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长岭断陷龙凤山次凹下白垩统烃源岩埋藏深,取心井分析资料少,利用常规的烃源岩有机地球化学分析难以表征烃源岩段有机碳的分布特征。以现有取心井样品分析化验资料为基础,利用ΔLogR技术可以对烃源岩有机碳含量进行精细刻画。传统ΔLogR模型在基线值、叠合系数确定等方面存在主观性大、具有区域适用性等问题,因此利用改进的ΔLogR模型及最优K值分析ΔLogR与实测有机碳含量之间的关系,减小计算误差。但是在两者的趋势之外仍存在许多异常点,这些异常点所产生的误差大大降低了计算有机碳含量的准确性。通过综合研究发现,烃源岩层段异常点存在的原因主要包括扩径、薄夹层及数据分析3个方面。异常点的剔除,能有效改善ΔLogR模型计算有机碳含量的精度,使计算结果与实测值相关系数R2达80%以上,能够客观反映烃源岩层有机碳含量。应用结果显示,龙凤山次凹下白垩统沙河子组为主力烃源岩层系,有机碳含量主要集中在1.0%~3.0%之间,营城组下部为次要烃源岩层系,有机碳含量较低,主要集中在0.6%~1.0%之间。
The Lower Cretaceous source rocks in the Longfengshan fault depression of the Changling fault depression are buried deeply and the data of coring well analysis are few. It is difficult to characterize the distribution characteristics of organic carbon in source rocks by conventional geochemical analysis of source rocks. Based on the existing analysis data of well core samples, the ΔLogR technique can be used to finely describe the organic carbon content of source rocks. The traditional ΔLogR model has some problems such as the subjectivity and applicability of the region in terms of the baseline value and the overlap coefficient, so the relationship between ΔLogR and the measured organic carbon content is reduced by using the improved ΔLogR model and the optimal K value Calculation error. However, there are still many abnormal points beyond the trend of the two. The errors caused by these abnormal points greatly reduce the accuracy of calculating organic carbon content. Through comprehensive study, it is found that there are three main reasons for the existence of anomalous points in the source rock strata: expanding, thin interlayer and data analysis. The removal of abnormal points can effectively improve the accuracy of ΔLogR model in calculating organic carbon content, making the correlation coefficient R2 between calculated and measured values more than 80%, which can objectively reflect the organic carbon content of source rocks. The application results show that the main source rocks are the Lower Cretaceous Shahezi Formation of Longfengshan, the organic carbon content is mainly between 1.0% ~ 3.0%, the lower part of Yingcheng Formation is the secondary source rock, the organic carbon content Lower, mainly concentrated in the 0.6% to 1.0%.