The purpose of this study is to investigate of experiments to reactive transport module for handling aquifer sequestration of carbon dioxide and modeling of simultaneous geochemical reactions. Two separate cases of laboratory carbon dioxide sequestration experiments, conducted for different rock systems, are modeled using the fully coupled geochemical compositional simulator and the relevant permeability relationships are compared to determine the best fit with the experimental results. This study determined that simulated changes in porosity and permeability could mimic experimental results to some extent. Increased porosities of 7% were found in the dolomite-calcite models and 20% for quartz-carbonate core flooding simulation systems respectively. This is comparable to published experimental results. The formation rock and brine compositions played a significant role for changes taking place in porosity. This study also compared the relevant permeability correlations for their effectiveness in representing the porosity and permeability changes in the carbon dioxide sequestration process. Civan's Power Law correlated experimental changes significantly better than the Kozeny-Carman, and other empirical equations for the permeability. Therefore it is concluded that Civan's Power Law equation of permeability could be an appropriate model for the carbon dioxide sequestration processes.
Over long time periods geological sequestration in some systems also show mineralization effects or mineral sequestration of carbon dioxide, converting the carbon dioxide to a less mobile form. However, a detailed study of these geological systems in many aspects, like petrophysical and geochemical, is needed before disposing of carbon dioxide into these formations. Depleted oil and gas reservoirs and underground aquifers are proposed candidates for carbon dioxide injection. This study is primarily evaluates the effects of carbon dioxide disposal on the geochemical and petrophysical properties of aquifers. For this purpose, two different experimental cases are modeled. The results of the simulation model are compared with published experimental measurements and the variations in porosity and permeability are evaluated with changes in injection rates, temperatures, brine concentration, formation composition etc.
In addition the viability of different permeability-porosity models for the carbon dioxide sequestration process is investigated. Large amounts of carbon dioxide can be injected into deep aquifers. Part of the injected carbon dioxide dissolves into brine which induces chemical imbalances into the system. The in situ pH decreases and the carbonic acid formed in this process react with different rock components to reestablish chemical equilibrium. The typical reactions are dissolution and precipitation reactions of rock matrix and rock components. This results in changes of some petrophysical properties of the formation like porosity and permeability which in turn affect the level of the carbon dioxide sequestration.
The rest of the carbon dioxide which does not dissolve in brine and is in a supercritical state at the conditions of most aquifers being considered may travel towards the top of the aquifer due to the buoyancy forces. The changes in the petrophysical properties because of the precipitation and dissolution reactions may help or hinder the mobility of the traveling carbon dioxide.
