Characteristic of Bazhenov carbonate rocks: Yaptiksalinsky megadepression, northern part of Western Siberia

The authors discuss the Bazhenov rocks in the northern part of Western Siberia by the example of core from the well drilled in the Minkhovsky License Area; the aim is find promising intervals for development planning. Brief description of the formation column and identified bedsets is presented to enable a unified correlation in remote zones and interpretation of data from different fields. The detailed consideration of the fourth bedset deposits is given for lithological and petrographic description and determination of carbonate interlayer genesis. There are two lithological cycles with transgressive-regressive sequence identified in the bedset section, which are represented (from top to bottom) by argillaceous-siliceous and carbonate rocks. The results of the complete analysis of carbonate interlayers show that they have an organic (biogenic) nature; they are the product of microbial communities life. The botryoidal formations composing both nodules and limestone interlayers. These formations are the result of recrystallization of protogenous aragonite marine cement. The botryoidal formations are indicative of the marine, smoother depositional settings, which are typical of steep sea slopes. There are multidirectional fractures found in limestone, which are completely filled with a substratum rock fragments; this is indicative of the periods of tectonic activation