Steam injection gravity drainage as a follow-up process for cyclic steam stimulation

Cyclic steam stimulation (CSS) is an effective method to recover extra heavy oil but it achieves a relatively low recovery factor (~26% before economic limit is reached) and is less energy efficient with higher emissions intensity than that of conventional oil production. After it reaches its economic limit, it remains unclear what is the follow-up recovery process where the energy and emission intensities can be minimized. Here, a detailed examination of the Liaohe extra heavy oil CSS and continuous Steam Injection Gravity Drainage (SIGD) operations is conducted to examine their energy and emission intensities. Further analysis is conducted by using detailed geological and reservoir models and a history match of the CSS and SIGD operations. The results reveal that CSS is an effective thermal recovery method to initiate production from extra heavy oil reservoirs and that SIGD using infill wells is an effective post-CSS recovery process to produce a significant fraction of the remaining oil from the reservoir. For the reservoir studied, the steam-to-oil ratio (energy efficiency) and emissions intensity of SIGD is slightly worse than that of the initial CSS operation.