利用改进的核磁共振技术探索页岩油可动性的关键问题

Shale oil mobility is the core geological problem faced by the effective development of shale oil in China. The evaluation of fluid mobility is related to the porosity structure, fluid composition and conformance efficiency of sandstone reservoirs. There is also a lack of targeted work for the mud-shale reservoirs with more development of nanoscale pore throat and more complex of the fluid solid interaction. Aiming at the weak link, the topic is to play a nuclear magnetic resonance integration of reservoir and fluid technology advantages to evaluate the shale reservoir pore structure, wettability and shale oil mobility. However, the theory, method and calculation model of the proven nuclear magnetic resonance imaging technology are all for the conventional reservoir and the tight sandstone reservoir, and can not be directly applied to the ultra-low porosity, organic-rich, solid-liquid complex shale reservoir, the need for its targeted improvement. In view of this, this project selected the typical continental shale oil basin as the target area, in the shale mineral composition, geochemical characteristics, fluid composition, micro-pore structure based on the use of improved nuclear magnetic resonance technology to complete the characterization of porosity-permeability of the shale oil reservoir, the "in situ" wetting, the shale oil storage and the dynamic mechanism research, and establish a new method for the evaluation of the shale oil mobility for the effective exploration and development of shale oil, theoretical guidance and technical support.

页岩油可动性是我国页岩油有效开发所面临的核心地质问题，有关流体可动性的评价，前人多是对砂岩储层开展孔隙结构、流体组成、驱替效率等相关工作，对纳米级孔喉更为发育、流-固相互作用更为复杂的泥页岩储层还缺少针对性工作。瞄准该薄弱环节，课题拟发挥核磁共振一体化表征储层和流体的技术优势，评价页岩储层的孔隙结构、润湿性及页岩油可动性。但目前已成熟的核磁共振评价技术，其理论、方法和计算模型都是针对常规储层和致密砂岩储层，还不能直接应用于超低孔渗、富含有机质、固-液作用复杂的页岩储层，急需对其进行针对性改进。鉴于此，本次立项选取我国典型的陆相页岩油盆地为靶区，在页岩矿物成分、地化特征、流体组成、微观孔隙结构研究基础上，利用改进的核磁共振技术，完成页岩油储层的孔渗表征、“原位”润湿、页岩油赋存及可动机理研究，建立一套适用于页岩油可动性评价的新方法，为页岩油有效勘探开发提供理论指导和技术支撑。

页岩的储集特性、石油在页岩中的赋存规律和可流动性是目前页岩油地质研究的核心和难点问题，核磁共振是表征三者并建立有机联系的有效实验技术。研究针对渤海湾盆地东营凹陷沙河街组、南襄盆地泌阳凹陷核桃园组和吐哈盆地台北凹陷西山窑组、三工河组泥页岩，以核磁共振技术为核心，开展了X射线衍射、总有机碳及岩石热解、低温氮气吸附-解吸、扫描电镜、高压压汞、X射线CT扫描、热重分析、离心分析、驱替分析及渗流模拟等实验工作。.系统开展了核磁共振技术在页岩孔隙系统、孔隙结构、孔隙度和渗透率研究中的应用，建立了基于核磁共振技术的页岩储集特性定量评价体系。定量计算了页岩核磁共振孔隙度和渗透率，建立了页岩孔隙系统核磁共振识别方法，定量评价了页岩储层孔隙结构的复杂性和非均质性。.通过分析不同流体饱和状态的页岩、粘土矿物及干酪根核磁共振弛豫特征，建立了页岩主要氢核组分核磁共振T1-T2识别图版，揭示了页岩油赋存状态。应用热重、离心-核磁共振分析，建立了页岩吸附/游离油定量评价方法，阐明了页岩吸附/游离油相互转换规律，并建立了页岩吸附/游离油T2谱定量评价模型及页岩油赋存模式。.采用离心-核磁共振分析了页岩油可流动量，表明页岩油可动量较低，可流动性较差，可流动量随游离油量增加而增加。利用驱替-核磁共振分析了驱替压力、孔隙结构、脆性矿物和黏土矿物对页岩油可动性的影响。通过物理模拟实验，揭示了页岩油渗流规律，分析了有效应力和边界层效应对页岩油渗流的控制作用，建立了有效应力和边界层效应共同控制的页岩油微观渗流评价模型,并利用页岩微观与宏观物性参数的耦合关系，将其转化为页岩油宏观渗流模型，实现了页岩油可动有利区预测。