The key geological factors determining fracturing effect in north Z23 ultra-low permeability reservoir are analyzed based on the fine geological model of reservoir established by using the Petrel software. According to the key geological factors（ reservoir thickness

permeability）

the target layers of sand unit 1

2 and 3 are classified into four types. Fracturing parameters of eight reservoir types are optimized by using numerical simulation and ENPV methods based on the fine geological model. The results show that the fracturing parameters vary greatly for reservoirs with intense heterogeneity. To obtain ideal productivity

long fractures are needed for the low permeability reservoir

while fractures with high flow conductivity is needed in reservoirs with relative high permeability. Field test shows that the hydraulic fracturing with fracture parameters optimized by using this method is effective.