Numerical simulation of non-isothermal supercritical water flow in ground pipeline and wellbore: An interactive sensitivity analysis and injection parameters optimization

Supercritical water injection is promising in enhanced heavy oil recovery, in which precise prediction and regulation of bottomhole parameters are the prerequisite for improving the recovery efficiency. However, dramatically changing thermophysical properties make it difficult to calculate the hydraulic and thermal resistances of supercritical water flow in ground pipeline and wellbore. In this work, a comprehensive mathematical model was established to simulate the non-isothermal flow of supercritical water from boiler outlet to bottomhole. Modified correlations of friction coefficients and convective heat transfer coefficients respectively developed for vertical and horizontal flow of supercritical water were coupled in momentum and energy conservation equations to calculate the hydraulic and thermal resistance. The model was validated by oilfield and laboratory data with the relative deviations of pressure and temperature less than 2%. The interactive sensitivity analysis was carried out by response surface method for injection parameters optimization. The results indicated that the heat loss in ground pipeline was comparable to that in wellbore once it reached 10 times longer than wellbore and should be taken into consideration. Increasing mass flux was found to be efficient for reducing the heat loss resulted from the decline of wellbore insulation. But there existed a matching combination of injection pressure and mass flux that making bottomhole temperature the highest. For a typical injection case with a poor insulation wellbore and limited injection temperature, a combination of high mass flux and low injection pressure was recommended for achieving targeted bottomhole temperature due to its high thermal efficiency.