The triassic reef in Sichuan Basin is the key period of the transition from ocean to land in upper Yangtze area. It has deposited a large set of carbonate rocks and evaporite rocks. Northeast parts of Sichuan Basin is a favorable area of triassic potassium, which has good potassium forming conditions and rich potash mineral resources, mainly of polyhalite. At present, the logging evaluation of traditional polyhalite mainly focuses on the response characteristic analysis and qualitative identification, while the quantitative evaluation method and regularities of distribution are few. With the discovery of a new type of polyhalite -- "salt crystal grain polyhalite rock", this paper is based on the idea of "oil and potassium co-exploration", Based on the existing drilling and logging data of puguang gas field, six kinds of key lithological sensitive information and logging identification patterns are implemented in puguang gas field of Sichuan Basin. In this paper, the methods of curve overlap and crossplot, potassium-thorium ratio are proposed to carry out the qualitative identification of polyhalite, to implement the development and regularities of distribution in the study area. It has the characteristics of large transverse variation and local enrichment, and there is a certain coupling relationship with the regional structure. The model of calculating rich potassium mineral by gamma spectral difference analysis is proposed. The potential of sylvite mineral resources in northeast of Sichuan Basin has been identified through the research on the logging evaluation and regularities of distribution, providing technical support for exploration and exploitation.