Facies Characterization of the Frade Field Reservoirs and Associated Deposits, Campos Basin, Rio de Janeiro State

Abstract

The Frade Field, located in the northern Campos Basin, corresponds to Oligo-Miocene deep-water reservoirs bracketed between the Azul and Cinza regional markers. Such depositional systems are of great economic significance, representing a large percentage of Brazilian hydrocarbon reserves and production. This paper presents the characterization of the facies that comprise the Frade Field reservoirs and associated deposits. The study included the analysis of 154 m of core from three wells, which are representative of four main field reservoirs. Twelve facies are recognized, of which two are conglomeratic, four are sandy, one is of mixed sand-mud composition and three are heterolithic. The interpretation of these facies indicates a depositional system dominated by the interaction of processes as diverse as debris flows, turbulent flows, bottom currents and slides. The reservoir facies are predominantly bipartite and turbiditic flow sands, whereas the non reservoir facies include mass-transport aprons and cemented debris flow rhodolithic conglomerates, both being very common in the described sequences. Overestimation of hydrocarbon volumes may occur should such facies be inadequately represented. However, when present as interbedded units within the reservoir facies, they generally do not have enough lateral continuity to significantly impair hydraulic connectivity of the reservoir.