Abstract:

hydrocarbon-bearing sequences have been found in Baimiao structure, located in the central part of Lanliao fault in Dongpu depression. According to the comprehensive analysis of authigenic illite dating and fluid inclusion methods,the reservoiring in Baimiao structure can be divided into 4 stages: the first stage is about in 38 Ma, corresponding to the deposition of 3rd member of Shahejie Formation; as a result of the strong tectonic movement, oil and gas reservoirs would be hard to preserve, so this stage would be of no significance for reservoiring of oil and gas.The second stage is in 28～31.4 Ma, equivalent to the deposition of Dongying formation, which is similar to the first stage.The third stage is about in 25.4～20.4 Ma, relative to the elevation-denudation period after deposition of Dongying formation, the strength of fault movement becomes weak with the pressure decreasing, which is favorable to the reservoiring of oil and gas.The fourth stage is in 2 Ma, which is the readjustment and redistribution period of oil & gas reservoirs.The formation of oil and gas reservoirs in Baimiao structure is closely related to active strength of Lanliao fault. With increasing the active strength, fluid pressure would become higher and higher, and even exceed the rupture strength of rocks; as a result, oil,gas and water would then be expelled in mixed phase; and when temperature and pressure decrease, oil,gas and water would be separated, the reservoirs would then be formed on the upper part of high-pressure system.Owing to this progress going round and round, a special three-storied pressure systems have been formed in Baimiao region.

Key words: authigenic illite, fluid inclusion, reservoiring stages, reservoiring process, Baimiao structure