准噶尔盆地吉木萨尔凹陷芦草沟组页岩油储层方沸石成因与甜点意义

Origin and significance of "sweet spots" of analcites in shale oil reservoirs in Permian Lucaogou Formation, Jimsar Sag, Junggar Basin

马聪 王剑 潘晓慧 陈俊 尚玲 刘金

MA Cong WANG Jian PAN Xiaohui CHEN Jun SHANG Ling LIU Jin

新疆页岩油勘探开发重点实验室, 新疆 克拉玛依 834000 中国石油 新疆油田分公司 实验检测研究院, 新疆 克拉玛依 834000 中国石油 新疆油田分公司 勘探开发研究院, 新疆 克拉玛依 834000

Xinjiang Key Laboratory of Shale Oil Exploration and Development, Karamay, Xinjiang 834000, China Experimental Testing Institute of Xinjiang Oilfield Branch Company, PetroChina, Karamay, Xinjiang 834000, China Exploration and Exploitation Institute of Xinjiang Oilfield Branch Company, PetroChina, Karamay, Xinjiang 834000, China

准噶尔盆地吉木萨尔凹陷二叠系芦草沟组页岩油储层中普遍发育方沸石，且与甜点段对应好，展示出“示烃矿物意义”。为全面深入了解方沸石对页岩油甜点的意义，采用偏光显微镜、全岩X衍射成分分析、电子探针BSE图像分析及矿物能谱分析等手段，对方沸石的岩石学和矿物学特征进行了综合研究，再结合地质背景探讨了成因及意义。吉木萨尔凹陷芦草沟组方沸石主要赋存于沉凝灰岩、碳酸盐岩质凝灰岩中，个别出现在凝灰质白云岩中，而方沸石岩极为少见。方沸石在岩石中的赋存状态包括纹层状、球粒状、块状、脉状。方沸石形成于高盐度、碱性、低温的热液条件下，埋藏过程中碱性长石及部分蒙脱石类黏土成岩转化形成自生方沸石；火山喷发活跃期火山物质经过热反应与蚀变形成次生方沸石。成岩早期形成的大量方沸石胶结物起到了抗压实作用进而保护原生孔，也为成岩中后期次生溶孔的形成提供物质基础，大幅提升了页岩油层的储集性能，因而方沸石富集段与页岩油甜点段对应良好。

As a hydrocarbon indicating mineral, analcite was always found in shale oil reservoirs and has good correspondence with "sweet spots" in the Lucaogou Formation, Jimsar Sag, Junggar Basin. The petrographic and mineralogical characteristics as well as geologic origins of analcite were studied using a polarized light microscope, whole rock XRD analysis, electron probe BSE image analysis and mineral energy spectrum, in order to discuss its significance for shale oil "sweet spots". The analcite is mainly found in sedimentory tuff and carbonate tuff with some in tuff dolomite, and the analcite rock is very rare. The occurrence of analcite in rocks is lamellar, granular, massive and vein-shaped. Analcite was formed in high salinity, alkaline, low temperature hydrothermal conditions. The diagenetic transformation of non-volcanic material during burial forms authigenic analcite. Secondary analcite was formed by reaction and dissolution of volcanic material and hydrothermal during volcanic jetting. Analcite cements in the early diagenesis protected native porosity, and afforded the formation of secondary solution pores during mid and late diagenesis which has a good correspondence with shale oil "sweet spots".

国家科技重大专项 2017ZX05001002;中国石油科技重大专项 2017E-0401

https://doi.org/10.11781/sysydz202004596