牛38井湖相烃源岩镜质体反射率负异常与有机组分含量相关性

对东营凹陷牛38井古近系沙河街组有机碳富集的沙三中、下亚段烃源岩(有机碳含量平均值分别达到2.0%、4.0%)进行了大量样品的分析测试及研究,发现该层段烃源岩存在明显的镜质体反射率Ro抑制现象(负异常),表现在2770～2900m处Ro值整体分布正常,而其下的2900～3370m处Ro值分布偏离正常发展轨迹.为考查Ro出现负异常的成因,对该井沙河街组湖相烃源岩出现的Ro负异常与有机组分相关性进行分析.研究结果表明,Ro异常值与壳质组含量、腐泥组含量呈正向线性统计关系,而与镜质组含量呈负向线性统计关系,与惰质组关系不明显.在剖面分布上,Ro抑制层段对应较高含量的壳质组与腐泥组.Ro值与H含量及H/O比呈负向线性统计关系,与O含量呈正向线性统计关系.研究结果初步显示高含量的壳质组、腐泥组与Ro负异常关系密切,壳质组和腐泥组中氢的富集,是导致Ro抑制现象的一重要成因.

Relationship between the suppression of vitrinite reflectance of lacustrine source rock from niu-38 well in Dongying Sag and the contents of organic components

The lacustrine source rock of the middle and low sub-members of member 3 of Shahejie Formation from is studied based on a lot of samples,and it is found that the source rock presents the obvious suppression of vitrinite reflectance.In 2 900～3 370 m,the actual Value of vitrinite reflectance is less than the predictive value of it according to its distribution law in 2 770～2 900 m.The abnormal value of the vitrinite reflectance is in 0.05%～0.25%.The relationship between the negative abnormal value and the contents of organic components in the source rock is analyzed.It is shown that,there is positive linear relation between the abnormal value of Ro and the contents of exinite and sapropelinite,there is negative linear relation between it and the content of vitrinite;and there is no obvious relationship between it and the content of inertinite.On profile,the layer with the suppression of Ro is corresponding to high contents of exinite and sapropelinite.There are negative linear relationships between the value of Ro and the content of hydrogen and the ratio value of H to O,and there is a positive linear relation between the value of Ro and the content of oxygen.The results show that the high content of hydrogenous exinite and sapropelinite is one of the main factors causing the suppression of vitrinite reflectance,and the suppression appears when the content of liptinite is over 40%(the content of hydrogen is about 2%).