Lacustrine turbidite of Chang-7 Member in the studied area consists of sihstone and fine sandstone with respect to grain size, which is feldspathic lithie sandstone, syrosem arkose and arkose with respect to mineral c...Lacustrine turbidite of Chang-7 Member in the studied area consists of sihstone and fine sandstone with respect to grain size, which is feldspathic lithie sandstone, syrosem arkose and arkose with respect to mineral constitution affected by provenance. There are such apparent signatures as lithology, sedimentary structure, sedimentary sequence and well logs, to recognize turbidite. During the paleogeographic evolution of Chang-7 Member, lake basin and deep lake are both at their maximum extent during Chang-73 stage, resulting in the deposition of Zhangjiatan shale with widespread extent and of turbidite with fragmental-like. Deep lake line is gradually moving toward lake center and turbidite sand bodies are gradually turning better with better lateral continuity, connectivity and more thickness, from stages of Chang-73, Chang-72 and Chang-7t, which can be favorable reservoir in deep-water.展开更多
To clarify the formation and distribution of feldspar dissolution pores and predict the distribution of high-quality reservoir in gravity flow sandstone of the 7^(th) member of Triassic Yanchang Formation(Chang 7 Memb...To clarify the formation and distribution of feldspar dissolution pores and predict the distribution of high-quality reservoir in gravity flow sandstone of the 7^(th) member of Triassic Yanchang Formation(Chang 7 Member)in the Ordos Basin,thin sections,scanning electron microscopy,energy spectrum analysis,X-ray diffraction whole rock analysis,and dissolution experiments are employed in this study to investigate the characteristics and control factors of feldspar dissolution pores.The results show that:(1)Three types of diagenetic processes are observed in the feldspar of Chang 7 sandstone in the study area:secondary overgrowth of feldspar,replacement by clay and calcite,and dissolution of detrital feldspar.(2)The feldspar dissolution of Chang 7 tight sandstone is caused by organic acid,and is further affected by the type of feldspar,the degree of early feldspar alteration,and the buffering effect of mica debris on organic acid.(3)Feldspars have varying degrees of dissolution.Potassium feldspar is more susceptible to dissolution than plagioclase.Among potassium feldspar,orthoclase is more soluble than microcline,and unaltered feldspar is more soluble than early kaolinized or sericitized feldspar.(4)The dissolution experiment demonstrated that the presence of mica can hinder the dissolution of feldspar.Mica of the same mass has a significantly stronger capacity to consume organic acids than feldspar.(5)Dissolution pores in feldspar of Chang 7 Member are more abundant in areas with low mica content,and they improve the reservoir physical properties,while in areas with high mica content,the number of feldspar dissolution pores decreases significantly.展开更多
