Study on Secondary Hydrocarbon Generation of Ordovician Hydrocarbon Source Rock in Tarim Basin

With the view of mechanism of secondary hydrocarbon generation of marine source rock and pattern of hydrocarbon generation and expulsion,Ordovician hydrocarbon source rock was taken as the object in Tarim Basin.The characteristics of Ordovician hydrocarbon source rocks in typical structural units included secondary hydrocarbon generation and different original maturities and hydrocarbon generation stages according to the study on tectonic-thermal evolution and hydrocarbon generation histories in Tarim Basin.Ordovician marine hydrocarbon source rocks with different original maturities under the natural condition were selected to discuss the pattern of secondary hydrocarbon generation according to the thermal pressure simulation.The results showed that the secondary hydrocarbon generation potential of Ordovician hydrocarbon source rocks in Tarim Basin was dominated by original maturity;secondary hydrocarbon generation production rate decreased regularly with the increase of original maturity;the hydrocarbon generation and expulsion potential of hydrocarbon source rock with low and middle maturities was high and there was relatively later hydrocarbon generation peak,and the potential of rock with high maturities was low;the difference between the amount of continuous hydrocarbon generation and the sum of the first and secondary was also dominated by original maturity;when the original maturities were low and middle,the amount and potential of hydrocarbon generation increased during the process of the first and secondary hydrocarbon generation,and the amount and potential decreased when the original maturity was high.