ESTIMATION OF HYDRAULIC CONDUCTIVITY FROM BOREHOLE FLOWMETER TESTS CONSIDERING HEAD LOSSES

Abstract

Recent numerical studies have demonstrated that the conventional interpretation of the borehole flowmeter test (BFT) may lead to considerable errors in estimates of the horizontal hydraulic conductivity (Kr) due to neglect of head loss across the electromagnetic borehole flowmeter (EBF). Even in uniform aquifers, the conventional interpretation underestimates Kr at the base and overestimates Kr at the top of the aquifer. In this paper, we derive exact analytical solutions for hydraulic head and streamlines induced by the BFT in a confined homogeneous aquifer. The solutions explicitly consider head loss across the EBF. The derived analytical solutions for head distribution in the vicinity of the pumping well and for volumetric flux to the well sections above and below the EBF can be used to interpret field BFT data. In uniform aquifers, this approach can be applied to obtain estimates of Kr from the conventional interpretation. Applications of this approach to the BFT field data set from a highly heterogeneous aquifer indicate that the constraint of aquifer homogeneity limits the applicability of this approach, but it can provide useful insights into the mechanism of flux redistribution near the borehole during the BFT.