| 东营凹陷沙河街组砂岩储层砂泥岩界面对长石溶蚀的影响 |
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| 引用本文： | 张永旺,蒋善斌,李峰.东营凹陷沙河街组砂岩储层砂泥岩界面对长石溶蚀的影响[J].地质学报,2021,95(3):883-894. |
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| 作者姓名： | 张永旺 蒋善斌 李峰 |
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| 作者单位： | 中国石油大学油气资源与探测国家重点实验室,北京,102249;中国石油大学(北京)地球科学学院,北京,102249;中国石油大学(北京)地球科学学院,北京,102249 |
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| 基金项目： | 本文为国家自然科学基金项目(编号41572113) 资助成果。 |
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| 摘 要： | 深部碎屑岩储层的原生孔隙损失严重,深层油气藏能否形成的关键问题之一是盆地碎屑岩致密储层是否发育次生孔隙。作为砂岩骨架颗粒的长石发生溶蚀反应,是中深部碎屑岩储层次生孔隙形成的重要作用。选取东营凹陷中部地区中央断裂带和牛庄洼陷发育的湖相三角洲-浊积岩砂体为研究对象,运用光学显微镜(OM)、扫描电镜(SEM)、X粉晶衍射(XRD)以及电感耦合等离子体发射光谱仪(ICP-AES)等分析测试技术研究了砂泥岩界面处砂岩长石溶蚀、高岭石形成分布以及次生孔隙发育特征。研究结果表明,随着压实作用进行,泥岩中的有机质热演化以及伴随的蒙脱石伊利石化是中深部砂岩储集层酸性孔隙流体的主要来源。揭示出砂泥岩层序中泥岩成岩作用对于砂岩骨架颗粒长石溶蚀以及自生高岭石形成、分布具有重要影响。砂泥岩界面对长石溶蚀的控制作用与泥岩中有机质含量、成熟度等地球化学特征有关。对于研究区埋深大于3000m的浊积岩砂体,由于被有效烃源岩包裹,烃源岩压实排出的有机酸对长石溶蚀产物Al元素具有较强的络合作用,导致砂泥岩界面处长石溶蚀程度较高,而高岭石含量较低,形成的次生孔隙不会被高岭石饱和充填,提高了砂泥岩界面处储层的孔隙度和渗透率。而三角洲前缘砂体埋藏较浅,远离有效烃源岩中心,泥岩中有机质含量普遍较低,生成有机酸的潜力较小,对砂泥岩界面处长石的溶蚀作用影响有限。通过油源断层或隐蔽输导体系沟通,深部的酸性流体可以沿着油气运移通道进入埋藏较浅的三角洲前缘砂体,对长石进行侧向溶蚀,导致含油气砂体内部高岭石含量相对较高。研究成果对于正确理解沉积盆地砂岩储层次生孔隙形成机制以及储集层评价、有利储层预测具有重要意义。
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| 关 键 词： | 东营凹陷 沙河街组 砂泥岩界面 长石溶蚀 次生孔隙 |
| 收稿时间： | 2020/9/7 0:00:00 |
| 修稿时间： | 2020/10/18 0:00:00 |
Influence of sandstone shale contacts on feldspar diagenesis in the sandstone reservoir of the Shahejie Formation |
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| ZHANG Yongwang,JIANG Shanbin,LI Feng.Influence of sandstone shale contacts on feldspar diagenesis in the sandstone reservoir of the Shahejie Formation[J].Acta Geologica Sinica,2021,95(3):883-894. |
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| Authors: | ZHANG Yongwang JIANG Shanbin LI Feng |
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| Institution: | (State Key Laboratory of Petroleun Resource and Prospecting,Beijing,102249;College of Geosciences,China University of Petroleum(Beijing),Beijing,102249) |
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| Abstract: | The primary pore loss of deep clastic rock reservoir is serious. One of the key problems determining whether deep reservoir can be formed is if secondary pores were developed in the tight reservoir of basin clastic rock. Feldspar dissolution plays an important role in the formation of secondary pores in middle and deep clastic reservoir.Polarized light microscopy, scanning electron microscopy (SEM) and an X- ray powder diffractometer (XRD) were used to characterize the diagenetic features of feldspar at sandstone- shale contacts of delta and related turbidite sandstone bodies in the Shahejie Formation, the central area of Dongying depression. The results show that the acidic pore fluid was generated during thermal maturation of organic matter and the illitization of montmorillonite in the interbedded shales. The results show that the mudstone diagenesis in the sequence of sandstone and mudstone has an important influence on the feldspar dissolution and the formation and distribution of authigenic kaolinite. The effect of sandstone- shale contact on feldspar dissolution is strongly controlled by the geochemical characteristics of organic matter in shale.For turbiditic sandstone bodies with a buried depth of more than 3000 m, due to the expulsion of organic acids from mudstone, the dissolution degree of feldspar alteration is relatively high at sandstone- shale contact, while the kaolinite content is relatively low. The secondary pores thus formed will not be filled with kaolinite, which improves the porosity and permeability of the reservoir at sandstone- shale contacts. However, the delta front sandstone body is shallowly buried, far from the center of the effective hydrocarbon source rock, and lower organic matter content in shale results in less generation of organic acid and lower influence onfeldspar alteration at sandstone- shale contacts. In the sandstone body, especially in the location containing oil and gas, the deep acidic fluid can enter the sandstone body along the migration path of oil and gas before its arrival and cause feldspar dissolution, resulting in relatively high kaolinite content in the oil and gas bearing sandstone body. The research results are of great significance to the formation mechanism of secondary pores in middle and deep sandstone reservoirs, reservoir evaluation and quantitative prediction of reservoir quality. |
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| Keywords: | Dongying depression Shahejie Formation sandstone- shale contacts feldspar alteration secondary pore |
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