麦盖提斜坡中—下奥陶统碳酸盐岩多期白云石化作用  

Multi-Stage Dolomitization of Lower-Middle Ordovician Carbonate Rocks in the Maigaiti Slope

作　　者：戴逸晨 高达[1] 黄理力 王斌[4] 周慧[2] 孙春燕[4] 张天付 朱传勇 赵玉茹 DAI YiChen;GAO Da;HUANG LiLi;WANG Bin;ZHOU Hui;SUN ChunYan;ZHANG TianFu;ZHU ChuanYong;ZHAO YuRu(School of Geosciences,Yangtze University,Wuhan 430100,China;Tarim Research Center of Petroleum Exploration&Development Research Institute,PetroChina,Korla,Xinjiang 841000,China;Hangzhou Research Institute of Geology,PetroChina,Hangzhou 310023,China;Tarim Oilfield Company,PetroChina,Korla,Xinjiang 841000,China)

机构地区：[1]长江大学地球科学学院,武汉430100 [2]中国石油勘探开发研究院塔里木盆地研究中心,新疆库尔勒841000 [3]中国石油杭州地质研究院,杭州310023 [4]中国石油塔里木油田公司,新疆库尔勒841000

出　　处：《沉积学报》2025年第1期169-181,共13页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41502104)。

摘　　要：【目的】为明确麦盖提斜坡中—下奥陶统碳酸盐岩的多期白云石化作用。【方法】在岩相分析基础上,利用LA-ICP-MS开展了原位微区微量及稀土元素测试,分析了白云岩成因及其对储层的控制。【结果】研究区中—下奥陶统白云岩(石)主要包括粉晶云岩、颗粒云岩、灰质云岩、中晶云岩和白云石充填物,沉积环境解释为局限台地颗粒滩和潮坪。各类白云岩(石)的稀土配分样式及高Na的特征共同指示白云化流体主要具有海源性,局部受热液作用影响。白云石化作用具有多期叠加的特征,蓬莱坝组沉积期,准同生白云化作用使潮坪沉积形成粉晶云岩,回流渗透白云化作用使得颗粒滩沉积发生云化形成颗粒云岩。鹰山组沉积期,埋藏白云化作用使白云石晶体持续生长,部分颗粒结构被破坏而形成中晶云岩,缝洞中白云石充填物不断形成。鹰山组颗粒灰岩在埋藏期因Mg^(2+)的区域性聚集,形成斑状分布的白云石。【结论】多期白云化控制了区内中—下奥陶统白云岩储层的差异,局限台地滩—坪体系早成岩期受回流渗透白云化作用形成的颗粒滩白云岩是最有利的储层。[Objective]To clarify the multi-stage dolomitization of the Lower-Middle Ordovician carbonate rocks in the Maigaiti Slope.[Methods]On the basis of lithofacies analysis and in-situ trace and rare earth element(REEs)tests using laser ablation inductively coupled plasma mass spectroscopy(LA-ICP-MS),we analyzed the origin of do-lomites and its control on the reservoir.[Results]The Lower-Middle Ordovician dolomites primarily include silt-crystalline dolomite,grain dolomite,calcite dolomite,medium-crystalline dolomite,and dolomite cement in frac-tures and vugs.The sedimentary environment is interpreted as a shoal and tidal flat in a restricted platform.The com-position and patterns of REEs in the dolomites and abundant natrium(Na)content indicate that the dolomitization fluid was of seawater origin and locally influenced by hydrothermal fluid.The dolomitization of the Lower-Middle Ordovician carbonates is characterized by a multi-stage process.During the deposition of the Penglaiba Formation,penecontemporaneous dolomitization caused tidal deposits to form silt-crystalline dolomite,and seepage-reflux dolomitization caused shoal deposits to form grain dolomite.During the deposition of the Yingshan Formation,burial dolomitization produced the continuous growth of dolomite crystals,and grain-supported textures were partially destroyed,resulting in medium-crystalline dolomite.In addition,fractures and vugs were continuously filled with dolomite.Lime-grainstones in the Yingshan Formation was partially dolomitized during burial,resulting in the patchy distribution of dolomite crystals.[Conclusions]Multi-stage dolomitization controlled the quality of Lower-Middle Ordovician dolomite reservoirs in the study area.In the shoal and tidal flat system in a restricted platform,the favor-able type of reservoir is grain dolomite formed by seepage-reflux dolomitization during early-stage diagenesis.

关 键 词：白云岩(石)化 白云化流体 稀土元素 白云岩储层 奥陶系 塔里木盆地 

分 类 号：P588.245[天文地球—岩石学]