Features of isolation and nature of low-resistivity oil-saturated reservoirs of the Middle Jurassic deposits of the Akshabulak Central field of the South Torgai oil and gas basin

At the current stage of development of the oil and gas industry of our country, additional exploration of existing fields, understudied promising areas, identification of missed horizons, methods of evaluation and development of non-standard reservoirs are of particular relevance. Reservoirs with low specific electrical resistivity can be referred to non-standard reservoirs, and there are some difficulties in assessing hydrocarbon prospects of these reservoirs. Low resistivity reservoirs can be productive reservoirs with high residual water saturation as well as reservoirs for which generally accepted interpretation techniques are ineffective. Proper analysis of the reasons that lead to underestimation of the resistivity of productive reservoirs allows choosing the most effective interpretation methods. The article is devoted to the study of the features of reservoirs with low electrical resistivity, their nature and role in the process of fluid accumulation. The basic methods of identification of low resistivity zones in reservoir rocks, their physical and chemical characteristics that cause low resistivity, including mineralogical composition, saturation, porosity, permeability and pore space structure, are considered, and their influence on the filtration-capacitance characteristics is analyzed. Approaches to integrating data from various methods (geophysical and geological-technological studies, laboratory measurements) are described. Special attention is paid to the influence of low resistivity on the interpretation of data from geophysical methods. The results of the study have significant practical potential for optimization of field development.