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

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 ohm m and about 107 ohm m 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.

Automated summary

The study in the southern Benue Trough area of Nigeria found that the resistivity range for groundwater-bearing fracture zones in pre-Santonian sedimentary succession varies in fractured shales and sandstones. Wider fractures tend to have lower resistivity and higher water content, while the width of fractures gradually decreases below 80 meters depth in the area. The spatial distribution of resistivity shows an increase with depth, except for the fracture zones.