Conventional continuous multiple medium theories are not suitable for describing the fractured-cavernous carbonate reservoir with big-size fractures and caves. An interpretation model for well test of naturally fractured vuggy reservoir has been developed with consideration of wells drilled outside a big cavity. The model equations are solved with the finite-element method. The analysis of the affecting factors of dynamic pressure at well bottom indicates that the pressure derivative curve of the late stage will go down and form a concave because of the high permeability of the cave. The scale and permeability of the cave mainly affect the amplitude of the pressure derivative reduction. The predicted model has a good agreement with the field test. This can provide a theoretical basis and guidance for well test interpretation of carbonate reservoir.

fractured-cavernous reservoir  /  carbonate rock  /  big-size cavity  /  numerical well test