The paper considers the issues of assessing the influence of various factors on the production of oil reserves of Jurassic deposits of Shaimsky oil and gas region. The study states the influence of the network of disjunctive tectonics dividing the deposit onto the network of blocks on the degree of oil recovery. Trace research was conducted. Dependencies showing that hydrodynamic connectivity between wells takes place along fault lines or close to them, which is caused by the formation of decompression zones with increased permeability, are obtained. It was found that in the central blocks of the deposit there are large effective oil-saturated thicknesses with higher reservoir properties, which does not allow faults with low displacement amplitude to disrupt the connectivity.

Reservoir pressure maintenance is an extremely important factor in field development. In enhanced oil recovery water flooding projects, it is essential to optimize the flooding efficiency in a timely manner and reduce uncertainties in inter-well hydrodynamic modelling. Usually, the inter-well space parameters are assessed using interference tests or tracer- based surveillance. These methods offer such advantages as reliable information on the flow communication in the target area and the reservoir connectivity in different zones of the field. However, the duration and cost of the described surveillance technologies pose a significant drawback, and therefore alternative physical and mathematical methods with simplified forecast models are widely spread. This paper describes a method for integrating the results of dynamic marker-based inflow production surveillance in horizontal wells and the Spearman's rank-order correlation method. This approach is applied to provide better interventions for reservoir pressure maintenance, optimization of in-fill drilling, update existing hydro-dynamic models and reduce the level of uncertainty in decision making.

Background: A significant proportion of the remaining oil reserves of the fields under development is confined to reservoir zones with low-permeability and undersaturated reservoir, thin reservoirs. Maintenance of oil production levels in such deposits is possible through methodological study and development of recommendations for optimizing and improving the development system, targeted application of technologies and methods for enhanced oil recovery. In turn, the methodological study for deposits with hard-to-recover reserves includes a systematic statistical and geological and technological analysis of the results of field development, an analysis of existing generally accepted methodologies, and theoretical studies. Thus, the creation of an integrated approach to regulating the development of oil fields, taking into account a detailed understanding of the geological structure, is an important task in the current state of the fields under development. Aim: The aim of the work is to develop an integrated approach to regulating the development of oil fields with hard-to-recover reserves based on methodological solutions of technological and statistical analysis, differentiation of research objects, retrospective analysis of the use of technologies and methods aimed at increasing oil recovery. The aim of the work is to form an integrated approach to regulating the development of oil fields with hard-to-recover reserves based on methodological solutions for geological-technological and geological-statistical analysis, differentiation of research objects, retrospective analysis of the use of technologies and methods aimed at increasing oil recovery. Materials and methods: Achieving this goal is possible using the following methods: statistical analysis, geological and field analysis, methodological solutions for studying the relationship "rock fluid", differentiation of research objects according to geological, geophysical and geological and field data. On the example of some stages, research algorithms are proposed. Results: A methodological solution is proposed for regulating the development of oil fields with hard-to-recover oil reserves. Conclusion: The proposed geotechnological approach to the development control will improve the technological efficiency of hydrocarbon reserves development due to a detailed understanding of the reservoir structure, differentiation into zones (areas) of the reservoir, study and analysis of their state of development, reasonable selection of priority and promising technologies and technical solutions to increase their production.

In pursuit of efficient oil and gas field development, including hard-to-recover reserves, the key objective is to develop and provide the rationale for oil recovery improvement recommendations. This paper presents the results of the use of the workflow process for optimized field development at two field clusters of the Yuzhno-Vyintoiskoye field using geological and reservoir modelling and dynamic marker-based flow production surveillance in producing horizontal wells. The target reservoir of the Yuzhno-Vyntoiskoye deposit is represented by a series of wedge-shaped Neocomian sandstones. Sand bodies typically have a complex geological structure, lateral continuity and a complex distribution of reservoir rocks. Reservoir beds are characterised by low thickness and permeability. The pay zone of the section is a highly heterogeneous formation, which is manifested through vertical variability of the lithological type of reservoir rocks, lithological substitutions, and the high clay content of reservoirs. The target reservoir of the Yuzhno-Vyintoiskoye field is marked by an extensive water-oil zone with highly variable water saturation. According to paleogeographic data, the reservoir was formed in shallow marine settings. Sand deposits are represented by regressive cyclites that are typical for the progressing coastal shallow water (Dulkarnaev et al., 2020). Currently, the reservoir is in production increase cycle. That is why an integrated approach is used in this work to provide a further rationale and creation of the starting points of the reservoir pressure maintenance system impact at new drilling fields to improve oil recovery and secure sustainable oil production and the reserve development rate under high uncertainty.

The main task in petroleum engineering is to achieve the maximum possible production of hydrocarbon reserves with low expenditures. Many reasons influence the economics of the project. And one of them is related to choosing the right location for drilling a well in order to produce unrecovered hydrocarbons. The choice of this place has a direct correlation with the geological aspects of an oil field. This paper showed that different facies have a great influence on reserves recovery on the example of the South-Vyintoyskoye field. The classification of facies involved the study of production data. This study was presented by analysis of core sample, application of models by Muromtsev, reading of well logs, and build-up of geological models. The construction of geological models involved work in IRAP RMS TEMPEST, CorelDRAW, Geoglobe, Roxar Program package. The subject of study was the reservoir rock BV7/3-4that is a part of the Barremian age formation. It was concluded that this reservoir rock is composed of mainly argillaceous sandstones, interbedded with siltstones and shales. Authors identified that this formation belongs to three different depositional facies. The facies classification showed that the A1 zone is associated with well-graded fine to the fine-grained size of sediments. The reservoir rock of this zone is composed of sediments that belong to the distribution channel of deltas. And as a result, it is characterized by its high flow rate of production wells. The reservoir rock of the A2 facies zone is composed of sediments that are related to the collapse of mouth bars and branches of deltas. This zone has difficulties in fluid migration due to the presence of heterogeneities and clay material as well as the drilling of new wells close to the given zone lead to the medium flow rate of production wells. The reservoir rock of the A3 facies zone is composed of sediments that belong to turbidity flows. In this zone, organic matter has been recognized as a group of ichnofacies such as "Cruziana". This zone is characterized by the low flow rates of the production wells.