Fractured-vuggy reservoirs originated from the development of paleo-karst fractured-vuggy system are the basic geological units for hydrocarbon accumulations of fractured-vuggy type.Importance should be attached to the connectivity within a fractured-vuggy reservoir and that among different fractured-vuggy reservoirs during the development of this kind of reservoirs

i.e.fractured-vuggy units are the basic development units of fracturedvuggy pools.However

both domestic and overseas literatures failed to offer a clear definition for fractured-vuggy reservoir and fractured-vuggy unit and the research on fractured-vuggy unit division still needs to be carried on. Taking the Ordovician fractured-vuggy pool in Tahe oilfield as an example

this paper presents basic concept and distribution mode for fractured-vuggy units and proposes principles and methods for their division.After the study on fractured-vuggy reservoir distribution

fluid properties and well productivity and inter-well connectivity in Tahe oilfield

the paper defines fifteen fracture-vug units in the principle producing area of the field

providing useful references for further development adjustment and management of the field.