Research On Natural Gas Hydrate Deposition In Gathering Pipelines

In the process of natural gas gathering and transportation,natural gas hydrates are often formed in gathering and transportation pipelines due to transportation conditions and geographical conditions.From the perspective of fluidity assurance,after the hydrate is formed in the pipeline,these crystalline ice-like solid particles are transported by entrainment and dissipate energy during collis ion with the pipe wall.Hydrates may accumulate and deposit under concentration-sens itive conditions,which increases the overall pumping cost and even poses a serious risk of pipe blockage.Therefore,it is of great s ignificance to study the deposit characteristics of natural gas hydrate in pipelines for the safety of oil and gas pipelines.By investigating the latest research progress on the research of hydrate deposition mechanism in pipeline transportation systems at home and abroad,the kinetics of hydrate solid particles generated in the pipeline was studied.Drawing on and improving the research results of previous scholars,using a combination of theoretical analys is and numerical simulation to establish a dynamic model of tube wall deposition:(1)Considering the water wetting of the inner wall of the pipeline and the adhes ion between the hydrate partic les generated in the pipe and the pipe wall,a dynamic model of natural gas hydrate deposition-pipe wall adhesion was established;(2)Considering the hydrate particles generated by the droplets entrained in the airflow in the pipeline,the collis ional aggregation or fragmentation of the partic les during the migration in the pipeline creates a dynamic model of natural gas hydrate deposition-partic le migration and settlement.HYSYS simulation commerc ial software is used to analyze the actual domestic natural gas gathering and transportation pipeline cases,and to predict the location and deposition of hydrate in the pipeline.It pointed out that hydrate deposition and blockage may occur along the pipeline,which depends to a large extent on the s ize of the hydrate partic les and the nature of the airborne.The development of numerical simulation of hydrate multiphase flow is the latest trend in hydrate-related risk assessment.The FLUENT simulation software was used to establish the hydrate partic le aggregat ion and deposition model in the pipeline to analyze the flow and deposition characteristics of the natural gas hydrate in the pipeline under different working conditions,and to conduct experimental verification.Numerical simulations were carried out on the deposition characteristics of natural gas hydrate in the straight pipe under the gathering and transportation conditions,and the main influencing factors affecting the deposition and plugging of the natural gas hydrate in the straight pipe section were determined;(2)Numerical simulation of the natural gas hydrate deposition characteristics in the bent pipe under the gathering and transportation conditions,and calculation of the deposition rate of hydrate partic le deposition under various cases.Finally,the main influencing factors that influence the deposition and plugging of natural gas hydrate in the vertical bend section are determined.By studying the hydrate deposition characteristics in the natural gas gathering and transportation pipeline,a s et of effective and fast predictive prevention tools are provided to avoid the occurrence of hydrate deposition clogging in the natural gas gathering and transportation pipeline and the safety of pipeline transportation.