Spatial Distribution of Incrustations around a Water Well after 38 Years of Use


Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, D-30655 Hannover, Germany; ++49-511-643-2373; fax: ++49-511-643-3661;


The spatial distribution of iron incrustations around an abandoned water well after 38 years of use was studied by analyzing the iron content of soil samples from 12 core borings. Three of these were performed inside the gravel pack, the rest at different distances in the adjacent aquifer. Incrustations had preferentially accumulated at the bottom of the screen coinciding with a zone of higher aquifer permeability. As expected, all cores from the annulus show buildup of iron oxides but the ones outside also showed elevated iron content up to 4 m away from the screen. Such distant incrustations are very difficult to remove, by mechanical or chemical methods. The common procedure of removing tubing and annulus material to install a new well at the same location could therefore give the replacement well a hydraulic disadvantage as the incrustations in the aquifer remain in place.