## 4 Non-Condensate-Gas-Assisted Steam Drive
### N\({}_{2}\)-Injection-Assisted Steam Flooding for Heavy-Oil Reservoir  
N\({}_{2}\)-assisted steam flooding technologies have been widely applied for heavy-oil reservoirs. Compared with steam, N\({}_{2}\) will not condense into water at low temperatures, nor dissolve in crude oil under a certain pressure like CO\({}_{2}\). It is a non-condensing, non-toxic, and harmless inert gas, and pressure has little influence on the characteristics of N\({}_{2}\). With the rapid development of N\({}_{2}\)-production technology, the costs of N\({}_{2}\) are reduced since the N\({}_{2}\) sources are not limited. Therefore, it is possible to apply the N\({}_{2}\)-assisted steam flooding technology to field-scale applications. The research shows that, during the steam injection period, N\({}_{2}\) injection can reduce the amount of steam injection, so as to reduce the water content in the well, slow down the bottom water coning, and increase the sweep range of the steam in the formation [72]. In recent years, field applications and laboratory experiments have shown that N\({}_{2}\)-assisted heavy-oil thermal technology can improve the development effect of heavy-oil reservoirs, as presented in Table 3.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ollield Name** & **Permeability** & **Oil Viscosity** & **Reservoir Temperature** & **Reservoir Pressure** & **Performance Evaluation** \\  & **(mD)** & **(mP-s)** & **(°C)** & **(Mpa)** & **Performance Evaluation** \\ \hline \hline \begin{tabular}{c} Shengli Lean Oilield \\ [73] \\ \end{tabular} & 1647 & \begin{tabular}{c} 902–3500 (surface \\ condition) \\ \end{tabular} & 60 & 8.6 & \begin{tabular}{c} Experiment with 29 wells, oil \\ increased 22,834 t and average \\ oil gas ratio increased by 0.30 \\ \end{tabular} \\ \hline \begin{tabular}{c} LuKeQin Oilfield [74] \\ \end{tabular} & 50–700 & \begin{tabular}{c} 9569–20,150 (50 °C € \\ surface condition) \\ \end{tabular} & 97–103 & 31–36 & \begin{tabular}{c} After 7 d of well soak with \\ nitrogen injection, the oil production increases from 3.8 t \\ to 7.8 t after nitrogen injection, and the daily oil production is 5.7 t after stabilization. \\ \end{tabular} \\ \hline \begin{tabular}{c} Xinqian 9 Block [75] \\ \end{tabular} & \begin{tabular}{c} 48.847 \\ (50 °C € \\ surface condition) \\ \end{tabular} & - & \begin{tabular}{c} \textless{}3 \\ \end{tabular} & \begin{tabular}{c} N\({}_{2}\) injection can prolong the \\ production cycle of a single \\ well, effectively improving the \\ well utilization rate and \\ Production time rate \\ \end{tabular} \\ \hline \
\begin{tabular}{c} Shengli Bamianhe \\ Oilfield [76] \\ \end{tabular} & 20–400 & 5000 (surface condition) & - & 10 &
\begin{tabular}{c} Compared with steam \\ stimulation, the periodic oil \\ production and water recovery \\ rate as significantly increased, and the periodic steam \\ injection amount is reduced \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Field application of N\({}_{2}\)-assisted steam flooding. The application of N\({}_{2}\)-assisted heavy-oil thermal technology has gradually become the main research direction of heavy-oil recovery to reduce the cost of heavy-oil recovery and improve the effect of heavy-oil recovery. However, the performance of N\({}_{2}\)-assisted steam flooding is limited due to the cold damage of steam injection, and heated N\({}_{2}\)-assisted steam injection could be used to improve the development performance to compensate for this disadvantage. Since 1970, the United States and Canada have performed N\({}_{2}\)-assisted experiments and achieved a series of results [78]. Since 1989, China has carried out experimental research on the use of N\({}_{2}\) to improve the steam-injection effect of heavy-oil reservoirs, and achieved good development results in typical blocks such as the Liaohe, Shengli, and Xinjiang Oilfields [72].