Assessment of reservoir properties of rocks based on core data from the Neftchala field

Analysis of the features of changes in the percentage content of rock fractions along productive horizons shows that the granulometric composition is not constant, and its fractions are distributed unevenly across stratigraphic horizons. High clay content and low clay content reservoirs are often found here. For example, in intervals with a predominance of fine-grained fractions, the clay coefficient is observed with fairly high values (Ccley≥0.30), and in a sedimentary complex with a predominance of coarse-grained fractions with relatively small values (Ccley≤0.35). At relatively small (5–20 %) clay values, the porosity and permeability gradient decreases. Thus, when changing the clay content from 5 % to 20 %, the porosity value decreases from 25 % to 22 %. At relatively large (С≥30) values of clay, the gradient of porosity and permeability decreases. Such a situation is more often observed in the clay-siltstone deposits of the region. From correlations of petrophysical parameters, it is known that at small values of porosity (10–16 %), the value of permeability increases, but does not exceed 0.1–0.22 mkm2. As the porosity increases, the value of permeability increases and Kcond=0.5–0.9 mkm2 with values of Kpor=23–28 %. The geological and statistical analyzes presented here show that there is a correspondence between the characteristics of changes in the indicator parameters of their layers. Correlations between the petrophysical parameters of the rocks in the Neftchala field increase depending on the depth. In clayey-sandy and sandy-sandy deposits, a decrease in the chaotic scatter of the values of these parameters led to an increase in the correlation coefficient. An increase in the correlation coefficient indicates further improvement in the sorting of reservoir rocks. Improved sorting indicates that the reservoir layers are more uniform. An increase in the chaotic scatter of petrophysical parameter values in clayey-siltstone and clayey deposits caused a relative decrease in the correlation coefficient. A decrease in the correlation coefficient also led to a decrease in the sorting of reservoir rocks. A decrease in diversity indicates that the layers are more heterogeneous. Thus, based on the results of the analysis of core data from the Neftchala field and the features of changes in the material and mineralogical composition of rocks, a study was made of the features of the distribution of parameters characterizing the petrophysical properties of rocks according to hypsometric and stratigraphic data. sections, analysis of the relationships between them using mathematical and statistical methods, its clay-sand and sand-sand deposits shows that the reservoir properties are high.