The characteristics and development pattern of carbonate buried hill reservoirs in the Southern Bohai Sea:a case study of Bozhong 28-29 Area
The spatial distribution of carbonate buried hill reservoirs in the Bozhong 28-29 Area of the Southern Bohai Sea is complex.Based on drilling,logging,core,thin section,and seismic data,the characteristics,main controlling factors,and development patterns of carbonate reservoirs in buried hills are analyzed.The results show that the buried hills in carbonate rocks have two sets of reservoirs devel-oped from surface karst and buried karst,with vertical zonation characteristics.Limestone and dolomite in the surface karst zone can serve as favorable reservoir rocks,controlled by structural fracturing and dissolution.Limestone reservoirs can develop within a range of 0-380 m from the buried hill surface,forming a wide band effect,while dolomite reservoirs generally develop within 0-100 m from the buried hill surface,with relatively thin reservoirs.The development of reservoirs in the buried karst zone is closely related to lithology,with limestone being relatively well developed.The development of reser-voirs in buried karst is mainly due to structural fracturing,followed by dissolution,with dissolution pores present in microcrystalline limestone and above.There are differences in the formation of frac-tured reservoirs in the surface karst zone and buried karst zone,with structural fractures being predomi-nant in the buried karst zone,while the surface karst zone exhibits a combination of karst pores and structural fractures,controlled by structural units and positions.The high position of the surface karst zone on the buried hill and the east-west trending main fault uplift anticline fold zone is a favorable area for the development of pores and fractures.The results have guiding significance for the next explora-tion of the carbonate buried hill reservoirs in the southern part of Bohai Sea.
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