Geochemical characteristics of crude oil and oil-source correlation in Yanchang Formation in Xingzichuan Oilfield, Ordos Basin

There are significant differences between the crude oil in different horizons of Yanchang Formation, as is shown by the property, group composition, gas chromatography of saturated hydrocarbon, biomarker of terpane and sterane, comprehensive geological analyses. The crude oil properties of Chang-4+5 and Chang-6 are generally consistent and isogenous, whose difference may be related to migration fractionation effect and crude oil maturity. However, there exist obvious variances in the crude oil property between Chang-9 or Chang-10 and Chang-4+5 or Chang-6, indicating different maternal properties. The crude oils in Chang-9 and Chang-10 have relatively higher maturity, mirrored by the biomarkers of Ts/ Tm, C₂₉ββ / (ββ+αα) and αααC₂₉20S / (20S+20R), etc. The content of regular sterane in the crude oils in Chang-9 and Chang-10 shows different genesis. Thus, the comprehensive geological analyses and oil-source correlation manifest that the crude oils in Chang-4+5 and Chang 6 come from the source rocks of Chang-7, while the crude oils in Chang-9 generate from the Lijiapan shale, and the crude oils in Chang-10 may stem from the effective source rocks of Chang-92.