One of the most common questions in early appraisal and development of either conventional or unconventional reservoirs is understanding the primary control on production yield (stb/mmscf) or gas-oil ratio (GOR) (stb/scf). Fluid and/or rock based geochemistry can be used in conjunction with engineering principles to understand what the primary mechanism(s) are that control the production yield. In some scenarios, yield can be improved, but in others not. Understanding the primary mechanism on production yield can lead to improved well completions for development of the existing assets or a pivot to testing different pressure and temperature or trap style reservoirs with higher liquids content potential. This presentation focuses mostly on general application principles and introduction to some specific analytical geochemical methods. The main produced yield control mechanisms that are readily identifiable from analytical geochemistry methods are production fractionation, source rock quality, geologic fractionation, and source rock or reservoir thermal maturity.