The article considers the factors influencing the electrical resistance and natural electrochemical activity of rocks of the volcanic-sedimentary sequence of the central zone of the north-eastern framing of the Krasnoleninsky arch. Differentiated petrophysical relationships are proposed to determine the oil saturation factor based on the data of standard well-logging. It was found that the electrical resistance is determined by the peculiarities of the structure of the void space and the nature of postmagmatic changes. In rocks with a low content of postmagmatic minerals, the presence of fractures contributes to the decrease in resistance, while cavities can increase the electrical resistivity of the rocks. Volcanic, volcanic-sedimentary, sedimentary rocks and deposits of the weathering crust containing increased amounts of clay minerals are characterized by low electrical resistance. The processes of albitization, carbonatization, silicification of volcanics contribute to an increase in electrical resistance.
The electrical indicators of volcanic-sedimentary and sedimentary rocks are reduced relative to most volcanic rocks, which is due to both the intergranular type of their void space and increased clay content. Among volcanic rocks with a low content of postmagmatic minerals, the average values electrical indicators are reduced in tuffs, which is due to the predominance of intergranular pores in their void space. For effusive rocks, clastolavas and lavoclastites in the void space of which caverns and cracks predominate, the average electrical indicators are increased. For each type of rocks within the group under consideration, several most probable values are noted, corresponding to a certain type of void space. The natural electrochemical activity of the rocks of the volcanic-sedimentary sequence is determined by diffusion-adsorption, filtration and redox processes. Clay volcanic, volcanic-sedimentary, sedimentary rocks, weathering crust deposits, basic volcanics are characterized by positive anomalies on the curve of spontaneous potentials, acidic volcanic rocks and volcanic-sedimentary rocks with a low content of adsorptive-active minerals are negative.
An example of determining the type of saturation and calculating the water saturation coefficient of rocks of a volcanic-sedimentary sequence according to the data of a standard complex of well-logging is given. The results obtained are confirmed by the data of core and well-log, the results of well tests.
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