Abstract: Like the homogenization temperature, the salinity of saline inclusions is also an important basis for fluid activity analysis. Based on the test data of fluid inclusions such as salinity and homogenization temperature, the characteristics of episode combinations and episodic activities of reservoir fluid were analyzed in Fushan sag. The results show that the fluorescence color is abundant, the homogenization temperature is of single peak, and the salinity of saline inclusion is characterized by the trend of first falling, then rising and falling again. The fluid inclusions can be divided into seven combinations, corresponding to the seven fluid activities of the Paleogene reservoir forming period:the first two fluid episodic activities were for early hydrocarbon expulsion, the middle three fluid episodic activities were for hydrocarbon accumulation, and the latter two thermal fluid activities were with higher thermal abnormality. According to the comprehensive analyses, characteristics of hydrocarbon reservoir accumulation analyzed about that it include the single stages of petroleum accumulation, and multiple in filling from various source rocks. The analysis result shows that the reservoir in Fushan sag was formed from 13 to 6 Ma in Neogene. The main period of hydrocarbon filling is consistent with the hydrocarbon expulsion peak, and another centralized filling period is consistent with the period of regional tectonic movement. The active period of abnormal thermal fluid is later than the time of hydrocarbon accumulation. It is considered that the abnormal thermal fluid activity is the main reason for the sudden rise of formation water salinity.

Key words: fluid inclusions, salinity, combination of episodes of fluid inclusions, episodic activities of fluid, accumulation characteristics, Fushan sag