塔里木盆地下寒武统泥质烃源岩成烃生物组合的构造-沉积环境控制因素

Tectonic-sedimentary constrains for hydrocarbon generating organism assemblage in the Lower Cambrian argillaceous source rocks,Tarim Basin

成烃生物组合是烃源岩研究的重要内容,目前关于成烃生物研究主要集中在生烃模拟实验,对成烃生物发育的地质控制因素研究在油气地质界还相对较少,然而这方面的研究是利用成烃生物预测优质烃源岩分布并指导油气勘探的重要环节。成烃生物面貌的研究结果表明,西山布拉克组和玉尔吐斯组主要以底栖藻为主,含浮游藻类,但西山布拉克组主要以底栖藻类和浮游藻类为主,而东二沟剖面玉尔吐斯组则以底栖藻类(红藻)为主。稀土元素地球化学揭示西山布拉克组和玉尔吐斯组沉积时均受热水作用影响,且西山布拉克组受影响程度要强于玉尔吐斯组。泥岩稀土、主量和微量元素分析发现,西山布拉克组和玉尔吐斯组均为还原环境,但西山布拉克组水体还原性强度要弱,水动力条件稍强,活跃的火山活动使得库鲁克塔格地区西山布拉克组沉积期古地貌起伏程度要强于柯坪地区。对比现代藻类分布模式,构造活动、水体深度以及古地貌上差异可能是导致南雅尔当山剖面西山布拉克组和东二沟剖面玉尔吐斯组成烃生物面貌不同的重要原因。

Hydrocarbon generating organism is an important object for the source rock research. The studies,so far,were focused on their hydrocarbon-generation potential via simulation experiments,and less attention was paid to the geological settings that affect development and distribution of hydrocarbon generating organisms. However,the development and distribution of hydrocarbon generating organisms is very important for predicting source rocks and guiding petroleum exploration. In this study,the Lower Cambrian Xishanbulake and Yuertus formations were selected from the Southern Yaerdangshan and Dongergou sections in Kuluketage and Keping districts,respectively. Researches on two formations demonstrate that the hydrocarbon generating organisms in the Xishanbulake Formation are dominated by benthic algae,and include some planktonic algae; whereas hydrocarbon generating organisms in the Yuertusi Formation are benthic algae. Anomaly of elements Ce and Eu and REE patterns of cherts in the two formations imply that the two sections were affected by hydrothermal fluid,and that the influence in the Southern Yaerdangshan section was stronger than that in the Dongergou section. Major and trace elements analyses of mudstones indicate that the Xishanbulake Formation have less reduction water,and more active volcano in the Kuluketage district which might be resulted in more undulating terrain than that in the Keping district during the Early Cambrian. Correlated with distribution of extant algae,it could be concluded that the difference in tectonic activity,water depth,and paleo-terrian may be the major cause for the difference in hydrocarbon generating organism assemblages between the Xishanbulake Formation in the Southern Yaerdangshan section and the Yuertus Formation the Dongergou section.