【摘要】 现场调查表明,砂质纹层、凝灰质纹层和天然裂缝广泛地存在于陆相页岩储层中。本文对鄂尔多斯盆地页岩储层中的纹层和天然裂缝进行了多尺度研究,并构建了三维地质结构模型。首先,基于二维裂缝现场调查,利用蒙特卡罗模拟方法建立了研究区域的三维裂缝网络模型。然后通过多种观测手段获得由宏观尺度到微观尺度的纹层结构特征。对多尺度纹层厚度的统计分析表明,米级、分米级、厘米级、毫米级和10微米级等不同研究尺度下的纹层平均厚度分别为2. 26 m,2. 09 dm,1. 70 cm,1. 48 mm和11. 7μm,呈现出分形特征,分形维数为1. 06;不同研究尺度下的单层厚度均服从负指数分布规律,即各研究尺度下厚度越大的纹层,其层数越少,反之越薄的纹层其数量越多。最后,根据上述纹层平均厚度及概率分布函数特征,建立了页岩的多尺度纹层结构模型,并将其叠加在裂缝网络模型上,生成不同尺度下的页岩三维地质结构模型。模型输出的裂缝、纹层参数与研究区域的真实地质参数有着较好的对比验证。这项研究工作可为页岩气储层的水力压裂数值模拟和物理模型试验提供更可靠的地质模型。更多还原

【Abstract】 Outcrops and core observations show that sandy and tuff aceous laminas and natural fractures are well developed in the continental shale gas reservoir. This study reports the distribution of laminas and natural fracture networks at different scales and established the 3-D geological structure models,with data obtained from outcrops,wells and cores of Yanchang shale from southern Ordos Basin. Firstly,based on two-dimensional fracture field investigations,a 3-D joint network model of the study area was built using the Monte Carlo simulation method. Then the laminations were identified from macroscopic scales to microscopic scales with multiple probe techniques.Statistical analysis of multi-scale layer thickness suggested that the average thickness of layers at multiple scales showed a fractal feature,with average layer thickness of 2. 26 m,2. 09 dm,1. 70 cm,1. 48 mm and 11. 7 μm,corresponding to meter scale,decimeter scale,centimeter scale,millimeter scale and 10-micro meter scale respectively,and that the layer thickness at studied scales all followed with an exponential probability distribution.The fitting curves indicated that most of laminas at each scale were relatively thin. In other words,the thicker the layer,the less the number of layers contained in shale. Finally,the lamination models were constructed and superposed over the joint network model to generate 3-D geological structure models at various scales. The models were validated by reproducing fracture and lamina parameters,which were fairly close to those measurements of realistic geological bodies in the study area. The findings of this work could shed light on the characterization and modeling of geological structure for the numerical simulation and physical model test of hydraulic fracturing in shale gas reservoir.更多还原