The Study Of Yingya Oil Pipeline Wax Deposition And Pigging Period

Yingmaili-Ya oil pipeline is waxy gas condensate pipeline.In the process of pipeline transportation,the temperature and pressure conditions will be changed,and when the temperature is below the wax appearance temperature,the was molecules which dissolved in the oil will precipitate on the pipeline wall as the form of crystallization.This phenomenon will lead to was deposition.The wax precipitation of oil can reduce the ffective inner diameter of oil pipeline and pipe transportation efficiency,increase the pigging frequency,and even result to blockage accident.All of this will will bring huge economic loss to the companies.So it's necessary for us to research the pigging period,calculate the economic pigging cyclye and ensure the safety of pipeline.In order to solve the wax deposition and pigging period,the research which are needed are as follows:(1)Experimental study of YingYa gas condensate.Collent three gas condensate samples,including separator,heating station and terminal separator,and pipeline structure and operation data of YingYa pipeline in the field trip.Using ion liquid chromatography tests the component molar fraction in the oil samples;using the HTHP rheometer tests the viscosity of three samples in different conditions;using differential scanning calorimeter tests the samples' wax crystal solubility coefficient and paraffin content.These experiments provides the basic data for further study.(2)The component molar fraction distribution in the waxy oil have significant impact on thermodynamic phase equilibrium calculation result,so it's necessary to study on the characterization method of the heavy fraction in oil component.According to the result of characterization,compare the different basic physical properties corelations for the single carbon component,and choose the correlation which is mathched the YingYa gas condensate.Using the EoS calculate the the liquid phase parameters,and using the P-UNIQUAC to calculate the solid phase parameters to establish the liquid-solid phase equilibrium model to calculate the wax appearance point(WAP).Finally,compare the WAP with the DSC experiment result to prove the accuracy of liquid-solid phase equilibrium model.(3)The research of was deposition kinetic model and deposition rate.The molecular diffusion,gravity settling and shear action are all have effection on was precipitation.Because of this,Burger model,Hsu model and Huangqiyu model are compared respectively,and Huangqiyu model is choosen because of its universality.The wax deposition rate was calculated in different heating temperature,and the results prove that wax depositon rate is lowest when the heating temperature is 75?.(4)Based on the was deposition model,the pigging period which is based on pipe transportation efficiency is established,and the definition of pipe efficiency is presented.After considerating the affection of wax deposition,the economic pigging period is also established.Finally,comparing the efficiency pigging period and economic pigging period,and the smaller one is the finally pigging period.