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The efficient and wide use of the isotope analysis has been extensively documented in the reservoir assessment and “sweet spot” identification. However, for a long while isotope analysis could only be performed in stationary laboratory via sophisticated instruments and significant turning-around time. Until very recently the isotope analysis could be done in the field, but only with methane isotope ratios. In this work, we present the novel real-time isotope logging technique for methane, ethane and propane (C1, C2 and C3), and demonstrate how to enhance the “sweet spot” prediction and hydrocarbon production. This new instrument, the Gas Chromatography-InfraRed Isotope Ratio Analyzer (GCIR2), represents the first of its kind field-deployable isotope ratio analyzer with high accuracy and precision. It is rigorously calibrated with the GC-IRMS (the isotope-ratio mass spectrometry) using standard gas. By field deployment during drilling, we can analyze hydrocarbon gas carbon isotope ratios with only minimal turning-around time. We analyze gases derived from both mud gas and cuttings by using this proprietary design of isothermal grinding. All this new information can be given to producers in a standard log format along with other logging parameters. Our results from field application case studies show that the analytical capacity of this instrument makes it possible for various applications in vertical and horizontal drilling. We demonstrate examples from vertical drilling with pairs of mud-gas and cutting-gas under well-controlled experimental conditions to assess nanoporosity and permeability. We also present the usefulness of this technique to …