Supercritical water injection into unconventional reservoirs: A comprehensive flow model of an injection well connected to a reservoir

Abstract

Supercritical water injection (SCW) is a promising thermal method for enhancing oil recovery from hard-to-recover reservoirs. The success of this technique relies heavily on the downhole properties of the injected fluid, particularly under high-pressure, high-temperature conditions. In this study, a model of SCW flow through thermally insulated injection tubing, comprising both vertical and horizontal sections, is developed. An engineering code was created to simulate SCW injection, incorporating a simplified reservoir model in the horizontal section as a boundary condition, with reservoir injectivity determined iteratively based on wellhead pressure. Numerical examples illustrate the model's performance by examining the effects of varying injection system parameters. High-precision correlations were employed to calculate fluid thermodynamic properties, enabling accurate simulations. Key factors such as initial SCW temperature, insulation thermal conductivity, and skin factor were analyzed to assess their impact on pressure, temperature, and specific enthalpy distributions along the tubing. The findings provide insights into optimizing SCW injection parameters, underscoring the potential of this approach for effective thermal recovery in unconventional reservoirs.