Abstract
CO2 convective mixing has been extensively studied for CO2 dissolution in saline water but very limited with the presence of oil. The objective of this work was to visually study the supercritical CO2 (sCO2) dissolution and convective mixing into oil at realistic reservoir temperature and pressure conditions with and without the presence of porous media.A specially designed high-pressure 2D-cell was used to investigate the sCO2 mixing into oil phases. Schlieren imaging method was used as the visualization method. The experiments were carried out at 100 bar and 50 °C using n-octane, n-decane, and crude oil as the main oils. Porous media with different permeability was prepared using glass beads.Convective fingering was found to accelerate the mixing of CO2 with n-octane and n-decane. It was not possible to visualize the CO2 convective fingering in crude oil due to the low opacity of the oil phase. The CO2 dissolution into oil phases was quite instantaneous and fast without the presence of porous media. The swelling of oil was measured as 55%, 50% and 11% for n-decane, n-octane and crude oil respectively without the presence of porous media. Boundary effects were affecting the CO2 mixing due to the circular shape of the 2D-cell. Having a water layer below the oil layer tends to dampen the CO2 transport from the oil phase to the water phase. CO2 dissolution into oil saturated porous media was slower compared to that without the presence of porous media. The mixing of CO2 was faster at higher permeability than at lower permeability. Visualization of CO2 convective mixing/fingers inside oil-saturated porous media using a Hele-Shaw cell yet to be achieved experimentally.
Highlights
For the past few decades, global temperature has been rising beyond human control mainly due to Greenhouse gas (GHG) emissions
Geological storage of CO2 of captured CO2 through an environmentally safe path is one way to contribute to the fight against climate change (Gibbins and Chalmers, 2008)
Injection of CO2 to ongoing and abandoned oil fields is a well-identified solution for the commercial utilization of CO2
Summary
For the past few decades, global temperature has been rising beyond human control mainly due to Greenhouse gas (GHG) emissions. Global or ganizations and different authorities have been trying to come up with directives and legalization to mitigate climate change by reducing greenhouse gas emissions (Mintzer, 1987, United Nations, 2015; Euro pean Commission, 2019). It is very important to optimize and improve the understanding of the Carbon Capture and Storage (CCS) value chain to maximize CO2 geological storage with minimum cost (Budinis et al, 2018). Injection of CO2 to ongoing and abandoned oil fields is a well-identified solution for the commercial utilization of CO2. EOR for CO2 utilization can reduce a sig nificant cost of the whole CCS value chain (Brock and Bryan, 1989; Blunt et al, 1993)
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