Study of Natural Reservoirs in the Volcanogenic-Sedimentary to Pre-Jurassic Complex of the West Siberian Oil-Gas Basin

This article provides a thorough analysis of the potential for petroleum within the Pre-Jurassic Volcanic-Sedimentary Complex (PJVC) of the West Siberian Sedimentary Basin. Based on existing petrogenetic classifications of the complex's volcanic rocks, the article develops a model of major eruptive cycles, delineating the distribution of reservoir and non-reservoir rocks. To minimise uncertainty in inter-well correlation, the article proposes a methodology for rock discrimination using standard wireline logging suites. This incorporates fracture analysis to evaluate the likelihood of petrogenetic types belonging to the reservoir or non-reservoir categories. The integrated interpretation of seismic data, well logs, core petrography and lithology enabled cycle elements to be identified within the seismic field and surfaces to be constructed representing conditional geological bodies associated with natural reservoirs. Applying this workflow to a field in Western Siberia involving over 300 wells revealed that the PJVC comprises a series of ten lenticular packages exhibiting an imbricate lateral overlap pattern, ranging from a single package in the east to three superimposed packages in the northwest. Further investigation into the hydrodynamic connectivity between these units is required, however, as this is complicated by the high levels of lateral and vertical heterogeneity and faulting. This investigation is necessary in order to build a complete PJVC model that is suitable for field development planning and appraisal drilling. Nevertheless, this study establishes a foundational framework for the efficient investigation of similar rock complexes in the future.