Abstract: The oil and water two-phase flow equation is established based on generalized Darcy's law, with which the effect of permeability anisotropy on the pressure calculation element selection after whole hydraulic fracturing is simulated and it is found that obvious errors may exist by conventional element selection method. Considering the formation permeability anisotropy and artificial fracture arbitrary angles, etc., a new method for such a selection suitable for five-spot, nine-spot and inverted nine-spot well patterns is proposed. The simulation indicates that calculation element selection is reasonable and the important analyzing wells within the element are of high calculating accuracy, which provides theoretic reference for complex anisotropy low permeability reservoir development by whole hydraulic fracturing process.

Key words: low permeability reservoir, anisotropy, hydraulic fracturing, calculation element, simulation