Abstract
Hydrochemical investigation of deep groundwater by using deep borehole requires various technical tasks through drilling borehole, sampling and analysis of groundwater to estimate reliable groundwater chemistry. For instance, the groundwater is contaminated by drilling water during drilling, mix with groundwaters in different aquifers, and react with atmosphere during sampling and analysis. We report the reality of hydrochemical investigation and the procedures for quality control in the investigation. Many kinds of investigation showed that the influence of drilling fluid contamination and mixture of groundwaters of different aquifers can be evaluated by managing the concentration of fluorescent dye and solutes in drilling fluids. In addition, it is necessary to measure in-situ pH and Eh groundwater to prevent reactions between groundwater and atmosphere, and degassing by pressure releasing.
