ブラジルカンポス堆積盆地の石油システム評価

Abstract

The Campos Basin, offshore Brazil, is a typical passive margin basin in the western South Atlantic, and the most prolific basin with about forty producing fields including deep-water giant fields. The Campos Basin is currently responsible for more than 80% of Brazilian oil production.The hydrocarbon accumulations are distributed throughout the stratigraphic column of the basin from Neocomian to Miocene. The most important oil accumulations in the basin are associated with deep-water fans distributed in the stratigraphic column from Cenomanian to Miocene. Almost all the hydrocarbon accumulations discovered to date are sourced mainly from Barremian to early Aptian lacustrine shales of the Lagoa Feia Formation in the pre-salt sequence. The oil pooled in the post-salt sequence migrated through a system associated with pre-salt normal faults, “salt windows” in the Aptian evaporite, listric faults and regional unconformities.The play fairway map was made based on considering the basement and the salt development, the fault distributions and the kitchen area. This map presented that the Campos Basin was divided into five structural zones. These zones could be closely related to the hydrocarbon potential. It was evaluated that the eastern part of Zone I and Zone IIa along the present day shelf edge provided more favorable condition for the hydrocarbon accumulation than other zones. The oil of Marlim Sul field is trapped in the blanket turbidites that pinch out toward the northwest landward. The thick mud deposits derived from the muddy turbidites was considered to be the important factor for establishing the stratigraphic trap.