Fundamental Study On The Simulated Process Of Mechanical Wax Removal

The transportation capacity of a crude oil pipeline can be improved by removing wax from its inner wall periodically with pig instrument.However,the wax removal process is operated inherently with a high potential risk due to its complexity,Limited research on the pipeline pigging process,highly dependent on the operation experience and the scarcity of theoretical guidance.Therefore,it is necessary to carry out an experimental study on the wax removal process.In this thesies,we propose a wax sample preparation method using field wax deposit and crude oil.The preparation parameters are determined by the lab-scale experiments.Using the wax removal apparatus,the pigging force is measured,and the effect of wax layer thickness,wax/oil ratio,experimental temperature,the hardness and the form of the cup on the shear resistance of the wax layer is investigated.It is concluded that the change of pigging process can be divided into four stages.The resistance in the stage of wax layer failure is defined as the shear resistance of wax layer.The shear resistance of wax layer increases with the increase in wax/oil ratio,wax layer thickness and the hardness of the cup,the lower experimental temperature is,the larger the shear resistance of the wax layer is.The shear resistance of wax layer is linearly related to the wax layer thickness and the yield stress of waxy layer,respectively.In the same experimental conditions,the shear resistance of disc pig is significantly greater than that of cup pig.Based on the above findings,a new wax removal model is established with the maximum relative error up to 30.4%.