The Research On Dissolution Law Of Natural Gas Injection Into Heavy Oil And Establishment Of Relevant Models

Heavy oil has good fluidity under formation conditions,but in the process of wellbore lifting,with the decrease of temperature,the viscosity gradually increases,leading to difficulty in wellbore lifting or even shutdown.Viscosity reduction by natural gas injection has become one of the important ways of heavy oil recovery.It is very important to study the variation of physical parameters such as viscosity and density after heavy oil dissolves natural gas for optimizing gas injection parameters.In this paper,a self-developed high temperature and high pressure oil-gas measurement system is used to study the change rule of solubility of natural gas in heavy oil and the change rule of saturated viscosity and density of heavy oil under high temperature and high pressure.It is found that the solubility of natural gas in heavy oil increases with the increase of pressure,but the extent of increase decreases gradually,forming a non-linear relationship;the higher the temperature,the smaller the solubility;at the same temperature and pressure,the solubility of natural gas in heavy oil with high alkane content is higher than that in heavy oil with low alkane content.The saturated viscosity of heavy oil decreases with the increase of temperature,pressure and gas solubility,showing a non-linear relationship.The saturated density of heavy oil decreases with the increase of temperature,pressure and gas solubility.Mathematical models for predicting the gas solubility,saturated viscosity and density in Tahe heavy oil under high temperature and pressure were established by regression analysis.The influence factors of temperature and pressure on gas solubility,saturated viscosity and density in heavy oil are comprehensively considered in the models.Compared with the experimental data,it is found that the average relative error of the models is less than 10%,and the prediction accuracy is better than the existing mathematical models,which provide a theoretical basis for exploitation of heavy oil by natural gas injection.