Purpose. The purpose of this work is to establish features of geological structure of complicated reservoir rocks, creation the petrophysics interpretation basics of integrated geophysical research for the results of the introduction of new, informative, and nuclear methods. Methodology. The methodology of the research is to determine the distribution of radioactive isotopes of U (Ra), Th, K40 in the rocks-reservoirs of the Neogene deposits of gas condensate fields in the Bilche-Volisk zone of the Pre-Carpathian depression for lithological division of thin cross sections and to estimate the character and nature of the isotope increased radioactivity. Results. As a result of these geophysical methods, petrography and gamma spectrometry on core samples, taken from the Neogene sediments, the following has been set: thresholds of intensity gamma fields for productive reservoir rocks was found, net-to-gross ratio of the Sarmatian and Helvetian stage was calculated; efficiency of gamma spectral method for the assessment of natural radioactivity was justified, petrophysical interrelation and correlation diagram of gas saturation distribution for the Lower Dashavsk series of Sarmatian stage were built. Originality. It is developed a methodology for estimating the nature of the increased radioactivity of the Neogene deposits of gas condensate fields in Bilche-Volisk zone of the pre-Carpathian depression, the essence of methodology is follows: concentrated ratio of uranium, thorium and potassium in the composition of rock is calculated for rocks of the Neogene sediments characterized by increased radioactivity. This takes into account the fact that the quantity of potassium content in the rock is caused by the shaliness volume and organic matter. Given the fact that the content of radioactive potassium in the sediments of the geological section of the Neogene system are unevenly distributed in the Helvetica, Badenian and Sarmatian stages, we calculated ratios of uranium plus thorium to potassium for each of these layers (factor A). Practical significance. An advanced technique of processing for gamma logging results and the efficiency of integrated geophysical studies of complex geological sections is presented. The examples of using the results of nuclear-physical methods allows to identify productive gas-saturated horizons. Study results allows to substantiate mineralogical structure of the rock-reservoir matrix and set boundary values of residual water saturation ratios.
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