Cryohydrogeological settings appraisal by shallow near-field TEM sounding: a case study of the western part of the Yakut artesian basin

The complexity of exploration, reserve estimation and development of groundwater fields in the Republic of Sakha (Yakutia) (Russia) is due to the variety of location conditions and thickness of permafrost rocks, as well as the structure of sediments containing aquifers. The relevance of the study is determined by the necessity to give a scientifically based prediction and search for the sources of technical water supply to be used in oil well drilling and provision of a reservoir pressure maintenance system. The article presents the analysis results of the materials of shallow near-field transient electromagnetic soundings carried out on the territory of the Republic of Sakha (Yakutia) in the period from 2016 to 2022. Description is given to the research methodology, conditions for determining the permafrost rocks in the geoelectric section, their morphological features in the territories located along the western border of the Yakut artesian basin with the involvement of drilling materials from 75 hydrogeological wells. The sparse geothermal knowledge of the area is noted. It was traced that the depth of the permafrost base decreases from northeast to southwest from 400 to 150 m. Within the Middle Botuoba field, discontinuous distribution of frozen strata has been mapped, talik zones with different water abundance have been identified, and a number of identified water supply facilities are operated. Cartographic materials obtained in the course of the research allowed to specify significantly the structure of cryohydrogeological systems of a number of oil and gas fields in the Republic of Sakha (Yakutia). The research results are of scientific and practical importance when predicting the areas with complicated well drilling associated with permafrost drilling (destruction of well walls, drilling tool sticking, gas shows), as well as when determining the location areas of interpermafrost and subpermafrost aquifers and minimizing the risks of drilling dry hydrogeological wells.