A Dynamic Simulation of Annular Multiphase Flow during Deep-water Horizontal Well Drilling and the Analysis of Influential Factors

A gas kick simulation model for deep-water horizontal well with diesel-based drilling fluid is presented in this paper. This model is mainly based on the mass, momentum, and energy conservation equations. The unique aspect of this model is the fluid-gas coupling and the change of mud properties after the gas influx from the formation. The simulation results show that the gas in an annulus dissolves first and it then escapes from the drilling fluid due to the gas solution in diesel. Therefore, it is possible to avoid existing gas hydrate by using oil-based drilling fluids. When gas kick occurred, it will be more dangerous, if the well has a longer horizontal section, a greater gas influx from the formation, and smaller displacement. The occurrence and development of overflow will be very quick in the condition of pumping; it will also be more dangerous, when diesel-based drilling fluid is used in the deep-water horizontal wells.