Hydrogeological conditions of the Markov oil-gas condensate field territory in connection with utility and drinking water supply (Ust-Kutsky Area of Irkutsk Oblast)

The Markov oil-gas condensate field is located in the north-eastern part of Ust'-Kutsky Area in Irkutsk Oblast. This area of interest is part of the Lena-Angarsk plateau in the south-eastern outskirts of the Central Siberian Plateau and belongs to the watershed space of the Bolshaya Tira and the Malaya Tira Rivers belonging to the Lena's basin. Tectonically the Markov oil-gas condensate field is situated in the south-western part of the Nepsk-Botuobinsk anticlise. Geologically the upper area of the section consists of Mid-Upper Cambrian, Upper Cambrian, Lower Ordovician, Mid-Upper Ordovician and Quaternary deposits. Hydrogeologically this area of interest is located within the Upper Lena secondary artesian basin which is a part of the Angara-Lena primary artesian basin. The Mid-Cambrian aquifer system (£₂) is the main productive division in the area of the Markov oil-gas condensate field. The deposits of the complex are presented by crumbling terrigenous sandy-argillaceous rocks (siltstones, marls, sandstones) of the Upper Lena suite. They are characterized by coefficients of water transmissibility and permeability from 11 to 183 m/per day and from 1.6 to 11.0 m/per day respectively. The inferred resources modulus of the Mid-Cambrian aquifer system is 0.54 l/s km2. The chemical composition of underground water was described by the results of the study of 22 samples of the Upper Lena suite aquifer. These samples were taken during the period from 2000 to 2013. According to the results of the analyses the water is fresh and weakly alkaline; by chemical composition it is hydrocarbon-calcium-magnesium. The comparative analysis of the underground water chemical composition showed that there were no considerable changes in the chemical composition of underground water during the years of investigation. The conditions analysis of the Markov oil-gas condensate field territory indicates that it is possible to get the required volume of good quality underground water for industrial use and drinking needs. According to quality, underground water is up to quality required for drinking water and that is why it can be used for water supply without prior water treatment. But it is possible if there is a package plan including the control of the technical condition of the well, monitoring of the underground water of the Upper Lena suite, monitoring observations of the water intake structure.

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