Visualization study of CO2-EOR in carbonate reservoirs using 2.5D heterogeneous micromodels for CCUS

• Published in: Fuel (Guildford) 2022-12, Vol.330, p.125533, Article 125533
• Main Authors: Lv, Qichao, Zheng, Rong, Zhou, Tongke, Guo, Xinshu, Wang, Wei, Li, Junjian, Liu, Zilong
• Format: Article
• Language: English
• Subjects: 2.5D micromodels; Carbonate reservoir; CO2 channeling; Enhanced oil recovery; Heterogeneity
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2022.125533

•A novel 2.5D micromodel creation method was developed to depict the heterogeneous carbonate reservoirs.•Pore-scale CO2 mobility and oil displacement in carbonate reservoirs for CCUS was investigated.•The limitation of bare surfactant foam for enhancing CO2-EOR in carbonate reservoirs was clarified.•Pore-scale mobility control mechanism of NPs-armored foam for enhanced oil recovery was revealed. Carbon dioxide enhanced oil recovery (CO2-EOR) is one of the significant technologies to increase oil production and also to reduce greenhouse gas emissions. Carbonate reservoirs distribute widely in the world and show an extremely potential for CO2 geological sequestration and enhanced oil recovery, which is a promising technology for CCUS. However, the complex interfacial properties and strong heterogeneity of carbonate reservoirs lead to serious CO2 channeling, resulting in poor carbon sequestration. Microfluidic experiments in synthetic characterization of strongly heterogeneous reservoirs are a novel method to study multiphase flow in porous media. In this study, a heterogeneous micromodel was prepared using sequential photolithography and calcium carbonate (CaCO3) in-situ growth technique, which was used to construct CaCO3 layer by crystallization on the microchannel surface. The micromodel was represented by a 2.5-dimensional (2.5D) network of pores and fractures at different depths, which was used to simulate the natural structure of carbonate reservoir. The morphological and structural characteristics of the 2.5D micromodel were characterized using scanning electron microscopy, atomic force microscopy, and profilometer. The surface wettability was characterized by determining the contact angle. The results showed that a 1–2 μm layer of CaCO3 grew on the microchannel surface, and the channel surface tended to hydrophobicity. The flow behavior of CO2 in reservoirs and the capacity of foam to control CO2 mobility were simulated using 2.5D micromodels. Among them, CO2 channeling is more obvious and realistic in micromodel. Accordingly, foams with and without nanoparticles (NPs) armor were used to control CO2 mobility. The bubble disproportionation, and liquid drainage of bare surfactant foam induced gas–liquid separation in fractures and pores. Subsequent big and soft bubbles illustrated poor CO2 mobility control performance, and the micro-fractures and pores were not effectively swept and stored with CO2. Extremely stable CO2 foam was obtained with the constr