渤海海域沙南凹陷烃源岩TOC测井预测模型优选及应用

Optimization of TOC well logging prediction models and their application to source rock evaluation in the Shanan Sag of Bohai Sea

针对渤海海域沙南凹陷油气勘探程度低,烃源岩样品取芯少,连续性差,烃源岩研究薄弱及勘探潜力争议较大等问题,基于沙南凹陷内6口单井的测井资料及泥岩样品实测TOC数据,分别应用多元线性回归法和改进的Δlg R法分层段建立沙南凹陷东三段、沙一二段、沙三段烃源岩TOC定量预测模型,对比优选后发现改进的Δlg R法和多元线性回归法中的四参数线性回归法可有效地预测沙南凹陷单井湖相烃源岩TOC纵向分布,并以改进的Δlg R法最优;选取改进的Δlg R法预测TOC曲线对两口代表性单井烃源岩进行评价,结果表明沙三段具有烃源岩占比地层厚度高、TOC高、好—优质烃源岩厚度大等特点,为凹陷主力烃源岩系,沙南凹陷勘探前景广阔。

Oil and gas exploration degree of the Shanan Sag of the Bohai Basin is relatively low due to lack of drilling cores and source rock samples.TOC logging prediction models for source rocks are established in this paper for the Members of E3d3、E3s1+2、E2s3 by the multiple linear regression method and the improvedΔlgR method based on the logging data and limited measured TOC data of the mudstone samples collected from six single wells.After comparison and optimization,it is found that both the improvedΔlgR method and the four-parameter linear regression method are effective to predict the TOC vertical distribution pattern of the lacustrine source rocks in single wells in the Sag and the improvedΔlgR method is obviously more efficient.Therefore,predicted TOC curve of improvedΔlgR is selected to evaluate the source rocks for two representative single wells.The result shows that the E2s3 is characterized by high ratio of source rocks,high TOC content and large thickness of high-quality source rocks.It is the main source rock of the study area and the Shanan sag must have good prospect for oil and gas exploration.The research results are helpful to the evaluation of source rocks in the Shanan sag and will provide solid scientific basis for further understanding of oil and gas exploration potential in the study area.