Abstract Although the exploration and development of tight gas have made great progress, the quantified study on gas migration and accumulation in sweet spots of tight gas reservoir is still limited. In this work, a computer program is developed to conveniently describe the different shape of sweet spots and the fractures in tight reservoir. Then, gas migration and accumulation processes are simulated, and the numerical simulation results are visualized and quantified. Based on the simulation results, the mechanism of gas migration and accumulation in sweet spots is revealed. The results indicate that the migration and accumulation of gas are two relatively independent processes. The gas migration process is determined by the permeability of rocks. The critical condition of gas accumulation in sweet spots is mostly determined by the capillary pressure difference between sweet spots and surrounding rock. The two migration patterns are clearly observed during the numerical simulations. When surrounding rock has seepage capacity for gas, the migration pattern tends to be piston-like displacement; when surrounding rock is impermeable for gas, the gas can only migrate into sweet spots through connected fractures. As a result, the migration pattern for this situation tends to be fingering displacement.

中文翻译：

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致密储层甜点区天然气运聚的数值模拟

摘要 尽管致密气勘探开发取得了长足的进步，但对致密气藏甜点区天然气运聚的量化研究还很有限。在这项工作中，开发了一个计算机程序来方便地描述致密油藏中甜点和裂缝的不同形状。然后，对天然气运移和聚集过程进行模拟，并将数值模拟结果可视化和量化。基于模拟结果，揭示了天然气在甜点区的运聚机制。结果表明，天然气的运移和聚集是两个相对独立的过程。气体运移过程由岩石的渗透性决定。甜点区天然气聚集的临界条件主要由甜点区与围岩之间的毛细管压力差决定。在数值模拟过程中可以清楚地观察到两种迁移模式。当围岩具有渗流能力时，运移方式趋于活塞式位移；当围岩不能渗透气体时，气体只能通过连接的裂缝迁移到甜点区。因此，这种情况的迁移模式往往是指法位移。气体只能通过连接的裂缝迁移到甜点区。因此，这种情况的迁移模式往往是指法位移。气体只能通过连接的裂缝迁移到甜点区。因此，这种情况的迁移模式往往是指法位移。