Performance analysis of SAGD wind-down process with CO₂ injection

Thermal recovery methods involving steam injection have long been considered as an effective means of extracting heavy oil resources. In addition, the high recovery performance of SAGD makes it a popular option for these non-conventional oil resources. Steam processes are energy intensive and result in generation of emissions which are detrimental to humankind and the environment. The use of non-thermal processes involving CO₂ as a miscible or immiscible gas phase in combination with steam for heavy oil recovery is considered as a viable alternative to limit the drawbacks of steam generation. These processes have the capability to enhance oil recovery through CO₂ utilization during production and also provide an avenue to dispose CO₂ after production. Numerical simulation studies have been carried out utilizing STARS (a three phase, multi-components reservoir simulator) to optimize a baseline SAGD process and wind-down process with CO₂ Injection. The baseline process was operated until maturity then CO₂ injection was used to initiate wind-down after 4, 6 and 8 years of a 12 year production operation. Following each of the wind-down processes, CO₂ disposal was undertaken for 25 years and the storage potential evaluated. The baseline SAGD process had a recovery factor of 76%. The SAGD wind-down processes with CO₂ injection after 4, 6 and 8 years had recovery factors of 54%, 77% and 79% respectively. This and other parameters proved the feasibility of SAGD wind-down process with CO₂ injection and its potential to enhance oil recovery. Copyright 2008, Society of Petroleum Engineers.