Sedimentary System Characteristics And Prediction Of Dominant Facies Zones Of Key Strata In Santos Basin Of Brazil

As a very important oil and gas producing area along the southeastern coast of Brazil,the Santos Basin has experienced three major sedimentary tectonic evolution stages,including the rift stage,the transition stage and the passive continental margin stage.In the transitional stage,a thick layer of evaporative salt rock is deposited in the basin,and the basin stratum is divided into pre-salt stratum and post-salt stratum.In this paper,in the sequence stratigraphic framework,using seismic and logging related data,combined with previous research results,the sedimentary system characteristics and favorable exploration zones of Barremian-lower Aptian(SSQ1)and middle Aptian(SSQ2)stratum?upper Cretaceous Cenomanian-Maastrichtian(SSQ5)and Paleocene-Eocene(SSQ6-SSQ7)stratum are analyzed and studied respectively,and relevant knowledge is obtained: Lakes,deltas and carbonate platforms are the main type of sedimentary facies in the presalt target stratum,and further subdivide the main subphase and microphase types.Delta and marine deposits are the main type of sedimentary facies in the post-salt target stratum,and in marine sediments,five sedimentary types are further identified and classified: coastal-shallow marine deposit,bathyal-pelagic deposit,mass transported deposits,feeder channel and turbidite blossom deposition.Through the comprehensive analysis of relevant data,the characteristics of sedimentary system and space-time evolution of key horizons are clarified.Then,a sedimentary model of isolated lacustrine carbonate platform was established in the pre-salt,which was mainly controlled by the unique tectonic pattern during the period of the basin,and also related to factors such as the climate of the period,water environment and microbial action;A delta-turbidite fan deposition model was established in the post-salt,which was mainly caused by the superposition of multiple factors such as basin tectonic movement,global sea level change relationship and river system.Finally,after comprehensive studies,it is forecast that the profitable exploration areas are primarily in the structural Highlands in the central part of the basin in the pre-salt,and the favorable exploration areas are mainly in the northern,central and southwestern parts of the basin in the post-salt.