Analog laboratory experiments of fracture networks formed due to forced folding and pore fluid overpressure

Forced folding of a low-permeable, competent sediment layer in response to magmatic sill intrusion, remobilisation of fluidized sand or fluid overpressure in underlying porous reservoir formations can cause the formation of complex fracture networks. The opening modes and geometries of these fractures affect the bulk permeability of the cover layer and, thus, are crucial for understanding fluid flow processes in sedimentary basins. We carried out analog experiments in the laboratory of the Institute of Geosciences, Friedrich Schiller University Jena (project: Mobilization of Unconsolidated Sediments Related to CO2 Storage) to simulate the evolution of fracture networks during forced folding, its differences between a 2D and 3D modelling approach and its variability depending on the rheological stratification of the cover. To produce a fluid overpressure in the layered analog materials, air was injected from the base of the layering and additionally through a point-like needle valve penetrating into the lowermost layer with a stepwise increasing air flux (Q). Pressure sensors recorded the air pressure at the base of the reservoir layer and in the needle valve. The experiments were monitored with a digital SLR camera and analyzed by the digital image correlation software DaVis 10.0 (LaVision GmbH) to calculate displacement and strain patterns in the analog materials. Furthermore, a fracture analysis was performed for which we measured length and dips or strikes, respectively, in the side view of the 2D experiments and in top view in the 3D experiments. Based on these data, opening modes of the fractures were determined and statistical analyses were applied. The outcomes of these analyses are shown in rose diagram and histograms. The data set presented here includes: […]当低渗透强硬沉积层因岩床（magmatic sill）侵入发生强制褶皱时，下伏多孔储层中的流态化砂运移或流体超压，均可引发复杂断裂网络的形成。这些断裂的开启模式与几何形态会影响盖层的整体渗透性，因此对于理解沉积盆地内的流体运移过程至关重要。本研究在耶拿弗里德里希·席勒大学地球科学研究所实验室开展了类比实验（项目名称：与二氧化碳封存相关的未固结沉积物运移），以模拟强制褶皱过程中断裂网络的演化、二维与三维建模方法的差异，以及盖层流变地层结构带来的变化。为在层状类比材料中形成流体超压，研究人员从层系底部注入空气，同时通过刺入最底层的点状针阀注入空气，空气流量（Q）逐步递增。压力传感器会记录储层底部及针阀内的空气压力。实验采用数码单反相机进行监测，并通过数字图像相关软件DaVis 10.0（LaVision GmbH公司）进行分析，以计算类比材料中的位移与应变场分布。此外，研究人员开展了断裂分析：针对二维实验的侧视图与三维实验的俯视图，分别测量断裂的长度、倾角或走向。基于上述数据，研究人员确定了断裂的开启模式并开展了统计分析，分析结果以玫瑰图（rose diagram）与直方图（histogram）的形式呈现。本数据集包含以下内容：[…]