ORGANO-CLAY COMPLEXES IN SOURCE ROCKS——A NATURAL MATERIAL FOR HYDROCARBON GENERATION
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摘要: 传统观点认为从烃源岩中分离出的干酪根是油气生成的母质,但它的处理方式破坏了有机质与矿物的原始赋存状态。为此,选取济阳坳陷埋深280~3 900 m烃源岩,提取μm的有机黏粒复合体,研究其结构和生烃特征。有机黏粒复合体主要由蒙皂石和伊利石组成,TOC为2.62%~9.78%,经H2O2处理后TOC仍高达1.23%~4.63%,表明烃源岩中有机质主要富集在有机黏粒复合体中。有机黏粒复合体加热到250℃时,在XRD曲线上的衍射峰(d001)在1.3~1.4 nm;加热至550℃时,衍射峰(d001)才移至1.0 nm处;并且在DTA曲线上350℃附近的放热峰极其稳定,这些特征表明有机质进入到黏土矿物层间域。在PY-GC (热解-色谱)曲线上,烃源岩和有机黏粒复合体都在250~550℃释放C20-C30的有机组分,并在450℃释放量达到峰值。由此可见,烃源岩中的有机黏粒复合体,是烃源岩中有机质富集的主体,具有较好的稳定性,并释放出与原油特征相似的有机组分,表明它是具有巨大潜力的天然的生烃母质。Abstract: Traditionally, it is believed that kerogen, a organic matter insoluble in organic solvents separated chemically from source rock, is a material for hydrocarbon generation[1].The procedure to treat samples as such, however, may destroy the original occurrence and relationship between organic matter and clay in source rocks. We extracted an organo-clay complex (μm) from the crushed source rocks in the depth of 280~3 500 m, in the Jiyang sag, East China. The complex is mainly composed of layered illite-smectite (I-S) and illite with a value of TOC up to 2.62%~9.78%. After treatment with H2O2, TOC remains as high as 1.23%~4.63%, suggesting that it is the components in which organic matters are enriched. The diffraction peak (d001) of the complex is 1.3~1.4nm at 250℃, and moves to 1.0 nm at 550℃ in XRD curves, and the exothermic peaks of the complex is extraordinary stable at 350℃ in DTA curves.; The result is consistent in both the XRD and DTA observations. It indicates that organic matter can enter the interlayer space of clay minerals. With PY-GC analysis, the organic matter of C5 and C25 is released from the complex in a temperature range of 250~650℃, and reaches a peak at about 450℃. Our findings reveal that organic matter can enter interlayer of clay minerals forming a kind of natural and highly stable organo-clay complex, and the composition of the organic matter in the complex is similar to the crude oil. As a kind of natural material, the organo-clay complex plays an important role in hydrocarbon generation in source rocks.
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