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    准噶尔盆地阜康凹陷中—上二叠统砂砾岩中自生沸石成因及对储层发育的影响

    Origin of authigenic zeolite and its influence on reservoir development in glutenites of the Middle–Upper Permian in Fukang Sag, Junggar Basin

    • 摘要: 针对准噶尔盆地阜康凹陷中—上二叠统砂砾岩中沸石成因及主要储集空间类型认识不清的问题,利用显微薄片、扫描电镜、能谱分析、X射线衍射等资料,分析了自生沸石的产出特征、成因以及对储层发育的影响。研究表明:(1)自生沸石以浊沸石为主,少量方沸石,主要呈连晶状和充填粒间孔隙的形式产出。(2)早期连晶状浊沸石、方沸石主要形成于早成岩A期;中期充填粒间孔隙的浊沸石、方沸石主要形成于早成岩B期;晚期交代状浊沸石主要形成于中成岩A晚期—B期。(3)早期沸石物质主要来源于斜长石、岩浆岩岩屑水化、水解和碳酸的溶解,主要为斜长石水化及斜长石钠长石化产物;中—晚期沸石的物质来自与干酪根热演化有关的有机酸、碳酸对斜长石、岩浆岩岩屑的溶解,主要为斜长石的钠长石化、富Ca2+环境中方沸石转化的产物。(4)砂砾岩呈现出“沸石强烈溶蚀—方解石不溶蚀(或弱溶蚀)”的特征,粒间浊沸石溶孔是最重要的储集空间类型;浊沸石整体溶蚀强烈,显著改善了储层物性,是砂砾岩成储的关键控制因素。

       

      Abstract: The origin of authigenic zeolites and the main reservoir space types in glutenite reservoirs of the Middle–Upper Permian in the Fukang Sag, Junggar Basin, remain unclear. This study utilizes methods such as optical microscope, scanning electron microscope (SEM), energy spectrum analysis, and X-ray diffraction (XRD) analysis to investigate occurrence characteristics, as well as the origin and its influence of authigenic zeolites on reservoir development in the glutenite reservoirs. The results are as follows: (1) Laumontites are identified as the predominant authigenic zeolites, with minor occurrences of analcimes in poikilitic and interparticle-pore filling forms. (2) Early-stage poikilitic laumontites and analcimes formed during phase A of eodiagenesis, while middle-stage interparticle-pore filling laumontites and analcime formed during phase B of eodiagenesis. Late-stage replacive laumontites formed during late phase A and phase B of mesodiagenesis. (3) The materials for early-stage zeolites originated from the hydration–hydrolysis of plagioclase and magmatic rock fragments, and the dissolution of CO2 from biological degradation, which formed through the hydration and albitization of plagioclase. Middle–late stage laumonites, related to the dissolution of plagioclase and magmatic rock fragments by organic acids and CO2 due to thermal evolution of kerogen, formed through plagioclase albitization and analcime alteration in Ca2+-rich solutions. (4) The glutenite is characterized by “intense dissolution of zeolite and no (or weak) dissolution of calcite”, with the intergranular laumontite dissolution pores being the most important type of reservoir space. The intense dissolution of laumontites significantly enhances reservoir quality and is a key controlling factor in the formation of glutenite reservoirs.

       

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