Characteristics and controlling factors of metamorphic buried hills fractures in Bonan Low Uplift,Bohai Sea Area
Regarding the terrestrial fault basin of the bedrock buried hill,the degree of fracture develop-ment plays a key controlling role in the formation of this type of buried hill reservoir.Taking the re-cently discovered over 100 million ton bedrock buried hill oilfield in Bohai,the BZ 26-6 oil and gas field,as an example,this study comprehensively utilizes drilling seismic logging,and analytical data to clar-ify the characteristics of fracture development in metamorphic rock buried hills,explore the main con-trolling factors affecting fracture development,and establish a reservoir development model.The results indicate that the main reservoir lithology of the buried hills in the study area is the Archean metamorphic granite,and the storage space type is mainly structural fractures.At the same time,dissolution pores formed along the fractures are developed.Vertically,the buried hill reservoirs can be divided into weathered fracture zones and bedrock fracture zones.The development of buried hill reservoirs is mainly controlled by lithology,structure,and weathering.The 90％of the rocks in the study area are meta-morphic granite rich in felsic minerals,which are the dominant lithology for fractures development.The strong compression orogeny during the Indosinian period provided key impetus for the development of buried hills fractures,and the differences in structural positions controlled the heterogeneity of reservoir development on the plane.The Yanshanian strike slip movement further formed new NE oriented frac-tures,resulting in the development of local fractures.The continuous exposure of the buried hill has caused weathering and leaching within 220 m from the top surface,significantly improving reservoir quality and controlling the vertical zoning of the buried hills reservoir.This result provides a reference for oil and gas exploration in the Bohai Bay Basin and other similar metamorphic buried hills.
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维普
