Further exploration of the Verkhnechonskoye field of technical groundwater: new research methods and results

The purpose of the research is to refine a geological model of the Verkhnechonsk field of technical groundwater (Eastern Siberia, Russia), reassess groundwater reserves by the industrial category and form a geofiltration model. The article deals with the main approaches used in conducting of field and desk researches. It also introduces the organization experience of large-scale pilot filtration work under time- and personnel-limited conditions at a large operating field. The work is based on the results of long-term regime observations, field experimental and filtration works carried out in 2019- 2020. It uses the information of a geological database on the water and oil intake facility of wells, including a complex of borehole studies, as well as the data on the geological and hydrogeological structure of the field according to archival and published sources. Visual ModFlow Flex software was used to create a geofiltration model. Having conducted and interpreted the works, the justification of a natural hydrogeological model different from the one adopted earlier was performed. Thus, the relationship of two water-bearing complexes – the Verkholensky-Ilginsky complex of the Upper-Middle Cambrian age and the Litvintsevsky complex of the Lower-Middle Cambrian age was proved. The works in the Visual ModFlow Flex resulted in the creation of a geofiltration model, which correlates well with the actual data, allows to identify impenetrable barriers, as well as predicts the geomigration of hydrogen sulfide. It is the first time that the underground water reserves of the field were included in the State balance sheet in full-scale according to the industrial category B. The reassessment was performed for three sites of the field, well loads were adjusted for optimal operation of water intakes. The obtained results of the conducted research imply that the use of geofiltration model is reasonable in the fields of complex geological structure and this model can be used on a permanent basis for monitoring and adjusting of the development mode. The organization experience of works at a large operating oil field can also be useful under the reserve reassessment at analogous fields.