Application of Resistivity Sounding In Environmental Studies: A Case Study of Kazai Crude-Oil Spillage Niger State, Nigeria

Abstract

A pipeline conveying crude oil from Escravos via Izom ruptured in the year 2000 and polluted the Kazai area, although the ruptured pipe was replaced and the site cleaned up, an examination of the point of spillage two years later gave the impression that the pipeline might be still leaking. The present work presents the use of Vertical Electrical Soundings (VES) techniques, and systematic trenching, to determine the source of this environmental problem. A total number of eight soundings along two profiles were carried out around the point of spillage, and data analysis revealed that the area is predominantly clayey in nature, and that the pipes are no longer leaking. Due to the plasticity of the clay when wet, it expands when in contact with rainwater and, as it does so, it entrapped any oil existing around it. However, when not in contact with water in the dry season, the clay shrinks and cracks, thereby releasing the trapped oils. This mechanism continued seasonally, and the oil released during the dry season, is the one responsible for the apparent leakage of the pipeline. Geoelectric models in the form of Vertical Isoresistivity Sections (VIS) and Isoresistiviy Maps were plotted. These were used to delineate the polluted zones, which were recommended for excavation and refilling.

Keywords: Vertical Electrical sounding, Geoelectric Models, Isopach map, Isoresistivity Map