In terrigenous rocks, feldspars are one of the main rock-forming minerals presented in the form of clastic grains, their autigenic varieties are rarely found. In the process of burial of sandy deposits, feldspars grains and fragments of volcanic rocks are most susceptible to changes and dissolution under the action of acidic pore waters. Feldspars are transformed into illite and then into kaolinite. Depending on the degree of dissolution of feldspars grains, their effect on reservoir properties is determined. As a rule, a number of other catagenetic transformations occur in parallel with this process, but the effect of dissolution of feldspars grains on the formation of final permeability can be decisive. Sandstones and siltstones mainly represent the rocks of the studied object; the mass shales fraction does not exceed 30%. Sandstones are medium- and fine-grained, the detrital material in them has a diverse shape: well-rounded and semi-rounded formations, angular fragments and chip-like relics of leached grains. Siltstones are mainly coarse-grained, the proportion of feldspars is 48–50%. According to the results of facies analysis, it was found that the rocks of the studied sediments were formed mainly in the conditions of three facies: delta plains and the periphery of estuarine bars; an active channel; and a beach. In order to ensure the process of modeling the reservoir properties testing of classification models was performed, according to the results of which the choice of a tool for petrophysical modeling of filtration heterogeneity was justified. Clarification of the permeability of the rocks of the object under consideration made it possible to more accurately characterize the spatial filtration heterogeneity, on the basis of which, using a capillary model of the transition zone, the results of assessing the nature of reservoir saturation were clarified, and oil-water contacts correlated with the results of well tests were substantiated.
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