Modeling of multiphase flow during underbalanced drilling considering velocity, temperature and pressure

Abstract

A clear understanding of multiphase flow with phase change is of great significance in productivity evaluation, process optimization, and production analysis, which is one of the focus issues of underbalanced drilling. In the process of underbalanced drilling, the annular flow is very complex. To drill safely and protect the reservoir, the dynamic separation process of dissolved natural gas and the characteristics of downhole multiphase flow are studied in this paper. Focusing on the characteristics of live crude oil and physical parameters in the wellbore, the authors creatively consider the influence of the velocity on the solubility and establish a mathematical model of multi-physical field non-equilibrium phase change and multiphase flow considering velocity, temperature and pressure. According to the established mathematical model, the solubility diagram of natural gas is drawn, and the evolution law of flow parameters is analyzed. The results show that the influence of the three factors on solubility is that the influence of pressure is greater than that of temperature, and the influence of temperature is greater than that of flow velocity. The effect of flow velocity on annular pressure, temperature and phase content does not seem to be very great in the natural gas solubility model. However, the dissolved gas in the wellbore separates earlier when considering the velocity than when the velocity is not considered. It is concluded that the research presented here confirms that the influence of flow velocity cannot be ignored. The innovative mathematical model in this paper takes into account the effect of flow velocity on non-equilibrium multiphase flow with phase change. By using the model developed, a better understanding can be obtained of what the phase change characteristics of downhole fluid are and how the multiphase flow laws will change, which is of great significance to reservoir protection and drilling safety.