Thermal recovery of heavy oil reservoirs: Modeling of flow and heat transfer characteristics of superheated steam in full-length concentric dual-tubing wells

Abstract

Accurately predicting the flow and heat transfer characteristics of superheated steam (SHS) in the wellbore is essential for efficiently developing heavy oil reservoirs. However, few studies have examined SHS flow in full-length concentric dual-tubing wells (CDTWs). In this paper, firstly, based on fluid dynamics and thermodynamics theories, a mathematical model for SHS flow in vertical and horizontal wellbores is proposed. Then, this model is solved using a finite difference method for spatial discretization and an iterative technique. Finally, model verification, type curve analysis, and sensitivity analysis are conducted sequentially. The results indicate that SHS temperature and pressure are independent variables, and the effect of friction energy on temperature is greater than its impact on pressure. The injection rate has a critical value, and the critical injection rates of the main controlling factors affecting the pressure drop and temperature drop of SHS in the vertical tubing are different. When the injection rate is below the critical value, the gravitational force of the SHS helps maintain high enthalpy. The SHS should be transported to the well bottom as quickly as possible. To enhance the uniform heating effect of the reservoir and improve heat utilization efficiency, a relatively small injection rate, high injection pressure, and low injection temperature are recommended. The uniformity of SHS pressure and temperature distribution in the horizontal annulus positively correlates with the uniformity of the reservoir's heat absorption rate. Achieving more uniform SHS pressure and temperature profiles in the horizontal annulus benefits the uniform heating of the reservoir.