A novel thermal compositional simulator considering pseudo-local thermal non-equilibrium

Abstract

Reservoir simulation is essential for applying EOR techniques in oil fields. Improving mathematical models and studying their assumptions are crucial to accurately predicting mass and energy transport in reservoirs. Local thermal equilibrium (LTE) is a common assumption in most thermal process simulators. It assumes that the rock and fluids at any location and time share the same temperature, implying instantaneous energy transfer between hot fluids and the reservoir. However, recent developments suggest that this assumption may not always be reliable. Alternative energy models, such as pseudo-local thermal non-equilibrium (pseudo-LTNE) or thermal non-equilibrium (LTNE), may provide a more accurate representation of energy transport within porous media. In this paper, a compositional thermal simulator was developed involving pseudo-LTNE phenomena in thermal recovery processes. The simulator involves the molar balance equations for multiphase, multicomponent flow with phase change, and the energy equations for both LTE and pseudo-LTNE conditions. Results demonstrated that (1) the LTE assumption might not be valid under certain conditions, such as high fluid velocities and high injection temperatures, (2) pseudo-LTNE might have a greater impact on simulations for heavy oil compared to light or intermediate oils, (3) during thermal displacements, the pseudo-LTNE conditions were identified near the injection well over short periods and near the production well over long periods. These findings highlight the importance of incorporating both pseudo-LTNE and LTNE thermal conditions in reservoir simulations to improve the accuracy and efficiency of EOR processes, as well as ensuring robust and reliable performance of simulators in different scenarios.