塔里木盆地奥陶系烃源岩二次生烃研究

为研究海相烃源岩二次生烃规律和塔里木盆地生排烃规律,以塔里木盆地奥陶系烃源岩为研究对象,首先通过构造-热演化史和生烃史研究得出,塔里木盆地典型构造单元奥陶系烃源岩具有二次生烃的特征,并且起始成熟度和生烃期次不同。然后选取自然条件下演化至不同起始成熟度的奥陶系海相烃源岩,采用热压模拟实验方法系统研究其二次生烃规律。研究表明:塔里木盆地奥陶系海相烃源岩二次生烃的主控因素是起始成熟度,二次生烃产率随起始成熟度增加规律性减小;低成熟和中成熟烃源岩具有大量生排油气潜力,出现相对延迟的生油高峰,高成熟烃源岩没有大量生油和生气的能力;两次不连续生烃量与一次连续生烃量的差值也受起始成熟度控制,具有阶段性;起始成熟度在低成熟到成熟阶段时,二次不连续生烃过程会增加烃源岩的生烃量,使生烃潜力增加,而高成熟阶段以后,二次不连续生烃过程就会减少烃源岩的生烃量,使生烃潜力减小。

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.