Numerical study of herringbone injector-horizontal producer steam assisted gravity drainage (HI-SAGD) for extra-heavy oil recovery

摘要

Steam assisted gravity drainage (SAGD) has already been successfully applied in the recovery of extra-heavy oil reservoirs. However, it has been demonstrated that extra-heavy oil above shale barriers is hard to be recovered and SAGD performance is significantly limited. In this study, a novel well pattern called herringbone injector-horizontal producer assisted gravity drainage (HI-SAGD) was proposed to recover the oil above shale barriers. A series of numerical simulations were conducted to investigate the feasibility and operation strategies of HI-SAGD. The mechanisms of applying HI-SAGD to enhance oil recovery were investigated. The sensitivities of shale barrier characteristics and branches of the herringbone injector were analyzed. The results from numerical simulations show that conducting HI-SAGD with appropriate strategies can significantly improve performance. The necessary start-up strategy is to conduct two cycles of cyclic steam stimulation (CSS) after steam circulation. Thus, oil above the shale barrier can be recovered. Higher oil rate can be achieved in the early stage of the process, and oil recovery factor is improved. Field application and numerical simulations show that HI-SAGD is a promising technology for the recovery of extra-heavy oil reservoirs, especially with shale barriers above the injector.