The use of an azimuthal resistivity survey to detect the flow direction of hydrocarbons in the unsaturated zone at Karbala Governorate, Iraq

Abstract

A non-symmetrical azimuthal resistivity survey was applied with three different types of electrode arrays (Wenner, Schlumberger and polar dipole–dipole arrays) at two sites near water wells contaminated with hydrocarbon materials in order to determine the flow direction of movement of a hydrocarbon mass in the unsaturated zone. A subsurface plume of hydrocarbons was determined to be moving in a north-easterly direction. It is found that all the used arrays showed the ability to delineate the extent of the hydrocarbon mass, but polar dipole–dipole array was the best method to delineate the exact axis of the plume in the unsaturated zone. A symmetrical azimuthal resistivity survey with a Wenner electrode array was applied in four stations near contaminated well 8 in order to detect the flow direction of contaminated groundwater from a spill from the well. This technique gave good results in detecting the flow direction and showed that the bulk of the contamination moved in a north-westerly direction. Contamination from this source then divided into two parts, with a major part moving a north-easterly direction, and the second part moving to the south-west. This work has indicated that resistivity techniques can be successful in determining the direction of flow of hydrocarbons in the unsaturated zone under suitable conditions.