毛细管力影响下页岩储层液化石油气压裂裂缝网络扩展形态研究

Study on fracture network development of LPG fracturing in shale considering capillary effect

页岩储层中广泛分布着从纳米级到毫米级的多尺度天然裂缝,这些天然裂缝显著影响着压裂后的缝网形态。液化石油气(liquefied petroleum gas,LPG)压裂液具有黏度和表面张力小的特点,在页岩储层中压裂后易形成裂缝网络。针对LPG在页岩储层中的压裂特性,同时考虑了天然裂缝尺寸及压裂液与储层润湿性的影响,建立了LPG压裂裂缝网络扩展模型。通过研究发现,天然裂缝宽度越小、初始长度越长、压裂液润湿性越强,天然裂缝越容易起裂、扩展,形成的裂缝网络形态越复杂,压裂效果越好。

Shale reservoirs are rich in multi-scale natural fractures, ranging from nano scale to macro scale, which deeply affect fracture network propagation. Liquefied petroleum gas （LPG） fracturing fluid features low viscosity and small surface tension and tend to form complex fracture network. Based on LPG characteristics and considering natural fractures width and fracuring fluid wettability, a fracture network propagation model that was suitable for LPG fracturing was built. From the simulation results, it can be concluded that small width natural fracture and strong wettability fracturing fluid lead to easy initiation and propagation of natural fractures and finally result in complex fracture network, which is benefit for shale gas development.