Study On Hydraulic Calculation Model And Simulation Of Gas Gathering Pipeline

Gas-liquid two-phase flow generally exists in the gas condensate gathering pipeline.In the process of gathering and transporting,the fluctuating terrain conditions also lead to the complicated flow conditions.Liquid phase that exists in the pipeline can accumulate in the low-lying areas,which may even block the flow of gas and affect the production of gas fields.It is necessary to effectively predict the effusion in the gas condensate pipeline so as to provide guidance for effusion removal.The hydrodynamic calculation of gas-liquid two-phase flow is the core subject of the study of effusion,the liquid holding rate and pressure drop are main parameters of hydraulic calculation.The main purpose of this paper is to establish a steady state model for gas-liquid two-phase flow in gas condensate gathering pipelines.The following research is mainly carried out.The steady-state mechanism model is established.S-T-B is developed as flow pattern discriminant criterion.Based on the double fluid model equations,the gas and liquid phase mass conservation equation,the gas liquid composite momentum equation are developed to build the model.For the flow pattern characteristics of stratified flow,annular flow,dispersed flow and slug flow,geometry equation and shear stress calculation equation are established respectively.For the fanning hydraulic friction coefficient involved in the calculation formula of the shear stress,this paper choses some experience formula with good adaptability to calculate.The steady-state experience model is established.S-T-B is developed as flow pattern discriminant criterion.According to the flow pattern,the suitable liquid holdup and pressure drop calculation model have been chosen respectively in a horizontal pipe and inclined pipe.The selected model is the empirical related formula based on experimental data or summarization.The calculation method of model equation is proposed.The mechanism model equation is a nonlinear ordinary differential equation set.The four order Runge Kutta method is proposed for iterative solution,and the numerical algorithm converges efficiently.The solution of the liquid holding rate in the empirical model is a highly complex nonlinear equation.The solution is solved by a dichotomous method,and the steady convergence is calculated,and the liquid holding rate can be controlled in a reasonable range.The solution of the liquid holdup in a dichotomy generally has a heavy root.The minimum root is chosen as the solution result.The programming method of programming is proposed.The program of steady state hydraulic calculation is written.The program is divided into three parts: input,analog calculation and output,including the assignment of initial parameters,mesh division,flow pattern discrimination,mechanism model calculation,combined experience model calculation,pipe segment parameter transfer and result's output.The experimental data are used to verify and improve the model.The experimental data on the experimental platform of Imperial University of science and technology and University of Tulsa are selected to verify the convective criterion,the stratified flow model,the annular flow model and the slug flow model and the shortcomings of the model calculation are found.Through the improvement of the critical parameters in the convective type discriminant,the model selection of the stratified flow model based on the apparent gas velocity range,the optimization of mechanism model and the empirical model,and the improvement of the flow parameters calculation formula of the slug flow,the optimization model is obtained.The actual pipeline operation data are used to verify the optimization model.The flow conditions of actual continuous rolling gas condensate pipeline are selected to verify and evaluate the optimization model.The actual pressure drop data are used to compare the pressure drop calculated by the optimized model and the software,it is found that the optimization model and the software simulation results can accurately simulate the actual flow situation.The optimization model is used to study the hydraulic characteristics of the undulating pipeline.The simplified single undulating pipeline is established and the simulation calculation is carried out by the optimization model.The effects of the parameters such as diameter,gas-liquid ratio,gas flow and pipe angle on the liquid volume and pressure drop of the pipeline are investigated.