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For over twenty years, gas chromatography has been used as a routine tool for characterizing crude oils. The chromatograms represent unique fingerprints of the oil which can be used for correlation. While gas chromatography has traditionally been applied to exploration problems, the technique is also very useful for development and production applications. This includes characterizing different reservoirs and determining the extent of vertical and lateral continuity. Recently, a new application of this reservoir typing through gas chromatography has been developed for production allocation calculations.In many fields, the producing wells are multizone completions, and the produced oil is, therefore, a mixture from the different zones. It is important to know the relative contribution of each zone to the mixture and to monitor changes in production with time. This allows the calculation of accurate production allocations, determination of which zone(s) are responding to the injection of water, steam, etc., and monitoring of well performance to identify problems, such as leaky casings.While production logging is the traditional tool for production allocation determinations, the chromatographic analysis has several advantages. It is a simple and inexpensive analysis, turnaround times are short, the analysis can be set up in a field laboratory, and the technique has been used successfully in several cases where conventional production logging techniques were inadequate. The technique uses a form of capillary chromatography with computer programs for processing the raw chromatographic data, matching chromatograms, and calculating the composition of oil mixtures based on individual and member oils. We have used this technology in our research laboratories and have tested it through field trials.In this paper we will describe the chromatographic production allocation technique and illustrate its use with two field examples. Based on our current experience and familiarity with CPI operations, this technique should be useful in the development and production of Indonesian oil fields, such as Minas, Duri, and Zamrud.