Assessment of the hydrocarbon potentiality of the Late Jurassic formations of NW Iraq: A case study based on TOC and Rock-Eval pyrolysis in selected oil-wells

Abstract

Abstract 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.