This article discusses the results of the study of hard-to-recover reserves development features. The research was carried out at Zarubezhneft JSC and the RUDN University. Geological factors are considered that affect the effectiveness of stimulating the formation during oil and gas deposits development (maintaining formation pressure, water-gas stimulation, injection of reagents that reduce oil viscosity, steam injection, and others). The article presents an extended scheme of typing the factors that determine the existence of accumulations with hard-to-recover hydrocarbon reserves including the issues of such deposits development. Cases are considered when the underestimation of zones of increased permeability caused by the development of fractures determines both the practical exclusion of the upper parts of hydrocarbon deposits from the development, and the possibility of forming paths for advanced watering, which negatively affect the development of oil and gas. Particular attention was paid to the analysis of the mechanism of formation and evolution of the fractured type of voids in carbonate deposits, which makes it possible to increase the reliability of determining the nature of the distribution of this type of voids in the volume of the deposit. On the example of a number of deposits of the Timan-Pechora oil and gas province, confined to carbonate reservoirs, two types of fractured layers are distinguished. The first occurs in the upper part of the strata, occurring on rocks with cavernous-pore and porous reservoir types, which are confined to parts of deposits that are often not taken into account when calculating hydrocarbon reserves. The second type is recorded in the central part of the reservoir section, which often determines the advanced waterflooding, which negatively affects the oil recovery factor.
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