鄂尔多斯盆地靖边气田马五段白云岩稀土元素特征及成岩流体示踪  

Geochemical Characteristics of Rare Earth Element of Dolostones from Ma5 Member of Majiagou Formation in Jingbian Gasfield,Ordos Basin:Implications for the Origin of Diagenetic Fluids

作　　者：王东旭[1] 王爱国[2,3] 张保国[1] 王震亮[2,3] 费世祥[1] 魏丽[2,3] 

机构地区：[1]中国石油长庆油田分公司,陕西西安710021 [2]大陆动力学国家重点实验室(西北大学),陕西西安710069 [3]西北大学地质学系,陕西西安710069

出　　处：《天然气地球科学》2015年第4期641-649,共9页Natural Gas Geoscience

基　　金：国家自然科学基金项目(编号:41172122);大陆动力学国家重点实验室开放基金(编号:BJ08133-5);中国石油长庆油田分公司项目联合资助

摘　　要：分析白云岩及储层形成过程的流体特征,对探讨白云岩形成机理和储层特征具有重要意义。以靖边气田马五段白云岩作为研究对象,分析其稀土元素特征,并探讨了其中蕴含的成岩流体信息。研究结果表明,海水标准化后所有样品的稀土元素配分特征相近,均表现为正Ce异常（δCe=12.2~14.7）,LREE稍富集,HREE配分曲线平坦,显示海水来源的特征。泥晶灰岩标准化后均表现为正Eu异常、LREE富集的特征,说明在白云岩化过程中,HREE减少最多,Eu减少最少,推测与热液流体的水—岩作用有关。与未溶蚀的白云岩相比,溶蚀白云岩的∑REE值减少30%,REE配分模式基本不变,且越接近古地表∑REE值和δCe值越大,符合成岩—成烃流体水—岩反应时REE的变化特征,而与大气水的淋滤效应明显不同。现今白云岩中的溶蚀孔可能主要与白云岩再次埋藏时的成岩—成烃流体有关。The analyses on fluid characteristics in dolostone and reservoir formation process are very helpful to investigate the formation mechanism of dolostone and reservoir. Selecting dolostones from Ma5 member in Jingbian Gas field as research subjects,their REE geochemical characteristics are analyzed,and the diage- netic fluids information contained are discussed. After standardization by seawater, all dolostone samples have similar REE distribution characteristics which show seawater source, positive Ce anomaly （3Ce = 12.2-14.7） ,slightly LREE enrichment, flat HREE distribution patterns. After standardization by micrite, all samples show positive Eu anomaly, slightly LREE enrichment, meaning that more HREE and less Eu are lost in dolomitization process. Thus, it is perhaps relevant with hydrothermal water-rock interaction. Compared with no-dissolution dolostones, dissoluted dolostones lost 30% ∑REE, but REE distribution pattern remain steady. Besides, the closer the ancient surface, the greater the ∑ REE and 3Ce. These REE characteristics are similar to the variation of REE occurring in water-rock interaction participation by diagenetic-hydrocarbon fluids, but different from the atmospheric water leaching effect. Therefore, the present dissolution holes in dolostones are perhaps primarily related with diagenetic-hydrocarbon fluid during the second burial diagenesis.

关 键 词：鄂尔多斯盆地 靖边地区 马五段 稀土元素 成岩流体 

分 类 号：TE121.3[石油与天然气工程—油气勘探]