© 2020 IOP Publishing Ltd. All rights reserved. The purpose of this work is to use methods of magnetic radiospectroscopy - electron paramagnetic resonance (EPR) and low-field nuclear magnetic resonance (NMR LF) to determine the quality of the rocks of fluid seals of "lingul clays" (depth 82-102 m) of the Ashalchinskoye field, combining traditional methods of studying the properties of the material composition of rocks and dispersed organic matter in them. The heterogeneity of the mineral composition by the distribution of the EPR signal intensity of the ion Mn2+ has been established; it is mostly dense carbonate in the upper part, below it passes into the magnesian calcareous and ends with the clay part. Mineral heterogeneity is consistent ...