Chronological characteristics of metamorphic buried hill strata and main controlling factors of reservoir development in the middle and northern section of Liaoxi Uplift,Bohai Bay Basin
Precambrian metamorphic buried hill is developed in the middle and northern section of Liaoxi Uplift.Accurate age deter-mination of buried hill,lithology and main controlling factors of reservoir development are inevitable for the fine exploration of buried hill.Results of mineral quantification analysis and zircon U-Pb dating show that Precambrian metamorphic rock in the middle and north-ern section of Liaoxi Uplift can be further subdivided into Archean metamorphic granite and Palaeoproterozoic metamorphic granite,which are different in lithology and mineral composition.The middle part represented by the buried hill of J25-AS is dominated by meta-morphic granite rich in feldspar and hornblende,with the formation age of 2 506-2 529 Ma during the Archean era,and the northern part represented by the buried hill of J20-B is dominated by metamorphic granite rich in quartz and biotite,with the formation age of 2 477-2 497 Ma during the Paleoproterozoic era.According to mineral composition,crack development and dissolution degree,Pre-cambrian metamorphic granite reservoir in the middle and northern section of Liaoxi Uplift can be divided into three types:medium dark mineral content dominated by hornblende-crack development-strong dissolution,low dark mineral content-strong crack development-weak dissolution,and high dark mineral content dominated by biotite-crack filling-weaker dissolution,among which the first and sec-ond types are conducive to the formation of effective reservoir.The effective reservoir development of Precambrian metamorphic rock in the middle and northern section of Liaoxi Uplift is mainly controlled by three important factors of dark mineral content and type,weath-ering and eluviation,and tectonism.Dark mineral content and type are the core controlling factors,followed by weathering,eluviation and tectonism.
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