Bai Mingxing, Liu Lu, Li Chengli, Song Kaoping
Department of Petroleum Engineering, Northeast Petroleum University, Daqing 163318, China.
Department of Petroleum Engineering, Xi'an Shiyou University, Xi'an 710065, China.
Materials (Basel). 2020 Feb 22;13(4):990. doi: 10.3390/ma13040990.
The injection of carbon dioxide (CO) in low-permeable reservoirs can not only mitigate the greenhouse effect on the environment, but also enhance oil and gas recovery (EOR). For numerical simulation work of this process, relative permeability can help predict the capacity for the flow of CO throughout the life of the reservoir, and reflect the changes induced by the injected CO. In this paper, the experimental methods and empirical correlations to determine relative permeability are reviewed and discussed. Specifically, for a low-permeable reservoir in China, a core displacement experiment is performed for both natural and artificial low-permeable cores to study the relative permeability characteristics. The results show that for immiscible CO flooding, when considering the threshold pressure and gas slippage, the relative permeability decreases to some extent, and the relative permeability of oil/water does not reduce as much as that of CO. In miscible flooding, the curves have different shapes for cores with a different permeability. By comparing the relative permeability curves under immiscible and miscible CO flooding, it is found that the two-phase span of miscible flooding is wider, and the relative permeability at the gas endpoint becomes larger.
在低渗透油藏中注入二氧化碳（CO₂）不仅可以减轻对环境的温室效应，还能提高油气采收率（EOR）。对于该过程的数值模拟工作，相对渗透率有助于预测CO₂在油藏整个生命周期内的流动能力，并反映注入CO₂所引起的变化。本文对确定相对渗透率的实验方法和经验关联式进行了综述和讨论。具体而言，针对中国的一个低渗透油藏，对天然和人工低渗透岩心进行了岩心驱替实验，以研究相对渗透率特征。结果表明，对于非混相CO₂驱替，考虑启动压力和气体滑脱时，相对渗透率会有所降低，且油/水相对渗透率降低幅度不如CO₂的大。在混相驱替中，不同渗透率岩心的曲线形状不同。通过比较非混相和混相CO₂驱替下的相对渗透率曲线，发现混相驱替的两相跨度更宽，且气体端点处的相对渗透率更大。
