--> Opportunities and Challenges in the Upper Cretaceous Turbidite Channel Play, Foz do Amazonas Basin, Equatorial Margin of Brazil

AAPG/SEG International Conference & Exhibition

Datapages, Inc.Print this page

Opportunities and Challenges in the Upper Cretaceous Turbidite Channel Play, Foz do Amazonas Basin, Equatorial Margin of Brazil

Abstract

Abstract

Foz do Amazonas is a frontier basin on the north-western part of the Brazilian Equatorial margin. The Zaedyus oil discovery across the border in French Guyana in 2011 proved the validity of the Upper Cretaceous turbidite play on the South American side of the Atlantic Ocean but the follow up drilling campaign was disappointing, with trapping mechanism being one of the critical issues. In 2013, Premier Oil and its partners, QGEP (operator) and Pacific Rubiales were awarded an exploration licence for Block FZA-M-90. 11,000 km2 of multi-client 3D seismic recently acquired in this area has resolved the deep water reservoir systems. Mapping these systems, for the first time, has allowed a detailed description of the reservoir architecture and provided insights into the understanding of trapping geometries.

New broadband 3D seismic revealed a thick syn-rift mega-sequence overlain by transitional and drift megasequences. In blocks FZA-M-90 and FZA-M-127 the syn-rift sediments are uplifted forming a large structure (“Oscar High”) that controls the orientation of the channel systems. Seismic facies analysis implies that the overlying drift sequence is largely composed of Upper Cretaceous slope channel complexes (Limoeiro formation). The overlying Paleocene/Oligocene sequence is represented by opaque seismic facies and is interpreted to be more mud prone, being the deep water equivalent of the shelfal Amapá carbonate platform, and provides the top seal for the play. In some areas, however, the top seal is compromised by the deep Middle Miocene erosional unconformity caused by a pulse of clastic sedimentation.

The superb imaging by the new 3D broadband seismic allows detailed interpretation of channel bodies revealing their internal architecture. The individual channels are up to 300m wide and can be traced updip to the paleoshelf/slope break. The channels complexes extend across the licenced acreage and terminal fans are not present within the block. The channel shapes vary from linear to sinuous but splays are rare. Lateral traps rely on a facies change within the channel complex. Seismic attribute mapping also shows that the majority of the channels are inter-connected incising one another. Identifying individual leads and prospects of economic size represents one of the main challenges in this play.