Abstract—It is not always easy to accurately predict bottomhole steam pressure, temperature and quality when we design concentric dual-tubing steam injection schemes due to the complexity of two-phase flow in the annulus, also, previous methods for estimating pressure gradient in annuli are time-consuming. In this study, a new model is established based on mass and energy balances to calculate steam pressure in the annulus. A more rigorous thermodynamic behavior of steam/water mixture is also taken into account. More importantly, one-to-one correspondence between pressure gradient and temperature gradient of saturated steam is reasonably developed and applied in further derivation. The results indicate that the proposed model is more accurate and convenient in predicting steam pressure than previous methods. Moreover, the steam pressure in the inner tubing drops faster than that of in the annulus even the wellhead mass flow rate of the former is lower. The variation law of steam quality in the inner tubing is different from that of in the annulus, depending on the net heat losses of mixture fluid in each tubing.

Index Terms—new model, steam pressure, concentric dual-tubing, annulus, heat transfer

Cite: Hao Gu, Linsong Cheng, Shijun Huang, Shuang Ai, and Shaolei Wei, "Concentric Dual-tubing Steam Injection: A New Model for Predicting Steam Pressure in the Annulus," Journal of Industrial and Intelligent Information, Vol. 2, No. 4, pp. 245-251, December 2014. doi: 10.12720/jiii.2.4.245-251