综合利用地球化学、扫描电镜、岩心薄片、测井等资料以及油井生产数据等,对鄂尔多斯盆地陕北地区三叠系延长组7段储层特征、烃源岩特征和致密油分布特征进行了分析,从烃源岩展布、输导体系和源-储组合关系3个方面对致密油差异富集控制...综合利用地球化学、扫描电镜、岩心薄片、测井等资料以及油井生产数据等,对鄂尔多斯盆地陕北地区三叠系延长组7段储层特征、烃源岩特征和致密油分布特征进行了分析,从烃源岩展布、输导体系和源-储组合关系3个方面对致密油差异富集控制因素进行了探讨,并总结了成藏模式。研究结果表明:(1)陕北地区长7段致密砂岩储层主要分布在一亚段(长71)和二亚段(长72),以灰色—灰白色长石砂岩和岩屑长石砂岩为主,长71和长72平均孔隙度分别为5.56%和7.32%,平均渗透率分别为0.097 m D和0.110 m D,长72储层物性更好;孔隙空间以溶孔为主,发育少量粒间孔。(2)研究区烃类主要来源于本地长72顶部和长73这2套烃源岩,平均厚度大于20 m,有机质丰度高,平均TOC值为3.02%,干酪根类型以Ⅰ型和Ⅱ1型为主,处于生烃高峰期,平均生烃量为270.2×10^(4)t/km^(2),长73烃源岩生烃潜力更大,供烃至长72储层,长71致密油来源于长72烃源岩;新安边地区三角洲前缘亚相末端的长72储层中致密油由湖盆烃源岩侧向供烃。(3)研究区致密油富集受烃源岩展布、砂体连通性以及源-储组合共同控制,在长72更富集,在新安边地区分布面积最大,安塞地区无大规模致密油聚集;纵向上和平面上致密油的聚集差异受控于烃源岩厚度和源-储组合关系,下生上储、上下生油而中间储集和砂泥互层时含油性更好;新安边地区三角洲前缘亚相末端的长72致密油聚集规模大于三角洲前缘主体,是由于三角洲前缘末端发育的局部连通砂体阻碍了湖盆烃类物质的侧向运移。(4)研究区致密油为“源控-砂控”成藏模式,远源河道优势砂体尖灭处和近源局部连通的砂体是有利勘探区。展开更多
To explore the genesis of the laminated calcite veins developed in the black shale of Chang 73 submember of the Ordos Basin,the petrology,microstructure and geochemistry of calcite veins are studied using thin section...To explore the genesis of the laminated calcite veins developed in the black shale of Chang 73 submember of the Ordos Basin,the petrology,microstructure and geochemistry of calcite veins are studied using thin sections,fluid inclusions,trace elements and isotopic geochemistry.The source,the time of formation,the mechanism of formation,and the dynamic background of the veins are discussed.The veins are mostly made up of calcite,mixed with lenticular or spindle-shape solid wall rock inclusions.Three structures are identified in the calcite minerals:fibrous,rhombic cleavage,and wedge-like structure.Trace elements and isotopes of carbon and oxygen confirm that the calcite veins were formed from a high density hydrothermal fluid.It is assumed that calcite veins formed prior to wall rock consolidation during the formation of the Qinling Orogenic Belt in the Middle and Late Triassic.The results show that the sedimentary sources of Chang 73 submember were influenced by hydrothermal materials besides terrigenous detritus.The fibrous calcite is different from the fibrous calcite reported in the morphology and mechanism of formation.In this way,the research complements and improves the morphology and the mechanism of formation of fibrous calcite.展开更多
文摘Lacustrine turbidite of Chang-7 Member in the studied area consists of sihstone and fine sandstone with respect to grain size, which is feldspathic lithie sandstone, syrosem arkose and arkose with respect to mineral constitution affected by provenance. There are such apparent signatures as lithology, sedimentary structure, sedimentary sequence and well logs, to recognize turbidite. During the paleogeographic evolution of Chang-7 Member, lake basin and deep lake are both at their maximum extent during Chang-73 stage, resulting in the deposition of Zhangjiatan shale with widespread extent and of turbidite with fragmental-like. Deep lake line is gradually moving toward lake center and turbidite sand bodies are gradually turning better with better lateral continuity, connectivity and more thickness, from stages of Chang-73, Chang-72 and Chang-7t, which can be favorable reservoir in deep-water.
基金Supported by the National Natural Science Foundation of China(42202176)CNPC-Southwest University of Petroleum Innovation Consortium Cooperation Project(2020CX050103).
