Reservoir properties of the Bazhenov formation

摘要

The work is devoted to interpretation of results received from a wide complex of laboratory petrophysical investigations of the Bazhenov formation rocks collected from the core in several fields in Western Siberia. The main goal is comparison and substantiation of evaluation results received from using of different methodologies of petrophysical rock properties measurements. It is necessary for identification of the most adequate and applicable methodology of petrophysical investigations realization for the Bazhenov formation. The Bazhenov formation draws attention of researchers for many years [2, 3, 4, 6]. It significantly differs from usual sedimentary rocks by both composition and physical properties. Lithological and petrophysical investigations of the Bazhenov formation core from different fields showed that it is represented by clayey-silty porous-fractured and fractured reservoirs characterized primarily by high variability of reservoir properties in the formation’s distribution area. The majority of reservoirs have low porosity (1-2%) and permeability of less than 0,1 mD. However in some well columns there are interlayers with porosity reaching 16%. Standard approaches of traditional in Russian Federation petroleum well logging practically don’t allow quantitatively estimate the composition and reservoir properties of natural reservoirs. That’s why it is extremely essential, on the one hand, to engage methods providing possibility of quantative definition of rock mineral-component composition and enhancing accuracy of its reservoir properties, effective porosity and permeability, and, from the other hand, to prepare new approaches for interpretation of the proposed complex. The problem of effective porosity and oil and gas saturation determination is complicated by the fact that these natural reservoirs contain big amount of kerogen while mineral component consists of a silicon dioxide, clayey minerals, pyrite, albite, carbonaceous minerals. Selection of them could be defined by the core but it is essential to estimate its weighting in column of a definite well. Therefore main factors that should be kept in mind while evaluating porosity are complex mineralogical rock composition, shale content and high content of organic matter (reaching 40% by mass). Existing methodology of reservoir identification and its properties evaluation by well logging don’t rely on detailed investigations of the Bazhenov formation composition. This situation is explained by an attempt to average accumulated data of the Bazhenov formation in the whole Western Siberian oil and gas basin not always confirming it by results from a real object core investigation. In the present work there are results of core investigations in some areas allowing adjusting the interpretation of well logging to evaluate reservoir properties of the Bazhenov formation.