Nano-modified CO2 for enhanced deep saline CO2 sequestration: A review and perspective study

Abstract

CO2 sequestration in deep saline aquifers has been well-established as a mode of reducing the anthropogenic emissions of CO2 and mitigating the risks associated with human-induced global warming. The long-term success of a deep saline sequestration project depends in particular on the volume of CO2 sequestrated and the prevention of risk of leakage. However, current practice still suffers from the slow solubility of injected CO2 in brine, making conventional versions of the process inefficient, uneconomical, and unsafe. Therefore, the aim of this study is to review current techniques and propose a new high-performance technique for CO2 sequestration in deep saline aquifers, by introducing nanoparticles into injected CO2. Nanoparticles are considered promising tools for improved seepage efficacy in the petroleum industry, and studies of CO2 sequestration have led to exciting developments in the last few years. Unfortunately, our knowledge of the complex interaction between nanoparticles, CO2 and reservoir pore fluid and its feedback on other operational and reservoir parameters are poorly understood. The first part of this article gives an overview of conventional mixing of CO2 and how nano-injection improves convective mixing, based on critical wavelengths and critical onset times calculated using thirty-two saline aquifers around the world. In addition, several different nano-injection methods and possible nanomaterials for deep saline sequestration are discussed. The second part of this article considers the influence of nano-injection on gravity, viscous and capillary forces and how these non-linear alterations change the conventional mechanism of CO2 plume development, and the propagation and transport characteristics of CO2 in porous media based on the wettability, interfacial tension and solubility modifications which occur with the introduction of nanoparticles into the CO2 stream. The proposed technique promises to enhance CO2 storage capacity, reduce operational and monitoring costs, and minimize the risk of leakage to nearby freshwater aquifers. This study generates valuable new science, applied in technology that can be used for real-world CO2 storage enhancement in pilot and field-scale projects. However, further research in related areas is required.