Forecast of cambrian carbonate reservoir properties of the Chonsk group of fields taking into account vertical heterogeneity

Introduction. The study of the Cambrian carbonate deposits of Eastern Siberia, particularly the Osinsky Horizon (Reservoir B1) of the Chonsk Group of Fields, is challenging due to its complex vertical heterogeneity and intense secondary processes, such as calcitization, which significantly affect the reservoir properties.

Aim. The aim of the work is to analyze the vertical heterogeneity of Reservoir B1, assess the impact of secondary processes on reservoir properties, and develop an improved approach to its geological modeling.

Materials and methods. Based on drilling data, core, and lithological studies (thin section analysis) from key wells, Reservoir B1 was subdivided into four packages. Lithofacies features, reservoir properties, and the distribution of secondary alterations for each package were analyzed. The relationship between calcite content and fracture density was additionally investigated using well-logging data.

Results. Four packages within Reservoir B1 were identified, differing in depositional environments, lithological composition, and degree of secondary alterations. The lower package (up to 40% of thickness) is characterized by a high degree of calcitization, leading to a significant deterioration of reservoir properties. The upper packages are composed predominantly of dolomites with better reservoir properties. No significant differences in porosity permeability relationships between the packages were revealed. No clear correlation between calcite content and fracture density was found.

Conclusion. To improve the reliability of the geological model of Reservoir B1, it is proposed to model each package separately using individual input statistics and settings that account for their distribution patterns. The developed approach is applicable for studying coeval deposits with similar sedimentation conditions in Eastern Siberia.

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