Efficiency of Grouting Materials being used as Water well and Borehole Sealing Agents 

Bentonite is an essential component of the grouting materials used for sealing the annular space of water and monitoring wells. 

by Professor Dr. habil. Christoph Treskatis

In different well fields the hydraulic efficiency of Bentonite-based sealing materials is proven to have failed. Leakage of surface water or contaminated groundwater into deeper aquifers may therefore result and endanger groundwater catchments for drinking water supply.A R&D-project was carried out by the DVGW in 2002 to investigate the behaviour of different Bentonite grouts in the field and laboratory.Material characteristics of five different mixtures as well as mixing, pumping and setting procedures were determined and monitored. Hydraulic tests and geophysical well-logging proved the different hydraulic efficiencies and permeabilities in the system “borehole wall - annular space - well casing”.Material characteristics and processing procedures on the drilling site may influence the “impermeability” of sealings in the annular space. Pumping procedures, polymer concentrations in the drilling mud and mineral composition of the Bentonite grouts tested influence the degree of permeability of the sealing system in the annular space. The grouting materials itself is considered more or less “impermeable”. Fluid migration could be observed in the annular space between the well tubes and the grout body as well as in fissures.These fissures result from discontinuities during the pumping and setting procedures in the field.

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published: DIV Deutscher Industrieverlag GmbH, GWF 13 / 2003 (December 2003), 12|2003
Keywords: Landfilling, Material Recovery