Hydrocarbon potential of Sargelu Formation and oil-source correlation, Iraqi Kurdistan

Sargelu Formation is one of the major petroleum source rocks in Iraq and the Middle East. In an effort to build on the previous work and add new interpretations, this investigates selected outcrops, bore holes, and crude oil samples from different localities in Iraqi Kurdistan. Sargelu Formation has rather uniform lithology with variable thickness throughout Iraqi Kurdistan. The thickness progressively decreases from about 485 m west of the Tigris River in the Mosul area toward north where it is 20-30 m thick and northeastern Iraq where it is about 50 m thick. Results of the studied samples show that the total organic carbon of Sargelu Formation decreases toward the north and northeastern parts of Iraq. The mean of total organic carbon (TOC) wt% is 11.1 in northwestern part in Tawke-15, and it is only 0.5 wt% in eastern part in Hanjeera locality. The organic material is characterized by type II and III kerogens. The thermal maturity increases to the east of the studied area. The organic matter is within the dry gas zone in the eastern part of the study area and is mature and immature in both the western and northwestern parts of the study area. Various diagrams and relationships between bulk properties and biomarkers help recognize different oil families in Iraqi Kurdistan. Four main oil families are recognized: (1) the Upper Jurassic Taq Taq; (2) the Lower Jurassic Tawke; (3) the Upper Jurassic Kirkuk; and (4) the Tertiary Kirkuk. The geochemical parameters suggest carbonate source deposited in reducing environments for the oils. The biomarker parameters show no evidence of molecular contribution from Sargelu Formation to the oils in Taq Taq, but Tawke and Kirkuk oils show a molecular contribution from Sargelu Formation.