Reservoir characteristics and favorable target prediction of the Jishan sandstone in the middle segment of the third member of the Shahejie Formation,Linnan Subsag
The Jishan sandstone in the middle segment of the third member of the Shahejie Formation of Paleogene in the Linnan Subsag of Bohai Bay Basin has a large potential for oil resources,but at present,the law of reservoir distribution in this area is unclear,which seriously restricts the subsequent development of the reservoir.Based on the basic data of drilling,logging,and seismic,and guided by the theory of seismic sedimentology and reservoir geology,the reservoir genetic types of the Jishan sandstone in the middle segment of the third member of the Shahejie Formation are analyzed,the favorable reservoir characteristics are defined,and their distribution is predicted.The study shows that the Jishan sandstone in the middle segment of the third member of the Shahejie Formation in the Linnan Subsag is a delta-turbidite fan sedimentary system,with microfacies types dominated by underwater distributary channels and estuarine dams,the development of sheet sand at the edge,and turbidite in the sag zone.The reservoir rock types are massive lithic fine sandstone,lithic siltstone,and pebbly sandstone,poorly sorted and rounded,with an average pore-throat radius of about 0.5 μm.The sandstones for estuarine bar and underwater distributary channel genesis have large thicknesses and good physical properties,which are favorable reservoir types.The application of RGB fusion reservoir inversion with three types of seismic attributes,namely,root-mean-square(RMS)amplitude,effective bandwidth,and phase spectrum corresponds well with the actual drilling situation,and can accurately predict the favorable reservoir distribution,which has important significance in guiding further exploration and development of the reservoirs in this area.
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