A coupled model for predicting thermophysical properties of saturated steam in dual-tubing SAGD horizontal wells with toe-point injection technique

In this paper, a coupled numerical model to simulate dual-tubing steam-assisted gravity drainage (SAGD) process with toe-point injection technique was developed, specially, a more rigorous approach was used to calculate the steam pressure. Based on the model, the distribution of thermophysical properties of steam along the wellbore is investigated. The results indicate that improving the annulus steam temperature uniformity in circulation stage and the annulus steam quality uniformity in production stage is the key to enhancing the reservoir heating uniformity. The influence of the heat transfer from the wellbore to the reservoir on reservoir heating is significant with a low steam injection rate, but the influence is weak with a high steam injection rate. The reservoir temperature nonuniformity is more likely to occur during production stage than during circulation stage, and more attention needs to be paid to optimizing the reservoir temperature uniformity during production stage. A "toe-good" heating effect can be observed with toe-point injection technique, and simultaneous dual-tubing injection technology is a suitable method for solving this problem. The findings of this study can help to better understand the relationship between the distribution of thermophysical properties of saturated steam along the wellbore and reservoir nonuniform heating.