Abstract:  In order to clarify the sedimentary characteristics and development model of evaporite in the Gaotai Formation in eastern Sichuan basin, the sedimentary model of evaporite and its relationship with oil and gas are discussed based on field observation, core description, thin section identification ,well logging and seismic data. The results show that: 1) The evaporites are mainly gypsum dolomite, gypsum rock and gypsumsalt rock, and there are two kinds of evaporite lithologic assemblage sequence: Gypsum lagoon and mixed lagoon. The evaporite thickness gradually increases from the west to the east. The sedimentary centers are located in the Wuxi line of Jianshen 1 Well area and the Shizhu line of Taihe 1 Well area, respectively. 2) Evaporite was formed in gypsum lagoon and mixed lagoon under the combined action of arid and hot paleoenvironment, closed environment formed by barrier beach, periodic fluctuation of seawater and provenance recharge, that is, sourcingcontrolled multilagoon genetic environment. 3) There is a negative correlation between the thickness of Gaotai Formation evaporite and the distribution of Longwangmiao Formation reservoir, that is, thick evaporite controlled the low gas reservoir, thin evaporite controlled the high gas reservoir. 4) The reservoir cap assemblages with evaporative rocks as cap formations include subrock reservoirs of mixed lagoon and interrock reservoirs of gypsum lagoon. The subrock reservoirs of thin evaporative rocks have large gas bearing scale, and the interrock reservoirs are of strong heterogeneity and thin thickness, showing the characteristics of mediumlow porosity and low permeability in general. Three favorable exploration zones for natural gas are developed in the study area. They are located in northern, central and southern regions, respectively, and are potential reserve exploration areas in the eastern Sichuan basin.

Key words: evaporite, eastern Sichuan basin, Gaotai Formation, gypsum lagoon, mixed lagoon, sedimentary model