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Establishing Sand Dispersion and Conceptual Geology Using High-Resolution Borehole Imaging and Core Data: An Integrated, Multiwell Approach for Field Development


Tapti-Daman field in Mumbai offshore always pose surprises in terms of missing reservoir sand while drilling new wells, based on the seismic analysis and available models. Understanding sand dispersion and conceptual Geology is critical when seismic data is of limited help; sanding issue even intricate the problem by reducing the full core recovery. Therefore, taking an alternative approach is imperative to understand the sedimentary environment and sand dispersion in the field, which will help in future well placement and field development. In this study, a multiwell integrated approach was adopted to unveil the reservoir Geology. This workflow aims at establishing high-resolution geological analysis based on image logs and core data along with conventional openhole logs in multiwell. A 2D facies model was constructed using normalized density and neutron logs; the cutoff of different facies was calibrated from core lithology. Multiwell correlation was performed using the lithofacies model in dip and strike section, which provides a clear idea about the reservoir thickness variation in the field. Dips derived from image log were combined with the true stratigraphic thickness to understand the different sedimentary bed-form geometry. More emphasis was given on different type of cross beds. Integration was performed of image-log-derived results with the lithofacies and core analysis to understand the depositional environment. An attempt was made to understand the reservoir quality of different sand units using the advanced analysis results. Multiwell facies correlation clearly reveals sand-body thickening direction toward the SW, which corresponds to the paleocurrent direction derived from image log. Integration of the multiwell dataset clearly indicates deposition in continental fluvial environment, where main reservoir sand is represented by bar sand. In this paper, two sand units are identified as the best reservoir quality based on analysis, which was further validated by testing results. These two units produced gas correspondingly at the rate of 1,77,209 m3/day and 2,38,667m3/day. The model developed so far is being used to refine the infill well program in the field.