文摘To clarify the formation and distribution of feldspar dissolution pores and predict the distribution of high-quality reservoir in gravity flow sandstone of the 7^(th) member of Triassic Yanchang Formation(Chang 7 Member)in the Ordos Basin,thin sections,scanning electron microscopy,energy spectrum analysis,X-ray diffraction whole rock analysis,and dissolution experiments are employed in this study to investigate the characteristics and control factors of feldspar dissolution pores.The results show that:(1)Three types of diagenetic processes are observed in the feldspar of Chang 7 sandstone in the study area:secondary overgrowth of feldspar,replacement by clay and calcite,and dissolution of detrital feldspar.(2)The feldspar dissolution of Chang 7 tight sandstone is caused by organic acid,and is further affected by the type of feldspar,the degree of early feldspar alteration,and the buffering effect of mica debris on organic acid.(3)Feldspars have varying degrees of dissolution.Potassium feldspar is more susceptible to dissolution than plagioclase.Among potassium feldspar,orthoclase is more soluble than microcline,and unaltered feldspar is more soluble than early kaolinized or sericitized feldspar.(4)The dissolution experiment demonstrated that the presence of mica can hinder the dissolution of feldspar.Mica of the same mass has a significantly stronger capacity to consume organic acids than feldspar.(5)Dissolution pores in feldspar of Chang 7 Member are more abundant in areas with low mica content,and they improve the reservoir physical properties,while in areas with high mica content,the number of feldspar dissolution pores decreases significantly.
文摘综合利用地球化学、扫描电镜、岩心薄片、测井等资料以及油井生产数据等,对鄂尔多斯盆地陕北地区三叠系延长组7段储层特征、烃源岩特征和致密油分布特征进行了分析,从烃源岩展布、输导体系和源-储组合关系3个方面对致密油差异富集控制因素进行了探讨,并总结了成藏模式。研究结果表明:(1)陕北地区长7段致密砂岩储层主要分布在一亚段(长71)和二亚段(长72),以灰色—灰白色长石砂岩和岩屑长石砂岩为主,长71和长72平均孔隙度分别为5.56%和7.32%,平均渗透率分别为0.097 m D和0.110 m D,长72储层物性更好;孔隙空间以溶孔为主,发育少量粒间孔。(2)研究区烃类主要来源于本地长72顶部和长73这2套烃源岩,平均厚度大于20 m,有机质丰度高,平均TOC值为3.02%,干酪根类型以Ⅰ型和Ⅱ1型为主,处于生烃高峰期,平均生烃量为270.2×10^(4)t/km^(2),长73烃源岩生烃潜力更大,供烃至长72储层,长71致密油来源于长72烃源岩;新安边地区三角洲前缘亚相末端的长72储层中致密油由湖盆烃源岩侧向供烃。(3)研究区致密油富集受烃源岩展布、砂体连通性以及源-储组合共同控制,在长72更富集,在新安边地区分布面积最大,安塞地区无大规模致密油聚集;纵向上和平面上致密油的聚集差异受控于烃源岩厚度和源-储组合关系,下生上储、上下生油而中间储集和砂泥互层时含油性更好;新安边地区三角洲前缘亚相末端的长72致密油聚集规模大于三角洲前缘主体,是由于三角洲前缘末端发育的局部连通砂体阻碍了湖盆烃类物质的侧向运移。(4)研究区致密油为“源控-砂控”成藏模式,远源河道优势砂体尖灭处和近源局部连通的砂体是有利勘探区。
文摘To explore the genesis of the laminated calcite veins developed in the black shale of Chang 73 submember of the Ordos Basin,the petrology,microstructure and geochemistry of calcite veins are studied using thin sections,fluid inclusions,trace elements and isotopic geochemistry.The source,the time of formation,the mechanism of formation,and the dynamic background of the veins are discussed.The veins are mostly made up of calcite,mixed with lenticular or spindle-shape solid wall rock inclusions.Three structures are identified in the calcite minerals:fibrous,rhombic cleavage,and wedge-like structure.Trace elements and isotopes of carbon and oxygen confirm that the calcite veins were formed from a high density hydrothermal fluid.It is assumed that calcite veins formed prior to wall rock consolidation during the formation of the Qinling Orogenic Belt in the Middle and Late Triassic.The results show that the sedimentary sources of Chang 73 submember were influenced by hydrothermal materials besides terrigenous detritus.The fibrous calcite is different from the fibrous calcite reported in the morphology and mechanism of formation.In this way,the research complements and improves the morphology and the mechanism of formation of fibrous calcite.
