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Experimental study of enhanced oil recovery by CO 2 huff-n-puff in shales and tight sandstones with fractures
Petroleum Science ( IF 5.6 ) Pub Date : 2020-12-05 , DOI: 10.1007/s12182-020-00538-7
Chao-Fan Zhu , Wei Guo , You-Ping Wang , Ya-Jun Li , Hou-Jian Gong , Long Xu , Ming-Zhe Dong

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.



中文翻译:

页岩和致密砂岩裂缝中CO 2吞吐正压提高采收率的实验研究

页岩中普遍存在的裂缝和干酪根对页岩储层中的CO 2吞吐正压至关重要。在裂缝-基质系统中研究CO 2吞吐-n-抽吸过程中,裂缝和干酪根对油采收率的影响非常重要。在这项研究中,开发了一种改进的CO 2吞吐-正吹实验方法,以估计裂缝性富含有机质的页岩和致密砂岩中的采收率和CO 2注入量。分别讨论了岩石性质,注入压力和注入时间对页岩和砂岩中采收率和CO 2利用效率的影响。结果表明,尽管CO 2在相同孔隙率的情况下,页岩的注入率要高于砂岩。此外,两个页岩样品的采收率远低于两个砂岩样品的采收率。这表明与致密砂岩相比,页岩需要更多的循环才能达到更高的采收率。此外,对于页岩中的CO 2吞吐-n-抽吸,存在最佳注入压力(接近最小混溶压力)和CO 2注入量。由于页岩中最佳的CO 2注入量大于砂岩中的最佳注入量,因此需要更多的注入时间来提高页岩中的油采收率。对CO 2有参考意义 页岩油藏中的吞吐正喷,目的是提高采收率(EOR)。

更新日期:2020-12-05
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