Pan Xiuxiu, Sun Linghui, Liu Qingjie, Huo Xu, Chen Feiyu, Wang Yuhan, Feng Chun, Zhang Zhirong, Ni Shumin
University of Chinese Academy of Sciences, Beijing 100049, China.
Institute of Porous Flow and Fluid Mechanics, Chinese Academy of Sciences, Langfang, 065007, China.
Nanoscale. 2025 Jan 16;17(3):1524-1535. doi: 10.1039/d4nr02474e.
The development potential of CO-enhanced shale oil recovery is significant, but shale reservoirs have developed nanoscale pores, often accompanied by fissures and micro/nanoscale fractures. This characteristic makes the micro-nanoscale CO flooding mechanism unclear. In this study, the minimum miscible pressure (MMP) of CO and -octane was determined from a microscopic perspective using the nanofluidic method. Based on this, the displacement behavior of CO in three types of micro-nano networks was investigated, and the degree of inter-fracture matrix utilization was studied for the first time using visualization techniques. It was found that compared to immiscible flooding, the stronger the heterogeneity, the more pronounced the improvement in recovery efficiency by miscible flooding. In addition, transfer and diffusion in the nanofracture network system are intense, and the displacement process can be divided into three stages: pressure-driven flow, matrix-fracture co-production, and matrix oil production. This study applies a novel nanofluidic method to extend the lower limit of the microscopic visualization experimental pore scale to 30 nm, filling the gap in experimental research on shale microscale flow and contributing to the understanding of the mechanism of CO-enhanced recovery in shale reservoirs. Additionally, it provides necessary references for microscopic flow simulation.
CO 强化页岩油开采的发展潜力巨大，但页岩储层存在纳米级孔隙，常伴有裂缝和微/纳米级断裂。这一特性使得微纳米级 CO 驱替机制尚不明确。本研究采用纳米流体方法从微观角度测定了 CO 与正辛烷的最小混相压力（MMP）。在此基础上，研究了 CO 在三种微纳米网络中的驱替行为，并首次运用可视化技术研究了裂缝间基质的利用程度。研究发现，与非混相驱替相比，非均质性越强，混相驱替提高采收率的效果越显著。此外，纳米裂缝网络系统中的传质和扩散强烈，驱替过程可分为三个阶段：压力驱动流、基质 - 裂缝共生和基质产油。本研究应用一种新型纳米流体方法将微观可视化实验孔隙尺度下限扩展至 30 nm，填补了页岩微观尺度流动实验研究的空白，有助于理解页岩储层中 CO 强化开采的机理。此外，还为微观流动模拟提供了必要的参考。
