Abstract:

The Bohai Sea is very rich in heavy oil reserves. At present,the thermal recovery rate is so low that the potential for tapping the potential is huge. It is of great practical significance to discuss the feasibility of gas injection exploitation in offshore heavy oil field. Through gas injection expansion experiments and multiple contact experiments, the effects of different gas injection media (CO₂,N₂,natural gas) on heavy oils with different viscosities in the Bohai Sea (general I?1, general I?2?A, general I?2?B) the solubilization,expansion,viscosity reduction effect and mixing mechanism.The experimental results show that the compatibility of CO₂ and heavy oil is better than natural gas and better than N₂, the viscosity reduction rates of CO₂ to the three types of heavy oil are 78%,85%,and 90%,respectively,and the viscosity reduction rates of natural gas to the three types of heavy oil are 29%, 69%,and 62%, respectively. CO₂ injection is more suitable for general I?2?B heavy oil, and natural gas injection is more suitable for general I?2?A heavy oil; the results of multiple contact experiments show that the mass transfer mechanism of CO₂ flooding is dominated by dissolution and condensate, the mass transfer mechanism of N₂ flooding is dominated by extraction and extraction, and the mass transfer mechanism of natural gas flooding is the condensate?extraction balance; in addition, the theoretical minimum miscible pressures are all greater than 43.00 MPa, so it is difficult to form miscible at the displacement front. The research results can provide important basis and technical support for gas injection to enhance oil recovery in Bohai heavy oil fields.

Key words: Offshore heavy oil, Gas injection development, Miscible, Enhanced oil recovery

摘要：

渤海稠油储量十分丰富，目前热采采收率低，挖潜潜力巨大，探讨海上稠油油田注气开采可行性具有重要的现实意义。通过注气膨胀实验及多次接触实验，研究了不同注气介质（CO₂、N₂、天然气）对渤海不同黏度稠油（普I?1类、普I?2?A类、普I?2?B类）的增溶膨胀降黏效果及混相机理。注气膨胀实验结果表明，CO₂与稠油的配伍性优于天然气和N₂，CO₂对3类稠油的降黏率分别为78%、85%、90%，天然气对3类稠油的降黏率分别为29%、69%、62%，注CO₂更适用于普I?2?B类稠油，注天然气更适用于普I?2?A类稠油。多次接触实验结果表明，CO₂驱的传质机理以溶解凝析为主，N₂驱的传质机理以萃取抽提为主，天然气驱的传质机理为凝析?抽提平衡；理论最小混相压力均大于43.00 MPa，因此在驱替前缘均难以形成混相。研究结果可为渤海稠油油田注气提高采收率提供重要依据及技术支持。

关键词: 海上稠油, 注气开采, 混相, 提高采收率