Characteristics of deep water depositional system in Campos basin, Brazil

Abstract

Abstract To make clear about the sedimentary facies types and distribution of deep water sandstone reservoirs in Campos basin of Brazil, this paper researches the characteristics of deep-water sedimentary system in Campos basin through the comprehensive analysis of drilling, logging and seismic data. There are 3 subfacies and 7 microfacies in the study area. There are 3 channels from south to north in Upper Cretaceous Maastrichtian, and the sedimentary incised valley and compound channels developed in micro-salt basin are the main deep water depositional types. The Paleocene to Eocene dominated by sedimentary incised valley and eroded compound channel deposits, also include 3 channel systems. From Oligocene to Miocene, the main deposition type is lobe, which is mainly distributed in central-north of the basin. Corresponding to deep water depositional stages, 3 kinds of depositional models are found. From Turonian to Maastrichtian of Upper Cretaceous, with tectonic uplift, strong source material supply, and the negative topography produced by salt rock movement providing favorable accommodation for sand deposition, the depositional model was terrigenous direct feed mechanism with sedimentary incised valley and compound channels in micro salt basin. From Paleocene to Eocene, as the amplitude of tectonic uplift reached the maximum and the accompanied erosion peaked, accommodation space offered by micro salt basin was leveled up; the depositional model was terrigenous direct feed mechanism with sedimentary valley and incised compound channels. From Oligocene to Miocene, because of sable tectonics, sea level fluctuation is the main controlling factor for deep water deposition, so the depositional model was wide shelf indirect feed mechanism with bypass incised valley and lobe. The analysis of the characteristics and controlling factors of the 3 types deep-water sedimentary systems during 3 different stages in Campos Basin can provide valuable reference for the oil exploration in deep-water deposits in the Campos Basin and across the world.