Clarification of the material composition of the pre-jurassic complex of the northern part of the Kaymys NGO

Abstract

Numerous researchers have extensively studied the material composition of pre-Jurassic deposits. Over the years, various authors have created geological structure maps of the pre-Jurassic basement of Western Siberia, covering both the entire region and specific areas.

The most recent version of such a map was produced in 2016, through collaboration among several research institutions. The geological structure depicted in the 2016 map is primarily based on interpretations of potential field data and results from deep drilling.

It is important to note that the vertical profile of the pre-Jurassic section remains poorly understood. In many wells, core samples were only collected from either the preroofed part or the bottom-hole parts of the section, leading to generally low core recovery rates. Descriptions of preJurassic cores found in well reports, particularly when lacking laboratory analysis, often fail to provide reliable information about the material composition. This study analyses core descriptions and thin-section examinations of pre-Jurassic deposits conducted by the authors at the core storage facility in Khanty-Mansiysk. It incorporates seismic survey reports from research teams that have worked in the area, along with published data from various researchers who have investigated the geological structure of the Yugansk Depression and its surrounding regions.

Authors studied core samples from several fields including Travyanaya, Larlomkinskaya, Novoyutymskaya, Merkulskaya, Severo-Yutymskaya, and Koimlykhskaya.

The results of this study suggest that revisions may be necessary in the mapped distribution of material and age complexes within the pre-Jurassic geological framework of the KhantyMansi Autonomous Area —Yugra.