摘要：

松辽盆地古龙页岩油勘探已取得战略性突破，青山口组底部“纯页型”至顶部“夹层型”页岩的含油性和产能差异明显，相对高产的“纹层型”页岩的毫米级不同纹层组合的含油性差异微观特征研究尚不清晰，导致页岩的含油性评价和赋存机理存在争议。本文以古页3HC单井段岩心为研究对象，利用普通薄片鉴定、有机地化实验、X射线衍射测试、氩离子抛光扫描电镜观察、气体吸附实验及热模拟生烃实验等研究手段，针对富有机质暗色纹层和贫有机质亮色纹层进行解析，建立了不同纹层组合模式，并开展了成烃成储过程下的不同纹层组合生烃、储集能力特征变化与含油性的相关研究，得出以下认识：(1)结合TOC含量和纹层类型将青一段页岩划分为“富有机质+混合质”二元纹层组合和“贫有机质+长英质”二元纹层组合两种模式。(2)将两种纹层组合的样品进行热模拟实验，成烃过程中受TOC含量控制富有机质混合质纹层组合指示更高的含油性评价指标(S₁)，成储过程含油性(S₁)主要受伊蒙混层等黏土矿物的影响，贫有机质长英质纹层储集空间发育更好。(3)当古龙页岩纹层在垂向上出现富有机质纹层/贫有机质纹层厚度为2:1时含油性最高，此时富有机质纹层的TOC含量大于2.15%、黏土矿物组分含量大于55%，具备很好供烃能力但储集能力差，生烃后运移到贫有机质纹层提供的储集空间中，“2:1组合模式”为最佳源储比，对“纹层型”页岩的发育最有利。(4)通过测井曲线(GR高值)、TOC含量(>2.15%)和黏土矿物含量(>55%)这一指标体系，来验证毫米尺度下建立的“2:1 组合模式”的可靠性，为古龙凹陷青山口组页岩油甜点预测与高效开发提供新方法。

关键词: 富有机质纹层, 贫有机质纹层, 纹层组合模式, 含油性, 青一段, 古龙页岩, 松辽盆地

Abstract:

Substantial advancements have been achieved in the exploration of Gulong shale oil in Songliao Basin. Pronounced disparities exist in oil-bearing capacity and productivity between the pure shale at the base of the Qingshankou Formation and the sandy interlayer at its top. However, the investigation of the microscopic characteristics underlying the oil-bearing differences in millimeter-scale assemblages of relatively high-yield lamina shale remains ambiguous, thereby fueling debates regarding the evaluation and genesis mechanisms of oil-bearing shale. This study integrates multiple analytical approaches, including conventional thin-section petrographic analysis, organic geochemical characterization, X-ray diffraction (XRD), argon ion polishing scanning electron microscopy observations, gas adsorption experiments, and thermal simulation experiments for hydrocarbon generation. The dark, organic-rich laminae and the bright, organic-poor laminae in the core of the Guye 3HC well section are analyzed to identify distinct lamina combination modes. The relationship between hydrocarbon generation, reservoir characteristics, and oil-bearing properties of these different lamina combinations during the hydrocarbon generation and storage processes is investigated. The results are obtained in four aspects. First, based on the total organic carbon (TOC) content and lamina types, the shale of the first member of Qingshankou Formation is categorized into two types: “organic-rich matter mixed” and “ organic-poor matter felsic” binary lamina combination modes. Second, Thermal simulation experiments were performed on samples from both lamina combination types. During the hydrocarbon generation process, the organic-rich mixed lamina combination, which is characterized by a high TOC content, exhibited a higher oil-bearing evaluation index (S₁). This outcome of S₁ during the storage process was primarily influenced by clay minerals, specifically the illite-montmorillonite mixed layer. In contrast, the organic-poor matter felsic lamina combination mode demonstrated superior reservoir development potential. Third, the oil content reaches its peak when the vertical thickness ratio of organic-rich to organic-poor laminae in the Gulong shale is 2:1. At this ratio, the TOC content of the organic-rich laminae exceeds 2.15%, while the clay mineral component content exceeds 55%. This combination exhibits strong hydrocarbon generation potential but relatively poor reservoir capacity. Following hydrocarbon generation, the hydrocarbons migrate into the reservoir space provided by the organic-poor laminae. The “2:1 combination mode” represents the optimal source-to-reservoir ratio for developing “lamina-type” shale reservoirs. Fourth, the 2:1 combination model, defined at the millimeter scale, was identified by high gamma-ray (GR) values, TOC content exceeding 2.15%, and clay mineral content exceeding 55%. This model offers a novel approach for predicting sweet spots and efficiently developing shale oil from the Qingshankou Formation in the Gulong Sag.

Key words: organic-rich laminae, organic-poor laminae, lamina combination mode, oil-bearing property, the first member of Qingshankou Formation, Gulong shale, Songliao Basin

中图分类号: 

• P618.13

• TE122