[en] The characterisation of the hydrogeochemical parameters controlling the radionuclide migration towards the biosphere implicates the development of a methodology including instrumentation and equipment for working in deep boreholes, according with the data in which we are more interested. This methodology consists of a systematic and detailed study of the boreholes (studies on the cores, geophysical parameters, hydraulic tests...) that allows to select zones for water sampling and characterisation. The selected areas are adequately isolated with a double packer system and coupled instrumentation for pumping water (pumps or gas lift systems). The isolated zone is cleaned by pumping, and the tracer concentration, tritium measures or the control of the stabilization of physico-chemical parameters, are good indicators of the representativity of the sample. Water, gases, particles, colloids and microorganisms sampling is made in glove boxes and the analysis are made in a mobile laboratory in situ for determining the more sensible parameters, avoiding the sample alterations with the transport. (Author) 18 refs