摘要： 松辽盆地古龙凹陷青山口组青一段和青二段底部(Q1~Q9)为典型的高有机碳含量的页岩,具有广阔的资源前景。岩相的划分和表征是页岩油气勘探开发的重要基础,如何快速准确识别岩相成为非常规油气储集层地质甜点研究的重点和难点。利用岩心、薄片、XRD和元素资料明确研究区地质特征,利用LithoScanner测井和成像测井切片实现单井纵向岩相的连续识别和划分。结果表明古龙页岩岩性主要为黏土质页岩、长英质页岩、介壳灰岩和云岩,多尺度纹层结构类型分为毫米级纹层状、厘米级层状和分米级块状。依据地质上可区分、测井上可识别的原则,将岩性和纹层结构耦合得到10类岩相。主要发育纹层状和层状黏土质页岩以及纹层状和层状长英质页岩,块状介壳灰岩和云岩多以薄夹层的形式出现在层间,块状页岩偶现。依据各小层内纵向上岩相叠置关系,岩相组合划分为5类,纹层状黏土质页岩与层状黏土质页岩互层的组合较为常见。青山口组整体处于气候湿润还原性较强的淡水湖盆的沉积环境,水体在Q7层达到最深而后逐渐变浅。在不同小层沉积环境有微弱变化,在各小层高水位时岩相主要类型为纹层状黏土质页岩,低水位时以层状长英质页岩为主。岩相类型的划分和快速识别为页岩油地质甜点和工程甜点的预测提供理论依据和指导,岩相组合类型的分类和发育模式为古龙页岩油富集机理的研究奠定基础。

关键词: 页岩岩相, 岩相组合, 测井表征, 青山口组, 古龙凹陷, 松辽盆地

Abstract: The bottom section the Qing 1 and Qing 2 Members of the Qingshankou Formation(Q1~Q2)in the Gulong Sag of Songliao Basin consists of typical high-organic-carbon shales with vast resource potential. The division and characterization of lithofacies play an important role in the evaluation of shale oil sweet spots. It's challenging to recognize lithofacies in a single well. In this study,core photos,thin sections,XRD as well as element data are used to detect the geological characteristic of the reservoir. Besides,LithoScanner and Schlumberger's fullbore formation microimager(FMI)are used to achieve the continuous identification and division of the lithofacies. The result shows that the lithology of the study area mainly consists of four types,including clayey shale,felsic shale,shell limestone,and dolomite. Various-scale laminated structures include millimeter-scale laminations,centimeter-scale bedding,and decimeter-scale structureless laminations. Consequently,ten types of lithofacies were then obtained by coupling lithology and lamina structure. Laminated and bedded clayey shales and laminated and bedded felsic shales are predominant,while massive shell limestone and dolomite mostly occur as thin interlayers,with massive shales occasionally developed. It is clear that the lithofacies assemblages under the control of stratigraphic cycles can be divided into five types. Laminated clayey shale interbedded with layered clayey shale is the most common type in study area. The Qingshankou Formation as a whole was deposited in a freshwater lake basin with a relatively strong reducing environment,with water depth reaching its maximum in the Q7 member and gradually decreasing afterward. There are slight variations in sedimentary environments within different subunits. The predominant lithofacies type varies with water depth,with laminated clayey shales dominating during high-water conditions and bedded felsic shales predominating during low-water conditions. The classification and rapid identification of lithofacies and lithofacies assemblage types provide insight into the shale oil exploration and development and guide for the prediction of shale oil geological sweet spots and engineering sweet spots.

Key words: shale lithofacies, lithofacies assemblage, logging evaluation, Qingshankou Formation, Gulong sag, Songliao Basin

中图分类号: 

• P521