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张治波,郭英海,郑伟清,等. 川东北地区五峰组–龙马溪组页岩地球化学特征及有机质富集模式[J]. 煤炭科学技术,xxxx,xx(x): x−xx. doi: 10.12438/cst.2023–0946
引用本文: 张治波,郭英海,郑伟清,等. 川东北地区五峰组–龙马溪组页岩地球化学特征及有机质富集模式[J]. 煤炭科学技术,xxxx,xx(x): x−xx. doi: 10.12438/cst.2023–0946
ZHANG Zhibo,GUO Yinghai,ZHENG Weiqing,et al. Geochemical characteristics and organic matter enrichment model of Wufeng-Longmaxi formations shale in northeast Sichuan China[J]. Coal Science and Technology,xxxx,xx(x): x−xx. doi: 10.12438/cst.2023–0946
Citation: ZHANG Zhibo,GUO Yinghai,ZHENG Weiqing,et al. Geochemical characteristics and organic matter enrichment model of Wufeng-Longmaxi formations shale in northeast Sichuan China[J]. Coal Science and Technology,xxxx,xx(x): x−xx. doi: 10.12438/cst.2023–0946

川东北地区五峰组–龙马溪组页岩地球化学特征及有机质富集模式

Geochemical characteristics and organic matter enrichment model of Wufeng-Longmaxi formations shale in northeast Sichuan China

  • 摘要: 四川盆地是我国页岩气开发的主力产区,川东北地区作为四川盆地的页岩气开发的接替区,备受关注。目的,为了探究川东北地区上奥陶统五峰组–下志留统龙马溪组富有机质页岩的控制因素及富集模式。方法,采用电感耦合等离子体质谱(ICP–MS)方法对川东北地区五峰组–龙马溪组14件页岩进行元素分析,并结合测井曲线特征,探讨五峰组–龙马溪组沉积体系、氧化还原条件、陆源碎屑输入、初级生产力和古气候关系。结果,识别出了3个三级层序(SSQ1,SSQ2和SSQ3),海平面经历了由高–低-高–低的过程,结合页岩元素的 V/Cr,V/(V+Ni),Ni/Co,Sr/Cu,Sr/Ba,T(℃)等参数,指示了五峰组–龙马溪组,经历了氧化–贫氧–缺氧还原–贫氧–氧化的淡水环境;气候经历了温暖湿润–干旱寒冷–温润湿润–干旱寒冷–温暖湿润演化过程,温度经历了降低–升高–降低–升高的过程。结论,川东北地区五峰组–龙马溪组有机质富集模式可划分为Ⅲ 阶段模式,第Ⅰ阶段,五峰组到龙马溪组底部沉积时期,有机碳逐渐增高阶段,第Ⅱ阶段,龙马溪组中部,有机碳富集阶段(甜点段),第Ⅲ阶段,龙马溪组上部,有机碳逐渐降低阶段。期望为川东北地区页岩气的勘探提供依据,下一步,将开展研究区重大地质事件对有机质富集的资源响应研究,深化页岩气富集模式。

     

    Abstract: The Sichuan Basin, located in southwestern China, is considered the primary producing area for shale gas development in the country. Its rich shale gas reserves have made it a significant contributor to China's energy production. Within the Sichuan Basin, northeast Sichuan has emerged as a region of particular interest for shale gas development. In order to investigate the controlling factors and enrichment patterns of organic matter-rich shales from the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in northeast Sichuan, inductively coupled plasma mass spectrometry (ICP–MS) was used to analyze 14 shale samples from the Wufeng Formation-Longmaxi Formation in northeast Sichuan. Combined with the characteristics of logging curves, the sedimentary system, redox conditions, terrestrial debris input, primary productivity, and paleoclimate relationship of the Wufeng Formation to the Longmaxi Formation were explored. As a result, three third-order sequences (SSQ1, SSQ2, and SSQ3) were identified, and the sea level experienced a process from high-low-high-low, which, in combination with the shale elemental parameters of V/Cr, V/(V+Ni), Ni/Co, Sr/Cu, Sr/Ba, and T (℃), indicated that the Wufeng Formation-Longmaxi Formation underwent an oxidized-poorly oxygenated-anoxic reduced-poorly oxygenated-oxidized freshwater environment; the climate has undergone a warm-humid, dry-cold, warm-humid, dry-cold, warm-humid evolution, and the temperature has gone through the process of decreasing – increasing – decreasing – increasing. The organic matter enrichment pattern of the Wufeng Formation-Longmaxi Formation in northeast Sichuan can be divided into a Ⅲ stage pattern. Stage Ⅰ, the depositional period from the Wufeng Formation to the bottom of the Longmaxi Formation, is a stage of gradual increase in organic carbon; stage Ⅱ, the depositional period of the middle part of the Longmaxi Formation, is a stage of enrichment of organic carbon (sweet-spot member); and stage Ⅲ, the depositional period of the upper part of the Longmaxi Formation, is a stage of gradual decrease in organic carbon. It is expected to provide a basis for the exploration of shale gas in northeast Sichuan, and the next step will be to carry out research on the resource response of major geological events to organic matter enrichment in the study area and deepen the shale gas enrichment model.

     

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