Enhanced oil recovery (EOR) technology coupled with underground carbon dioxide sequestration is introduced. $CO_2$ can be injected into an oil reservoir in order to enhance oil production rate and $CO_2$ EOR can be turned into CCS in a long term sense. Coupling $CO_2$ EOR with CCS may secure a large scale and consistent $CO_2$ source for EOR, and the $CO_2$ EOR can bring an additional economic benefit for CCS, since the benefit from enhanced oil production by $CO_2$ EOR will compensate costs for CCS implementation. In this paper, we introduced the characteristics of $CO_2$ EOR technology and its market prospect, and reviewed the Weyburn $CO_2$ EOR project which is the first large-scale $CO_2$ EOR case utilizing an anthropogenic $CO_2$ source. We also introduced geotechnical elements for a successful and economical implementation of $CO_2$ EOR with CCS and they were a miscroseismic monitoring during and after injection of $CO_2$, and determination of minimum miscible pressure (MMP) and maximum injection pressure (MIP) of $CO_2$.