Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inh...Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inhabited may be obscured by the post-depositional alteration due to metamorphism at depth and weathering near the Earth’s surface.Among over 50 Cambrian BST biotas,the Chengjiang and Qingjiang deposits are well known for their richness of soft-bodied taxa,fidelity of preservation,and Early Cambrian Age.While alteration via weathering has been well-investigated,the thermal maturity of the units bearing the two biotas has not yet been elucidated.Here we investigate peak metamorphic temperatures of the two deposits using two independent methods.Paleogeotemperature gradient analyses demonstrate that the most fossiliferous sections of the Chengjiang were buried at a maximum depth of∼8500 m in the Early Triassic,corresponding to∼300°C,while the type area of the Qingjiang biota was buried at a maximum depth of∼8700 m in the Early Jurassic,corresponding to∼240°C.Raman geothermometer analyses of fossil carbonaceous material demonstrate that peak temperatures varied across localities with different burial depth.The two productive sections of the Chengjiang biota were thermally altered at a peak temperature of approximately 300°C,and the main locality of the Qingjiang biota experienced a peak temperature of 238±22°C.These results from two independent methods are concordant.Among BST deposits for which thermal maturity has been documented,the Qingjiang biota is the least thermally mature,and therefore holds promise for enriching our understanding of BST deposits.展开更多
页岩气储层的气水两相渗流能力对其产能有着重要影响,但尚无直接通过测井等地球物理手段评价页岩气流动能力的方法。目前已通过岩心聚焦离子束-扫描电镜(Focused Ion Beam-Scanning Electron Microscope,FIB-SEM)扫描建立页岩无机孔隙...页岩气储层的气水两相渗流能力对其产能有着重要影响,但尚无直接通过测井等地球物理手段评价页岩气流动能力的方法。目前已通过岩心聚焦离子束-扫描电镜(Focused Ion Beam-Scanning Electron Microscope,FIB-SEM)扫描建立页岩无机孔隙、有机孔隙和微裂缝的三维数字岩心模型,基于流体体积法(Volume of Fluid,VOF)开展了不同润湿条件下的页岩孔缝结构气驱水渗流模拟并得到了端点含水饱和度等特征。该文基于模拟结果得到的不同孔隙类型流动能力的认识,结合大面积拼接扫描电镜(Modular Automated Processing System,MAPS)中提取的不同类型的孔隙统计,获得了每块岩心的等效流动能力。将岩心的等效流动能力与岩石物理实验和测井响应进行综合分析,提出了无量纲渗流能力的概念,建立了基于测井资料评价流动能力的模型。实际测井资料处理结果表明,所提出的评价模型具有较高的准确度,可以获得连续的页岩气流动能力剖面,可用于指导页岩气勘探开发。展开更多
基金supported by the Natural Science Foundation of China(Nos.41930319,41621003,and EAR-1554897)the 111 Project(No.D17013)the Natural Science Basic Research Plan of Shaanxi Province(No.2022JC-DW5-01).
文摘Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inhabited may be obscured by the post-depositional alteration due to metamorphism at depth and weathering near the Earth’s surface.Among over 50 Cambrian BST biotas,the Chengjiang and Qingjiang deposits are well known for their richness of soft-bodied taxa,fidelity of preservation,and Early Cambrian Age.While alteration via weathering has been well-investigated,the thermal maturity of the units bearing the two biotas has not yet been elucidated.Here we investigate peak metamorphic temperatures of the two deposits using two independent methods.Paleogeotemperature gradient analyses demonstrate that the most fossiliferous sections of the Chengjiang were buried at a maximum depth of∼8500 m in the Early Triassic,corresponding to∼300°C,while the type area of the Qingjiang biota was buried at a maximum depth of∼8700 m in the Early Jurassic,corresponding to∼240°C.Raman geothermometer analyses of fossil carbonaceous material demonstrate that peak temperatures varied across localities with different burial depth.The two productive sections of the Chengjiang biota were thermally altered at a peak temperature of approximately 300°C,and the main locality of the Qingjiang biota experienced a peak temperature of 238±22°C.These results from two independent methods are concordant.Among BST deposits for which thermal maturity has been documented,the Qingjiang biota is the least thermally mature,and therefore holds promise for enriching our understanding of BST deposits.
文摘页岩气储层的气水两相渗流能力对其产能有着重要影响,但尚无直接通过测井等地球物理手段评价页岩气流动能力的方法。目前已通过岩心聚焦离子束-扫描电镜(Focused Ion Beam-Scanning Electron Microscope,FIB-SEM)扫描建立页岩无机孔隙、有机孔隙和微裂缝的三维数字岩心模型,基于流体体积法(Volume of Fluid,VOF)开展了不同润湿条件下的页岩孔缝结构气驱水渗流模拟并得到了端点含水饱和度等特征。该文基于模拟结果得到的不同孔隙类型流动能力的认识,结合大面积拼接扫描电镜(Modular Automated Processing System,MAPS)中提取的不同类型的孔隙统计,获得了每块岩心的等效流动能力。将岩心的等效流动能力与岩石物理实验和测井响应进行综合分析,提出了无量纲渗流能力的概念,建立了基于测井资料评价流动能力的模型。实际测井资料处理结果表明,所提出的评价模型具有较高的准确度,可以获得连续的页岩气流动能力剖面,可用于指导页岩气勘探开发。
