碳酸盐岩缝合线有机质富集与油气运移作用研究

In carbonate rocks,organic matter distribution is stronger nonhomogeneous and stylolite is important position of organic matter enrichment and fluid migration. In China,there are large area of marine & terrestrial carbonate rocks in them stylolite develop universally.In this project, the key research object is the carbonate rocks in wells & outcrops from the Cambrian-Ordovician of Ordos & Bohaiwan basins and/or lacustrine Permian Lucaogou formation in Junggar & Santanghu basins. Firstly, occurrence relation between organic matter composition and minerals is reaserched in carbonate rock stylolites by analysis of organic petrology, argon ion cutting light, scanning electron microscope and energy spectrum to stylolite,matrix and lamina. Secondly, by analyzing organic matter aboundance, organic maceral components, structure and contents of trace elements,minerals & acid soluble matter, the interior relation is determined between petrology and organic matter enrichment in stylolites. Thirdly, through organic geochemistry characteristics contrast,it is determined that the difference of organic matter aboundance,components of organic maceral,soluble oranic matter & hydrocarbon molecules between stylolite,matrix and lamina in carbonate rocks and primary hydrocarbon migration role is analyzed.At last,by analysis of pore aboundacne,fluorescence asphalt distribution,fluid inclusion,and isotopes of carbon,oxygen & strontium,et al, fluid migration role is determined synthetically and fluid transfusion pattern is established in stylolite.

碳酸盐岩有机质分布具有较强非均质性，其中的缝合线是有机质富集和流体运移的重要部位。中国海相与陆相均有碳酸盐岩，其缝合线广泛发育。本项目重点选择鄂尔多斯、塔里木盆地与渤海湾盆地海相寒武-奥陶系和/或准噶尔与三塘湖盆地湖湘二叠系芦草沟组的钻井与露头碳酸盐岩样品进行研究。首先通过碳酸盐岩缝合线、基质与纹泥层的有机岩石学、氩离子剖光、扫描电镜与能谱分析等，确定缝合线有机显微组成与矿物组成之间的赋存关系。然后通过有机质丰度、有机显微组分与岩石结构、微量元素、矿物成分与酸溶物含量之间的关系分析，确定缝合线岩石学与有机质富集之间的内在联系。再通过有机地化特征对比，确定缝合线、基质与纹泥层之间有机质丰度、有机显微组成、可溶有机质与烃类分子组成的差异，分析缝合线的初次运移作用。最后进行缝合线与围岩基质、纹泥层的孔隙发育、荧光沥青分布、流体包裹体与碳氧锶同位素等分析，综合确定缝合线流体输导作用，建立缝合线的流体输导模式。

该基金项目以四川盆地奥陶系马家沟组(O)、鄂尔多斯盆地寒武系-奥陶系(∈-O)和北京门头沟下苇甸寒武系(∈)等海相碳酸盐岩以及准噶尔盆地二叠系(P)芦草沟组湖相富含缝合线的碳酸盐岩样品为研究对象，通过对碳酸盐岩缝合线和基质的有机碳(TOC)、岩石热解(Rock-Eval)、饱和烃色谱-质谱分析(GC-MS)、岩心观察、岩石薄片鉴定和扫描电镜等，确定了缝合线有机质含量特征及其影响因素、有机质的赋存特征与及其与矿物组成的关系及流体输导特征。.1) 不同类型的碳酸盐均可发育缝合线，缝合线形态以锯齿状为主，与岩层面近乎平行。大多数缝合线绕过岩石颗粒，部分缝合线切割岩石颗粒，表明缝合线的压溶特征。.2) 碳酸盐岩缝合线的有机质丰度明显高于基质且具有更高的生烃潜力，有机质丰度高低不是缝合线发育的绝对条件。缝合线具有更多的白云石、黄铁矿、黑色沥青、固体有机质及泥质。黄铁矿含量高于2.6％时，TOC含量随黄铁矿含量增加而升高。.3) 缝合线的排烃效应比基质更好，缝合线与基质饱和烃谱图差异明显。对于深度相近的样品，基质的谱图相似，而缝合线谱图变化明显，表明缝合线是烃类运移的通道和聚集的场所。缝合线有机质的成熟度小于基质，可能受外来的运移烃的影响。.4) 碳酸盐岩缝合线更发育孔隙和微裂缝，多为微米级的粒间溶蚀孔隙，镜下呈椭圆状、溶蚀港湾状及不规则形状等。孔隙和微裂缝的直径均大于甲烷分子直径和石油流体分子平均直径。缝合线中微米级的溶蚀孔、粒内孔、粒间孔、晶间孔和微裂缝等均有利于流体的运移。