页岩气储层微观孔隙发育机制及其演变定量模拟

Development of microspaces is the key to find the shale gas reservoir. The types of microspaces of reservoir in gas shale with strong anisotropy are complexed and diversified. It is significant in practice and in theory for evaluating and predicting of the favourable shale gas reservoir,analyzing the mechanism of accumulation and guiding the deployment and adjustment of exploration and development to study the developmetal mechanism of the microscopic pores in shale gas reservoir and quantitative simulation of their evolution.According to the observation of available cores, scanning electron microscope for thin section with argonion polishment, Nano-CT imaging, X-ray microanalysis and so on, the types and structures of micro-nano pores are researched with the authorized classification and naming. Then the variational regularity of the structures of every kind of microscopic pores such as matrix pores,organic pores and so on, with variation of the factors such as type and content of brittle minerals and clay minerals, organic type and TOC,organic maturation et al.,and the main controls will be emphatically analyzed,The further discussion of the evolutive characteristics of the microscopic pore structures will be followed by the quantitative simulation of the thermal evolution of the shale gas reservoir. Finally, the developmental mechanism of every kind of microspace will be determined,and the distribution model of the favourable microspaces in gas shale will be established, which will both provide the scientific foundation for evaluation and prediction of the high-quality shale gas reservoir.

微观储集空间发育是寻找页岩气藏的关键。页岩气储层非均质性强，微观储集空间类型复杂多样，开展页岩气储层微观孔隙发育机制及其演变定量模拟研究，对评价和预测优质页岩气储层、分析成藏机理、指导勘探开发方案的部署及调整都具有重要的实践意义和理论指导意义。本项目以济阳拗陷沾化凹陷沙河街组主力烃源岩为研究对象，通过岩心观察、氩离子抛光扫描电镜观察、纳米CT成像技术、X衍射分析等手段，开展页岩气储层微米-纳米级储集空间类型和结构特征研究，并建立系统分类体系和命名原则，重点分析各类微观孔隙结构（基质微观、有机质微孔等）随各种因素（脆性矿物种类和含量、粘土矿物种类和含量、有机质类型和TOC、有机质成熟度等）的变化规律及主控因素，并通过热演化定量模拟实验，进一步探讨各类微观孔隙结构的演变特征，明确各类微观孔隙的发育机制，最终建立页岩气优质储集空间分布模型，为优质页岩气储层评价及预测提供科学依据。

页岩气储层微观孔隙类型多样，孔隙发育机制及控制因素复杂。本项目以沾化凹陷沙河街组主力烃源岩和奥连特盆地白垩系烃源岩为研究对象，通过岩心和薄片观察、X-衍射、（氩离子）抛光扫描电镜、高压压汞、氮气吸附和二氧化碳吸附及热演化模拟等实验手段，对泥页岩的物质组成、微观孔隙类型、孔径大小和孔隙发育控制因素进行分析，明确各类微观孔隙的发育机制及其变化规律，对于页岩气储层评价及预测具有重要的理论和实践意义。. 结果表明，沙河街组泥页岩具有碳酸盐矿物含量高、黏土矿物含量低的特征，矿物组成主要包括方解石、黏土矿物和石英，伴有少量白云石、黄铁矿及其他矿物；综合考虑孔隙产状、赋存位置、成因和孔径大小等因素，依据科学、系统、简便、实用等原则，制定了页岩微观孔隙综合分类方案，并厘定了孔隙和裂缝的尺度评价标准。不同孔隙类型对应的孔径大小存在差异，粒间孔和粒内孔均以纳米级孔隙为主，而有机质孔以纳米级孔隙为主。构造裂缝以宏观毫米级为主，成岩裂缝以微米级为主，而有机质收缩微裂缝以纳米级为主。沙河街组泥页岩氮气吸附曲线形态分为4种类型，均表现出狭缝型孔隙，孔径以中孔为主。二氧化碳吸附实验测得的孔径分布具有双峰及多峰现象，孔径集中在0.3nm~0.9nm。高压压汞测得孔径主要集中在7nm~10nm。沙河街组泥页岩整体以发育中孔隙为特征。页岩微观孔隙发育受五大因素控制，沉积环境与构造背景及其控制的岩性与矿物组成控制孔隙的类型及结构；有机质丰度影响有机质孔和微裂缝的发育，TOC与页岩平均孔径及孔隙体积呈正相关性；干酪根类型和Ro直接控制了有机质孔的演化；页岩储层的总孔隙度随着热演化程度的增加表现为先下降后增高又下降的趋势。不同孔径大小的孔隙随着Ro的变化趋势不一样。脆性矿物含量高、不稳定组分含量高、TOC高、II型或III型干酪根为主、处于高成熟度的层状泥页岩更发育微孔隙和微裂缝。研究成果将为预测优质页岩气储层分布及进一步制定页岩气勘探开发方案提供重要的科学依据。