Abstract: Traditional reservoir numerical simulation software just only consider the static fractures but cannot simulate the impact of fracture expansion on well network development during long-term water injection, and the simulation results are poorly fitted to the actual production dynamic data. To address this problem, a characterization method for complex dynamic fracture networks is developed based on the embedded discrete fracture model (EDFM) with dynamic improvement of pre-processing algorithms. The study shows that an efficient waterflood-induced fracture simulation method is established by coupling cross-fracture discrimination criteria, which can efficiently simulate the dynamic changes of fractures during reservoir injection and development and reflect the influence of natural fractures on the main fracture propagation path; the results are consistent compared with Abaqus software, while the computational efficiency is higher. The application example shows that the method has good adaptability for numerical simulation of waterflood-induced fractures, can accurately achieve the fitting of the water cut rising rules of the field water injection well cluster, which and has good reference significance for production dynamic analysis of ultra-low permeability reservoirs and later well pattern adjustment.

Key words: ultra-low permeability reservoir, waterflood-induced fracture, cross fracture, numerical simulation