Inclusions in Jurassic sandstone reservoirs in Yanqi basin are mainly distributed in Jianghe Formation and Badaowang Formation

their homogeneous temperature is between 101℃～110℃ and 121℃～130℃

carbon numbers of n-alkane appear in double- peaks state

main front peak with 18 or 20 carbon numbers

Main back peak with 26 or 27 carbon numbers. These features indicate that accumulations of oil and gas took place twice in the basin during the middle-late Jurassic

namely

the first phase is believed to be mainly for low matured oil & gas generation

migration and accumulation in Badaowang Formation in the late Jurassic

and the second phase is for the maturation of oil & gas in end Jurassic. It is believed by analyzing the history of hydrocarbon generation that the accumulation of oil and gas should have taken place once more in this region by the end Tertiary

this event has not been detected because of the inactive diagenesis and low abundance of the inclusions.