Identification of Osinsky horizon organogenic structures by 2D and 3D seismic survey data in the north-eastern part of the Nepa-Botuoba anteclise

Abstract

The fields of Eastern Siberia belong to the one of the main centers of hydrocarbon production in the eastern part of Russia. The main part of hydrocarbon reserves is located in the area within the Nepa-Botuoba anteclise, where the Lower Cambrian deposits are major production objects. The main purpose of this research is to provide a detailed study of the inner space and features of organogenic structures of the Cambrian period, as well as to determine the procedures for detecting reef structures by seismic research methods. Statistical processing of the available factual material on reservoir properties has shown a very uneven distribution of cavernosity (porosity). It is found that pores were formed as a result of leaching of shaped formations in loose packing locations of epigenetic dolomite grains, along the cementing substance in the intergranular spaces, along cracks and stylolite seams. To identify organogenic structures in the Osinsky horizon of the Nepa-Botuoba anteclise on the basis of seismic studies some additional methodologies have been selected. Identification of single reef structures in the Osinsky horizon of the Lower Cambrian based on the analysis of seismic amplitudes was carried out by means of a 2D and 3D seismic survey. According to the data of seismic studies, the Nepa-Botuoba anteclise features the development zones of both linear and single carbonate structures. It is also revealed that there is an increase in effective thicknesses in wells located in the annular anomaly. Summing up the results and analyzing the compared materials, it can be concluded that the main identification method of ring zones in wells is the method of longitudinal wave slowness measurement. A comprehensive analysis of 2D and 3D seismic survey data by the common depth point method as well as by a number of other methods using a specific algorithm allowed us to identify individual formations of organogenic (riphogenic) structures in the carbonate section of the north-eastern part of the Nepa-Botuoba anteclise.