Groundwater in the Mesozoic hydrogeological basin of the Middle Ob (a case study of the Ust-Balykskoye oil field)

Abstract

Despite the fact that there is the large amount of accumulated factual material, formation of hydrogeochemical conditions of deep oil and gas horizons in the Middle Ob and the West Siberian megabasin still contains many questions. This is due to numerous hydrogeodynamic and hydrogeochemical anomalies that don't have an unambiguous explanation. The presence of inversion hydrogeochemical zoning in the Lower Cretaceous and Upper Jurassic deposits and the presence of low-mineralized reservoir water of a sodium-bicarbonate composition are the peculiarity of groundwater in the considered territory. A change in the genetic type of water, a decrease in mineralization, a decrease in the content of calcium ion, and an increase in the amount of bicarbonate ion in the Mesozoic hydrogeological basin are associated with the transformation of mineral and organic matter in sedimentary rocks, when they are immersed, at the water expelling stage. The determination of the origin of low-mineralized reservoir water of a sodium-bicarbonate lying at significant depths is of great practical importance, since the relationship between the inversion of groundwater and oil content has been revealed, so this fact can be considered a search criterion for petroleum potential.