In deep heavy oil reservoirs, substantial heat losses during steam injection are often associated with suboptimal steam chamber development, significantly reducing the efficiency of steam flooding. A novel steam chamber expansion model was introduced, incorporating a wellbore heat loss coefficient derived from vapor-liquid interface theory and heat transfer principles. Compared to existing models, the modified model was shown to predict a more pronounced steam override and a larger steam-swept area at the reservoir top. Validation against field monitoring data reveals a deviation of only 7.61%, demonstrating strong agreement with actual development conditions. Further analysis of the wellbore heat loss rate and steam chamber morphology shows that the heat loss rate peaks early in the injection process and subsequently decreases over time. It is observed that the wellbore heat loss rate increases with greater reservoir depth. Additionally, the mobility ratio is found to be negatively correlated with steam chamber development, while the shape factor is positively correlated, with larger shape factors resulting in a wider steam-swept area and a reduced impact of steam override. The research is closely integrated with theoretical concepts and practical applications, enabling rapid and accurate predictions of steam chamber front positions, optimizing steam injection parameters, and informing the design of development strategies for medium to deep heavy oil reservoirs.