Oil generation threshold depth of Songliao Basin: Revision and its significance

A systematic analysis was carried out on the relation curve of hydrocarbon transformation ratio vs. buried depth and that of vitrinite reflectance (Ro) vs. buried depth in Binbei area, major source rock area (Qijia-Gulong Sag and Sanzhao Sag), and major source rock layer (Cretaceous Qing-1 Member, Qing-2 – Qing-3 Members) in Songliao Basin, to re-determine the oil generation threshold depth of the basin. The oil generation threshold depth of the major source rocks is likely to range from 1400 m to 1700 m, rather than 1 200 m in the previous estimation. The change of oil generation threshold has different effects on the resources potential and exploration orientation of various areas: For the major source rock areas, increase of oil generation threshold depth will cause decrease of oil generation and expulsion quantity, with no evident effect on the resources potential of major source rock area but with certain effect on the exploration orientation and favorable target evaluation. For the Binbei area with shallower buried depth of source rocks, it will have great effect on the exploration potential, exploration orientation, and favorable target evaluation. For the southeastern uplift area with great denudation in the basin, the oil generation threshold depth is reduced to about 700 m, which will improve the exploration potential of Chaoyanggou terrace, Changchunling anticline, and Binxian-Wangfu area.