To achieve economic production from shale gas reservoirs hydraulic fracturing is required. This stimulation technology facilitates the interconnection of the multiple pore systems with the wellbore. Particularly, shale gas reservoirs exhibit a dual porosity system linked to the free and adsorbed fluid phases, being the adsorbed phase a significant control on the long-term production. The adsorbed volume is strongly related to the total organic carbon (TOC) and thus, it is often assumed that higher hydrocarbons in place occur within the high TOC intervals. This study evaluates this relationship and the impact of the adsorbed phase to OGIP (original gas in place) and production behaviors. Analysis of petrophysical data and log-derived TOC of the Duvernay Formation reveals that variations in mineralogy impacts the quantity of TOC. It is observed that increase in carbonate contents correlate with lower organic contents, whereas increase in quartz and clays correlate with higher organic contents. Results of Langmuir isotherms indicate that methane adsorption capacity is directly proportional to the TOC content. Further, this study analyzes production data of two multi-fractured horizontal wells by analyzing the relative contribution of the adsorbed phase to the free gas. It is found that contribution of the adsorbed phase is maximum during the initial phase of the production cycle which declines as the reservoir pressure drops. The estimated relative contribution of the adsorbed phase to OGIP is nearly 50% which is significant to be considered negligible. Further, the contribution from the adsorbed phase is found to be 45% in the early phase of the production which drops down to 25% after 10 years of the production. Finally, this study illustrates that the relation of TOC with fluid characterization and recoverable reserves is complex and should be analyzed with the variation in adsorption and desorption capacity of lighter and heavier components.

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