Application of borehole log data for determination and mapping of filtration parameters

The accurate determination of the filtration parameters of thick aqueous complexes that comprise sandy and clayey beds using the traditional hydraulical tools is rather problematic. It is because under unconfined aquifer conditions values of the calculated parameters depend on both duration and intensity of pumping. Additionally, the parameters that calculated from pumping test's data characterize only a small locality. Consequently, extrapolation of the results for a larger territory requires particular approach. The application of wireline log data for this purpose could be successful if relations between the hydrogeological and geophysical parameters would be established. A correlation between permeability and formation factor in clean terrigenous formations is theoretically well known. However, presence of clay particles affects the process of conductivity that results in necessity to apply corrections while formation factor is being calculated. The empirical relationship between the corrected formation factor and permeability was derived using data of detailed hydrogeological-geophysical investigation in 28 borehole. The boreholes have penetrated approximately 200-220 m of the Upper- Middle Devonian water-bearing terrigenous complex within a well field for public water supply of Panevezys town in Central Lithuania. According to this relationship the average values of permeability and hydraulic conductivity were calculated using log data from more than 200 boreholes. As a result, maps of these parameters were compiled for the territory of the Baltic artesian basin.