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Electrofacies Analysis and Shale Gas Potential of the Carynginia Formation (Perth Basin, Western Australia)


As the unconventional activities in petroleum industry are globally increasing, the importance of evaluating shale gas potentials in different parts of the world becomes crucial. In recent years, shale gas plays of Western Australia are also being carefully looked at and the Permian Carynginia Formation (Perth Basin) is considered as one of the primary targets in the region. There are about 341 wells in the Perth Basin, of which 187 wells penetrate the Carynginia Formation. 32 wells crossing the Carynginia Formation, have been studied and about 600 Rock-Eval data were analyzed to reconstruct burial history and develop thermal modeling. The Carynginia sediments show a trend of increasing maturity from north to south, favoring the occurrence of gas shale near the basin's center. After a detailed study of different well logs, well reports and core observations, 6 wells were selected for shale gas layers identification. Detailed electrofacies studies have been developed, including cluster analysis and its correlation with shale-gas prone lithofacies. Based in burial history and thermal modeling, 3 Types of wells have been considered. Type 1 includes wells Geelvink 1A, Jurien 1 and Narlinque, with modeled maturation for gas and log data analysis pointing to layers with good potential for gas shale production (high GR, IND, DT and low SP). Type 2 includes wells Cadda 1 and Mt Horner 1, with modeled maturation only for oil, but electrofacies data pointing to layers with shale-gas potential (high GR, IND, DT, and low SP); this situation may be due to the presence of Type III kerogen, more prone to gas generation, even within the late-oil window. Type 3 is represented by Mondara 1 well, with insufficient maturation and no electrofacies characteristics of shale-gas. This study illustrates a case of electrofacies cluster analysis applied to shale gas prone units, as a well log tool to identify and characterize the presence of shale-gas layers.