Abstract: The reservoir lithology of upper Xia ga nchaigou oil reservoir in Ga sikule a rea of Qingha i Oilfield dominates in a lga limestone, with strong a nisotropism a nd change of physica l property.The stora ge spa ce types include primary porosity, secondary porosity and fra cture. Due to FMI technique ha ving the advantages of highresolution and a lot of geological information, it ca n be used to recognize, differentiate and evaluate alga limestone, siltstone a nd limestone reservoirs. The FMI image of alga limestone reservoir features in floc or cloud-like, outer boundary being not straight, a symmetry interna l structure, disorder bedding, loca l dissolution; T he FMI ima ge of siltstone reservoir and calca reous siltstone features in bright-yellow, brown-yellow strip; and The FMI image of limestone and ma rlite features in white,bright-yellow a nd white bla ck interbedded strips. Open fracture a nd highly conductive fracture show as dark sinusoidal curve on the FMI image, and high resistivity fracture shows a s brightyellow and white sinusoidal curve on the FMI image. More developed fractures, better permeability of reservoir has.The dissolution fracture shows a s locally enla rging a long the fracture, dispersed stellar or beaded dark spot on the FMI image.

Key words: FMI logging, a lga limestone, oil reservoir, reservoir;eva luation;Qaidam Ba sin