Geochemical variability of oils from Jurassic petroleum system in the east of Persian Gulf

Abstract

The Late Jurassic petroleum system has created a distinct oil family in the Jurassic and Cretaceous reservoirs in the eastern part of the Persian Gulf. Although the oils in this oil family indicate genetic affinity with the Middle Surmeh source rock, some oil samples show geochemical deviation compared to others. The purpose of this study is to gain a better understanding of these geochemical differences among 23 oil samples from the Jurassic oil family in the eastern Persian Gulf. To achieve this, physical and chemical properties of oil samples, biomarker ratios, stable carbon isotope data, and multivariate statistical methods were used. The chemometric analysis of twenty source-related parameters differentiates three genetic subfamilies (Jurassic principal subfamily, Resalat-Dariyan, and Balal-Surmeh) from Jurassic petroleum system oils. The Balal-Surmeh and Resalat-Dariyan samples are distinguished from principal subfamily based on depositional environment and maturity parameters. The Balal-Surmeh samples show a more marine characteristics and a high maturity level due to the contribution of Permo-Triassic condensates or Silurian Sarchahan shales as a secondary source. It seems that the limited oil generation of the low mature organic-rich interlayers of Dariyan Formation caused a low maturity level in the Resalat-Dariyan samples.