Oil and gas producing companies use hydrodynamic models to predict hydrocarbon production and adopt the best development option. The choice of model type depends on the geological features of oil-saturated reservoirs and the composition of hydrocarbons in the field under consideration. The paper describes the importance of applying a dual environment model for carbonate reservoirs of high-viscosity oils, the share of world production for which is steadily increasing. An example is given on the basis of one oil field in the Samara region (hereinafter referred to as the object), which is characterized by superviscous oil and the presence of a system of fractures in carbonate deposits. The importance of taking into account the system of fractures for carbonate reservoirs in this work is realized by comparing the results of the adaptation of single and double porosity models for the Bashkirian carbonate reservoir of the considered development object. Differences in the filtration properties of oil-saturated rocks containing a developed system of fractures in their structure are  given in comparison with rocks that include only a porous structure.
The single and dual media models were compared after they were adapted to the development history. The results of the history  matching of models showed the need to take into account the system of fractures when creating a hydrodynamic model of carbonate reservoirs, due to the inability of the single-medium model to reproduce the actual fluid production from wells without significant adjustment of reservoir properties. In the process of adaptation, differences in the initial oil reserves were revealed. The calculation results showed that for carbonate reservoirs of superviscous oil, filtration occurs mainly through a system of fractures, which account for most of the depleted reserves. The development of reserves from the matrix structure is difficult. The novelty of this work is the proposed assumptions for removing uncertainties and the developed plan for adapting the dual environment model to the history of development. The obtained results show the need to apply the dual environment model in the design of the development of high-viscosity oil carbonate reservoirs. On the example of a real field, it was shown that the use of a dual-medium model makes it possible to avoid rough adaptation methods, take into account reserves in the fracture system, understand the ratio of reserves recovery from fractures and matrix and their mass transfer processes to each other, which in turn determines the development strategy and improves
predictive properties of models when calculating development options.