In wells producing from multiple zones using a single tubing string, accurately determining the individual contribution from each zone is crucial for reserves evaluation and future projections. Gas analysis obtained during the production phase and drill stem tests can provide valuable information about zonal contribution, which can be utilized to assess the current contribution. We analyzed the available data and recommended to the client to install a Gas Chromatograph to obtain live gas composition data from the reservoir. Once sufficient data had been gathered, we analyzed the trends of key gas components and drew our conclusions based on the available data. We were successfully able to predict the downhole zonal contribution from individual reservoirs. The percentage of zonal contribution was later confirmed when the client conducted a production logging survey, which validated our findings. Our services eliminated the costly requirement of downhole logging surveys, production loss, and risks related to well interventions. When correlated with live gas chromatograph data, it is possible to predict live zonal contribution without the need for well intervention.