鄂尔多斯盆地富县区域延长组长8层段致密砂岩储层微观结构特征研究

发布时间：2018-02-24 15:05

  本文关键词： 孔喉分布 微观结构 致密成因 致密时间 成藏时间 富县 鄂尔多斯盆地　出处：《西北大学》2017年硕士论文　论文类型：学位论文

【摘要】：鄂尔多斯盆地富县区域三叠系延长组长8地层为三角洲前缘沉积,多发育粉-细砂岩,储层物性极差。以前人的定义为依据,富县地区绝大部分长8储层可归类为致密储层。致密储层的孔隙结构非常复杂,储层的微观结构在控制油气富集方面起着重要的作用。本文通过场发射扫描电镜、高压压汞、CT、核磁共振与铸体薄片等多种研究方法对富县地区三叠系延长组长8致密砂岩储层微观孔喉特征、致密成因、致密砂岩储层致密史与成藏史耦合关系、长8致密砂岩油富集规律等进行研究,取得了以下新认识:长8储层孔隙度和渗透率的平均值分别为8.59%、0.42×10-3μm2,归类为特低孔-特低渗类型。高压压汞、场发射扫描电镜、CT、核磁共振等分析方法统计表明长8储层平均孔隙半径及喉道半径分别为1.2μm和O.Iμm,隶属细孔-微细喉储层;长8致密砂岩储层发育孔隙结构可划分为三类,其中I类和II类孔隙结构对致密油富集贡献最大。成岩作用对长8致密砂岩储层有重要的影响,压实作用造成的孔隙度减少比例平均62.35%;胶结作用主导的孔隙度减少比例平均23.84%;溶蚀作用增孔率平均6.56%。压实作用是储层致密的主要成因,储层中的碳酸盐、绿泥石膜、伊利石以及云母等填隙物加剧了储层致密。综合力学平衡与岩心实验分析方法,得到富县长8致密储层的上限:孔隙度≤11.2%,渗透率≤0.55×10-3μm2,临界孔喉半径≤0.6μm。利用力学方法、录井分析法、有效孔喉法得到长8致密砂岩储层油气充注下限:孔隙度多4.5%,渗透率≥0.04×10-3μm2,源储界面的储层孔喉直径≥15.77nm,储层内部的孔喉直径≥24nm。根据埋藏史和孔隙度演化历史分析,长8致密砂岩储层致密化时间从中侏罗世末(157Ma)开始,到早白垩世早期(128Ma)完全致密。包裹体观察及测温结果表明长8致密砂岩油藏有两次油气充注,地质年代分别为97Ma至103Ma,和112Ma至121Ma左右,对应早白垩世末-中期。说明长8致密油藏的致密时间早于成藏时间。根据烃源岩与储层配置关系及长8含油层分布特征分析发现长8致密砂岩油的分布受烃源岩展布及储层的控制,储层含油特征受物性及孔隙结构控制。
[Abstract]:In Fuxian, Ordos Basin, Yanchang formation of Yanchang formation in Fuxian County, Ordos Basin, is composed of delta front sediments, mostly siltstone and fine sandstone, and the reservoir physical properties are extremely poor. Most Chang 8 reservoirs in Fuxian area can be classified as dense reservoirs. The pore structure of dense reservoirs is very complex, and the microstructure of reservoirs plays an important role in controlling oil and gas enrichment. Various research methods, such as high pressure mercury injection, nuclear magnetic resonance (NMR) and casting thin slice, are used to study the microcosmic pore throat characteristics, dense origin, tight history of tight sandstone reservoir and the coupling relationship between the history of dense sandstone reservoir and the history of reservoir formation in the Triassic Yanchang Chang 8 tight sandstone reservoir in Fuxian area. The enrichment law of Chang 8 tight sandstone oil has been studied, and the following new understandings have been obtained: the average porosity and permeability of Chang 8 reservoir are 8.59 ~ 0.42 脳 10 ~ (-3) 渭 m ~ (2), respectively, which are classified as the type of ultra-low porosity and ultra-low permeability. Field emission scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) analysis show that the average pore radius and throat radius of Chang 8 reservoir are 1.2 渭 m and O. I 渭 m, respectively, which belong to micropore and microlarynx reservoir, and the pore structure of Chang 8 tight sandstone reservoir can be divided into three categories. The types I and II pore structures contribute most to the enrichment of dense oil, and diagenesis has an important effect on the tight sandstone reservoir of Chang 8. The porosity reduction caused by compaction averaged 62.35%; the proportion of porosity decrease led by cementation was 23.84; the average porosity increased by dissolution was 6.56.The compaction was the main cause of formation compaction, the carbonate and chlorite film in the reservoir, The porosity of Fuxian 8 tight reservoir is obtained by comprehensive mechanical balance and core experiment analysis method: porosity 鈮，

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