Experimental and Numerical Investigation of
Carbon Sequestration in Deep Saline Aquifers
Abstract
Because of the global
warming threat posed by greenhouse gases, mainly by CO2, some strategies were proposed.
Along those, disposal and long term of storage of greenhouse gases is important
for reducing global warming. Aquifers represent the most widely available
and the second largest, naturally occurring potential store for CO2. Although
there are a number of mathematical modeling studies related to injection of CO2
in deep saline aquifers, experimental studies are limited and most studies
focus to sandstone aquifers as opposed to carbonate ones.
Potential CO2 sequestration
capacity of a carbonate aquifer formation located in S. East Turkey was
evaluated using computerized tomography (CT) monitored experiments. Porosity
changes along the core plugs and the corresponding permeability changes are reported for differing CO2 injection rates, pressures
and temperatures with differing salt concentrations. CT monitored experiments
are designed to model fast near wellbore flow and slow reservoir flows.
It was observed that permeability initially increased
and decreased for slow injection cases. As the salt concentration decreased the
porosity and thus the permeability decrease was less
pronounced. Orientation of the core plugs was influential in
rock-fluid-carbon dioxide interactions. For vertically aligned cores high
injection rates resulted in an increase then decrease of permeability. On
the other hand horizontally aligned cores represented
a decrease in permeability due to CaCO3 precipitation. It was
observed that CO2 sequestration by solubility trapping is larger
compared to mineral trapping. The results are discussed
using a finite difference, non-isothermal compositional numerical simulator
where solution and dissolution of carbonates via chemical reactions are
considered. The calibrated model was then used to
analyze field scale injections and to model the CO2 sequestration capacity of a
potential carbonate aquifer formation located in S. East Turkey.
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