Oil source and entrapment epoch of the Ordovician oil reservoir in the Kongxi burial-hill zone, Huanghua depression, North China

An oil flow obtained from the Middle Ordovician Fengfeng Formation carbonat e reservoir in the well KG-3, Kongxi burial-hill zone in 1993 marked a brea kthrough in petroleum exploration of the high-mature Lower Palaeozoic strat a, North China. Both the Lower member of the Fengfeng Formation and the Sec ond Member of the Upper Majiagou Formation in the Middle Ordovician are sup posed to be the main source beds. Oil generation peaks range from 1.08 to 1 .64 in R-o, showing a "lag effect" of oil generation in high-mature carbona te source rocks under multicyclic tectonic movement conditions. The Kongxi burial-hill zone adjoins a potential Ordovician source kitchen. The KG-3 Or dovician burial-hill reservoir has undergone Two oil filling events, i.e., an early event in the Late Carboniferous-Permian and a more significant lat e event in the early Eogene.