Abstract: The Ordovician carbonate rocks in Tahe oilield is a complex reservoir with low porosity, low permeability, fractures and vugs, serious heterogeneity as well as variety of fluid properties, along with multiple faults and complicated structural shapes. For fractured reservoir,electrical imaging information can be used to directly or visually reflect the dip or dip angle of fractures and development of vugs and dissolved pores, etc. It is now the most advanced and optimal well log technique applied to fractured reservoirs. In addition, dual laterolog of conventional well log can offer differential amplitudes which may depict characters of fractures to a certain extent. Hence, combination of conventional well logs, electric imaging data and XMAC information could be adopted to identify the reservoir with pores, vugs and fractures. This paper proposes a method of "Weight evaluation” for classification and quantitative evaluation of the Ordovician reservoir in Tahe oilfield on the basis of the actual production situation. By production testing verification, its coincidence rate is up to 92.3%。Furthermore, prediction of lateral distribution of developed thickness of the Ordovician Grade I reservoir is made,and the results accord with real geological conditions of Tahe oilfield. This method is good for extensive application.

Key words: Tahe oilfield, carbonate rock, well log response, reservoir characteristic, prediction