oa Geochemistry of Light Hydrocarbon Compounds (LHC) in Crude Oils from the Levantine Basin, Offshore Israel

The geochemistry of light hydrocarbon compounds (LHC) has been assessed in twelve crude oils reservoired in Oligo-Miocene to Miocene sands from five fields (A, B, C, D and E) located in the Levantine Basin, Offshore Israel. The objective is to evaluate the impact of evaporation in interpreting correlation (oil-oil) and transformation (evaporative fractionation, water washing, biodegradation and maturity) processes of the oils.

The analytical workflow included an initial qualitative chromatographic separation on the crude oil samples to recognize the main compound classes, followed by an isolation and quantification of the light hydrocarbons compounds (LHC) to obtain the peak and ratios required to conduct the interpretation. These results (termed ‘time2’) were compared against LHC ratios obtained when the wells were initially drilled (hereby and thereafter referred toas ‘time1’). Similarities and important differences were observed during the comparison, indicating that evaporation has impacted the most recently analyzed samples, therefore affecting the interpretation of key transformation processes such as fractionation, biodegradation, maturity and water washing. Identifying these alterations early in the oil geochemistry (light to heavy molecular weight characterization) workflow will reduce uncertainties when performing oil – oil correlations, grouping oils and the whole understanding of the petroleum systems.