MEASUREMENT OF NATURAL FLOW VELOCITIES IN THE CHASSOLE DEEP BOREHOLE - GPF-3 PROGRAM

In the framework of the programme << Geologie profonde de la France 3 >>, the dynamics of the deep flow of the Cezallier massif, France, was studied using the single point dilution method in the borehole S2 of Chassole. Iodine 131 was injected every 10 metres between 670 m and 850 m levels and 6-gamma loggings were performed between 620 m and 850 metres within a delay of 18 hours. As a first step, a qualitative analysis of the profiles allowed the characterization of the hydraulic circulations and transport phenomena in the borehole. Several permeable layers were identified at depths of 442, 710 and 825 metres based on the estimation of vertical velocities. As a second step, the previously detected phenomena were quantified. The hydraulic balance calculated at the 710 metres level allowed the estimation of a regional flux in the corresponding fracture.