No breakthrough has been made in tight oil exploration of the Yanchang Formation in southeastern Ordos Basin because of the low level of research on tight oil accumulation conditions.In order to evaluate tight oil exploration prospect of the Yanchang Formation

we studied in-detail the tight oil accumulation conditions in the study area studying respects of sedimentary microfacies

reservoir rock

cap rock and hydrocarbon migration.The high quality source rocks of Chang 7(7

th

Member of the Yanchang Fm)are widely developed in the southeast region of the basin.The reservoir of the Yanchang Formation is tight. The favorable source-reservoir combination provided good geological conditions for tight oil accumulation.The Chang 6

Chang 7 and Chang 8(the 6

th

7

th

and 8

th

Members of the Yanchang Fm)intervals are the main targets for exploration of tight oil in the Yanchang Formaiton in the study area.Tight oil reservoir formation and enrichment are controlled by sedimentary microfacies and quality reservoirs. Based on the study of inclusions temperature

thermal history

illite dating

saturation pressure and other methods

the tight oil accumulation period in Yanchang Formation is set at the Early Cretaceous and was controlled by the Late Mesozoic tectonic thermal event

thus tight oil accumulation occurred in late stage.