Extraction of shale oil with supercritical CO2: Effects of number of fractures and injection pressure. (1st February 2021)

• Record Type: Journal Article
• Authors: Yu, Haiyang; Xu, Hang; Fu, Wenrui; Lu, Xin; Chen, Zhewei; Qi, Songchao; Wang, Yang; Yang, Weipeng; Lu, Jun
• Is Part Of: Fuel. Volume 285(2021)
• Publication Date: 2021-02-01
• Subjects: Shale oil -- Supercritical CO2 -- Low-temperature nitrogen adsorption -- Fracture -- Injection pressures; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2020.118977
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Shale sample properties were characterized by low-temperature nitrogen adsorption. The effects of number of fractures on extraction efficiency were studied. The influences of injection pressure on extraction efficiency were investigated. Weighing method and nuclear magnetic resonance (NMR) were used to quantify oil recovery. Abstract: Experimental works and numerical simulation approaches have revealed that CO2 huff-n-puff could be a promising enhanced oil recovery (EOR) method of shale oil reservoirs. Latest studies have shown that supercritical CO2 (SC-CO2 ) can effectively extract oil from extremely tight reservoirs. The main emphasis of this paper is to study the influence of number of fractures and injection pressures on SC-CO2 extraction. In this study, low-temperature nitrogen adsorption experiments were firstly conducted to analyze pore size distribution, specific surface area and pore volume of shale samples from Shengli Oilfield, China. Then, we selected three shale cores with no fracture, one fracture and two fractures respectively to study the influence of number of fractures on extraction recovery (ER). In the end, the other six shale cores were used to study the influence of different injection pressures on ER. Weighing method and nuclear magnetic resonance (NMR) method were used to calculate the ultimate ER of each core. The low-temperature nitrogen adsorption experimental results show that the overall distribution of pore size is in the 1.7 ~ 79.19 nm interval. Mesopores contribute predominantly to the specific surface area (62.3% ~ 75.5%) and total pore volume (70.8% ~ 81.6%). In the SC-CO2 extraction experiment, the existence of fractures can obviously increase ER, but more fractures do not necessarily lead to higher ER. Moreover, a higher injection pressure results in a higher ER under immiscible condition, however, the incremental ER tends to decrease. After reaching the minimum miscible pressure, the further increase of injection pressure does not have a strong influence on the final ER.