f Evaluation of Resistivity Method in Delineation Ground Water Hydrocarbon Contamination Southwest of Karbala City

The studied area lies in Karbala Region. The field work performed near six wells drilled since seventh well contaminated with hydrocarbon materials, distributed over the studied area; at the southwest, southeast and northwest of Karbala. Electrical resistivity method in different field techniques was carried out. Non symmetrical azimuthal resistivity survey was applied with three different types of electrode arrays: Wenner, Schlumberger and polar dipole - dipole in two sites. It is found that all the used arrays show the ability to delineate the contaminated water plume, but polar dipole-dipole array was the best to delineate the exact axis of that plume. Symmetrical azimuthal resistivity survey with Wenner electrode array was applied in four stations near contaminated well 8 in order to detect moving direction of contaminated water spill from the well. This technique gave good results in detecting spill direction Azimuthal resistivity techniques can be successful in detecting contaminated water spill under proper conditions. Shallow vertical electrical sounding (VES) technique with Schlumberger electrodes array (maximum distance between current electrodes was 50m) was conducted in two sites; (25) VES points near contaminated well 3 and (45) VES points near contaminated well1 in order to separate the contaminated zone from the clear one. This technique can give good results in delineating contaminated and clear zones when there is high resistivity contrast between them. Deep VES survey in four VES points was applied in order to study the deep hydrocarbon contaminantbearing layer (layers) with respect to its depth and thickness in its actual deep position. It is found that deep VES technique is not effective to detect this hydrocarbon contaminant-bearing layer (layers) in its actual position at the surveyed area. 2D imaging technique in two sites was applied. Near contaminated well 3, in two transects with (30m) long by using Wenner electrode array coincided in position with two VES sections. It is found that 2D imaging technique was better than VES technique in delineating subsurface distribution of contamination at the surveyed area. Also 2D imaging was applied in (8) transects near a pit of contaminated water near contaminated well 6. The outcomes suggested that the 2D imaging technique is a successful and powerful in separating contaminated zone from clear one and in detecting underground seepage depth and moving direction.