An Improved Steam Injection Model with the Consideration of Steam Override

The great difference in density between steam and liquid during wet steam injection always results in steam override, that is, steam gathers on the top of the pay zone. In this article, the equation for steam override coefficient was firstly established based on van Lookeren’s steam override theory and then radius of steam zone and hot fluid zone were derived according to a more realistic temperature distribution and an energy balance in the pay zone. On this basis, the equation for the reservoir heat efficiency with the consideration of steam override was developed. Next, predicted results of the new model were compared with these of another analytical model and CMG STARS (a mature commercial reservoir numerical simulator) to verify the accuracy of the new mathematical model. Finally, based on the validated model, we analyzed the effects of injection rate, steam quality and reservoir thickness on the reservoir heat efficiency. The results show that the new model can be simplified to the classic model (Marx-Langenheim model) under the condition of the steam override being not taken into account, which means the Marx-Langenheim model is corresponding to a special case of this new model. The new model is much closer to the actual situation compared to the Marx-Langenheim model because of considering steam override. Moreover, with the help of the new model, it is found that the reservoir heat efficiency is not much affected by injection rate and steam quality but significantly influenced by reservoir thickness, and to ensure that the reservoir can be heated effectively, the reservoir thickness should not be too small. La différence de densité entre la vapeur et le liquide lors de l’injection de vapeur humide conduit toujours à un débordement de vapeur, en d’autres termes, la vapeur s’accumule sur le dessus de la zone de production. Dans cet article, l’équation pour le coefficient de surcharge de vapeur a d’abord été établie sur la base de la théorie de la surcharge de vapeur de van Lookeren, puis le rayon de la zone de vapeur et la zone de fluide chaud ont été dérivés selon une distribution de température plus réaliste et un bilan énergétique dans la zone de production. Sur cette base, l’équation d’efficacité thermique du réservoir en tenant compte de la surpression de la vapeur d’eau a été développée. Par la suite, les résultats prévus par le nouveau modèle ont été comparés à ceux d’un autre modèle analytique et à CMG STARS (un simulateur numérique à réservo