Application of the resistivity method in characterizing fractured aquifer in sedimentary rocks in Abakaliki area, southern Benue Trough, Nigeria

Abstract

Resistivity range for groundwater-bearing fracture zones was studied in the fractured shales and sandstones of pre-Santonian sedimentary succession in Abakaliki area, southern Benue Trough, Nigeria using vertical electrical sounding (VES) data and borehole lithologs. The results of the study indicate that resistivity of water-bearing fracture zones in the shales is ≤ 52 Ωm and about 107 Ωm in sandstones. These fractures occur at a depth of ≥ 18 m in shales but shallower (≥ 6 m) in sandstones. The wider the fracture, the more the resistivity tends to zero, and the higher the volume of water present in it. While the layer models define the water-bearing layer, the synthetic model defines depth to the top of the fracture and fracture thickness. The wideness of the fractures decreases gradually below 80 m depth. The spatial distribution of resistivity in the area indicates that resistivity increases with depth except for the fracture zones.