Hydrocarbon Potential and Depositional Environment of the Shiranish Formation in Northern Iraq

Abstract

Shiranish Formation at three localities in Northern Iraq (Pulkana, Dokan, and Sufaya) was studied to determine hydrocarbon generation potential and conditions of the depositional environment. For this purpose, 15 rock samples were collected from subsurface sections (Pulkana and Sufaya oil fields) and 5 surface samples from the Shiranish outcrop in the Dokan area. These samples were subjected to Rock-Eval pyrolysis analysis, in addition to biomarker analysis of the bitumen extract of one sample. Total organic carbon, S2, and hydrogen index values of the Formation samples from the Sufaya oil field, and the Dokan outcrop were generally low; indicating that Shiranish Formation is non-hydrocarbon source rocks. On the other hand, the Total organic carbon, S2, and HI of the Shiranish Formation for Pulkana oilfield samples are generally high; indicating that Shiranish Formation can be regarded as a fair source of rocks. Tmax and biomarker data indicate that the organic matter of the Shiranish Formation is immature-early mature. Moreover, the hydrogen index, oxygen index, and biomarker data indicate that the Shiranish Formation contains type II and II/III and was deposited under an anoxic depositional environment at Pulkana. At Sufaya and Dokan, Shiranish Formation contains type III and IV kerogen deposited in a more oxic environment.