Geochemical Investigation and Effect of Sedimentary Environment Changes on Pabdeh Formation Hydrocarbon Potentiality in Mansuri Oilfield

Pabdeh Formation is one of the most important probable source rocks in Mansuri oilfield being under investigation. In this study, hydrocarbon potential of Pabdeh Formation is evaluated. Also effect of sedimentary environment changes on geochemical and hydrocarbon potential variation is studied. To achieve this, hydrocarbon potential of Pabdeh Formation with Rock Eval pyrolysis was investigated. Besides that, gas chromatography and gas chromatography- mass spectrometry data were utilized. Based on this study, in the Late Eocene age, relative sea level had raised, while in the Oligocene age, falling in sea level was occurred. Variation in sea level caused Pabdeh Formation to be heterogeneous in hydrocarbon potential. Pabdeh Formation in Mansuri oilfield from geochemical aspects is divided into three divisions. Lower and Upper zones in this formation, have fair (0.5-1% TOC) to good (1-2% TOC) hydrocarbon potential and contain kerogen type III. These zones have gas production potential. Middle zone, has very good (2-4% TOC) to excellent (>4% TOC) potential and contains kerogen type II and mixed type II and III. Middle zone has oil production potential. Rock Eval data as well as thermal history modeling demonstrate that; Pabdeh Formation is in early oil window, started yielding petroleum since 5-6 million years ago.