Geochemical composition of oils in the Dunga Field, western Kazakhstan: Evidence for a lacustrine source and a complex filling history

The onshore Mangyshlak Basin, located in western Kazakhstan along the eastern coastline of the Caspian Sea, is a prolific hydrocarbon province and home to numerous oil and gas fields. The primary reservoirs are Jurassic clastic sandstones, but the Dunga Field contains hydrocarbons in Lower Cretaceous (Valanginian, Barremian, Aptian, Albian) clastic and carbonate reservoirs. The general perception is that these petroleum accumulations were charged from marine source rocks of likely Middle Triassic age. A detailed organic geochemical investigation of oils from the Cretaceous reservoirs of Dunga Field suggests that all were generated from the same lacustrine source rock facies (organofacies C) in mature kitchens in the offshore Mangyshlak Basin, followed by a complex filling history. The oils are characterised by relatively high wax content, low sulfur content (mainly