Paleoenvironment of deposition of Miocene succession in well BK-10 of Bengal Basin using electrofacies and lithofacies modeling approaches

Integrating well log and core samples data were applied to interpret paleoenvironment of deposition of Miocene succession for understanding of reservoir facies model from a well Bakhrabad (BK)-10 of Bengal Basin. Miocene succession was subdivided into two depositional sequences/models which contain 9 para sequence sets and 35 para sequences. Detailed examination of well log data, based on considering GR (gamma ray) log shapes, size, lithologic variations permit a subdivision into five electrofacies models, e.g., bell, funnel, cylindrical, egg/bow and linear shape models. The succession consists of alternating shales, shaly sand, silts and sandstones, with minor mudstones. The study revealed eight distinct lithofacies models namely, shale dominated facies, heterolithic sandstone facies, cross bedding facies, parallel laminated shale with alternate sand/silt facies, ripple-lamination facies, bioturbation facies, wavy bedded facies and laminated shale facies. The depositional models for the Miocene sediments encountered in the studied well BK-10 inferred to be that of delta-front setting and fluvio-deltaic to shallow marine environments. Based on lithofacies and electrofacies models associations, Miocene succession interpreted as a coarsening upward deltaic progradation; although more repetitive marine transgression and regression sedimentary processes might have an impact on the architecture of reservoir facies model.