A 2D Hele-Shaw cell was built to study microfracture nucleation, growth, and network formation during internal fluid production. Fluid is slowly produced into a low permeability solid, which leads to a local fluid pressure increase that controls the nucleation of microfractures that grow and then connect to create flow pathways. This process occurs during the primary migration of hydrocarbons in source rocks, which is the main topic of our study. It may also occur in other geological systems, such as the expulsion of water during dehydration of clay-rich sediments in sedimentary basins or serpentinite rocks in subduction zones and the transport of magmatic melts. Our system consists of a transparent, brittle gelatin material mixed with yeast and sugar. The consumption of sugar by yeast leads to CO₂ formation, resulting in microfracture nucleation and growth. We varied three parameters, (1) anisotropy (i.e., number of layers), (2) lateral sealing, and (3) rate of fluid production. We tracked fluid movement through the opening and closing of microfractures within the system. Microfracture nucleation density is similar in a layered system to previous studies (0.45 microfracture per cm²). However, we observed that lateral confinement (0.31 microfracture per cm²) and rate of expulsion (0.99 microfracture per cm²) affect nucleation density and the geometrical characteristics of the microfracture network. The size, extent, and geometry of the microfracture network are dependent on all three parameters investigated, where lateral confinement and a higher rate of expulsion result in greater microfracture network connectivity. Layers control the angle of intersection between microfractures. Furthermore, layering and sealing have an impact on fracture topology. Results also show that the microfracture pattern significantly influences the fluid expulsion rate. Our results have direct applications to understanding how fluid migration occurs in low-permeability rocks through the development of a connected microfracture network produced by internal fluid generation.

构建了一个 2D Hele-Shaw 单元来研究内部流体生产过程中的微裂缝成核、生长和网络形成。流体缓慢地产生为低渗透性固体，这导致局部流体压力增加，从而控制微裂缝的成核，这些微裂缝生长然后连接以形成流动通道。这一过程发生在烃源岩中烃类的初次运移过程中，这是我们研究的主要课题。它也可能发生在其他地质系统中，例如沉积盆地中富含粘土的沉积物或俯冲带中的蛇纹岩岩石脱水过程中的水分排出以及岩浆熔体的输送。我们的系统由透明、易碎的明胶材料与酵母和糖混合而成。酵母对糖的消耗会产生 CO ₂形成，导致微裂缝成核和生长。我们改变了三个参数，（1）各向异性（即层数），（2）横向密封，和（3）流体生产速率。我们通过系统内微裂缝的打开和关闭来跟踪流体运动。层状系统中的微裂缝成核密度与以前的研究相似（每 cm ² 0.45 个微裂缝）。然而，我们观察到横向限制（0.31 微裂缝/cm ²）和排出率（0.99 微裂缝/cm ²) 影响形核密度和微裂缝网络的几何特征。微裂缝网络的大小、范围和几何形状取决于所研究的所有三个参数，其中横向限制和更高的排出率导致更大的微裂缝网络连通性。层控制微裂缝之间的交叉角度。此外，分层和密封对裂缝拓扑结构有影响。结果还表明，微裂缝模式显着影响流体排出速率。我们的研究结果可直接应用于了解通过内部流体生成产生的连接微裂缝网络的发展如何在低渗透率岩石中发生流体迁移。