Study On Flow Assurance Of Waxy Crude Oil Pipeline In QingXian

The total length of the oil pipeline from Qing Yang to Xian Yang is about 225 km,with a designed transport capacity of 5 million tons.Oil pipeline construction of a total of three various process stations,but also the construction of 9 valve rooms.It was completed and put into operation in 2006,and has been transporting high viscosity waxy crude oil,but wax deposition occurred inside the pipeline.Since then,the pipeline has been cleaned once every six months or even longer according to experience,which has been in an uneconomic operation condition.In recent years,due to the great adjustment of the operation volume,the thermal and hydraulic conditions of the pipeline have also changed greatly,and even caused the condensing pipe accidents.Therefore,this paper studies the flow assurance under different working conditions of the pipeline.Firstly,the main parameters of the sample crude oil were measured in the laboratory,including density,freezing point,viscosity,gelatin content,yield value,wax extraction point,specific heat capacity and total hydrocarbon map,which provided basic data for the wax deposition model,pipeline thermodynamic-hydraulic calculation and economic model.In this paper,the convolutional neural network method is used for the first time to establish a wax deposition model,and the model is trained with laboratory experimental data.The main factors affecting wax deposition are: shear stress,viscosity,radial temperature gradient,oil wall temperature difference,flow rate,among which the shear stress,viscosity and radial temperature gradient are the main reasons.Based on the mathematical model,the software was developed and programmed to predict the wax deposition thickness of the pipeline in different seasons,running times and lengths.According to the paraffin formation in the pipeline,the division of pipeline method is used to program,and the curve of pressure drop and temperature drop along the pipeline can be drawn by the developed software.The influence of paraffin formation on the flow area and the influence of physical parameters with the change of pipe length are fully considered in the software development process,so the prediction result is more accurate.According to the curve of pressure drop and temperature drop at different time and flow rate,the critical flow rate of pipeline operation is simulated to provide guarantee for the safe operation of pipeline.Finally,through economic optimization of Qing Xian Pipeline,the oil transportation cost of the pipeline under different transportation volume and different temperature is simulated,and the optimal operation scheme and pigging cycle of the pipeline are obtained.