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在鄂尔多斯盆地榆林气田的上倾部位,不存在构造、地层和沉积岩性圈闭条件.应用偏光显微镜、荧光显微镜、包裹体均一温度、拉曼光谱测试等手段研究了成岩作用的历史,揭示出三期地质流体的活动,分别发生在晚三叠世、晚侏罗世和早白垩世末期,并发现圈闭的形成明显受成岩作用影响.在第一和第二期流体作用期间,酸性流体进入了储层,引起溶蚀和胶结作用,储层的孔渗条件得到一定程度的改善,但是此后盆地的再次沉降引起的再压实作用使得储层致密化.到早白垩世末期,盆地内古生界主力气源岩进入大规模生排期,气田上倾部位的气水过渡带内胶结作用继续进行,进一步降低了孔隙度和渗透率.榆林气田的成藏机理因此发生了从深盆气到成岩圈闭的转换,有利于较长时间地保留天然气.
There are no structural, stratigraphic and sedimentary lithologic traps in the upwelling part of the Yulin gas field in the Ordos Basin.The history of diagenesis was studied using polarization microscopy, fluorescence microscopy, homogenization temperature of inclusions and Raman spectroscopy, revealing that the tris The geologic fluid activities occurred in Late Triassic, Late Jurassic and Early Cretaceous, respectively, and the formation of traps was found to be significantly affected by diagenesis. During the period of the first and second fluids, acid fluid entered The formation of the reservoir caused dissolution and cementation, and the porosity and permeability of the reservoir were improved to a certain extent, but then the compaction caused by the re-subsidence of the basin made the reservoir densification.At the end of the Early Cretaceous, the paleozoic The main gas source rock of the boundary zone has entered a large-scale bio-generation period and the cementation in the transition zone of gas and water in the updip part of the gas field continues to further reduce the porosity and permeability.The accumulation mechanism of the Yulin gas field thus takes place from deep basin gas to Transformation of diagenetic traps will help retain natural gas for a longer period of time.