determined and the safety of stable operation of hydrate pipeline was evaluated.