黔西上二叠统龙潭组菱铁矿层的沉积成因及地质意义

发布时间：2018-03-20 09:30

  本文选题：菱铁矿　切入点：隔水阻气层　出处：《地学前缘》2017年06期 　论文类型：期刊论文

【摘要】：基于黔西地区晚二叠世含煤地层钻井岩心观察及样品分析测试结果,研究了煤系中含菱铁矿与黄铁矿层的岩石学特征,划分了6种含菱铁矿与黄铁矿层的垂向沉积序列,归纳总结了5种菱铁矿与黄铁矿的发育模式,指出含菱铁矿层的发育对"多层叠置独立含煤层气系统"的发育具显著的控制作用。研究结果表明,研究区内菱铁矿中CO_2的来源与沉积有机质和海相碳酸盐岩有关,其中,形成于海平面上升背景下的菱铁矿中CO_2的同位素特征与海相碳酸盐岩同位素特征相似,形成于海平面下降背景下菱铁矿中的CO_2主要来源于沉积有机质,海平面持续较高背景下的发育的菱铁矿则受沉积有机质与海水的共同影响,此外成岩环境的改变导致形成菱铁矿与黄铁矿的共生组合。含煤岩系中含菱铁质(黄铁矿)的泥岩及粉-细砂岩具低孔、低渗特征,可作为含气单元间的隔水阻气层,这种岩层的分布受控于沉积环境及区域海平面变化,对"多层叠置独立含煤层气系统"的形成具有分划性的阻隔作用。
[Abstract]:Based on the core observation and sample analysis of late Permian coal-bearing strata in western Guizhou, the petrological characteristics of siderite and pyrite layers in coal measures are studied, and six vertical sedimentary sequences of siderite and pyrite layers are divided. Five development models of siderite and pyrite are summarized, and it is pointed out that the development of siderite bearing strata has a significant effect on the development of "multi-layer superposition independent coal-bearing methane system". The origin of CO_2 in siderite is related to sedimentary organic matter and marine carbonate rocks. The isotopic characteristics of CO_2 in siderite formed in the sea level rise background are similar to those of marine carbonate rocks. The CO_2 in siderite formed in the background of sea level drop is mainly derived from sedimentary organic matter, while siderite, which develops in a higher sea level, is affected by both sedimentary organic matter and sea water. In addition, the change of diagenetic environment resulted in a symbiotic association of siderite and pyrite. The mudstone and silt-fine sandstone containing rhombotite (pyrite) in the coal-bearing rock series have low porosity and low permeability, which can be used as water barrier and gas barrier between gas-bearing units. The distribution of the strata is controlled by the sedimentary environment and the regional sea level change, which has a partition effect on the formation of "multi-layer independent coal-bed methane system".
【作者单位】： 中国矿业大学煤层气资源与成藏过程教育部重点实验室;中国矿业大学资源与地球科学学院;贵州省煤层气页岩气工程技术研究中心;贵州省煤田地质局;
【基金】：国家自然科学基金项目(41102100,41541046,41672146) 国家科技重大专项项目(2016ZX05044-002-001)
【分类号】：P618.31
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本文编号：1638488