## 4 Conclusions  
This paper analyzed the effects of the top water-bearing zone, i.e., aquifer, on the production performance of the SAGP process. Assuming two different aquifers, i.e., finite and infinite cases, the production performance and the gas saturation were observed. The presence of the top water-bearing zone overlying the oil sands deposit can be problematic in terms of the energy efficiency, as well as the oil recovery. The steam loss and the water influx interrupt the growth of the steam chamber. The fixed-size thief zone is more favorable than the infinite case for conducting the SAGP process. The oil sands formation with the finite-sized aquifer produces more oil and less water compared with the case of the infinite aquifer. The amounts of the water influx and the steam loss can be case-sensitive to the boundary definitions. With the increasing mol % of nitrogen, the producing time with energy efficiency increases, but the chamber growth is limited. If the size of the heat thief zone is fixed, the optimum operations of the SAGP process would be available; 0.1 mol % of nitrogen is most effective from the perspective of energy-efficient operations while 2 mol % would be the better option to enlarge  
\begin{table}
\begin{tabular}{c c c} \hline
**Nitrogen Male Fraction (mol \%)** & **Maximum _STEP_ (Unitiless) * & **Production Period Until \(SOR\) = 8 (Days) * \\ \hline
0 (regular SAGD * & 0.0317 (0.0312) * & 463 (376) \\
0.1 & **0.0349 * (0.0297)** & 483 (436) \\
0.5 & 0.0334 (0.0247) & 487 (429) \\
1.0 & 0.0333 (0.0241) & 489 (427) \\
2.0 & 0.0323 (0.0234) & **491** (424) \\
3.0 & 0.0307 (0.0232) & 477 (429) \\
5.0 & 0.0263 (0.0230) & 474 (441) \\
7.0 & 0.0237 (0.0216) & 464 (443) \\
10.0 & 0.0218 (0.0184) & 451 (**445 * * )** \\ \hline \end{tabular}  
* To distinguish the value according to the finite and the infinite aquifer. The format is “the value of the finite case (that of the infinite case)”;
* This condition means steam-assisted gravity drainage (SAGD) operation without nitrogen injection;
* It represents the maximum value (bold and underlined).  
\end{table}
Table 4: Summary of the nitrogen mole fraction affecting the simple thermal efficiency parameter (_STEP_) and the production time until the steam to oil ratio (_SOR_) is 8.  
the producible period without significant heat loss in this study. For the infinite aquifer with mass transfer at the boundaries, the continuous water influx and the significant heat loss interrupted the thermal operations.  
This study was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2017R1D1A1B04033060) and also by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry and Energy (MOTIE), Korea (no. 20172510102150).  
[PERSON] performed the numerical simulations for SAGP operations. [PERSON] contributed to the preparation of the whole paper, the model development, and analyzed the results. [PERSON] participated in methodology discussions and the thermal simulations. Authorship must be limited to those who have contributed substantially to the work reported.  
The authors declare no conflict of interest.