A model for predicting thermophysical properties of water at supercritical state in offshore CDTW

Firstly, based on the pipe flow theory, a governing model, comprised of the energy and momentum balance equations, is established for supercritical water (SCW) flow in the vertical tubes. Then, the effect of heat loss to seawater as well as formation is taken into consideration of the mathematical model. The thermophysical properties of SCW are calculated through interpolation method from the pressure-temperature based tables. Besides, the heat exchange between the the integral joint tubing (IJT) and annuli is also considered. Results show that: (a) Seawater and the thermal exchange inside the offshore wellbores are two main factors contributing to the profile change of thermophysical properties in IJT and annuli. (b) Different from the heat and mass transfer characteristics of wet steam flow in wellbore, SCW possesses some unique features. For instance, the pressure is not sensitive to temperature while the temperature is sensitive to heat loss.