**1. Introduction**

The growing concern over the climate change caused by global warming due to a high emission of greenhouse gases (essentially carbon dioxide (CO2 )) has increased the interest in finding various techniques to resolve this problem. The injection of this gas for enhanced oil recovery has been tested with full success in several fields over the world.

Traditionally, oil recovery operations have been subdivided into three stages: primary, secondary, and tertiary as shown in **Figure 1**. Historically, these stages described the production from a reservoir in a chronological sense. Primary production, the initial production stage,

**Figure 1.** Oil recovery stages [1].

resulted from the displacement energy naturally existing in a reservoir; the driving energy may be derived from the expansion of the gas cap or an active aquifer, from the liberation and expansion of dissolved gas, from gravity drainage, or from a combination of all these mechanisms. Secondary recovery, the second stage of operations, usually was implemented after primary recovery declined. Traditional secondary production processes are gas injection, water flooding, or water alternative gas injection (WAG). Tertiary recovery or enhanced oil recovery (EOR) is a term used to describe a set of processes intended to increase the production of oil beyond what could normally be extracted when using conventional oil production techniques, while traditional oil production (primary and secondary stage) can recover up to 35–45% of the original oil in place (OOIP). The application of an EOR technique is typically performed toward what is normally perceived to be the end of the life of an oil field, and tertiary production used miscible gases (e.g., CH4 , CO2 ), chemicals, and/or thermal energy to displace additional oil (5–15%).
