This article discusses some aspects of the methodology for preparing sludge and core samples for lithological and petrophysical studies. Methods for obtaining rockmaterial(sludge, core) are described interms of determiningthemoment of openingthe reservoir layer,tyingthe core in depth, and sampling the sludge. A sludge collector has been proposed that makes it possible to obtain sludge of overall fractions washed from the drilling fluid. The effectiveness of the harmonic analysis method, which takes into account the lithology of the studied section and changes in drilling parameters to optimize the frequency of sludge sampling during drilling, is shown. A system for placing sludge sampling points has been justified to increase the information content of the study of well sections. An analysis of the actual material on the connection of sludge to formations using natural gamma activity in wells drilled in the conditions of the Saratov Volga region was carried out. The distribution of the residual values of the burial depths according to the sludge and well logging allowed us to conclude that in the vast majority(> 75%) of cases, the binding of sludge during geological testing is carried out with satisfactory accuracy. The implementation of some elements of the above described interpretation techniques is shown using the example of one of the wells located in the northwestern part of the near-shore zone of the Caspian basin.