Sedimentation Stages of the Temir Carbonate Platform Formation in the Caspian Sedimentary Basin during the Late Paleozoic

This study presents the results of a comprehensive lithofacies and seismic facies analysis of the Paleozoic deposits of the Temir carbonate platform. Structural interpretation of seismic data allows for the differentiation of the eastern flank of the Pre-Caspian sedimentary basin into distinct facies zones. A series of maps constructed along key reflective horizons helped to refine the subsalt stratigraphic framework and explain previously negative drilling outcomes. The conducted analysis refined the structural framework, enabled seismic stratigraphic and lithofacies interpretation, and facilitated the development of a sedimentation model for the evolution of the Temir carbonate platform during the Late Paleozoic. The results of this study refer that in the OstanSuk-Jurun Depression, the Visean-Bashkirian and Moscowian deposits consist of clastic rocks – shelf clays and sands, alternating with coarse-grained clastic deposits formed by underwater channel flows. In the platform center, carbonate and carbonate-clastic deposits were formed in lagoonal conditions of the shallow shelf, transitioning into deep-water shelf deposits during the Late Paleozoic. Various organic constructions developed in the inner part of the platform, ranging from biogenic reefs to barrier-reef systems, similar to the Tashir, Bozoba, and Kenkiyak structures. Several structures formed on the shelf edge (OGP2 and OGP3) in the southern part, corresponding with the Tashir and Bozoba reef masses. Two isolated structures are distinguished on the structural map (OGP3) west of the Bakhtygarin-Bozoba constructions, presumably of the patch-reef type, based on structural factors. In the Tashir structures and Bozoba, the drilled wells did not penetrate the full thickness of the KT-2 interval. The range of commercially productive sub-salt intervals may be expanded to include the deeply buried Middle–Upper Devonian to Early Carboniferous carbonate succession (KT-III). The exploration and appraisal program is expected to provide a substantial increase in hydrocarbon reserves in the Late Paleozoic biogenic buildups and constitute a significant set of hydrocarbon traps.