Geological structure and occurrence conditions of the Bazhenov formation within THE South Tambey gas condensate field

Background. In the 21st century, exploration works in the previously discovered Jurassic deposits has been launched in the north of the Yamal Peninsula. The South Tambey field was no exception, where 3D seismic surveys and exploration drilling have been carried out over the past 10 years to study of Jurassic sediments and rocks of the Bazhenov formation. Due to the lack of a data sufficient sample in the northern regions of the Western Siberia, formation was poorly studied. The main ideas were formed on wells scattered at great distances from each other without the possibility of a clear correlation. After receiving new drilling materials, it became possible to examine the deposits of the Bazhenov formation in more detail.

Aim. Determination of the structural features and occurrence conditions of the Bazhenov formation.

Materials and methods. The research was based on the logging data of exploration and production drilling. A detailed correlation of well sections was performed, which was compared and analyzed with the core description and interpretation of seismic survey materials.

Results. The lithological characteristics of rocks obtained by core description are presented, the atypical neighborhood of stromatolites and radiolarians in the section is noted. Based on a detailed correlation, the Bazhenov formation was divided into three intervals with characteristic geophysical logging values and distribution features over the area. The clinoform occurrence with development in the north-west direction is determined. Based on the areal variability, it is proposed to distinguish two types of the Bazhenov formation, and approaches to their tracing are considered.

Conclusion. The study of the Bazhenov formation revealed a co-directionality of the spatial orientation of the faults, the progradation of the Achimov clinoforms, and changes in the thickness of the Bazhenov formation. A hypothesis has been put forward about a single tectonic regime that prevailed in the Upper Jurassic and Lower Cretaceous. It is proposed to consider flower (keyboard) tectonics as the main factor that determined the structure and occurrence conditions of the Bazhenov formation.

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