Research on aerated MPD gas and liquid two phase flow pattern

Aerated Managed Pressure Drilling（MPD）is developed on the basis of aerated underbalanced drilling（UBD）. It is a drilling technology that mainly focuses on narrow safe density window formation. Through the study in this paper, the multiphase flow of the circulating system is simplified into gas and liquid two phase flow, a circulating system physical model of aerated MPD is established, and the transition criteria and pressure drop model of gas and liquid two phase flow are summed up systematically. Through a lot of simulating experiments, the transition criterion and pressure drop model of conventional gas and liquid two phase flow is verified and revised, the pressure drop model applicable to aerated MPD is developed. Through the analysis of flow pattern sensitive factors, gas and liquid ratio, ground back pressure, and flow geometry are major affecting factors affecting. The research result provides theoretical basis for pressure control of aerated MPD.