Abstract: The lithologic feature, spatial type and reservoir quality in Yingshan carbonate reservoir of Middle-Lower Ordovician in Yuqi area of Tarim basin are analyzed comprehensively by using core observation, cast thin section, cathodology, SEM, porosity and permeability analysis and mercury injection method, etc., and the reservoir is synthetically evaluated then. The results show that the main rock types in Yingshan formation are micritics, calcarenite and dolomite, of which, micritics and calcarenite have the best development and the widest distribution. The carbonate reservoirs belong to cave, fracture-pore and fracture types with intermediate physical property. The cave reservoir develops widely in the west slope of Yuqi area, but cave filling is very compact. Fracture-pore reservoir is relatively a better kind of reservoir. The key factors influencing the reservoir quality are structure, karst and diagenesis. The favorable reservoirs are distributed along Wellblock YQ2 -YQ3 -YQ4 -LN13 in western Yuqi area. This conclusion provides an important theoretical basis for the next exploration in Yuqi area and its vicinities where carbonate rocks are partially eroded.

Key words: Tarim basin, carbonate rock, reservoir, characteristic, evaluation