Origin of the low-wax heavy oils in Well Shu-1, Hailaer Basin, Northeast China

The crude oils in the Well Shu-1, Bayanhushu Sag, Hailaer Basin, can be defined as low-wax heavy oils with a density of 0.932 g/cm~(3), and wax content of 6%. The oils contain about 30% saturated hydrocarbons and over 30% resin. The carbon isotopic composition of the crude oils ranges from (-34‰) to (-31‰). The oils are rich in isoprenoid and β-carotane hydrocarbons, showing a predominance of phytane to pristane with Pr/Ph0.9. The steranes are characterized with high ααα-20R configuration steranes of C_(27), C_(28), C_(29), low ααα-20S and αββ configuration steranes, and no diasteranes. The terpanes are dominated by pentacyclic terpanes with high concentration of gammacerane, and low content of tricyclic terpanes. The information indicates that the oils in Well Shu-1 are low maturity oil, and the organic matter generated the oils is dominated by alga which is deposited in highly reductive environment with salt or hyper-saline water. The crude oils are derived from low maturity of source rocks, the Cretaceous Nantun Formation.