Experimental study of enhanced oil recovery by CO2 huff-n-puff in shales and tight sandstones with fractures

• 作者: Chao-Fan Zhu Wei Guo You-Ping Wang Ya-Jun Li Hou-Jian Gong Long Xu Ming-Zhe Dong
• 来源期刊: 石油科学（英文版）
• 年，卷（期）: 2021,（3）
• 所属期刊栏目: PETROLEUM ENGINEERING & MECHANICS
• 页码范围: 852-869
• 页数: 18页
• 语种: 英文

摘要

The fractures and kerogen,which generally exist in the shale,are significant to the CO2 huff-n-puff in the shale reservoir.It is important to study the effects of fractures and kerogen on oil recovery during CO2 huff-n-puff operations in the fracture-matrix system.In this study,a modified CO2 huff-n-puff experiment method is developed to estimate the recovery factors and the CO2 injectivity in the fractured organic-rich shales and tight sandstones.The effects of rock properties,injection pressure,and injection time on the recovery factors and CO2 usage efficiency in shales and sandstones are discussed,respectively.The results show that although the CO2 injectivity in the shale is higher than that in the sandstone with the same porosity;besides,the recovery factors of two shale samples are much lower than that of two sandstone samples.This demonstrates that compared with the tight sandstone,more cycles are needed for the shale to reach a higher recovery factor.Furthermore,there are optimal injection pressures(close to the minimum miscible pressure)and CO2 injection volumes for CO2 huff-n-puff in the shale.Since the optimal CO2 injection volume in the shale is higher than that in the sandstone,more injection time is needed to enhance the oil recovery in the shale.There is a reference sense for CO2 huff-n-puff in the fractured shale oil reservoir for enhanced oil recovery(EOR)purposes.