Estimating Aquifer Parameters with GeoelectricSoundings: Case Study from the Shallow BeninFormation at Orerokpe, Western Niger Delta, Nigeria

摘要

A study of the use of geoelectric sounding employing Schlumberger configuration in delineating aquifer(s) and estimation of hydraulic parameters has been carried out at Orerokpe, Western Niger Delta. Twenty (20) depth soundings were carried out with a maximum current electrode spacing of 400 m. The acquired depth sounding data were interpreted by partial curve matching and computer iterative techniques. The results identified four geologic layers which include; top soil, clay/sand, sandy clay/clayey/sand and sand. The sands of the third and fourth geologic layers constitute the aquifer, the depth to the aquifer varied between 6.4 m and 28.1 m with a mean depth of 17.5 m. The thickness of the aquifer varied between 15.1 m and 67.1 m with a mean thickness of 28.24 m. The hydraulic conductivity (K) value measured in a reference well was combined with electrical conductivity (σ) obtained from geoelectric sounding data, the resulting diagnostic relation (Kσ = constant) was combined with Dar-Zarrouk parameters to estimate the transmissivity and hydraulic conductivity values of the aquifer. The results indicated that the transmissivity values of the aquifer varied between 418.6 m2/day and 1637.3 m2/day while hydraulic conductivity values varied between 10.50 m/day and 45.71 m/day. The estimated parameters indicated that the aquifer in seventy five (75) percent of the study area have high aquifer potential while the remaining twenty five (25) percent have moderate aquifer potential.