Explosive operations carried out in wells include: analysis of the basics of the physics of the explosion and its mechanical effect; calculations of explosive charges and electric explosive network; description of means and methods of carrying out the explosion (torpedoing, perforation); study of geological and hydrogeological factors affecting the explosion; hydrogeological calculations of wells in the zone of action of the explosion and safety techniques for its implementation, etc.

Perennially frozen rocks on the territory of the USSR are found in areas with different geomorphologic and geological-structural structure and occupy 49.7% of the country's territory. In the section of any region, three zones are clearly traceable.

The gallery method of calculating well flow rate at steady filtration, developed by Academician A. P. Krylov, is widely used in the operation of oil fields with water-pressure reservoir regime. Analysis of this method in relation to pressure unconfined aquifers shows that it can be used for approximate hydrogeological calculations of circular groundwater intakes. At the same time, rows of production wells are conditionally replaced by galleries identical to them in outline and size. Oil withdrawal from the reservoir with water pressure regime leads to simultaneous movement of oil and water in it, i.e. to two-phase filtration, which in hydrodynamic calculations through the ratio of dynamic viscosities of oil and water is replaced as if single-phase filtration.

The theory and practice of injection of homogeneous viscous liquids and binding solutions into porous and fractured, dry and water-bearing rocks is covered in many works published in the USSR and abroad. All works on the content can be divided into two groups. The first group includes works by S.K. Abramov, N.N. Bindeman, N.N. Verigin, G.N. Kamensky, E.E. Kerkis, V.S. Kozlov, V.M. Nasberg, A.I. Silin-Bekchurin, I.A. Skaballonovich, Instruction and Methodological Guidelines for Experimental Injections I-20-52 and others. They consider the theory and practice of water injection into porous and fractured rocks in connection with the study of their filtration properties and the design of drainage and hydraulic structures.

The Yakutian artesian basin belongs to the largest basins of the USSR. Its area is more than one million square kilometers. The basin occupies a central position among other hydrogeological areas of the north-east of the USSR - the Khatanga basin (in the north), Olenek and Tungus basins (in the north-west and west), the Verkhnelensky basin, the Aldan hydrogeological massif (in the south), the East-Verkhoyansk and West-Verkhoyansk folded hydrogeological areas (in the east and north-east).

In this paper, on the basis of hydrogeological studies carried out in 1951-1955 on the territory of the Yakutsk basin, a brief characterization of the chemical composition of groundwater from the point of view of its suitability for water supply to settlements located in the basin.The paper uses materials of hydrogeological studies carried out by the author in 1951-1953, and some analyses on the chemistry of the waters of the Yakutsk artesian basin, collected in 1954-1955 by hydrogeologist E. A. Baskov.

The city of Yakutsk is located in the central part of Yakutsk. Yakutsk is located in the central part of the complex Yakutsk artesian basin, within the flat Prilenskaya lowland, which declines gently to the north. Absolute altitudes in the Yakutsk area are 100-120 meters. The climate of the region is sharply continental, the average annual temperature is minus 10°. The thickness of permafrost in Yakutsk reaches 200 meters.

Yakutsk artesian basin is one of the largest basins in the USSR in terms of area and thickness of sedimentary strata, different in composition, age and origin. The area of the basin is more than one million square kilometers. The thickness of sedimentary deposits is measured in kilometers. In terms of area, this basin exceeds the Dnieper-Donets, Moscow, Verkhnelensk, Kansk, Irkutsk, Khatanga, Nizhnezeisky artesian basins and the largest basin in Western Europe - the Paris basin. Thus, the Yakutsk artesian basin occupies a central position among the following hydrogeological areas of the USSR: the Khatanga basin in the north, the Tunguska basin and the Anabar hydrogeological massif in the west, the Verkhnelensk basin and the Aldan hydrogeological massif in the south, and the Verkhoyansk hydrogeological folded area in the east.

In the present work, on the basis of physiographic, permafrost conditions and geological and structural features, for the first time in the literature, a brief description of the hydrogeology of one of the areas of the southern part of the Yakut artesian basin - the vicinity of the town of Olekminsk - is given. The work utilizes materials of the thematic party of the All-Russian Geological Institute - YaSU, which was headed by the author in 1951 -1953, and some literature data on the geology and hydrogeology of the Olekminsky district of the YASSR. The area considered in this paper, occupying a small area of the left bank of the Lena River in the vicinity of Olekminsk, is located in the southern part of the Yakut artesian basin, discovered in 1939-1940 by a team of hydrogeologists and permafrost scientists (Prof. N. I. Tolstikhin, M. I. Sumgin, Associate Professor V. M. Maksimov, Prof. V. M. Maksimov, Prof. N. I. Tolstikhin, M. I. Sumgin, and Prof. V. M. Maksimov). V. M. Maksimov, Ph.D. in Geology and Mineral Sciences A. M. Efimov, P. I. Melnikov, and Ing. V. A. Obruchev. The town of Olekminsk is a district and cultural center. It is connected with other settlements of Yakutia by dirt roads, water and air routes. The Lena River serves as the main waterway for transportation of goods and passengers from Olekminsk downstream and upstream of the river. This old waterway continues well beyond the boundaries of the study area, linking Olekminsk with Yakutsk and the village of Ust-Kut, from which it passes. Ust-Kut, from which runs a highway and railroad to the village of Zayarsk (on the Angara), linking the area with the Siberian railroad.

We find a brief description of the sources in the vicinity of Yakutsk in the works of G. N. Ognev and I. M. Svetozarov. However, due to the specifics of their work, they could not give characteristics of these sources in connection with the geological structure of the area. In this article I will complement the previous ones researchers with new materials about sources obtained in 1939 as a result of the work of the hydrogeological team of the Yakut expedition of the USSR Academy of Sciences. Work was carried out on the right and left banks of the river Lena from the village Kachikatsy-Pokrovskoe to N.-Kangalas mines. The first group of sources is an indicator of sub-permafrost waters. These waters in the area are associated with Cambrian limestones and lower horizons of Jurassic sediments. Sub-permafrost waters are of undoubted practical interest both for the water supply of the city of Yakutsk (where the Cambrian lies at a depth of 450 m) and for the settlement currently underway in the Yakut Autonomous Soviet Socialist Republic. The second group of sources, associated with the upper aquifer, has no practical significance for water supply purposes. In conclusion, we present a map showing the general picture of the location of sources in the vicinity of the city of Yakutsk.