The article discusses the features of the structure of the void space that affect the filtration properties of volcanic rocks. The features of the formation of primary and secondary void space of volcanogenic rocks are described. The primary void space is represented by shrinkage cracks, degassing voids, perlitization (in lavas), crushing cracks (in lava clastic), voids associated with loose packing of fragments (in pyroclastic), interclastic pores (in sedimentary-volcanogenic, volcanogenic-sedimentary and sedimentary rocks) . The formation of voids of secondary origin is due to tectonic, hydrothermal-metasomatic processes. Comparison of permeability and porosity characteristics of volcanogenic and sedimentary rocks is made. It is shown that a characteristic feature of volcanic rocks is the complex structure of void space. The dimensions of the voids exceed the dimensions of the channels connecting them by two or three orders of magnitude. This distinguishes volcanic rocks from sandy-argillaceous and carbonate ones, where the discrepancies in the sizes of voids and narrowings between them generally do not exceed one or two orders of magnitude. This factor predetermines the reduced filtration properties of volcanic rocks. According to the analysis of thin section images (imaging analysis), NMR studies of fully water-saturated core samples, capillary studies of volcanic rocks, significant discrepancies in the sizes of voids according to various methods were revealed, indicating a significant difference in the sizes of void bodies and channels connecting them. It is shown that with an increase in the discrepancy between the sizes of void bodies (according to image analysis) and the channels connecting them (according to capillary studies), the filtration properties decrease. Permeability increases with an increase in the size and content of filtering void channels. At the same time, in order to achieve one value of the permeability coefficient, the proportion of voids of small size should be greater than that of large ones. It is proposed to describe the relationship between the filtration and reservoir properties of volcanogenic rocks using a dumbbell model that describes the void space as an interconnected system of void bodies (macrocapillaries) and channels connecting them (microcapillaries). The model takes into account differences in the equivalent cross sections (capacitive, filtration, electrical) of macro- and microcapillaries interconnected by electrohydrodynamic analogy. It is proposed to determine the permeability of fractured volcanic rocks using empirical dependences on fracture porosity.
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