泥页岩有机非均质性评价及其在烃源岩分级评价中的应用--以辽西拗陷中元古界蓟县系为例

SHALE ORGANIC HETEROGENEITY EVALUATION METHOD AND ITS APPLICATION IN SOURCE ROCKS GRADING EVALUATION:A Case Study of Mesoproterozoic Jixianianin in Liaoxi Depression

泥页岩有机质丰度存在较强的有机非均质性,利用有限的测试样品难以表征整套烃源岩层的生烃潜力.以辽西拗陷辽凌地2井为研究对象,对蓟县系主要烃源岩层铁岭组与洪水庄组进行剖析,在有机质地球化学特征研究的基础上,利用烃源岩层的测井响应特征,采用变系数ΔlogR技术刻画该井烃源岩TOC,进而实现烃源岩分级评价,得到不同丰度级别烃源岩的空间分布特征.结果表明,洪水庄组烃源岩有机质丰度一般在2%以上,明显高于铁岭组,有机质类型都以Ⅱ型为主并含少量Ⅰ型干酪根,烃源岩都处于生气高峰期的过成熟阶段,应为蓟县系主力烃源岩层.

It is difficult to characterize hydrocarbon potential of the whole source rock layer with limited test samples due to the strong heterogeneity in organic matter abundance(TOC)of shale.Taking LLD2 well in Liaoxi Depression as the research object,the paper analyzes the main source rocks of Tieling Formation(Jxt)and Hongshuizhuang Formation(Jxh),and makes the grading evaluation as well as spatial distribution characteristics of source rocks with different abundance grades in terms of TOC through variable coefficientΔlogR on the basis of organic geochemical study and logging response characteristics of source rocks.The results show that the organic matter abundance of Jxh is generally above 2%,significantly higher than that of Jxt,both dominated by the organic matter type II with a little I-type kerogen.The source rocks are in the over-mature stage of gas-generation peak period,probably serving as the main Jixianian source rock layer.