A mathematical model for estimating oil drainage rate in SAGD process considering wellbore/formation coupling effect

The aim of this work is to present a new mathematical model for estimating oil drainage rate in rising and expanding steam chamber stages in Steam-assisted gravity drainage (SAGD) process, more importantly, vertical-wellbore/formation and horizontal-wellbore/formation coupling effects are taken into consideration. In this study, a function of steam chamber height is introduced and the expressions for oil drainage rate in the rising and expanding steam chamber stages are derived in detail. Then, an example is given to introduce how to use the proposed method. The results indicate that heat injection power per meter reduces gradually along the horizontal wellbore, which affects both steam chamber height and oil drainage rate in the SAGD process. Moreover, it is found that when production time is the same, the calculated oil drainage rate from the new method is lower than that from Butler's method, but the production period in the rising steam chamber stage for the former is longer than the latter.