Abstract: After 60 years of exploration, over 70% of the resources have been discovered in Qianjiang Sag. The exploration degree of conventional sandstone oil reservoirs is high. Saline lacustrine carbonate rocks deposit with a low degree of research and exploration, which is a potentially important area for increasing reserves. In this study, by strengthening the basic research of lithofacies and logging interpretation,the old well data are re-recognized. It is considered that the lacustrine carbonate rocks of Qianjiang Formation are deposited several layers in vertical direction, which cumulative thickness is more than one hundred meters.Four main rock types are identified: granular carbonate,micritic carbonate, mixed granular rock and mixed fine grain rock. The favorable areas of carbonate rocks are zonally distributed. Study shows that shale, micritic carbonate and mixed granular rock are high-quality source rocks of Qianjiang Formation, granular carbonate and granular mixed rock are high-quality reservoirs. The carbonate reservoir of the Qianjiang Formation has the characteristics of ‘lithofacies control reservoir, reservoir physical property control rich’ oil enrichment controlling factors. Researching new insights guides the exploration in lacustrine carbonate reservoirs, significant achievements have been made in Tan Kou and Zhong Shi area, confirming a total resource volume of carbonate reservoir Over 100 million tons, becoming a new area of succession for exploration and reserve enhancement. It is an important guide and reference for deepening the oil exploration of salina lake carbonates in Jianghan Basin, as well as expanding the exploration of new areas in the similar faulted basins in the east.

Key words: Qianjiang Sag；saline lake；Qianjiang Formation, carbonate reservoir；oil accumulation recognition, exploration breakthrough;important implications