PETROLEUM CHARACTERS AND FORMATION MECHANISM IN THE DAMINGTUN SAG OF THE LIAOHE BASIN

Oil from Damingtun Sag can be divided into normal oil with waxy content is less than 20% and high waxy oil with wax is more than 20%.Comparing with normal oil,the depositional environment of source rocks of high waxy oil is characterized by poorer shale,higher salty and relative restricted weak reduction water body,and the organic matters are mainly composed of higher plant and lower grade aquatic creatures based on physical nature,sterane and terpene analysis of crude oil.Detail oil-rock correlation shows that high waxy oil originates from "oil shale" of Es⁴⁽²⁾,whereas normal oil sourced from shale of Es⁴⁽¹⁾ and Es³⁽⁴⁾.Formation of high waxy oil is mainly controlled by the organic matter of source rocks and the sedimentary environment.The low thermal condition makes the high waxy oil to be preserved in the sag.