Abstract: The physical simulation and numerical models were used to study the production mechanism of CO₂-assisted steam flooding process combined vertical and horizontal wells.The reduction of oil viscosity and oil swelling and decrease of oil-water interfacial tension were analyzed.The reasonable injection methods,injection ratio and injection amount of CO₂ and steam were optimized.The results showed that the proposed CO₂-assisted steam flooding process combined vertical and horizontal wells was available for deep heavy oil reservoirs after cyclic steam stimulation.Because the deep heavy oil reservoirs with the depth ranging from 1 300 m to 1 700 m have a lot of heat loss in well bore and lower steam quality at well bottom,by means of adding CO₂ in steam flooding process,the steam flooding can achieve good performance under the lower steam quality conditions,and the quick response can be obtained after changing the cyclic steam stimulation into steam flooding.

Key words: deep heavy oil reservoir, combined vertical and horizontal wells, CO₂-assisted steam flooding, cyclic steam stimulation, enhanced oil recovery

摘要： 利用物理模拟及数值模拟方法,研究了在蒸汽中添加CO₂改善直井与水平井组合蒸汽驱开发效果的生产机理,主要包括降低原油黏度、使原油体积膨胀、降低油水界面张力等。优选出了CO₂与蒸汽的合理注入方式、注入比例和注入量。模拟结果表明:CO₂辅助直井与水平井组合蒸汽驱是深层稠油油藏高轮次吞吐后进一步提高采收率的有效技术。对于埋深为1 300~1700m的稠油油藏,由于井筒热损失大,使井底蒸汽干度降低。而在注蒸汽的同时添加CO₂,不仅可以有效地弥补蒸汽干度低,难以达到蒸汽驱要求的不足,而且还可以缩短蒸汽驱初期的低产期,提高采油速度。

关键词: 深层稠油油藏, 直井与水平井组合, 蒸汽+CO₂驱, 蒸汽吞吐, 提高采收率