松辽盆地白垩系青山口组页岩沉积环境及其含油性特征

Sedimentary environment and oil-bearing characteristics of shale in Cretaceous Qingshankou Formation in Songliao Basin

白昕 陈睿倩 商斐 张楠

BAI Xin CHEN Ruiqian SHANG Fei ZHANG Nan

1. 中国石油大学(北京) 油气资源与探测国家重点实验室, 北京 102249; 2. 中国石油大学(北京) 地球科学学院, 北京 102249; 3. 中国石油勘探开发研究院, 北京 100083

1. State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China; 2. College of Geosciences, China University of Petroleum (Beijing), Beijing 102249, China; 3. Research Institute of Petroleum Exploration & Development, Beijing 100083, China

松辽盆地上白垩统青山口组页岩地层厚度大、分布广泛，有机质丰度高，蕴含了丰富的页岩油资源。对页岩地层形成时沉积环境的研究，以及对页岩油富集层段含油性特征的探索，可为页岩油富集层段与甜点的预测提供理论依据。结合前人的研究成果，通过对比松辽盆地中央坳陷区不同凹陷的2口典型井——古龙凹陷GY8HC井和三肇凹陷ZY1井部分样品的总有机碳(TOC)含量、热解数据、有机显微组分类型以及主、微量元素，深入研究了2个凹陷青山口组页岩的含油性差异与沉积环境特征，进而对含油性差异的影响因素进行了分析。研究区青山口组2口典型井的页岩含油性相关指标显示，ZY1井页岩TOC含量显著高于GY8HC井，但其游离烃含量与含油饱和度指数比GY8HC井低。页岩形成时的地球化学环境控制着有机质的富集。对比2口井样品的主、微量元素发现，ZY1井青山口组沉积时期气候更加湿润、水体还原性强，且其古生产力以及古水深要显著高于GY8HC井。这些条件都有利于有机质的保存，因而形成了ZY1井页岩更高的有机质丰度。GY8HC井有机质类型是以腐泥质为主的Ⅰ型干酪根，且处于成熟—高成熟阶段；而ZY1井有机质类型以Ⅱ1型干酪根为主，Ⅰ型含量较少，并处于低熟—成熟阶段，因此，GY8HC井页岩的生油潜力更好。

The Upper Cretaceous Qingshankou Formation in the Songliao Basin contains thick, widespread, and organic matter-rich shale layers, offering abundant shale oil resources. Studying the sedimentary environment during shale formation and exploring the oil-bearing characteristics of shale oil enrichment intervals provide a theoretical basis for the prediction of the intervals and sweet spots. Based on previous research, the study compared organic carbon content, pyrolysis data, types of organic macerals, and major and trace elements of samples from two typical wells of different sags, well GY8HC in the Gulong Sag and well ZY1 in the Sanzhao Sag, in the central depression zone of the Songliao Basin. The analysis delved into the differences in oil-bearing characteristics and sedimentary environment of the Qingshankou Formation shales in two different sags, further analyzing the factors influencing these differences. The oil-bearing indicators of shales from the two wells in the Qingshankou Formation of the Songliao Basin showed that the total organic carbon (TOC) content in well ZY1 was significantly higher than that in well GY8HC. However, the free hydrocarbon content (S1) and oil saturation index (OSI) in well ZY1 were lower than those in well GY8HC. The geochemical environment during shale formation controlled organic matter enrichment. Comparing major and trace elements in samples from both wells, it was found that the climate in well ZY1 was more humid during its sedimentary period, the water body had stronger reducing conditions, and its paleoproductivity and paleo-water depth were significantly higher than those in well GY8HC. These conditions were favorable for the preservation of organic matter, thereby forming a higher organic matter abundance in the shale of well ZY1. In addition, it was found that the organic matter type in well GY8HC is mainly Type Ⅰ, sapropelic kerogen, at a mature to highly mature stage, whereas well ZY1 contains mainly Type Ⅱ1 kerogen, with less Type Ⅰ, at a low to mature stage. Therefore, the shale in well GY8HC possesses better oil generation potential.

中国石油勘探与生产分公司科技支撑项目“松辽盆地综合地质研究与预探目标优选”子课题“松辽盆地致密油/页岩油富集机理与甜点区评价”(KT2018-06-01)资助。

https://doi.org/10.11781/sysydz2024051063