Oil and Gas Institute, Ministry of Science and Education of the Republic of Azerbaijan, Baku, Azerbaijan¹ ; Azerbaijan State Oil and Industry University, Baku, Azerbaijan²

A. B. Hasanov, Senior Researcher¹, Professor², Doctor of Physical and Mathematical Sciences, adalathasanov@yahoo.com
V. Sh. Gurbanov, Executive Director¹, Professor², Doctor of Geological and Mineralogical Sciences

Azerbaijan State Oil and Industry University, Baku, Azerbaijan
G. G. Abbasova, Lecturer

Among many influences on oil and gas extraction efficiency, one of the main factors is the natural or artificially modified hydrodynamics of fluid flow in reservoirs. Even the most favorable natural hydrodynamics in the subsoil is usually complicated by unavoidable operations carried out above productive horizons and aimed to provide well performance (hydraulic fracturing, etc.). Naturally, such operations are carried out with the aim of intensifying oil and gas production, as well as increasing oil recovery factor. Under the impact of these operations, productive reservoirs, which are porous and permeable media, drop into various destructive states which are characterized by density of cracks per unit volume of rocks and by the fluid dynamics in reservoirs. This article examines the process of deformation of reservoirs with the formation of a branched system of cracks having a fractal structure, and also models the mechanism of crack formation with regard to the change in the fractal dimension of a crack system. The authors identify the stages in the crack formation process, according to which, at the initial stage of cracking, a chaotic system of cracks appears, accompanied by an increase in the fractal dimension of the system up to a value of 1.6. At the next stage, with a slow increase in the fractal dimension from 1.6 to 1.73, cracks begin to unite and form a rupture area. Further, the fractal dimension holds practically constant, and when its value reaches 1.75, discontinuity takes place in the medium. The inevitable deviations of the modeled media from the described pattern of crack formation are explained by the fact that real-life geological media most often have a certain multi-level discontinuity of the internal structure and possess defects of various hierarchical levels, which leads to fluctuations in distribution of micro- and macrostresses at these discontinuities.

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