Abstract: A method for the determination of depth of a fluid-saturated stratum and type of a fluid, such as mineralized water, oil and gas released during drilling, comprising pretreating the drilling mud before feeding to a well so as to maintain the original value of its redox potential at a stable level. The supply of the drilling mud to the well is suspended upon a change in the redox potential indicating to the presence in the drilling mud of a fluid saturating the stratum. After a certain time lapse the supply of the drilling mud to the well is renewed. The time of restoration of the drilling mud supply to the well and the time of appearance of the batch of the drilling mud diluted with the fluid saturating the stratum are marked and are used to determine the depth of the stratum. The redox potential of the batch of the drilling mud saturated with the fluid is measured and compared to known normal values of redox potential to determine the type of the fluid.