鄂尔多斯盆地上古生界致密砂岩气藏天然气运移机制

Exploration has confirmed that the Upper Paleozoic of the Ordos Basin(UPOB) is one of the most abundant basins in tight sand gas resources in China, however, as far as the gas migration mechanism and the pattern of hydrocarbon accumulation in the UPOB have been controversial. It has not yet been systematically carried out the difference of the migration driving force of the various layers and all kinds of driving force contributing to the natural gas accumulation of the different layers. Based on the modern hydrocarbon accumulation geology theory and advanced experimental technologies, combined macro-study and micro-study, geology and geochemical analysis, simulation experiments and the geologic integrated research, this project, as the core of the gas migration mechanism, applied more comprehensive analysis methods to analysis the driving force and the pattern of gas migration and also study the numerical simulation of gas diffusion migration in the various layers and the physical and numerical simulation of natural gas driven by abnormal pressure from the basic geological conditions of gas migration and the geological response of the geochemical fractionation effects caused by migration, the ancient reservoir temperature-pressure and the fracture development characteristics in the reservoir. The analysisi above reveal the natural gas migration mechanism and various driving force contributing to the natural gas accumulation of the different layers in the UPOB large gas fields, also propose a corresponding pattern of natural gas accumulation and enrichment.

鄂尔多斯盆地是我国致密砂岩气资源最丰富的盆地，有关上古生界致密砂岩天然气运移机制及成藏模式的认识目前还存在争议，特别是不同层位天然气运移动力的差异和各种动力对不同层位天然气成藏的贡献目前还尚未开展系统研究。本项目以现代油气成藏地质学理论与先进的实验测试分析技术为依托，采用宏观与微观研究相结合、地质与地球化学分析相结合、模拟实验与地质综合研究相结合的思路，以天然气运移机制为核心，从天然气运移的基本地质条件和运移产生的地球化学分馏效应、储层古温压状态、储层裂缝发育特征等地质响应入手，运用多方法综合分析各层位天然气运移动力及方式，并开展天然气扩散运移数值模拟、异常压力驱动的天然气物理和数值模拟研究，揭示鄂尔多斯盆地上古生界不同层位天然气运移机制及不同动力对不同层位天然气成藏的贡献，并建立相应的天然气运移聚集与富集模式。

鄂尔多斯盆地是我国致密砂岩气资源最丰富的盆地，有关上古生界致密砂岩天然气运移机制及成藏模式的认识目前还存在争议，特别是不同层位天然气运移动力的差异和各种动力对不同层位天然气成藏的贡献目前还尚未开展系统研究。本项目对主运移期天然气运移输导体系特征、天然气运移成藏地质响应和不同运移动力及方式的成藏贡献开展了系统研究。通过本项目研究，揭示了半封闭-封闭成岩流体系统成岩作用特征与致密砂岩储层形成过程；认识到了浓度梯度驱动的天然气分子扩散作用在致密大气田形成过程中的重要作用，探讨了天然气分子扩散运移与生烃增压运移的关系和成藏贡献；系统论证了生烃增压在致密砂岩气藏形成过程中的作用，提出了超压成因新分类，总结了超压成因判识方法；深化完善了准连续型成藏理论，建立了鄂尔多斯盆地致密砂岩气藏双驱动—双运移—双流向—三要素控藏模式；全面分析和总结了致密大气田的形成条件与富集规律，认为烃源、储层、盖层以及运移通道是控制准连续型致密大气田形成和分布的主要因素，提出了致密砂岩气藏“源盖控藏、储层甜点富集”的成藏富集理论。研究成果对鄂尔多斯等中国主要含油气盆地致密砂岩气的勘探开发起了重要指导作用。