Evidence for a Working Hydrocarbon System in the Western Barbados area of the Tobago Fore Arc Basin

Snarvold, Halvor; Thomas, Mike; and Sallis, Dick¹
[email protected]

The Tobago Fore Arc Basin lies between Barbados to the east and the Windward Islands to the west and covers an area of some 40,000sqkm. Within this vast area there have only been four wells drilled to date, offshore from Tobago. This drilling has resulted in 2 gas discoveries.

Historically, there has been very little/no exploration undertaken over the majority of the basin for a variety of reasons including lack of available seismic data and available acreage, especially in Barbados. However since ~ 2008, about 3,200 kms of long offset data has been acquired, which has helped to cast light on this under-explored area. Regional seismic lines show up to 10,000 metres of sedimentary section in the basin centre, which could provide ample hydrocarbon source rock kitchens. The existence of the Woodbourne oil field, onshore Barbados, and the results of analysis of sea bed samples from offshore Barbados (indicating the presence of hydrocarbons likely to be derived from the world class La Luna source rock), demonstrate the generation of thermogenic hydrocarbons in the basin.

The good quality seismic data has proved the existence of robust 4 way dip closures, and large stratigraphic plays including updip pinch outs, and large channel system features.

Seismic character suggests an alternating sand-shale sequence, which together with DHI’s such as flat spots, gas chimneys and amplitude anomalies, indicates the considerable potential of the basin.

The recent Centrica discoveries of Cassara and Sanoche to the south of the basin further indicates a working system. These reservoir sands are of local origin in a combined structural stratigraphic trapping configuration. The reservoir rock possibilities exist in Eocene to Oligocene age Orinoco Delta derived sands and locally reworked sands, of Miocene, age from the Barbados Ridge. Reservoir sands equivalent to the reservoir sands in Cassara are also present on the margins of the basin.

Recent significant oil discoveries to the SE in Surinam and French Guyana have led to an increase in exploration activity in the region. We believe it is only a matter of time before the full potential of this overlooked basin is fully appreciated.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013