四川盆地及邻区中上寒武统洗象池群碳同位素特征与芙蓉统底界标志

发布时间：2018-06-26 05:02

本文选题：四川盆地 + 晚寒武世　；参考：《天然气工业》2017年10期

【摘要】：四川盆地中上寒武统洗象池群为一套以台地相为主的白云岩,过去一直未能找到有效的方法来确定上寒武统的底界标志,导致对该层位的天然气勘探工作较为滞后。以岩屑碳氧同位素剖面的建立为依托,发现洗象池群中部存在着碳同位素正漂移事件且这一现象可全球比对,可作为识别芙蓉统(相当于上寒武统)的重要标志。进而结合电性曲线特征,确定了芙蓉统底界的划分标志,初步找到了解决芙蓉统划分难题的方案。研究结果表明:(1)洗象池群沉积时该区古地貌为西高东低的缓坡碳酸盐岩台地,沉积了一套西薄东厚的薄层—中厚层白云岩地层,纵向上可分4个层段;(2)四川盆地及邻区芙蓉统底界划分标志可以由碳同位素SPICE(Steptoean Positive Carbon Isotope Excursion)事件与电性曲线特征结合来确定;(3)芙蓉统底界的碳同位素标志是区域可对比的正漂移所对应的SPICE事件,电性标志是SPICE事件对应的洗象池群中部自然伽马值低峰,而岩性标志则是该自然伽马值低峰所对应的泥质云岩。该研究成果有助于对该盆地及其邻区洗象池群的进一步细分并推进其沉积演化与储层分布规律研究,以加快对该层系的勘探步伐。
[Abstract]:The Xixiang Group of the Middle and Upper Cambrian in Sichuan Basin is a set of dolomite dominated by platform facies. In the past, it has not been possible to find an effective method to determine the bottom boundary mark of the Upper Cambrian, which leads to the lagging of natural gas exploration work on this formation. Based on the establishment of the carbon and oxygen isotope profile of cuttings, it is found that there is a positive drift event of carbon isotope in the middle of the wash elephant pool and this phenomenon can be compared globally, which can be used as an important marker to identify the hibiscus (equivalent to the Upper Cambrian). Combined with the characteristic of electric curve, the dividing mark of the bottom boundary of hibiscus system is determined, and the scheme to solve the problem of dividing hibiscus system is preliminarily found. The results are as follows: (1) the paleogeomorphology of this area is a carbonate platform with low slope in west, high and east, and a set of thin and medium thickness dolomite strata in the west, thin and east thick. Vertically, it can be divided into 4 layers; (2) the criteria for the division of the bottom boundary of the Furong Series in Sichuan Basin and its adjacent areas can be determined by combining the characteristics of the carbon isotope spice (Steptobean potential carbon Isotope Excursion) event with the electrical curve; (3) the carbon isotope marker of the bottom boundary of the Furong Series is a regional pair. The spice event corresponding to the positive drift of the The electrical marker is the natural gamma value low peak in the middle of the wash elephant pool corresponding to spice event, while the lithologic marker is the shaly dolomite corresponding to the natural gamma value low peak. The research results are helpful to further subdivide the wash elephant pool group in the basin and its adjacent areas and to advance the study of sedimentary evolution and reservoir distribution in order to speed up the exploration of the strata.
【作者单位】：中国石油勘探开发研究院;
【基金】：国家科技重大专项(编号:2011ZX05004) 中国石油西南油气田公司科技项目“四川盆地及其邻区洗象组地层划分对比及沉积演化规律研究”(编号:XNS14NH2015-002)
【分类号】：P534.41;P597

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