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The AAPG/Datapages Combined Publications Database
Environmental Geosciences (DEG)
Abstract
Environmental Geosciences, V.
2013. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.
DOI:10.1306/eg.11281212009
Characterization of near-surface fractures for hydrogeological studies using azimuthal resistivity survey: A case history from the Mamu Formation, Enugu (Nigeria)
Ahamefula U. Utom,1 Benard I. Odoh,2 Daniel K. Amogu,3 Amobi C. Ekwe,4 Boniface C. E. Egboka5
1Department of Geological Sciences, Nnamdi Azikiwe University, Awka, Nigeria; [email protected]
2Department of Geological Sciences, Nnamdi Azikiwe University, Awka, Nigeria; [email protected]
3Department of Geology, University of Nigeria, Nsukka, Nigeria; [email protected]
4Department of Geology, University of Nigeria, Nsukka, Nigeria; [email protected]
5Department of Geological Sciences, Nnamdi Azikiwe University, Awka, Nigeria; [email protected]
AUTHORS
Ahamefula U. Utom received a master
s degree in applied geophysics from Nnamdi Azikiwe University (Nigeria) in 2012, specializing in hydrogeophysics and environmental geophysics and is employed as an assistant lecturer with the Department of Geological Sciences at Nnamdi Azikiwe University. He is currently a DAAD scholar and doctoral candidate in environmental and engineering geophysics at Eberhard Karls University of Tubingen, Germany.
Benard I. Odoh holds a Ph.D. in applied geophysics from Nnamdi Azikiwe University, Awka, Nigeria. His research area is hydrogeophysics. He is a senior lecturer and director of the water resources capacity building network in the Department of Geological Sciences, Nnamdi Azikiwe University, Awka, Nigeria.
Daniel K. Amogu received B.Sc. and M.Sc. degrees in geology from the University of Nigeria, Nsukka, specializing in structural geology. He is currently a doctoral candidate in structural geology and worked as an academic staff of the University of Nigeria, Nsukka, between 2001 and 2009. Amogu currently works for Shell Petroleum Development Company of Nigeria as an exploration geologist in the prospect maturation team, Onshore Niger Delta.
Amobi C. Ekwe holds an M.Sc. degree and a Ph.D. in applied geophysics from the University of Nigeria, Nsukka (Nigeria), specializing in rock physics, seismic inversion, and hydrogeophysics. He worked as a lecturer in the Department of Geology, University of Nigeria, Nsukka, between 2009 and 2012. He is currently a Lecturer in the Department of Physics/Geology/Geophysics at the Federal University Ndufu-Alike Ikwo, Ebonyi State, Nigeria.
Boniface C. E. Egboka holds an M.Sc. degree and a Ph.D. from the University of Waterloo, Ontario, Canada. He is a consultant and professor of environmental hydrogeology and the vice chancellor at Nnamdi Azikiwe University, Awka, Nigeria. He is a fellow of the Nigerian Academy of Science, the Nigerian Mining and Geosciences Society, and the Nigerian Association of Hydrogeologists.
ACKNOWLEDGEMENTS
We thank the Department of Geology, University of Nigeria, Nsukka (Nigeria), for providing some of the materials used in this study. We also thank two anonymous reviewers for their invaluable comments and constructive suggestions. This research has been supported in part by the Alexander and Geraldine Wanek grants-in-aid from the AAPG Foundation.
ABSTRACT
Two azimuthal resistivity surveys were completed using the square array within the Mamu Formation, Enugu area, Nigeria, to characterize the orientation and porosity of fractures. The target consists of a shallow (
30 m [98 ft]) fracture zone that corresponds to the average completion 
depth
for the water supply wells in the study area. Fracture orientation, fracture porosity, and coefficient of anisotropy of the investigated media were determined from the azimuthal resistivity data. Results of the survey data indicate that the fractures trend generally in the northwest–southeast direction at depths of 7.1, 10.0, 20.0, and 28.3 m (23.3, 32.8, 65.6, and 92.8 ft). The fracture porosity ranged between 0.68% and 17%. The coefficient of anisotropy (
) ranges between 1.00 and 1.12. Fractures at localities with relatively high values of possess relatively high fracture porosity and relatively low specific surface area and thus are more likely to be permeable. These interpretations were in agreement with the information collected at bedrock outcrops during this and previous studies. It is therefore true that the data obtained from this study will enhance the understanding of the permeable zone, fluid migration pattern, and vulnerability of the groundwater to mine drainage problems in the Enugu area.
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