Complex hydraulic-fracture-network propagation in a naturally fractured reservoir

摘要

The formation of a complex hydraulic fracture network in a naturally fractured reservoir is strongly influenced by the distribution of pre-existing natural fractures and the interaction performance of multiple fractures. A numerical model containing a large number of (3120) pore pressure cohesive elements is built for modelling the randomly crossing and branching of hydraulic fractures. The effects of the distribution and cementation strength of pre-existing natural fractures on the propagation of complex hydraulic fracture networks are investigated. The interaction of multiple fractures and the interference effect among adjacent hydraulic fracture branches are also interpreted. The natural fracture is fractured before the hydraulic fracture tip reaches it when the cementation strength of natural fracture is low. The complexity of the hydraulic fracture network could be significantly affected by the cementation strength of pre-existing natural fractures and their distributions. Complex hydraulic fracture networks require much higher injection pressure than that for relatively regular fractures. Hydraulic fracture branches restrict the development of the fracture in length, but promote the formation and development of the complex hydraulic fracture network.