烃源岩抬升过程中的生排烃转换、压力保存与页岩油气富集

It is well known that there will have important influences on the hydrocarbon generation and expulsion and petroleum enrichment when the source rocks have been uplifted and cooled from their peak burial depths and temperatures. This is a frontier issue of fundamental research in petroleum geology and geochemistry, but has gained relatively little systematically and profoundly attention. To investigate this issue, the project aims to conduct a detailed study on the mechanisms of hydrocarbon generation and expulsion, and overpressure preservation during source rock uplift, and the potential shale oil and gas target after exhumation charge. Guided by theory of petroleum geology and geochemistry, we chose a typical continental exhumed basin to carry out the research using the technology of petroleum geochemical analysis and basin simulation. First, the process of hydrocarbon generation and expulsion during uplift will be characterized in detail, and then establish a mode. And also factors and mechanism of affecting hydrocarbon generation and expulsion will be addressed from the characteristics of source rock and its external environment. Second, the postexhumation dissipation of pressure will be investigated. Third and finally, the implications for unconventional shale resources after experiencing the exhumation charge will be discussed combined with the characteristics of hydrocarbon generation and expulsion. These results and understandings can add new theoretical complements to the classical theory of petroleum generation. In addition, it can also provide new theoretical and experimental data for the study of accumulation mechanisms and rules of shale oil and gas, which could be used in practical exploration. Therefore, the project can have fundamentally theoretical and practical exploration implications.

烃源岩的抬升对生排烃和油气富集具有重要影响，但尚未得到系统深入的研究，是油气地质地球化学基础研究的前沿内容。本项申请，拟针对烃源岩抬升过程中的生排烃转换、压力保持，以及与页岩油气的富集关系等3方面重要科学问题，以油气地质-地球化学理论为指导，以油气地球化学分析技术和盆地模拟技术为支撑，精选我国典型陆相优质烃源岩为研究对象，首先刻划烃源岩抬升地质过程中生排烃的转换过程，建立模式，并从烃源岩本身特性（内因）及所处外部环境（外因）等方面分析影响生排烃的因素和机理。在此基础上，研究抬升过程中压力的变迁与演化规律，进而结合生排烃的特征，系统阐明抬升过程对页岩油气富集的意义，总结规律。研究结果可望是对现有经典现代油气生成理论的新补充，相关认识还可直接应用于具体的含油气盆地勘探部署，可望具有重要的基础理论与实践应用意义。

烃源岩的埋藏与抬升是含油气盆地一个常见的地质过程和现象，对页岩的生排烃和页岩油气的富集具有重要影响，但在过去的研究中关注不够，尤其是生排烃的转换、压力的保持，以及与页岩油气的富集关系等科学问题。本项目在综合分析烃源岩排烃作用影响因素基础上，重点研究了页岩非均质性、烃类微运移、有机地球化学特征、烃源岩抬升的影响，以及烃源岩抬升过程中地层压力保存情况，并获得以下结论和认识。.1、分析了烃源岩排烃影响因素，可划分为内因和外因，其中内因包括烃源岩基质岩石矿物组成和烃源岩所含有机质ATM特性两个方面；外因包括因构造运动引起的微裂缝发育和地层抬升等因素。其中，地层抬升结果会导致盆地发生卸载减压，使储层内砂体回弹，引起烃源岩和储集层内部能量释放，有利于烃源岩的排烃。.2、在分析影响页岩自由烃含量因素基础上，提出了用自由烃差值法来计算和衡量页岩内部烃类微运移作用的强度，从微观上判断烃源岩的排烃性质和强度。结果表明，烃源岩内部微观排烃作用可划分出强排烃、弱排烃和外来烃三个等级。.3、为了更准确计算烃源岩内部微观排烃效率，提出了用热解图版法恢复原始生烃潜力来计算烃源岩排烃效率。研究结果表明：热解图版法比传统的人为赋值法计算过程更为合理，获得的结果更为准确。.4、在相同或相近的有机质ATM特性条件下，烃源岩抬升对排烃作用有重要影响。研究结果表明，随着烃源岩抬升幅度增加，排烃效率呈对数增加，表明烃源岩抬升幅度对烃源岩排烃效率有明显的控制作用。.5、通过对泌阳凹陷25口井测井资料的分析计算，预测出它们地层压力值。发现以凹陷中部深凹区为中心，向东南陡坡带及向西北缓坡带方向地层抬升幅度和剥蚀前后压力差呈线性增大；且在地层抬升幅度越低的时候线性相关性很高，随着地层抬升幅度升高这种线性相关性略微降低，但整体相关性依然能达到0.9489。这说明该地区不整合面之下地层剥蚀前后压力差主要受地层抬升幅度控制，其它因素对其存在影响但较小。