Oil-polluted groundwater in central and west Iraq as indicator of potential new hydrocarbon plays

Abstract

The old land of Iraq is characterized by the presence of many oil seepages that date back to the Babylonian time. During the last few years, the country has witnessed an accelerating pattern of earthquakes that may have activated some of the major old faults and released entrapped hydrocarbons that eventually mixed with groundwater. The recent phenomenon of mixing hydrocarbons with this water has resulted in significant economic losses. Many geochemical analyses were conducted for four samples of oil contaminated with groundwater in the Karbala and Najaf regions and compared them with five samples of seep oil in the Ramadi region and one sample of bitumen extracted from the Lower Fars (Fatha) formation of Kifl-1 oil well, to find out the origin of these oils and to identify potential reservoirs that could hold important undiscovered oil reserves. Results indicate that the groundwater oils were highly mature and originated from Lower Cretaceous carbonate sources deposited under upwelling deep water, anoxic conditions. This is roughly corresponding to the bitumen extract sample of the Lower Fars Formation taken from the Kifl-1 oil well, confirming that these oils belong to the reservoir units in this formation and may therefore contain economically amounts of oil.