Integrated Thermodynamic and Multiphase Flow Coupling Model for Wellbore Behavior in In-Situ Combustion Lifting Operations—A Case Study of Hong-Qian ISC Test Area in Xinjiang

As a key alternative to steam flooding in heavy oil thermal recovery, the insulation effect of flue gas accompanying in-situ combustion (ISC) directly affects wellbore heat loss control and system energy efficiency. Addressing bottlenecks such as unclear thermodynamic mechanisms and difficulties in gas-liquid collaborative regulation in ISC development, this study focuses on the Xinjiang Hong-qian ISC test area and constructs a wellbore thermodynamic model coupled with multiphase flow states. Based on production dynamic monitoring and multi-field coupled heat transfer theory, the regulation mechanism of flue gas annular flow state on heat conduction is revealed, and a dynamic response parameter optimization method is innovatively proposed. The research indicates that: (1) The annular flow of flue gas exhibits critical characteristics in flow regime transition. Turbulent flow significantly reduces wellbore temperature compared to laminar flow, and rational regulation of gas production rates can effectively suppress thermal losses; (2) Temperature abrupt changes are prone to occur at well depths of 200–300 m. Even though the bottom-hole fluid temperature remains elevated, substantial liquid production volumes can lead to a transition from turbulent to laminar flow patterns. This regime shift markedly diminishes heat release phenomena, consequently resulting in lower wellhead temperatures. This study breaks through the limitations of traditional single-factor regulation and establishes a wellbore thermodynamic analysis method, providing a theoretical framework and practical paradigm for the optimization of heavy oil ISC technology.