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刘晓,张启燕,史维鑫,等. 北羌塘盆地东部上三叠统波里拉组碳酸盐岩矿物特征分析[J]. 岩矿测试,2024,43(3):440−448. DOI: 10.15898/j.ykcs.202212010227
引用本文: 刘晓,张启燕,史维鑫,等. 北羌塘盆地东部上三叠统波里拉组碳酸盐岩矿物特征分析[J]. 岩矿测试,2024,43(3):440−448. DOI: 10.15898/j.ykcs.202212010227
LIU Xiao,ZHANG Qiyan,SHI Weixin,et al. Mineralogical Characteristics of Carbonate Rocks of the Upper Triassic Bolila Formation in the Eastern Part of the North Qiangtang Basin[J]. Rock and Mineral Analysis,2024,43(3):440−448. DOI: 10.15898/j.ykcs.202212010227
Citation: LIU Xiao,ZHANG Qiyan,SHI Weixin,et al. Mineralogical Characteristics of Carbonate Rocks of the Upper Triassic Bolila Formation in the Eastern Part of the North Qiangtang Basin[J]. Rock and Mineral Analysis,2024,43(3):440−448. DOI: 10.15898/j.ykcs.202212010227

北羌塘盆地东部上三叠统波里拉组碳酸盐岩矿物特征分析

Mineralogical Characteristics of Carbonate Rocks of the Upper Triassic Bolila Formation in the Eastern Part of the North Qiangtang Basin

  • 摘要: 北羌塘东部上三叠统波里拉组是羌塘盆地重点油气勘探目标层位,受沉积和成岩作用影响,地层压实作用强烈,矿物颗粒极小,属于致密油气储层。本文采用数字岩心技术——背散射扫描电镜成像技术(MAPS)和矿物成分定量分析技术(QEMSCAN),对波里拉组矿物进行微观尺度扫描和分析,表征其矿物成分、颗粒形态、空间分布及结构特征。结果表明:波里拉组方解石以泥晶为主,胶结作用明显,物性致密,孔径小(<5μm),局部发生白云化作用,白云石主要为粉-细晶,以自形晶为主,多呈线接触。矿物在纵向呈规律变化:底部为泥灰岩,陆源碎屑含量较高(>56.57%),其次为方解石(25.79%),磨圆度较差,成分成熟度和结构成熟度均较低;中段陆源碎屑矿物和方解石呈条带交错分布,方解石较石英含量增加(方解石47.43%,石英28.54%),沿晶间普遍发育的草莓状黄铁矿簇直径可达10μm,整体为氧化界面之下的还原环境;顶部以方解石为主(>90%),颗粒直径多为10~50μm,颗粒间多呈线接触,粒间孔几乎不发育,局部发生层状白云化作用。矿物特征显示波里拉组沉积物源受浅海碳酸盐岩沉积环境和陆源碎屑输入双重影响,具有典型的混积岩特征,沉积环境从早期陆源碎屑供给较为充足,到晚期以碳酸盐岩沉积为主,整体为海相碳酸盐沉积。

     

    Abstract: Carbonate rocks of the upper Triassic Bolila Formation in the eastern area of the North Qiangtang Basin are important tight oil and gas reservoirs. Due to the influence of sedimentation and diagenesis, the mineral particles are mostly less than 1mm. Analytical methods such as modular automated processing system (MAPS) based on the backscattered electron and automatic mineral identification system (QEMSCAN) were used to analyze the minerals and to research their composition, morphology and structure on a microscopic scale for four samples. The vertical variation of the minerals shows that at the bottom, the mineral composition is dominated by quartz and calcite, and the roundness of mineral particles is poor. The quartz content is relatively high in the middle. The terrigenous minerals and calcite bands are staggered. At the top, the carbonate mineral content is more than 90%, and layered dolomitization occurs locally. Mineral characteristics indicate that the source of Borila Formation sediments is affected by both shallow marine and terrigenous clastics. The supply of terrigenous clastics was relatively sufficient in the early stage. Subsequently, the supply of terrigenous clastics decreased, and the content of carbonate minerals increased gradually. The sedimentary environment was dominated by carbonate deposits at the late period of the Borila Formation.

     

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