3. Thermal Effects in Multiphase Flow Analysis for Offshore Oil Systems

In this paper, a numerical study on the stationary state for the multiphase flow of oil in a pipeline-riser system is presented. The developed model considers that the flow is one-dimensional and three-phase throughout the system. The liquid and gas phases are considered compressible. Furthermore, it is assumed that oil and water have the same speed and are homogenized. The flow pattern in the pipeline and riser is determined based on the local state variables and inclination angle. The characterization of fluids is done according to the black-oil model. The conservation equations were solved numerically using MATLAB software [1]. For a constant separator pressure as boundary condition, the pressures calculated by the model with the thermal effects were higher than those obtained by the isothermal model. The average difference between them was 2.3%. The deviations occurred due to the effect of temperature on the mass transfer, compressibility, expansion, and the thermophysical properties of the phases. The stationary analysis shows that the temperature has a secondary effect on the flow in offshore systems. However, deviations about the isothermal model must be taken into account in order to improve the reliability of numerical results and better production planning.