上扬子区下寒武统富有机质页岩沉积环境及其对有机质含量的影响

发布时间：2019-05-24 10:40

【摘要】：选取上扬子区3个下寒武统地层剖面,对岩石样品进行了有机碳含量和主、微量元素测试,结合前人研究成果,分析了早寒武世不同沉积阶段生物初级生产力及氧化还原条件的变化特征,及其对有机质富集的影响。结果表明:第Ⅰ-Ⅱ阶段,浅水陆棚以缺氧铁化海水为主,具有较高的初级生产力;深水陆棚为缺氧硫化环境,生物初级生产力较低;斜坡—盆地区为缺氧铁化环境且上升洋流带来大量营养物质,生物初级生产力最高。第Ⅲ阶段,陆棚区与开阔海沟通良好,为氧化环境,有机质难以有效保存;斜坡—盆地区演化为氧化—贫氧环境,由于初级生产力依然很高,大量有机质在氧化分解之前快速堆积埋藏而形成有效烃源岩。总体而言,陆棚区富有机质页岩主要受海水氧化还原条件控制,有机质在还原环境中更易保存;斜坡—盆地区富有机质页岩中有机质含量主要受生物初级生产力和沉积环境控制,相同沉积条件下,有机质丰度相较于陆棚区更高。下寒武统富有机质页岩是页岩气勘探开发的有利层系,有机质含量可影响页岩中的含气量,因此发育的陆棚及斜坡—盆地相页岩是页岩气勘探开发的层位。
[Abstract]:Three Lower Cambrian strata profiles in the upper Yangtze area were selected to test the organic carbon content and main and trace elements in the rock samples, combined with the previous research results. The variation characteristics of biological primary productivity and redox conditions in different sedimentary stages of early Cambrian and their effects on the enrichment of organic matter were analyzed. The results showed that in the first and second stage, the shallow shelf was dominated by anoxic ironized seawater, which had high primary productivity, while the deep water shelf was in anoxic vulcanization environment and the biological primary productivity was low. The slope-basin area is anoxic ironized environment and the rising ocean current brings a lot of nutrients, and the biological primary productivity is the highest. In the third stage, the shelf area communicates well with the open sea, so it is difficult to preserve the organic matter effectively for the oxidation environment. Slope-basin area evolved into oxidation-oxygen-poor environment, because the primary productivity is still very high, a large number of organic matter is rapidly accumulated and buried before oxidative decomposition to form effective source rocks. Generally speaking, the organic shale in the shelf area is mainly controlled by the redox conditions of seawater, and the organic matter is easier to be preserved in the reduction environment. The content of organic matter in organic shale in slope-basin area is mainly controlled by biological primary productivity and sedimentary environment. Under the same sedimentary conditions, the abundance of organic matter is higher than that in shelf area. Lower Cambrian organic shale is a favorable strata for shale gas exploration and development, and the content of organic matter can affect the gas content in shale. Therefore, the developed shelf and slope-basin shale are the strata of shale gas exploration and development.
【作者单位】：中国地质大学(北京)能源学院;页岩油气富集机理与有效开发国家重点实验室;中国石化页岩油气重点实验室;中国石化石油勘探开发研究院;
【基金】：中国石化科技部项目(G5800-13-ZS-KJB018)资助
【分类号】：P618.13

【相似文献】