Study Of Pressure Drop Model For The Gathering And Transportation Pipelines In Changqing Oilfield

Based on the multiphase flow research achievements,the viscosity model of Changqing oilfield water-in-oil emulsion was established with experimental results.A new CQ combined drop model for Changqing oilfield was proposed by using Matlab program analysis.The influence of gas-oil ratio,liquid flow rate,water content and pipe inclined angles on the gathering radius was studied.When the winter soil temperature is low,water-in-oil emulsion in Changqing oilfield unheated gathering and transportation pipelines have the typical non-Newtonian behavior.The influence of the water volume content,temperature and shear rate on the apparent viscosity for water-in-oil emulsion was scientifically studied.According to the experimental study,the viscosity model of Changqing oilfield water-in-oil emulsion was established by L-M algorithm and universal global optimization algorithm.Temperature drop in undulating multiphase pipelines is different from that in horizontal pipelines.The temperature drop is larger in the downhill section of pipelines due to the low liquid holdup in downhill pipe sections.And the temperature drop is smaller in the uphill section of pipelines because liquid holdup in uphill pipelines is larger.In order to reduce the error,relation formula used for thermodynamic calculation took the fluctuating angle influence into consideration.Through calculation and analysis it is found that soil temperature at the depth of the buried pipeline is about 3 ℃ in winter.Parameters such as the gas-oil ratio,the liquid flow rate and the pipe inclined angles have great influence on temperature in multiphase pipelines.However,water content has little effect on temperature in multiphase pipelines.Simplified models of pipeline were used to calculate pressure drop.According to the study,it is unsuitable to use the method of Dukler Ⅱand Beggs-Brill for pressure drop calculation.Therefore other pressure models were used to calculate Changqing pressure drop.The results show that the rank of each model’s relative errors(from low to high)was:(1)CQ pressure drop model for one-section pipeline;(2)MUBE combined pressure drop model for three-section pipeline;(3)Xiao-Brill pressure drop model for one-section pipeline;(4)MUBE combined pressure drop model for one-section pipeline.To reduce the errors and the amount of calculation,CQ pressure drop model for one-section pipeline was determined to be the optimum pressure drop model for Changqing oilfield unheated gathering and transmission pipelines.Using the method of CQ pressure drop model for one-section pipeline,the influence of the gas-oil ratio,the liquid flow rate,the water content and the pipe inclined angles on the gathering radius was studied,which is of great guiding significance for optimization design and economic-safe operation of field gathering system.