Aging Regular Research On Wax Deposition Of The Waxy Crude Oil Pipelines

When the phenomenon of wax deposition occurs in the pipeline,the flow radius of the pipeline and the conveying capacity are both reduced.The studies found the aging phenomenon of deposition,which means the increase of wax content in sediment.It directly increases the difficulty of cleaning.Pigs are widespread used to remove wax deposits,but the cleaning mainly based on experience.It is helpful to understand the changes of wax content and hardness of sediments in the pipeline.The hardness of the deposits is critical on the force of the pig.The problem of resolving the required force for stripping wax deposits is a prerequisite for movement simulation of the pig.There are some progresses in the research on the mechanism,influencing factors and prediction models of single-phase crude oil wax deposition,and the relative mechanical research of aging is relatively few.In this paper,the experimental study on the influencing factors of oil wax deposition's aging was carried out by using modified cold-finger device.The influence of various factors on the aging of wax deposition was analyzed and the self-designed cleaning experiment was carried out.The main contents and conclusions of this paper are as follows:(1)Diesel oil and different types of paraffin are used to prepare different kinds of simulated oils.The density,pour point,viscosity and wax point of the simulated oil and other basic physical parameters are determined by corresponding experiments.(2)Improved the traditional cold-finger test device.After improving,the device has less fuel consumption and more convenient operation.The effects of oil temperature,cold temperature,temperature range,oil content and carbon number distribution on the aging of wax deposition were analyzed.The higher the oil and wall temperature and the higher the temperature range result the smaller rate of deposition,longer sediment "aging",greater wax content of the sediment and more obvious the change of the wax content.Among them,the wall temperature on the wax deposition rate of a greater impact.The higher the wax content of the oil and the higher the content of the low carbon content result the higher wax content in the sediment and the more obvious the change of the molecular content of the high carbon number wax.(3)Based on the investigation of the shear stress measurement of deposited wax at home and abroad,a device was designed and constructed to study the force of the pig in the pipeline when the wax contents of the deposition were different.After aging,the shear stress of the deposited wax increases exponentially with the wax content.When the thickness of the sediment is same,the smaller the diameter,the greater the pressure difference required for the pig to overcome the shear resistance.Using this rule,the pressure difference calculation of the pig and the calculation flow of the pressure drop are carried out with the example,which has a certain guiding role on the pig.