Abstract
Carbon dioxide (CO_2) geological storage in deep saline aquifers is a key measure to mitigate global warming. However, it still faces a variety of technical challenges such as enhancing CO_2 effective storage capacities. In this paper, a preliminary model is developed to simulate CO_2 migration during nanofluid-based supercritical CO_2 geological storage in saline aquifers. The main mechanisms, including Brownian motion, thermophoresis, thermal energy transfer, and interfacial tension, are included in the proposed conceptual model. Based on the high-resolution space-time conservation element and solution element (CE/SE) method, the model is used to simulate CO_2 migration and distribution in the in-situ heterogeneous saline aquifer. It can be inferred that the involvement of nanoparticles decreases shear stresses opposing flow and enhances CO_2 mobility in the flow boundary layer. In addition, nanoparticles increase shear stresses outside the boundary layer and retard CO_2 velocity. These competitive mechanisms result in homogeneous migration of CO_2 in the saline formation. One preliminary suggestion is that nanofluids enhance homogeneous CO_2 transport in the reservoir and mitigate the negative effects of stratigraphic heterogeneity on migration and accumulation of the CO_2 plume. CO_2 effective storage capacity may be greatly elevated by means of nanofluid-based CO_2 geological sequestration. The concept of nanofluid-based CO_2 geological storage may be potentially conducive to large-scale commercial CO_2 geological storage and useful for exploration of geothermal resources in deep-seated hot rocks. The effects of CO_2 solubility and geochemical reactions on nanofluid flows may be considered in a future study.
Highlights
Carbon dioxide (CO2) geological storage in deep saline aquifers is a new field of study associated with climate change and environmental protection and provides insight into strategies to mitigate greenhouse gas emissions (Pang et al, 2012)
Based on the Oberbeck-Boussinesq approximation, assuming local thermal equilibrium and homogeneity, and without considering particle agglomeration or deposition on porous surfaces, Nield and Kuznetsov (2009, 2010, 2011) established conservation laws involving continuity, momentum, nanoparticle diffusion, mass transfer, and thermal energy. They analyzed the effects of thermophoresis and Brownian motion on double-diffusion convection in porous media saturated by a nanofluid and found a similarity solution which was referred to as the relationship parameter between stream function and similarity
As nanoparticle transfer continued, the shear stresses in the fluid boundary layers decreased, and the relative velocity between the two phases increased
Summary
Carbon dioxide (CO2) geological storage in deep saline aquifers is a new field of study associated with climate change and environmental protection and provides insight into strategies to mitigate greenhouse gas emissions (Pang et al, 2012). Based on the Oberbeck-Boussinesq approximation, assuming local thermal equilibrium and homogeneity, and without considering particle agglomeration or deposition on porous surfaces, Nield and Kuznetsov (2009, 2010, 2011) established conservation laws involving continuity, momentum, nanoparticle diffusion, mass transfer, and thermal energy. They analyzed the effects of thermophoresis and Brownian motion on double-diffusion convection in porous media saturated by a nanofluid and found a similarity solution which was referred to as the relationship parameter between stream function and similarity. Bhadauria and Agarwal (2011) presented the convection stability of nanofluids in a porous medium
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