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The relevance of the development of a methodology for the operational assessment of the bottomhole formation zone (the permeability of the bottom-hole formation zone and the skin factor) is primarily due to economic considerations, since existing approaches to its definition based on hydrodynamic studies lead to shortages and increased risks of failure to ensure the output of the well. In this regard, the use of modern methods of working with big data, such as deep learning of artificial neural networks, will ensure monitoring of the condition of the bottom-hole zone of the well formation without stopping them for hydrodynamic tests, which will reduce losses for oil production enterprises. It will allow for operational analysis for effective and timely application of intensification technologies, enhanced oil recovery. The authors analyzed the existing methods for determining the bottom-hole characteristics of the formation and machine learning approaches in the direction of solving this problem. The article presents a methodology for the operational assessment of the state of the bottom-hole formation zone: the permeability of the near bottomhole zone (NBHZ) and the skin factor using artificial neural network training approaches based on geological, operational data and the results of interpretation of hydrodynamic studies on the example of sandstones of oil fields in the Perm Region. A fully connected neural network was used to predict the NBHZ permeability. The article presents the results of testing various neural network architectures: the number of layers and neurons in layers with the choice of the best one. Some techniques were used to prevent over-training of models. The author’s methodology for assessing the skin factor of wells is proposed using a comprehensive analysis of the constructed statistical models and training models of artificial neural networks to solve the regression problem. In future studies, it is planned to use recurrent and convolutional neural networks to study the dynamic components of the formation of the bottom-hole formation zone and create an integrated approach to solve the problem.

To date, significant foreign and domestic experience has been accumulated in the construction and operation of horizontal, multilateral and multilateral wells, as well as the restoration of an idle well stock by drilling sidetracks and sidetracks into various productive formations: low-permeability and highly dissected, with low values of effective oil-saturated thicknesses, degraded hydrodynamic connection with the contour area, etc. In this regard, it becomes extremely important to make a decision on choosing the optimal well profile in specific geological and physical conditions. The relevance of the work is also confirmed by the fact that at some development sites there is a decrease in the oil production rate of horizontal wells to the level of directional wells in the initial period of operation. Based on a significant difference in the reservoir properties of oil fields in the Perm Territory, all the analyzed objects operated by horizontal wells are combined into several groups: “northern” (N) and two “southern” (S1 and S2 ). The main parameter in the selection of groups was the coefficient of mobility of oil. The well-by-well technical and economic assessment performed in the article, based on the actual values of production over a long period, made it possible to identify the optimal well profile depending on the geological and physical characteristics of the reservoir. Combining the main geological characteristics that affect the technological parameters of well operation, with an economic assessment, the dependences of the net present value on the formation hydraulic conductivity were built. Dependences built for the first time make it possible to reasonably select the well profile in specific geological and physical conditions. Also in the work for a variety of geological and physical conditions, the value of the minimum profitable oil production for various well profiles is determined. Thus, the basis has been created, which is necessary for determining the profile of wells when planning production drilling.

At present, a large number of scientific works devoted to the study of the features of the geological structure and the development of oil deposits in complex carbonate reservoirs are based on the use of any one research method. This article shows the advantages of the integrated use of modern methods of core research, including X-ray microtomography and electron microscopy, as well as data from hydrodynamic and field studies of wells. The advantage of the approach used is the ability to study the deposit at three levels: core-well-development object, it is reasonable to transfer micro-survey data to the regularities of the implementation of technological processes of oil production. The objects of research in this article are the Famennian oil deposits of two neighboring fields, which, at first glance, are analogues in terms of the similarity of the enlarged geological and physical characteristics. Comprehensive studies of core samples from these deposits made it possible to establish differences both in the mineral composition of rocks and in the structure of their void space, especially in the size and distribution of pore channels. So, with approximately equal porosity for one of the deposits, the presence of two types of voids and a twofold prevalence of the size of the largest of them were established. According to the complex of laboratory methods for studying the core, the reservoir is classified as a porous type (no cracks were found). The performed interpretation of the hydrodynamic studies confirmed this fact, made it possible to establish the presence of a dependence of the reservoir permeability on the formation pressure (deformation of the void space of the reservoir), and also to build the corresponding individual dependence for each well. Comparison of the equations approximating the dependence data showed a more pronounced deformation of the reservoir, which is characterized by the presence of large pores and caverns. That is, a complex of laboratory and hydrodynamic studies made it possible to establish the probability of deformation of the void space of a carbonate reservoir even in the absence of cracks in it. In turn, the reservoir deformation is singled out as the most probable cause explaining the different rates of decline in well flow rates of the fields under consideration.

Determination of the current reservoir pressure in oil production wells selection zones is an urgent task of field development monitoring. The main method for its determination is hydrodynamic studies under unsteady conditions. At the same time, the process of restoring bottomhole pressure to the value of reservoir pressure often lasts a significant period of time, which leads to long downtime of the fund and significant shortfalls in oil production. In addition, it seems rather difficult to compare reservoir pressures with each other in the wells due to the different timing of the studies, since it is impossible to simultaneously stop the entire fund for measuring the reservoir pressure in the field. The article proposes a new method for determining the current reservoir pressure in the extraction zones, based on the construction of multidimensional mathematical models using the data of geological and technological development indicators. As the initial data, the values of reservoir pressure, determined during processing of the materials of hydrodynamic studies of wells, as well as a set of geological and technological indicators, probably affecting its value, were used (initial reservoir pressure for each well, the duration of its operation at the time of study, liquid rate, bottomhole pressure, the initial permeability and the current collector in the drainage area, GOR accumulated values oil, and liquid water, and skin factor). In the course of the research, several variants of statistical modeling were used, in the process of which the regularities of the reservoir pressure behavior during the development of reserves were established, individual for the object of development. The obtained models are characterized by a high degree of reliability and make it possible to determine the desired value with an error of no more than 1.0 MPa.

Acid treatment technology has become widespread in the development of carbonate layers in oil fields. Virtually every well in the history of its production has been acid treated downhole, ultimately providing millions of tons of incremental oil production globally. Despite the considerable amount of theoretical and practical research devoted to this technology, the problem of controlling the efficiency of acid treatments remains topical. In this connection, the purpose of this paper is to study the influence of known and available in field conditions geological and technological parameters on the efficiency of acid stimulation in carbonate reservoirs. Laboratory studies (in free volume, filtration and X-ray tomography tests) using two hydrochloric acid compositions and carbonate rock samples of the same geologic age from oil fields of Perm krai to determine the dependencies were performed. Acid treatments were modeled by varying technological parameters (volume, rate and pressure of injection of acid compositions, reaction time of acid with rock) under thermodynamic conditions corresponding to reservoir properties. Statistical processing of empirically obtained data allowed us to note the predominant role of technological parameters to achieve a successful result of acid stimulation. Multivariate statistical models describing the process of formation of acid treatment efficiency in carbonate reservoirs have been developed. It was found that the reservoir stimulation efficiency varies in direct proportion to the increase in the injection pressure of the acid composition and the volume of agent used due to the development of wormholes. The efficiency of acid treatment at dolomite content in the rock is significantly lower, which requires increasing the rate of composition injection and reaction time to achieve the highest stimulation result. Thus, the paper provides a basis for further development of the process of controlling the effectiveness of acid treatments in carbonate reservoirs of oil fields.