塔里木盆地玉北地区中下奥陶统鹰山组溶洞充填物稀土元素特征及其意义

发布时间：2018-06-24 20:55

本文选题：储集层 + 岩溶洞穴　；参考：《古地理学报》2017年03期

【摘要】：中下奥陶统碳酸盐岩古岩溶型储集层的特征、演化及纵横向分布是塔里木盆地玉北地区勘探关注的重要问题,而YB7井在鹰山组钻遇的溶洞及其充填物为研究该地区中下奥陶统古岩溶作用提供了契机。研究区YB7井中下奥陶统鹰山组溶洞充填物以长石石英砂岩为主,文中将其稀土元素组成特征与该地区志留系依木干他乌组和克孜尔塔格组、泥盆系东河塘组、石炭系巴楚组及塔中地区志留系柯坪塔格组和塔塔埃尔塔格组进行对比,以分析其物源及溶洞的演化时限。结果显示:4个溶洞充填物样品稀土元素配分模式表现为轻稀土轻微富集,重稀土稍显亏损,具有明显的Ce负异常和轻微的Eu正异常,与东河塘组和柯坪塔格组的特征较为接近。溶洞充填物的ΣREE平均为36.48μg/g,与东河塘组最为接近,而与柯坪塔格组相距甚远。玉北地区缺失柯坪塔格组,至巴楚组沉积前一直处于构造高部位,故柯坪塔格组不具备为YB7井溶洞提供物源的基础。玉北地区西部局部钻遇东河塘组,而YB7井周边缺失该组,故综合稀土元素组成特征、沉积特征及构造背景认为,YB7井溶洞充填物来源于东河塘组,其形成于暗河系统,且东河塘组沉积后至巴楚组沉积前是玉北地区重要的岩溶储集层发育时期。
[Abstract]:The characteristics, evolution and vertical and horizontal distribution of paleokarst reservoirs of carbonate rocks in the Middle and Lower Ordovician are the important problems of exploration in Yabei area of Tarim Basin. The karst cave and its backfill in YB7 well in Yingshan formation provide an opportunity to study the paleokarst in middle and lower Ordovician in this area. In YB7 well, the cavern filling of Yingshan formation of Lower Ordovician is mainly composed of feldspar quartz sandstone. In this paper, the REE composition of YB7 well is related to the Silurian Yimugantawu formation and Kiziltag formation, and the Devonian Donghetang formation. Carboniferous Bachu formation and Silurian Kepingtag formation and Tata Ertag formation in Tazhong area were compared to analyze their provenance and evolution time of karst cave. The results showed that the REE partitioning patterns of the four cavern filling samples showed slight enrichment of LREE, slight depletion of heavy REE, obvious negative ce anomaly and slight EU positive anomaly, which were close to the characteristics of Donghetang formation and Kepingtag formation. The average 危 REE of cavern filling is 36.48 渭 g / g, which is the closest to Donghetang formation and far away from Kepingtag formation. The Kepingtag formation is absent in the north of Yubei area and has been in the high position of the structure until the Bachu formation, so the Kepingtag formation does not have the foundation to provide the material source for the karst cave of YB7 well. In the western part of Yubei area, the formation of Donghetang formation is locally drilled, and the periphery of YB7 well is missing. Therefore, the composition of rare earth elements, sedimentary characteristics and tectonic background indicate that the cavern filling of YB7 well originated from the Donghetang formation and formed in the dark river system. The period from Donghetang formation to Bachu formation is an important karst reservoir development period in Yubei area.
【作者单位】：中国石化石油勘探开发研究院;中国石化西北油田分公司勘探开发研究院;中国地质大学(北京)地球科学与资源学院;
【基金】：国家科技重大专项(编号:2016ZX05005-002) 中国石化科技部项目(编号:P13069,P14123,P15090)联合资助~~
【分类号】：P534.42;P618.13

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