Analysis Of Gas-liquid Two-phase Flow Law Of Marine Riser

In the development of offshore oil and gas fields,serious slug flow is harmful to oil and gas pipelines.It will increase wellhead back pressure,reduce wellhead production and damage pipeline connecting elements.It is necessary to accurately judge and effectively control the occurrence of slug flow.Firstly,aiming at the flow state of gas-liquid two-phase flow in a marine riser pipe,the phase distribution and pressure distribution of gas-liquid two-phase flow in a horizontal section-An upward inclined section(10degrees)-a horizontal section system are analyzed by using FLUENT numerical calculation software.The trajectories of phase distribution in a pipe during the formation and discharge of three different slugs are described respectively.The formation and disappearance of internal pressure gradient layer are described.According to the variation process of maximum pressure in pipe with time,different pressure cover transfer processes are divided into different stages,and a one-to-one relationship is established with the change process of slug in pipe.Secondly,through OLGA software,the flow rate difference,horizontal pipe-riser diameter difference and the flow state of riser suddenly in riser under multi-pipeline conditions are calculated.The flow state and gas/liquid flow and pressure/temperature distribution along the riser are analyzed when the horizontal pipe diameter and flow are the same in marine multi-pipeline system.The conclusion shows with the increase of total flow rate at the entrance,the flow state in the vertical pipe changes from laminar flow +bubbly flow + slug flow-laminar flow + bubbly flow.When the total flow rate at the entrance increases to a certain extent,the flow state in the vertical pipe must be laminar.Finally,the variation of flow state and related parameters between riserand two horizontal pipes is analyzed when the diameter and flow rate of horizontal pipe are not the same.The conclusion shows that for multi-pipe flow,the difference of flow rate between horizontal pipe and vertical pipe is related to the sum of total flow rate of both,but not to the flow rate of branch pipe.The liquid flow rate and temperature distribution along the pipe are affected by the flow state in the pipe.When the diameter of horizontal pipe section remains unchanged,the flow state and flow parameters in vertical pipe are mainly related to its minimum diameter.The smaller the minimum diameter,the greater the variation of the relevant parameters.