Study On The Effect Of Light Component Dissolution On The Rheology Of Crude Oil

The crude oil produced from the formation will dissolve various light components,and the crude oil transportation in the pipeline may also be accompanied by the escape and dissolution of light components.The existence of light components will significantly change the rheological properties of crude oil.In most cases,the dissolution of light components into crude oil will lead to the decrease of viscosity,freezing point and other rheological parameters of crude oil;on the contrary,the escape of light components will make these parameters increase.In the process of oil transportation,with the change of pressure and temperature along the pipeline,the dynamic change process of light components escaping and dissolving is likely to occur,which leads to the complex rheological changes of crude oil in the pipeline,which is difficult to monitor,and also brings safety problems to production.In this paper,the rheological behavior of saturated gas soluble crude oil was studied in the medium of methane,ethane,propane and butane.The main research contents are as follows:In order to avoid the problem that propane and butane are easy to liquefy at room temperature and lead to infinite dissolution,all test pressures are controlled below the saturated vapor pressure of each component.A hand pump gas pressurization device is designed to pressurize the gas discharged from the cylinder to the required pressure.In addition,the device can be used to mix different gases in proportion.The maximum bearing capacity of the experimental device is 5MPa.Low temperature rheology and viscosity temperature characteristics of crude oil are important indexes in crude oil transportation process,which are related to shutdown and restart of pipeline and pressure drop along pipeline.Therefore,orthogonal experiments were designed to study the effects of light components,dissolved gas pressure,temperature and other parameters on the rheological properties of crude oil.The main influencing factors of different rheological indexes were found out,and the refining experiments were carried out.The results show that the effect of static pressure can promote wax precipitation of crude oil,resulting in the deterioration of rheological properties,while the dissolution of light components in crude oil can slow down wax precipitation and improve the rheological properties of crude oil.For Daqing crude oil,the effect of light component dissolution is much greater than that of static pressure within the experimental pressure range,so the rheological properties of Daqing saturated gas soluble crude oil gradually improve with the increase of gas dissolution pressure.In order to quantify the variation of viscosity temperature characteristics of gas soluble crude oil,a large number of experiments were carried out to obtain a large number of data and establish the apparent viscosity model of saturated gas soluble crude oil.The model is modified on the basis of power-law rheological equation to correlate light component type temperature dissolved gas pressure shear rate,which is more applicable than the traditional viscosity model of dissolved gas crude oil.