Geological sequestration of CO2 has been recognized as an important strategy for reducing the CO2 concentration in the atmosphere. Simple and easy to use modeling tools would be valuable in assessing the performance of a deep well operation during and after injection. Presented here is a semi-analytical model to simulate the deep well injection of CO2 for geological sequestration. Equations governing the radial injection of an immiscible CO2 phase into saturated confined formations (representing deep saline aquifers and reservoirs), its axisymmetric flow around the injector and eventual buoyancy driven floating with simultaneous dissolution were formulated. The effect of pertinent fluid, reservoir and operational characteristics on the deep well injection Of CO2 was investigated. The results indicate that the injected CO2 initially grows as a bubble radially outward, a part of which eventually dissolves in the formation waters, floats toward the top due to buoyancy and settles near the top confining layer. It was shown that the formation permeability and porosity, as well as the rate and pressure of injection, all have a significant influence on the growth and ultimate distribution of the immiscible CO2 phase. Further, dissolution Of CO2 also was shown to have a significant effect on the growth and distribution of the CO2 bubble.