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塔中地区西北部石炭系已开发TZ10、TZ40等多个海相碎屑岩油藏,CⅢ油组(石炭系III油组)含砾砂岩段为其主要的产油层段。通过岩心观察、分析化验资料、测井及地震资料等对含砾砂岩段的沉积相类型进行了研究。分析结果表明,研究区石炭系含砾砂岩段主要为细砂岩、含砾细砂岩,形成多期相互叠置的正韵律砂体,砂岩岩石类型以岩屑质石英砂岩、岩屑砂岩为主,成熟度中等;发育冲刷面、滞留沉积、平行层理、交错层理等层理构造;砂岩粒度概率曲线以2段式为主,悬浮总体含量较高;含砾砂岩段灰色泥岩、褐色泥岩均有发育;泥岩微量元素反映出淡水、咸水古盐度特征;测井形态组合、三维地震属性均显示河道沉积特征。结合区域地质背景,认为研究区CⅢ油组含砾砂岩段为辫状河三角洲沉积,发育三角洲平原的分支河道、越岸沉积以及三角洲前缘的水下分支河道、支流间湾、河口砂坝及席状砂等多种微相类型。辫状河三角洲河道的频繁侧向迁移垂向上形成了砂体的多期叠置,平面上形成了砂体的大面积分布,成为良好的油气储集体,寻找以河道砂体为主的岩性地层油藏是滚动勘探开发的主要目标。
The Carboniferous in the northwestern part of Tazhong area has developed a number of marine clastic reservoirs such as TZ10 and TZ40. The gravelly sandstone section of CⅢ oil group (Carboniferous III oil group) is the main oil-producing section. The types of sedimentary facies in gravelly sandstone are studied through core observation, analysis of laboratory data, logging and seismic data. The results show that the Carboniferous pebbly sandstone in the study area is mainly composed of fine sandstone and gravel fine sandstone, forming positive rhythm sand bodies superimposed over each other. The types of sandstone are mainly quartzite sandstone and lithic sandstone, Maturity is moderate; the development of erosion surface, sediment deposition, parallel bedding, staggered bedding and other bedding structure; sandstone particle size probability curve of two-stage-based, higher overall suspended content; gravel sandstone gray mudstone, brown mudstone The trace elements in mudstone reflect the features of paleosalinity of freshwater and brackish water. The combination of logging patterns and 3D seismic attributes show the characteristics of river sediments. Combined with the regional geological background, it is considered that the gravelly sandstone section of CⅢ oil group in the study area is braided river delta sedimentation, which is characterized by the branch channels and overlying sediments in delta plain, underwater branch channels in delta front, tributary bay, estuary sand dam and Shaped sand and other micro-phase type. The frequent lateral migration of the braided river delta forms the multi-period superposition of sand bodies in the vertical direction, forming a large area distribution of sand bodies in the plane and becoming a good oil and gas reservoir, looking for the lithology mainly of channel sand body Formation reservoir is the main target of rolling exploration and development.