Reservoir characteristics and controlling factors of the Paleogene Sha-2 member in 36-3 structure,Eastern Shijiutuo uplift,Bohai Sea
Various data including core description,conventional thin sections,casting thin sections and SEM,in combination with conventional physical properties of reservoirs and exploration results,were used to systemically analyze reservoir poroperm characteristics,reservoir space types and influencing factors of reservoir properties of the 2nd member of Shahejie Formation.The study indicates that Shahejie Formation reservoirs are mixed carbonate/siliciclastic rocks dominated by bioclastic dolostone with thin sandy conglomerate interbeds.The poroperm characteristics are very good,with average porosity of 27.6% and permeability of 442×10-3μm2.The reservoir spaces are dominated by primary pores(mostly intergranular pores and skeletal pores)and secondary pores.Sed-imentation and diagenesis are the two key factors controlling the physical properties of reservoirs.Dissolution and dolomitization contribute to high quality reservoir spaces.In addition,the distribution of high quality reservoirs is also delineated.It is believed that dolostone reservoirs are favorable for hydrocarbon accumulation,thus are potential exploration targets in the future.