Determination of Aquiferous Zones in the Freshwater South-East Niger Delta, Using Vertical Electrical Sounding (VES) Method

Vertical Electrical Sounding (VES) was applied in investigating the subsurface layers along Adibawa-Zarama pipeline route in the Niger Delta, Nigeria in an attempt to determine the depth of aquifer. A total of thirty (30) VES sets were executed using Schlumberger array of a maximum half current electrode spacing of 50m and interval distance of 250 m along the 6.75 km Adibawa-Zarama route. The fundamental parameters of resistivity, conductance, anisotropy and depths were computed using Resist software. Transverse resistivity is generally higher than longitudinal resistivity, and it ranges from 70.49 Ω m to 936.30 Ω m while those of longitudinal ranges from 31.37â Ω m to 585.81Ω m. Anisotropy value ranges from 1.01 to 1.75 which is an indication that the layers are laterally inhomogeneous. The 1st layer has a resistivity range of 40.00 Ω m - 453.00 Ω m the 2nd layer resistivity range is 17.00 Ωm - 320 Ω m, 3rd layer has resistivity range of 130.00 has resistivity range of m - 1400.00 Ω m, 4th layer has resistivity ranges from 23.00 Ω m - 1450.00 Ω m, the 5th layer has resistivity range of 220.00 Ω m - 4950.00Ω m, while the 6th layer has resistivity range of 600.00 Ω m - 3997.00 Ω m. The minimum and maximum thicknesses for the respective first five layers in sequence are: 1.45 m and 3.0 m, 0.75 m and 4.10 m, 1.42 m and 15.04 m, 3.10 m and 23.20 m, and 7.00 m and 18.90 m. The saturated layers occur mostly in third, fourth and fifth layers are at depths 12.87 m and 26.02 m and 38.97 m respectively. Clay was located at a depth from 0m to 5m, while beyond these depths the formation is clayey sand to sandy clay, fine sand, clayey sand and sand of various grades. Tying results of the geoelectric survey to various lithologies reveals that resistivity is affected by lithology and fluid content of the rock. The aquifer is thick and is located between 12.87 m and 38.97 m.