页岩孔隙(缝)空间的跨尺度表征方法研究

Complete characterization of the multiscale pore (fractures) space of shale is the main content of shale reservoir evaluation. In this proposal, a new reconstruction method which combines the CCSIM-TSS method (the cross correlation based simulation-three step sampling method) with the optimization method is proposed to reconstruct stochastically 3D models of the shale sample based on 2D images and some experiment constrain conditions. Based on the large-area SEM image, the statistical method and the new reconstruction method with multiple constrain conditions are combined together to reconstruct the digital core for every typical component. Furthermore, a multiscale superposition algorithm is presented to merging the different scale digital cores together to obtain the representative and high resolution (sub nanometer) digital core for each layer. Based on the analysis results of X-ray EDS (energy dispersive spectrum), the mineral compositions of each layer in the shale sample are obtained. Then the reconstruction method for vertical beddings of shale is developed, and combined with the representative digital core for each layer it is used to generate the trans-scale digital core with multi-beddings (nanometer-micron-centimeter). Through this digital core, the characterization of the multiscale pore (fractures) space of shale can be presented continuously, and the results of this proposal can provide theoretical support for the evolution of the shale reservoir.

实现页岩多尺度孔隙（缝）空间的完备表征是页岩储层研究的核心内容。本申请拟将CCSIM-TSS方法与基于目标函数的重构算法相结合，以实验数据和图像数据为约束，发展多数据约束的三维重构算法，精细刻画页岩复杂的三维孔隙结构。基于超大面积扫描电镜(SEM)图像，将统计分析方法与多数据约束的三维重构算法相结合，分别重构页岩各典型组分的三维数字岩心。发展多尺度叠加算法，将各尺度数字岩心嵌套组合在一起，构建页岩层理内部具有代表性的（百微米视野）、高分辨率（亚纳米）的数字岩心。基于EDS矿物分析，获得页岩各层的矿物分布特征（平方厘米量级）。在此基础之上，发展垂向分层重构算法，并结合各层内的三维孔隙（缝）结构特征，构建含多个层理的跨尺度数字岩心（纳米-微米-厘米），实现页岩孔隙（缝）空间的完备表征，为页岩储层评价提供理论指导。

页岩多尺度孔隙（缝）空间极大地影响着储层油气的储存和运移，因此构建能完备表征多尺度孔隙（缝）空间的数字岩心是页岩油气勘探开发的重要基础。在本研究中，我们发展了二维多尺度特征提取方法，快速提取大面积高分辨率扫描电镜图像中各组分的特征，为数字岩心重构提供必要数据。接着，我们发展了多数据约束重构算法，构建有机孔数字岩心，实现了强非均质性、各向异性明显的有机孔隙簇的表征。在此基础之上，我们进一步将多数据约束重构算法与统计分析方法相结合，发展了多尺度多组分重构算法，并提出lREV (layer representative elementary volume) 的概念，建立了层内lREV尺度的数字岩心。最后，基于大面积高分辨率SEM (Scanning electron microscope)图像和ESD(Energy Dispersive Spectroscopy)图像，以实验数据为约束，发展了层理缝重构算法、跨尺度优化算法，建立了REV尺度的数字-实验岩心，实现了页岩多尺度孔（缝）结构的完备表征。依托建立的方法体系可以对页岩孔（缝）结构进行表征和研究，为下一步我国页岩气勘探开发奠定基础。