The expansion of unconventional oil and gas development has placed a new emphasis on better understanding well performance. This paper discusses a new chemical tracer technology which allows operators to empirically measure what sections of an existing well are most productive and remove uncertainties from future well development. Comparison of production rates, stimulation design and petro-physical characteristics of the well allows targeted stimulation of the most productive sections in subsequent wells using the best stimulation practices available. Hydrocarbon tracer results allow an improved design of landing zone strategy, number of perforations to use, cluster or stage spacing and number of clusters or stages in future wells. Although a new technology, in-situ hydrocarbon tracer tagging has been proven effective in over 30,000 stages in plays across North America and is now providing completion evaluations worldwide. This technology provides the knowledge of a PLT without the cost and risk associated with entering the well, and as an added benefit, provides information on well spacing when adjacent wells are sampled and tested for tracer presence. This paper discusses the concept of the technology and illustrates its use and benefits through review of multiple case studies.