The Ordovician in Tahe oilfield are rich in oil and gas resources.It develops caves

vugs and fractures filled with different materials due to karstification.Different reservoir spaces and fillers form a variety of fracture-vug complex types.So the conventional logging responses are complex and it is very difficult to identify the fracture-vug complex types.Based on outcrops

cores

borehole image logging data

six fracture-vug complex types are determined.They are unfilled cave type

sand and shale-filled cave type

breccias-filled cave type

calcite-filled cave type

fractured-vuggy type and fractured type

respectively.In combination with the differences of lithologies and physical properties between different fracture-vug complex types

their characteristics of dual lateral

natural gamma

sonic

neutron and density logging and distribution patterns are analyzed.Nine crossplots sensitive to fracture-vug complexes are selected from the pairwise logging response cross plots and are integrated with decision tree to formulate a step by step fracture-vug complex type identification method.This method is applied to real well data processing and interpretation in Tahe oilfield.Compared with of cores and geologic logging

the coincidence rates of the identification results with core and geologic logging data are greater than 85%.The method can reduce the confusion among the conventional logging responses of different fracture-vug complex types

thus increase the accuracy of identification results.