The article describes the original technique of predicting the effectiveness of hydrochloric acid treatment of the bottom hole zone of a carbonate reservoir. The technique consists in determining the technological effectiveness of the oil recovery stimulation procedure at productive wells using hydrodynamic simulation based on the calculated value of skin factor change. In the course of the study, a number of parameters affecting the intensity of flow coefficient decline in the near-wellbore zone during acid treatment have been established. The paper presents a comparison of data on the actual change of the skin factor after acidizing jobs at the fields of Perm Krai (Russian Federation) and the calculated values obtained using the presented technique. This scientific research includes an example of practical application of the proposed technique for the target well of the Kokuyskoye oil field in Perm Krai, its results with a minor deviation coinciding with the actual values of the flow rate. In the conclusion to the study, it is noted that using the proposed technique, recommendations can be provided on the selection of acid composition and technology of its injection into formation for the preliminary evaluation of the cost effectiveness of the designed procedure.

The work intends to develop a conceptual model of the Permo-Carboniferous deposit of the Usinskoye field. In the furtherance of this goal, the authors have addressed the tasks of designing a specialised table format to describe thin sections of carbonate core samples and create a database based on the developed format for the subsequent analysis. The paper deals with studying the Permo-Carboniferous deposit of the Usinskoye field, located in the Komi Republic. A unique database of 1,710 described thin sections from 12 wells was created based on the developed format. The classification of carbonate rocks by R.J. Dunham supplemented by Embry and Kloven (based on the dominating fabric in limestone, type of cementing agent and their relationships in the rock) was used as a basis. According to rock material compositions and textural properties, the following nine rock lithotypes were identified: Mudstone, Wackestone, Packstone, Grainstone, Boundstone, Floatstone, Rudstone, Crystalline Carbonate (Dolomite), and Clayey Carbonate Silicite. By following the rock lithology type identification results and the seismic data, three main facies zones were determined in the section of the mid- Carboniferous and Lower Permian sediments: carbonate shoal (inner ramp zone), organogenic buildup (middle ramp zone) and shallow marine shelf plain (mid-ramp zone, partially outer ramp zone). A moderately deep marine shelf plain facies (outer ramp zone) was provisionally defined. Following the study results, two profiles of the Mid-Carboniferous and Lower Permian sediments of the Usinskoye field were plotted along two well lines. The presented sections support the conceptual model developed. Based on the core sample findings, the zone of organogenic build-ups stands out in the eastern part of the field, dating back predominantly to the Late Carboniferous and Early Permian periods. An inner ramp with the carbonate shoal facies supposedly exists in the field north-west. The conducted work has resulted in the development of a conceptual model of the Permo-Carboniferous deposit of the Usinskoye field, which can be used for further development of more reliable 3D facies models, commercial-scale estimations of reserves and field development designs.

The main purpose of the work is evaluation of the potential of oil source rocks of the Domanik age in the Volga-Ural and Timan-Pechora oil and gas provinces as a unconventional hydrocarbon source on the basis of generalization of the materials of earlier completed and new standard and special core studies. The maps of the content and maturity of organic matter were built, the lithological composition of the Domanik horizon was evaluated, and the comparative evaluation of the domanikite parameters at the commercially developed fields of the USA and Canada was performed.

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The paper analyzes a methodology aimed at differentiation of porosity, permeability and petrographic properties depending on facies attributes. Based on the Dunham classification, we offer in-depth studies of the influence of rock fabric, including full-size core samples, on changes in porosity and permeability. The work deals with the Permo-Carboniferous deposit of the Usinskoye field. Reservoir properties of the considered strata are highly heterogeneous. Along with highly porous and cavernous rocks, there are low porous and fractured varieties in the section, which refer to rocks of various lithological compositions. The porosity and permeability properties were analysed for more than 9,000 standard core samples and approximately 1,000 full-size core samples, taking into account the scale factor and including microfractures, large caverns and rock matrix, commensurable with the sample sizes.The analysis of the maximum variation range is of particular importance for structurally complex carbonate reservoirs. Furthermore, based on the conducted lithologic, petrographic and petrophysical studies, the authors identified four types of reservoirs and eight different types of lithogenesis, as well as estimated geological and physical parameters for each of them. Based on the cumulative correlation plots, four zones of heterogeneity were identified. They are subject to the influence of properties of the core samples of different lithogenesis types. This is the first time that the influence of various petrotypes/lithotypes on changes in the reservoir porosity and permeability has been studied for the Usinskoye field based on the petrographic and petrophysical research findings. All the conducted experiments show that the rocks of the Permo-Carboniferous deposit of the Usinskoye field are extremely heterogeneous in their permeability properties that vary much. Thus, it is necessary to differentiate the core-to-core petrophysical correlations depending on a void space fabric and lithology of rocks.