Abstract: On the basis of research of control factor and distribution characteristic of the karst weathering crust development of Lower Ordovician carbonate rocks in Tazhong area, integrated with conventional well logs, the karst is divided into hypergene karsts, vertical percolation karsts and horizontal underwater current ones. Also, the electric imagine chart and the log response mode are built up using natural gamma ray spectrometry logs, dual laterologs and porosity logs. The lateral correlation study of the karsts in 4 wells is conducted.

Key words: Tarim basin, Tazhong area, carbonate rock, weathering crust, karst, log response