Estimation of Aquifer Parameters in Fractured Sedimentary Rocks from Resistivity Data and Lithologs – A Case Study in Abakaliki Area, Southeastern Nigeria

Abstract

Groundwater exploration in the Abakaliki area of southeastern Nigeria has faced significant challenges due to the complex nature of the rock units. Despite limited groundwater studies in this region, little is known about the aquifer parameters in the fractured and/or deformed sedimentary rocks. The knowledge of aquifer properties associated with the weathered/fractured zones enhances the delineation of groundwater-saturated zones and predictability of groundwater availability. The main objective of this study is to estimate key aquifer parameters of these fractured rocks and examine their relationship with lineament distribution. This was achieved by integrating resistivity data and lithological profiles to better understand the aquifer characteristics. The study combined field investigations with the use of 1-D resistivity measurements and lithological analysis to address this challenge. DarZarouk parameters were calculated from 1D resistivity surveys carried out using the Schlumberger array. From the results of this research, the Longitudinal conductance (S= 0.1-15 mhos) is inversely proportional to the aquifer resistivity ρ . The shale aquifers i 2 have higher S than their sandstone counterparts. The transverse resistance is lower (<1,425 Ωm ) in the shale aquifers 2 than in the sandstone aquifers (> 1,425Ωm ). The hydraulic conductivity (k = 2.7-230.2 m/day) increases in younger beds due to less lithification and influences groundwater availability. The k is fracture-dependent and inversely proportional to ρ . There is a direct correlation between the calculated k values in this work and their empirically i 2 derived counterparts for the aquifer systems. Transmissivity (T = 62-5,736 m /day) is inversely proportional to TR, suggesting discrete flow in the study area. The results of the reflection coefficient (R = ≤ -0.632) and fractured C -4 2 contrast (F = 2.39×10 -1.10×10 ) indicate that groundwater occurrence is more fracture-dependent than lithology C within the location of this study.

Publication Info:

Author: Obasi, I.A. , Onwa, N.M. , Ahmed II, J.B. , Aigbadon, G.O. , Igwe, D.O. , 6 1 1 3 7 Akakuru, O.C. , Onwe, I.M. , Chukwu, C.N. , Akudo, E.O. and Chibuike, A.

Volume: 60

Issue: September

Published By: Journal of Mining and Geology Vol. 60(2) 2024. pp. 217 - XXX © Nigerian Mining and Geosciences Society (NMGS, 2024-09-01