Abstract: With the development of Fuling shale gas field production,the marine shale reservoirs in Fuling Gas Field show obvious heterogeneity and complex lithology. Based on the comprehensive and accurate ECS(Elemental Capture Spectroscopy Sonde)special well logging data of Wufeng-Longmaxi Formation shale,the siliceous component sources were analyzed,and according to the ECS special well logging data and thin section,combined with the different sources of siliceous components,the ternary diagram of shale mineral component was established to accurately divide shale lithofacies. The log response characteristics of different shale lithofacies were analyzed by using conventional logging data,and uranium-free gamma ray and density logging which are sensitive to shale lithofacies were selected to establish shale lithofacies identification logging plate. The result shows that the shale facies identified by conventional logging data is in accordance with the recognition results by ECS special logging data. When the TOC mass fraction of Wufeng-Longmaxi Formation shale is greater than 2%,the source of siliceous components is dominated by biogenic factors,when the TOC mass fraction is less than 2%, the source is mainly terrigenous debris. Eight kinds of lithofacies of Wufeng-Longmaxi Formation shales were identified,including siliceous shale,mixed siliceous shale,clay-rich siliceous shale,carbonate-rich siliceous shale,mixed shale,argillaceous-silty mixed shale,clay-rich silty shale and silty-rich argillaceous shale. The most favorable shale lithofacies was defined as the siliceous shale and mixed siliceous shale with high siliceous content and high TOC content. The result could effectively improve the accuracy and practicability of shale lithofacies classification and it is significant for the efficient development of shale gas resources.

Key words: viscoelastic wave equation, Q model, imaging condition, finite difference;amplitude-preserved migration, data processing