It is known that main oil reservoirs are allocated in terrigenous sedimentary rocks representing a structured matrix with texturally organized pore space. In turn, the typical structured matrix is composed of mineral grains of various sizes that look like chaotic systems. This paper describes detailed analytical review of cores grain-size analysis results from wells of one of the well-known oil deposits in Azerbaijan. The studies covered the most typical for the region productive reservoirs containing pelitic, aleuritic, fine-grained sand and medium-grained sand fractions. Results of fractions content variation depending on depth are presented in the form of circular diagrams of porosity changes according to the fractional composition and mechanical compaction of sediments. The calculation of the pairwise correlation coefficient between the fractions and the parameters averaging the particle size distribution and reflecting the sorting of the rocks showed that they are independent and unrelated by any functions. At the same time, the influence of individual fractions, and most importantly their ratio on the value of intergranular porosity, is not equal. Detailing of the modeling process of multimodal distribution has shown that the use of fractal concepts is more efficient in this issue. To assess reservoir characteristics of the oil rocks, alternatively the dependence between fractality index and oil saturation was calculated.

Keywords: intergranular porosity, terrigenous reservoirs, grain packing, fractality index, particle size analysis, dominant fractions

 

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