川西坳陷上三叠统烃源岩排烃特征与排烃史

四川盆地西部(简称川西)前陆盆地构造具有多期性,导致油气生成和聚集过程的复杂性,其中烃源岩排烃特征和排烃史的研究,对于明确油气成藏期,理清油气藏成因类型具有重要的意义。为此,应用排烃门限理论,利用生烃潜力法研究了川西坳陷上三叠统烃源岩的排烃特征和排烃史。结果表明:①川西坳陷上三叠统烃源岩在早侏罗世(J1)末期即开始进入排烃门限,晚侏罗世(J3)早期—中期开始进入排烃高峰期;②马鞍塘组—小塘子组烃源岩的排烃高峰期处于J3p—K,T3x3烃源岩排烃高峰期处于J3sn—J3p,T3x5烃源岩排烃高峰期处于K1—K2;③川西地区不同层段不同地区进入排烃门限和排烃高峰期的时间存在差异:马鞍塘组—小塘子组和须家河组三段烃源岩,鸭子河地区排烃时间相对较早,马井、孝泉—新场—合兴场地区次之,大邑和丰谷地区较晚,须五段烃源岩在洛带排烃时间较早,马井、孝泉—新场—合兴场和丰谷地区次之,大邑地区和鸭子河地区最晚。

Characteristics and history of hydrocarbon expulsion of the Upper Tertiary source rocks in the western Sichuan Depression

The foreland basin in the western Sichuan Basin has experienced multiple stage tectonic movements, resulting in a complex process of hydrocarbon generation and accumulation. A study on the features and history of hydrocarbon expulsion is of great significance to defining hydrocarbon pooling stages and their genetic types. The hydrocarbon expulsion threshold theory and the hydrocarbon generation potential method are used to study the features and history of hydrocarbon expulsion of the Upper Tertiary source rocks. The following conclusions are obtained. ①The source rocks in the western Sichuan Depression entered hydrocarbon expulsion threshold at the end of the Early Jurassic (J1), and reached peak hydrocarbon expulsion at the early middle Late Jurassic (J3). ②The source rocks in the Ma'antang Xiaotangzi formations reached peak expulsion at J3p  K, while that of T3x3 was at J3sn - J3p, and that of T3x5 at K1- K2. ③The source rocks in different intervals and different areas reached peak hydrocarbon expulsion at different times. The source rocks in the Ma'antang Xiaotangzi formations and the third member of Xujiahe Formation in the Yazihe area reached peak expulsion relatively early, while those in the Majing, Xiaoquan Xinchang Hexingchang areas were relatively late, and those in Dayi and Fenggu areas were the latest. In contrast, the source rocks in the fifth member of the Xujiahe Formation reached peak hydrocarbon expulsion early in the Luodai area, later in the Majing, Xiaoquan Xinchang Hexingchang and Fenggu areas, and the latest in Dayi and Yazihe areas.