9. Shallow/Near-Surface Structural Applications
Model Tank Electrical Resistivity Characterization of LNAPL Migration in a Clayey-sand Formation
Adepelumi Adekunle Abraham
Geology Department, Obafemi Awolowo University, Nigeria.
Abstract
Model tank time-lapse 2D electrical resistivity experiment was undertaken to monitor the leakage of petroleum products from underground pipelines into a clayey-sand aquifer. Numerical modeling was employed to simulate the electrode arrays that will resolve the post-leakage subsurface image most efficiently. Of the four arrays tested, dipole-dipole array proved most effective and was adopted for the laboratory studies. Pre-injection surveys were conducted to assist in discriminating between features caused by hydrocarbon accumulation and those due to natural geologic variability. Subsequently, controlled injection of diesel-oil into the model tank was undertaken at regular interval over a period of three days. Experimental evidence obtained from the studies indicates that high resistivity build up few hours after injection is directly related to hydrocarbon accumulation. Rather than biodegradation of the hydrocarbon, a more probable explanation for the observed decrease in resistitvity observed few hours after injection is simply that the hydrocarbons drained to a deeper level after pooling temporarily at a shallow level.
Last modified: Thu Apr 27 20:28:58 2006