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Abstract
Geological storage of carbon dioxide has been recognized as one of the most effective options for mitigation of industrial emissions. Deep saline formations, otherwise called saline aquifers, are among the potential sequestration targets. To enhance the confidence regarding some of the key issues, such as site selection, planning, injection itself and long term monitoring of sequestration site, management of uncertainties is an essential step.

This paper consists of two main parts. In the first part, CO2 storage in Mt. Simon sandstone in Ohio State, USA, is modeled using two compositional simulators – TOUGH2-ECO2N and CMG-GEM, which results provide an initial assessment for storage capacity of this site and discuss possible safety issues. In the second part, objective is reached using combination of experimental design and response surface methodology. Experimental Design (DOE) is an unbiased, rapid approach for obtaining probabilistic results. The purpose of Response Surface Methodology (RSM) is to fit simulation results to a response surface using analytical or numerical functions. In this study, DOE and RS methodologies were jointly applied to investigate the effect of uncertainties of key saline aquifer parameters on long-term CO2 storage in the form of solubility trapping and on the total storage capacity. The selected parameters in this study are: absolute permeability, global porosity, end point saturations, irreducible liquid saturation, temperature, aqueous phase salinity, vertical to horizontal permeability ratio, diffusion coefficient of CO2 in brine and relative depth of perforation interval.

Mt. Simon is expected to be a safe, secure CO2 storage formation within selected site due to several factors such as regionally extensive caprock and seals including Eau Claire Formation (Cambrian) and Knox Dolomite (Cambo-Ordovician) and high CO2 storage capacity with favorable reservoir properties. This conclusion is supported by the results of modeling performed using both TOUGH2 and CMG GEM simulators. It is expected that 15-17 Mt of CO2 could be safely injected into Mt. Simon formation during 25 years via one vertical injection well while staying below fracturing pressure. It was demonstrated that combination of DOE and RSM techniques could be successfully applied for research into CO2 sequestration.

Introduction
The continuous rising of industrial emissions worldwide at unprecedented scale drives humanity to search for mitigation measures. One of the proposed mitigation measures is sequestration of carbon dioxide. CO2 GS (carbon dioxide geological storage) is one of the most talked about but least understood topics among the populace. CO2 GS involves capturing carbon dioxide from industrial emitters and sequestering it underground, which “sequestration” term defines a permanent safe confinement of gas in underground strata, where it would be injected by using conventional oil and gas industrial practices such as via vertical and/or horizontal injection wells. Canada has the same environmental issues as other developed and developing countries. The problem of the greenhouse gas (GHG) emissions increase and meeting the Kyoto emission goals is the most critical issue in the Canadian environmental policy development today. All GHG emissions could be categorized into two main components: the emissions caused by the activities of individuals and industries. An underlying principle is that without demand by individuals, the industry would not exist. Total emissions caused by individuals (residential plus transportation sector) accounted roughly for 35% in Canada as of 2004. In an attempt to make a forecast for the future we also should take into consideration the expected growth of the Canadian population to about 50 million in 2050 [1]. The population growth will drive demand for food and energy, goods and services, which, in turn, will cause the significant increase of GHG emissions from this sector.