The Middle Jurassic Sargelu Formation is evaluated for its hydrocarbon generation potential in three wells near Duhok Governorate, Northern Iraq using ten borehole cutting samples analyzed by Rock-Evil pyrolysis, gas chromatography coupled with gas chromatography-mass spectrometry (MSS) and stable isotope. The results showed that the total organic carbon and genetic potential of the formation ranges from 0.5 to 11.6 wt.% and 1.7 to 66.3 mg HC/g of rock, respectively indicating fair to excellent source rock petroleum potential, with hydrogen index values between 270 to 555 mg HC/g TOC. The results also show kerogen Types II and mixed II/III reflecting thermal maturity within the oil generation zone. The estimated ratios of Pr/Ph, Pr/n-C17 and Ph/n-C18 from the extracted bitumen reveal primary accumulations of marine organic matter under reducing conditions. The δ 13 CSat and δ 13 CAro for the extracted bitumen range from-29.5 to-27.5‰ and-28.4 to-27.2‰, respectively. The biomarkers results indicate a significant contribution of marine organic matters preserved under relatively anoxic conditions.

The Late Jurassic Naokelekan and Barsarin formations of northwestern Iraq have been investigated in three wells to assess their potentiality for hydrocarbon generation. The results of Total Organic Carbon content (TOC) and Rock-Eval Pyrolysis reveal fair to excellent content of hydrocarbon and suggest that the depositional conditions were suitable for the production and preservation of organic matter. The Thermal Maturity Proxy indicates that the studied formations were mature stage of hydrocarbon generation, with an exception of three samples from the Naokelekan Formation in Shaikhan-8 well, and two samples from the Barsarin Formation in Atrush-1 and Shaikhan-8 wells were at an immature stage. The S1 and TOC relationship shows that all the samples are indigenous in nature. Most of samples from the Naokelekan Formation belong to kerogen Type II/III, and that in the Barsarin Formation belongs to kerogen Type II is dominant. The Pr/Ph, Pr/n-C17 and Ph/n-C18 ratios for the extracted bitumen of both the formations indicate that they were originated from marine organic matter under reducing conditions. The δ13CSat and δ13CAro range from −28.7 to −27.7‰ and −28.8 to −27.7‰ respectively. These biomarkers show high contribution of marine organic matters preserved under relatively anoxic conditions in the studied formations.

The Middle–Late Jurassic Sargelu, Naokelekan, and Barsarin formations of northwestern Iraq have been investigated in the Shaikhan oilfield (well Shaikhan-8) to assess their potential for hydrocarbon generation.The results of total organic carbon analysis and rock-eval pyrolysis revealed a good-to-excellent hydrocarbon content and suggest that the depositional conditions were suitable for the production and preservation of organic matter. The thermal maturity proxy indicates that the studied formations were at the start of the hydrocarbon generation period. Most of the samples from the Sargelu and Barsarin formations belong to kerogen type II, whereas those of the Naokelekan Formation belong to kerogen type II/III. The Pr/Ph, Pr/n-C17, and Ph/n-C18 ratios of the extracted bitumen indicated that the organic matter originated from marine sources under reducing conditions. The stable carbon isotope composition of the saturated and aromatic hydrocarbon fractions ranged from –28.3 to –27.7 ‰ and –28.0 to –27.7 ‰, respectively. The biomarker results show a high contribution of marine organic matter that was preserved under relatively anoxic conditions. The profiles of the burial and thermal maturity history show that the simulated generation zones, based on the calculated vitrinite reflectance, indicate immature (0.44%–0.6%)-to-early oil generating (0.6%–0.75%) source rock. The low thermal maturity of the studied formations relative to the depth may be attributed to the low geothermal gradient and heat flow.