Abstract: The 1^st and 2^nd Members of Shahejie Formation in A oilfield in Shijiutuo uplift,Bohai Bay Basin,are rare proli-fic thick reservoirs with complex lithologies.Six lithologies are identified,mainly including limy sandstones,oolitic dolomites,dolomitic sandstones.There are various factors challenging reservoir description of the A oilfield,including complex lithologies,poor quality of seismic data,and sparse appraisal wells,large difficulty of fan delta reservoir description,and poor understanding of reservoir spatial distribution.This paper applied a well-logging and seismic comprehensive method,i.e.‘four step’ method,using ECS logging,core and seismic data.It consists of reservoir rock typing based on sedimentary facies,sedimentary modeling based on paleo-geomorphy restoration,reservoir framework reconstructing based on fine isochronous stratigraphy and reservoir prediction based on facies constraints.By using this four step method,sandbodies of 5 phases are identified and mapped in the 1^st and 2^nd Members of Shahejie Formation.In addition,good-quality reservoirs are predicted by using seismic technique,and 9 new development wells are proposed for emplacement on the Ⅰ-2 sand body with type Ⅰ reservoirs.This ‘four step’ method is very useful in estimating producible oil reserves,layer division,and well pattern optimization in similar oilfields.

Key words: thick-layer, complex lithology, paleo-geomorphology, sedimentary model, isochronous stratigraphy, reservoir typing, Bohai Bay Basin