The article is devoted to the reservoir properties analysis of the OI-II formation at the Srednebotuobinskoye oil-gas-condensate field, which is one of the largest in Eastern Siberia. The field was discovered in 1970. The main target is the ancient Vendian sandstones of the Botuobinsky horizon. The production started in 2013. The second largest reservoir is the OI-II formation, but this object is still at the stage of exploration. Reservoir zones of the Osinsky horizon with improved properties are distinguished according to 3D seismic data and have an annular shape in plan ("ring anomalies"). The ring anomalies are limited not only in area, but also in depth – they occupy only a part of the section of the Osinsky horizon. Since earlier the assessment of the properties of the formation was carried out over the entire section of the formation, the ring anomalies, as an interval in the section, was not distinguished. Due to this, there was no correlation between the zone of improved reservoir properties and ring anomalies. In the present study, it is customary to compare properties in three intervals when analyzing the properties of the Osinsky horizon: only the ring, the zone outside the ring (above and below) and the entire Osinsky horizon. For a more confident identification of the ring anomalies intervals inside the Osinsky horizon according to log data, the subsidiary of Rosneft Oil Company - RN-Exploration LLC applied the approach of constructing probability density maps based on the values of the interval time of the p-wave and neutron porosity. Thanks to a new approach for the allocation of objects and reservoir properties estimation by, the boundaries of the intervals of ring anomalies in wells were clarified, a drilling rating on wells was compiled, a plan for further study of anomalies was made.
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