Geodynamic and Lithofacies Features of Deposit Formation of the AV<sub>1</sub><sup>1-2 </sup>Horizon of the Samotlor Field

Abstract

An era of a high-gravity oil of the Samotlor field formations AV2-5 and BV8-10 is near to its end. The production deposits of the AV11-2 horizon are the main reserve of oil production and the basic prospect in this area. Stratigraphically, the AV11-2 horizon belongs to the Alym suite of the early Aptian Age that was distinguished as an individual unit at the 1967 interdepartmental stratigraphic meeting with the stratotype in the Uvat test well. This part of the section started to form around 400,000 years ago and is represented by siltites with interlays of clays and sandstones, primarily bioturbated ones, which causes the specific lens-clustered laminarity of these rocks (Ryabchik) with rare double leafs and single pancake-shaped primitive foraminifers such as saccamina. Specific features of the geological structure and oil-and-gas content of the AV11-2 horizon within the area under consideration were in various aspects described earlier in the works of many researchers [1-8]. Nevertheless, when new geological and geophysical information had been accumulated, the need arose to cover this issue once again. Since it makes us consider the geological modeling of formations in the horizon from quite a different angle, we need to create various structural models of HC reservoirs, development flow diagrams, etc. The research objective is to define the genesis of producing deposits of the AV11-2 horizon and identify fascia complexes in them. Using a system of special studies and methods for analyzing geological development and structure (paleotectonic, grain size, fascia, electrometric, etc.), the areas of sedimentation and fascia systems were diagnosed within the area under research.