A Thermodynamic Model On Wax Precipitation

During the transportation of waxy crude oil,the heavy component in crude oil will separate out and stick to the wall of pipe if the temperature is below the wax appearance temperature.This not only greatly decline the effective flow area,increase the frictional losses along pipelines,which increasing the power consumption greatly,but also it may clog up the pipeline when a huge amount of wax existing,and a series safety accident may occur.However,wax deposition in pipelines is only the tip of the iceberg.In the oil-gas reservoirs,wellbores and ground oil facilities,wax deposition does exist,which brings serious hidden danger and additional energy loss.Therefore,accurate prediction of wax appearance temperature and wax deposition is of great significance to the petroleum industry.In this paper,the chemical composition of oil and gas system and wax deposition mechanism and influences is investigated,wax deposition is regarded as a complicated physicochemical process and is an result of kinds of mechanism.The thermodynamic phase equilibrium method is used to describe the balance of vapor-liquid-solid.By comparing the existing equation of state,the PR EOS is adopted to account for the non-ideal of gas and liquid phase.In order to ensure the accuracy of calculation,the heavy fractions in crude oil are characterized.The ideal solution theory is used for solid phase,and an empirical formula is used to correct the wax amount.The model is verified by using data in some literatures.The research shows that the model has good convergence and stability,and the calculated values are in good agreement with the experimental data.And the statement of '"the phase equilibrium point is more close to the wax dissolution point" is proved.Finally,this paper introduces the working principle of BP neural network,and thinks that when a lot of production data are gathered in oil production,the BP neural network can be used to predict the mass of wax.