The importance of an integrated approach to the decommissioning of hydrogeological objects on the example of the "Homolje Neresnica" groundwater source near Kučevo

Abstract

Proper decommissioning of abandoned or damaged wells and boreholes is of particular importance for preventing groundwater contamination, loss of pressure in confined aquifers, hydraulic connection between different aquifers, and changes in groundwater quality. This paper presents the decommissioning of the exploratory hydrogeological borehole K‐1 within the “Homolje Neresnica” groundwater source. The source is used for bottling natural mineral water and taps a karst aquifer in Lower Cretaceous limestones. The aim of the study was to adequately decommission the damaged borehole, protect the captured aquifer, and ensure undisturbed exploitation from wells KB‐1 and KB‐2. Methodologically, a phased approach was applied, comprising: assessment of the borehole condition (underwater camera inspection, CBL logging, air‐lift cleaning), sealing of the intake section with quartz gravel and a bentonite plug followed by cementation, perforation of casing sections with insufficient cement bonding and injection of new cement into the casing and annulus, as well as final cutting, removal of the steel casing, and complete cement backfilling up to the ground surface. The implemented activities resulted in hermetic sealing of the entire borehole and a complete cessation of artesian flow, thereby preserving groundwater quality and the existing exploitation regime. The research highlights the importance of a phased, professionally supervised approach to decom‐ missioning old or damaged structures under complex hydrogeological conditions.