f Water well logging for determination of fracture aquifers in the bohemian massif

Abstract Fracture aquifers are of great interest in consolidated sedimentary formations as well as hard crystalline rocks because of their extra drainage capacities. Logging tools are designed to respond to different characteristics of the borehole environment. Some tools respond preferentially to lithology, some primarily to the void volume, and other to fluid saturations and fluid movement. We will discuss the last issue, being the most important according to our meaning. Our research has been focused on study of hydrodynamic regime of water in the boreholes. The methods dealing with the properties of the fluid filling the borehole, are measured only in cleandly wells where mud has been replaced by water (in casing boreholes, if necessary). Hydrodynamical tasks in an area, using boreholes are solved by modifying the physical properties of the water in the boreholes with tracers, when using logging measurements. Under these conditions, the changes of physical properties of the liquid into the borehole, brought information about the water coming from an aquifer. In most cases the fluid is modified with respect to its conductivity (RL), temperature (TL), intensity of colouring (PL). The configuration of the measured time series curves of RL, PL and TL shows whether there is an horizontal filtration across the borehole, which would be manifested by an increase of RL and/or PL values in time in the same depth interval, or vertical flow, i.e. the boundary between pure and marked fluid moves in time along the vertical axis of the borehole. Studying the fracture aquifers in the Bohemian Massif we have been processed the logging data from boreholes deeper than 50 m. The analyzed data from well logging of each borehole give evidence about the temperature, mineralization of the underground water, distribution, water yields and petrohraphical composition of the borehole cross-sections. The main goal of the contribution is to discuss the possibilities of the deep water circulation and to determine the relationship between results of the borehole geophysical measurements and pumping tests. The study of individual water wells in the Boheinian Massif takes one to the follow conclusions: The water yields of the well doesn't depend on the petrographical composition of the borehole section, The water inflows occur as in the upper disintegrating zones as in the deep places in the wells, relating to tectonics, Mineralization, composition and temperature of the underground waters are rather changeable, The coefficient of permeability Kf determined according to logging used to be a little higher that the Kf according to pumping, but the difference is moving between a half of order.