A long history of using of fossil fuels has resulted in increased atmospheric CO2 concentrations. This anthropogenic process has influenced global climate change. One possible way to retard this increasing atmospheric concentration is to geologically sequester CO2 emissions. Successfully implementation of this technology requires a full understand of associated risks and detailed resource optimization. It is important to choose the appropriate level of complexity when selecting the type of simulation model to apply to this problem. Many risk assessment and optimization tools require large numbers of realizations. In most cases, using a full scale numerical CO2 leakage model for this process becomes computationally prohibitive. Therefore, faster CO2 leakage estimations are needed. An excellent semi-analytical multi-phase CO2 leakage algorithm has been developed by Celia et al.(2011). In the following work, three possible accuracy improvements to this algorithm are proposed and explored. Differences between leakage rates and pressure distributions are compared between existing and modified methods. Improvement suggestions are then made from these observations.