Structure and depositional environment of the Vasyugan Horizon (Upper Bathonian–Oxfordian) in the Aleksandrovskoe arch area (West Siberia)

An integrated sedimentological study of the Vasyugan Horizon in the Aleksandrovskoe arch area was performed, during which its depositional environments were reconstructed and a series of paleogeographic maps was plotted. It has been established that shallow-marine, marginal-marine, transitional, and continental depositional environments existed here at various stages. Most of the arch area is characterized by sections of the transitional Naunak–Vasyugan and Vasyugan–Naunak types; the westernmost part, by sections of the Vasyugan type, and the easternmost part, by sections of the Naunak type. The sand beds of the J1 horizon are low-quality reservoirs, whereas those on the western slope and the northern pericline of the Aleksandrovskoe arch are of better quality.