Abstract
The gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analyses for crude oils from Kareem reservoir in the wells El Hamed-1, 3, and 5 are used to provide information on source organic matters input, depositional environment, and maturation level. Data include normal alkane and acyclic isoprenoids distribution, terpane, and sterane aliphatic biomarkers. Pristine/phytane (Pr/Ph), Pr/nC17, and Ph/nC18 ratios indicated mixed organic sources of organic matters (kerogen type II, III) dominantly (kerogen type III) with a less effect of biodegradation and mature stage of occurrence. The diasteranes/steranes ratio showed generally low ratios as in most marine carbonate sources, while algal-bacterial organic matter contribution for the oil samples suggested dependence on the predominance of C23 tricyclic terpane relative to the C19 tricyclic terpane, and the C25 tricyclic terpane greater than C24 tricyclic terpane. The gammacerane index indicated that a low-salinity environment of deposition for the initial organic matters existed in the analyzed samples.