泥页岩生烃演化过程中的油气滞留效应及对其含油气性的影响

The oil & gas bearing of shale is a critical parameter for the resource evaluation and favorable area selection of shale oil & gas, however, the key geological factors controlling the oil & gas bearing of shale and its mechanisms and prediction methods have been controversial. Based on the research outcome so far, in this project, a typical study of the shale oil & gas bearing has been carried out from the perspective of oil & gas retention effect of source rocks, including the key geological factors and its function mechanisms, which mainly focus on the following researches: ① Analyzing the geological characteristics and related geological and geochemical parameters of oil & gas retention effect of shale. And illuminating the patterns and differences of oil & gas retention of shale by analyzing the samples of different organic matter types from the typical areas systematically. ② Simulating the oil & gas bearing and the variation characteristics of oil & gas bearing retention of shale in the process of hydrocarbon generation evolution. Investigating the changes of property and quantity of oil & gas retention of shale under different evolution conditions through physical simulation experiments, and combined with the analysis of micro-geological and geochemical parameters of shale after hydrocarbon generation, establishing the geological model of oil & gas retention of shale. On this basis, this project analyzes the coupling relation between oil & gas bearing and oil & gas retention effect of shale, reveals its micro-geological mechanisms and establishes the geological model.

泥页岩含油气性是页岩油气资源评价和有利区优选的关键参数，但其主控地质因素及作用机理不清、预测方法不完善。本项目基于已有研究成果，从常规油气领域广泛认识到的烃源岩滞留油气作用这一角度出发，开展泥页岩含油气性主控地质因素、作用机理的探索，着重开展以下研究工作：①泥页岩滞留油气作用地质特征及相关地质地化参数分析，通过典型地区不同有机质类型岩石样品的系统剖析，阐明泥页岩中油气滞留的方式和差异；②生烃演化过程中泥页岩滞留油气性变化特征及含油气性模拟，通过物理模拟实验研究不同演化条件下泥页岩滞留油气性质和数量的变化，结合生烃转化后泥页岩微观地质地化特征参数分析，确定泥页岩滞留油气地质模式，并在此基础上，分析泥页岩滞留油气作用与含油气性之间的耦合关系，揭示其微观地质机理，并建立地质模式。

项目围绕拟解决的科学问题，选择了鄂尔多斯盆地长7段页岩和渤海湾盆地东濮凹陷沙河街组泥页岩为样品，重点开展了泥页岩生烃过程中有机—无机组构变化与有机质孔隙变化规律的研究，同时探讨了生烃过程残留烃量的变化。其中，东濮凹陷沙河街组泥、页岩成熟度在0.78%~1.72%的Ro范围内，处于成熟和高成熟阶段。矿物组成中，粘土含量平均值高达50.786%；脆性矿物平均含量为46.93%，有较好的脆性与可压裂性。泥、页岩中孔孔隙在孔径为2~5nm范围内分布较为集中；在Ro（%）处于0.9%~1.5%范围内孔隙度较大，受到生烃作用与成岩作用的双重影响呈先增加后逐渐减小的趋势；孔隙度与总孔体积、平均孔直径呈正相关性。随泥、页岩有机质的演化，氯仿沥青“A”和S1（mg/g）分别与成熟度的变化呈先增加后减小的趋势。随着粘土含量增高，孔隙度减小。氯仿沥青“A”分别与孔隙度及有机碳含量呈正相关性。由此可见，含有较大孔隙度、有机碳含量较高的泥、页岩含油性越好。有机质分布能控制有机孔的分布和联通特征，泥、页岩中有机质含量高的位置是有机孔分布的主要位置，TOC越低，有机质生烃越倾向于形成小孔径有机孔，生成的有机孔数量越少。大孔和中孔共同控制有机孔孔隙体积。有机孔内比表面积由成熟阶段至高成熟再到过成熟阶段依次增大再减小，控制有机孔内比表面积孔隙类型由中孔转化为微孔。有机质生烃改善有机孔间联通性。