吉木萨尔凹陷二叠系芦草沟组凝灰岩类特征及其与油气的关系

发布时间：2018-05-04 20:54

  本文选题：吉木萨尔凹陷 + 芦草沟组　； 参考：《西北大学》2017年硕士论文

【摘要】：吉木萨尔凹陷位于新疆准噶尔盆地东部,盆地内部的中二叠统芦草沟组分布广泛、厚度巨大,是致密油勘探和开发的有利层位。芦草沟组形成于陆内裂谷背景下还原-弱氧化的咸化湖泊环境,沉积时期受火山活动和碱性岩浆-热液活动的影响,形成了一套与火山喷发和热液活动密切相关的特殊岩类和矿物组合。综合考虑研究区区域构造背景和沉积环境,在大量岩心及薄片观察的基础上,认为芦草沟组含油层段主要发育凝灰岩、沉凝灰岩、(含)凝灰质泥晶白云岩等受岩浆-热液活动影响的岩石,将其统称为凝灰岩类。根据火山碎屑的不同,又可将凝灰岩分为碳酸质凝灰岩与安山质凝灰岩。研究区凝灰岩类主要由石英、长石、方解石、白云石等矿物组成,少见岩屑组分。其中电子探针数据中长石的里特曼指数均大于3.3,甚至大于9,为碱性长石,表明火山碎屑来源为碱性-过碱性岩浆,霓石的发现佐证了这一点。碳酸质凝灰岩中成层发育星散状的方解石,被纹层包绕,方解石周围的有机质成熟度较其它部位更高,内部的流体包裹体呈环带状分布。结合荧光及阴极发光特征,判断方解石为碳酸质岩浆碎屑,带来的热量加速了周围有机质的成熟,并在之后热液活动的影响下发生加大作用,在此过程中捕获了烃类包裹体。地球化学特征显示,芦草沟组安山质凝灰岩的物源主要为中酸性火山岩,与博格达南缘二叠系火山岩具有类似的稀土元素配分模式,表明二者具有亲缘性。进一步的扫描电镜和核磁共振测试发现,凝灰岩类中原生孔隙和次生孔隙均很发育,其中又以溶孔和剩余粒间孔最为常见,并且凝灰物质的含量与自由流体饱和度存在正相关的关系。综合以上特征,认为凝灰岩类既是一种优质的烃源岩,又具备良好的储集性能,对研究区有机质的富集和保存起到了至关重要的作用,凝灰物质的不均匀分布是导致研究区致密油呈非均质性分布的重要原因。
[Abstract]:Jimusar Sag is located in the eastern part of Junggar Basin, Xinjiang. The Lucaogou formation of the Middle Permian in the interior of the basin is widely distributed and has a huge thickness, which is a favorable horizon for the exploration and development of dense oil. The Lucaogou formation was formed in the reduction-weakly oxidized saline lacustrine environment in the context of intracontinental rift and was influenced by volcanic activity and alkaline magmatic hydrothermal activity during the sedimentary period. A set of special rock and mineral assemblages closely related to volcanic eruptions and hydrothermal activities have been formed. Considering the regional tectonic setting and sedimentary environment of the study area, based on the observation of a large number of cores and thin slices, it is considered that tuff is mainly developed in the oil-bearing formation of the Lucaogou formation. The tuffaceous mudstone dolomite, which is affected by magmatic hydrothermal activity, is called tuff. According to the difference of pyroclastic, tuff can be divided into carbonate tuff and Anshan tuff. Tuff is mainly composed of quartz, feldspar, calcite and dolomite. The Ritman exponents of feldspar in the EPMA data are all greater than 3.3 or even more than 9, which indicates that the volcanic clastic origin is alkaline-ultraalkaline magma, which is confirmed by the discovery of aegirinite. Scattered calcite is formed in layers of carbonated tuff. The maturity of organic matter around calcite is higher than that of other parts. Combined with fluorescence and cathodoluminescence characteristics, calcite is determined to be carbonaceous magmatic clastic, resulting in heat to accelerate the maturation of surrounding organic matter, and then increase the effect of hydrothermal activity, and capture hydrocarbon inclusions in the process. Geochemical characteristics show that the source of Anshan tuff in the Lucaogou formation is mainly intermediate-acid volcanic rocks and has a similar REE distribution pattern with the Permian volcanic rocks in the southern margin of Bogda indicating that they are related to each other. Further scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) measurements showed that both primary and secondary pores were well developed in tuff, among which dissolved pores and residual intergranular pores were the most common ones. And there is a positive correlation between the free fluid saturation and the content of coagulant. Combined with the above characteristics, it is considered that tuff is not only a kind of high quality source rock, but also has good reservoir performance, which plays an important role in the enrichment and preservation of organic matter in the study area. The heterogeneous distribution of tuff is an important reason for the heterogeneous distribution of dense oil in the study area.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13;P587
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本文编号：1844611