| As the development of offshore oil and gas fields gradually enters the deep sea and ultra-deep sea,the formation and blockage of natural gas hydrates in deep-water submarine gathering and transportation pipelines are facing great challenges.Conventional hydrate suppression methods have significant technical limitations and high costs.The risk control technology of hydrate flowing in the form of slurry to avoid hydrate blockage has become a hot research topic at home and abroad in recent years.Research on the multiphase flow mechanism of hydrate slurry and blockage safety,and theoretical analysis on the growth mechanism of hydrate in the pipeline transportation system are of great significance to the flow safety guarantee of oil and gas pipelines and the industrial application of hydrate.First,based on Zerpa’s treatment method for the hydrate phase in the pipeline,hydrate is introduced into the Danielson slug flow model as a separate phase,and the slug flow model developed by Danielson is improved.Based on the mass conservation equation,energy conservation equation,hydrate kinetics model and Camargo-Palermo model,a transient multiphase flow hydrate mechanism model is systematically established,and the liquid phase continuity equation and hydrate phase continuity equation are given,temperature equation,pressure equation and other control equations and the numerical solution method of the model,using the Exxon Mobil loop data to verify the hydrate volume fraction,temperature drop and pressure drop calculated by the model,the results are in good agreement with the experimental data.Secondly,based on the coupling of CFD and PBM,the numerical simulation of hydrate slurry is carried out in this paper,and the PBM model of hydrate particle aggregation dynamics is introduced to describe the aggregation and fragmentation effect of hydrate particles in the pipeline.According to the experimental data in the literature,the three-dimensional geometric model of the elbow was established,and the ANSYS Fluent software was used to simulate and solve it,and the distribution laws of hydrate slurry flow velocity,hydrate volume fraction and hydrate particle size under different flow conditions and their effects on hydrate in the pipe were studied.Influence of slurry flow characteristics.The simulation results are in good agreement with the relevant experimental data in the literature.Thirdly,the ISCA-BP hydrate formation prediction model was established based on the data-driven modeling method.By comparing with the simulation results of the thermodynamic models vd W-P,Du-Guo,PP,Chen-Guo and BP models,the absolute relative error of the model is 1.990%,the average absolute relative error is only 0.339%,the smallest error.In the system containing acid gas and alcohol and salt,the ISCA-BP model is verified with experimental data,and the results show that the simulation prediction results of the ISCA-BP model have the smallest error compared with other thermodynamic models,and have a higher agreement Spend.The data-driven model was applied to gas field field tests,and the application effect was good.Finally,a risk management method for hydrate slurry plugging was constructed,using the improved ILHS algorithm and POD algorithm based on discrete data and cubic spline interpolation,and using the transient multiphase flow hydrate mechanism model built in this paper for calculation,using commercial software OLGA-CSMHy K verified the model and developed a hydrate reliability evaluation model for multiphase pipelines in combination with the operation of multiphase pipelines.The model can quantitatively analyze the uncertainty parameters of hydrate blockage risk assessment,obtain its influence on the pipeline blockage probability,and calculate the hydrate blockage probability at any position of the pipeline.Four levels of hydrate pipeline blockage risk management are defined,and the safety of stable operation of hydrate-containing slurry pipelines is evaluated. |
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