The Study On Rheological Property Of Horizontal Bubbly Flow Of Water-based Drillling Fluid

The bubbly flow is a wide phenomenon in oil and gas drilling engineering.The rheological property of bubbly flow is more complicated than single-phase flow after gas cutting due to the interaction between gas and liquid.The rheological property of bubbly flow has a great effect on pressure drop,which is one of the key problems that plagued the control of wellbore pressure in drilling engineering.Therefore,it is significant for drilling safety to study the rheological property of bubbly flow.In the thesis,the author builds an apparent viscosity model of horizontal bubbly flow considering the wall resistance,bubble coalescence and bubble breakup in terms of energy dissipation.Then,the model is verified by experimental data in the literature and the proportion of the pressure drop induced by such three factors is deeply analyzed.The results show that the wall resistance is the main reason of pressure drop,followed by bubble breakup and bubble coalescence.In order to further verify the accuracy of the model,the author designs and builds the system of rheological property of horizontal bubbly flow.The pressure drop is measured by changing the flow of gas and liquid and liquid apparent viscosity,respectively.Then the apparent viscosity are calculated.On the basis of that,the effect of gas velocity,liquid velocity and the liquid apparent viscosity on horizontal bubbly flow are explored.The results show that the calculation error of theoretical model are within ±20%.The apparent viscosity of bubbly flow decreases with the increase of liquid velocity and increases with the increase of gas velocity.When the liquid velocity is low,the apparent viscosity of bubbly flow increases with the increase of the apparent viscosity of liquid.When the liquid velocity is high,the trend is opposite.The effect of temperature and pressure on the apparent viscosity of horizontal bubbly flow is simulated on the fluent platform according to the experimental condition.The liquid phase are water and water-based drilling fluid while the gas phase is air.The results show that when other conditions are certain,the apparent viscosity of bubbly flow decreases with the increase of temperature and increases with the increase of pressure.