Understanding the physics of injection techniques required for large scale geological sequestration of CO2 is very important in order to mitigate the global warming in an effective and economical manner. In this paper, an analytical solution is presented to formulate the size of the CO2 droplets in terms of process parameters for Ex Situ Dissolution Approach (ESDA). The proposed solution is valid for turbulent bubbly flow regime and explicitly accounts for mass transfer and pressure changes along the pipeline length. Some technical and economic aspects of the ESDA are also addressed. In addition, the governing equation of mass transfer was numerically solved using the MATLAB (R) software. Comparison of the numerical and analytical results shows a good agreement for wide ranges of thermodynamic and flow conditions. The proposed analytical solution is very useful to estimate the length of pipeline required for full dissolution of CO2 droplets prior to injection into the ground. Results presented in this study indicate that the wellbore tubing could eliminate the need of horizontal mixing pipe in the ESDA. (C) 2012 Elsevier B.V. All rights reserved.