**Abstract**

The use of carbon dioxide (CO2) as an improved oil recovery (IOR) method has been a common practice in petroleum engineering. In this chapter, various technical aspects of application of CO2 to increase oil recovery are discussed. From the required laboratory tests prior to field applications to postinjection monitoring of injected plume, the required onshore and offshore facilities, the environmental considerations, and challenges concerning the application of CO2 for EOR purposes have been covered in this chapter. Moreover, the emerging methods and industry trends in applications of CO2 for EOR will be discussed. The second part of this chapter is dedicated to CO2 sequestration as a method to mitigate CO2 emitted due to the anthropogenic activities. CO2 sequestration is the injection of large quantities of CO2 into underground reservoirs (oil and gas, aquifers, and coal deposits) where it can be securely and permanently stored.

**Keywords:** improved oil recovery, enhanced oil recovery, CO2 sequestration, CO2-EOR, CO2 miscibility
