Geochemical correlation of oil and source rocks from selected exploratory wells within Northern Mesopotamian basin, Iraq

Abstract

Geochemical exploration processes were applied to characterize, analyze, identify, and correlate, 11 crude oils and five source rock samples (core and cuttings), which were recovered from oil exploratory wells within the Mesopotamian basin; this basin is considered as one of the most formative, potential, and promising basin in the Middle East. Remarkable total organic carbon (TOC) identifies good source rocks encountered from Upper and Middle Jurassic deep wells and also extracts from Upper Cretaceous Shiranish formations. Two main families recognized (family A) subsidy to subfamily (a) and subfamily (b), generated by different source rock types, and different ages has been established on the basis of biomarker. This family was generated by marine carbonate–intrashelf subbasin source rocks, occurring in Jurassic–Cretaceous–Neogene reservoir rocks in both Zagros Fold Belt and Mesopotamian basin which are geochemically similar to the extracts from the Middle–Upper Jurassic age (Sargelu and Naokelekan Formations), yielding the majority of petroleum oil and gas fields in Iraq. (Family B) of the Upper Triassic Kurra Chine Formation, shallow marine–lagoonal environment, Upper Cretaceous Shiranish formation. Shale beds of the Middle Jurassic Sargelu formations are the major sources of oil in Iraq; these strata were deposited in euxinic marine environment, and most of rock sample are highly mature, with TOC attaining 16.20 wt% and average hydrogen index (HI) of 499 with relatively low values of oxygen index (OI) and maximum temperature (Tmax) 446.