HYDRAULIC BOREHOLE CHARACTERIZATION THROUGH THE APPLICATION OF MOMENTMETHODS TO FLUID CONDUCTIVITY LOGS

In any type of groundwater transport problem (contaminant solutes, hea t, etc.), knowledge of the location and properties of Pathways of incr eased hydraulic conductivity is essential. However, answering such que stions in strongly heterogeneous media, such as fractured rock, can be very difficult and budget-intensive with standard geophysical or hydr ogeological field investigations. We present a new testing concept and analysis procedure based on a time sequence of wellbore electric cond uctivity logs, which provides the exact location and the outflow param eters (transmissivity, formation fluid conductivity) of flowing featur es (fractures, faults, layers) intercepted by the borehole. Previously the quantitative analysis of this time sequence of electrical conduct ivity logs was based on a code, called BORE, used to simulate borehole fluid conductivity profiles given these parameters. The present repor t describes a new direct (not iterative) method for analyzing a short time series of electric conductivity logs which is based on moment qua ntities of the individual outflow peaks, and applies it to synthetic a s well as to field data. The results of the method are promising and a re discussed in terms of the method's advantages and limitations. In p articular it is shown that the method is capable of reproducing hydrau lic properties derived from packer tests well within a factor of three , which is below the range of what is recognized as the accuracy of pa cker tests themselves. Furthermore the new method is much quicker than the previously used iterative fitting procedure and is even capable o f handling transient fracture outflow conditions.