Calculation Of Multiphase Flow For Well Control In The Dual Gradient Drilling

As the reserve and produce of oil&gas in the land become limited, petroleum producing companies must search for oil&gas in increasing hostile environments, the deepwater areas. Dual gradient drilling (DGD) technology is developed to face the situation, and to carry out deepwater drilling more safe and successful.In this paper, based on the study in the drilling technology of gas-lift dual gradient drilling, a numerical model is developed for the gas-liquid flow calculation in the riser's annulus when it injects nitrogen in the regular drilling. The model is scattered, and a computing method is built to calculate the nitrogen injection rate. With this method, a formula is gotten to calculate the nitrogen injection rate when dual gradient drilling. The air voids inside the riser and the pressure difference between the wall of the riser are also calculated out, for figuring out the how the maximum difference pressure loading in the riser.On the basis of the well control study in the gas-lift dual gradient drilling, a kick simulation model and a shutting down model are built up. They also are scattered and the computing method are given. In the kick simulation, the changing pattern of the mud return rate, the SPP and the pit gain are calculated out. In the shutting down simulation, it is figured out the feasibility that stopping the nitrogen injection to shutting down the well.Additionally, with studying the technology of the Subsea Mud lift Pump System (SMD) we represent the advantage of the Riserless Mud Recovery system (RMR) in shallow gas detection and control when drilling in the top hole. In the last part, a gas-liquid flow calculation model is built to fit the unique feature in the kick simulation of SMD.