库车盆地烃源岩特征及生烃史特征

Characteristics of source rocks and hydrocarbon generation in the Kuqa basin, northwest China

库车盆地中主要发育有三叠系湖相泥岩与侏罗系煤系地层两套烃源岩,它们都顺盆地走向呈东西向展布,沉积中心接近现今克依背斜带的位置.三叠系湖相泥岩有机碳含量中等,有机质类型属Ⅲ型,属于中等偏差烃源岩;侏罗系湖沼相泥岩有机碳含量高,有机质类型属Ⅱ2-Ⅲ型,属于中等偏好烃源岩.碳质泥岩与煤岩生烃潜量低,有机质类型属Ⅲ型,为差烃源岩.模拟研究表明,生油强度以侏罗系湖沼相泥岩为最大,三叠系湖相泥岩次之,侏罗系煤岩与碳质泥岩较小;而生气强度以侏罗系湖沼相泥岩和煤岩为最大,三叠系湖相泥岩次之,侏罗系碳质泥岩最小.此外,模拟结果还表明,克依背斜带是库车盆地的主力生烃区,生烃能力最强,其次为拜城凹陷,生烃能力稍差.

There are two major types of source rocks which are composed of Triassic and Jurassic formation in Kuqa basin of northwest China. The deposition centers of these source rocks distribute near the KelasuYiqikelike anticline belt lie along the direction of east and west. While the Triassic lake facies mudstone falls into the type of middle to bad source rock, the Jurassic lakeswamp facies mudstone,carbonaceous mudstone and coal belong to the types of middle to good source rock and bad source rocks respectively. Furthermore, simulation work indicates that the ranks of the density of oil generation from big to small are Jurassic lakeswamp facies mudstone and coal, Triassic lake facies mudstone and Jurassic carbonaceous mudstone. Besides this, the simulation also indicates that the KelasuYiqikelike anticline belt which has the more ability of hydrocarbon generation compared with the Baicheng depression is the major source area.