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French Guiana is underlain by the Guiana Shield, one of 3 cratons making up the South American Plate. It is a Precambrian block that forms the major part of the northern highlands and coast in French Guiana, Suriname, Guyana, and parts of Venezuela and Brazil.
The rocks of the Guiana Shield consist of meta-sediments and meta-volcanics with limited sedimentary cover. This cover thickens near the coast and offshore into the Guyana-Suriname Basin. French Guiana has no onshore potential.
Guyana-Suriname Basin - In Jurassic and early Cretaceous times, at the northwestern edge of the Shield off French Guiana and part of Suriname, an area called the Demerara Rise formed the southern extremity of the Central Atlantic Rift and Ocean. Sedimentation here was in an inner shelf environment with continental influxes. In the Early Cretaceous shallow marine to open marine deposition began in response to the opening of the Atlantic Ocean.
The Atlantic Ocean opened east of the Demerara Rise during the Early Cretaceous. Here the continental shelf is narrow with water depths rapidly deepening to 3,000 m. Drilling commenced in 2011 in the hope of finding analogous fields to those discovered in West Africa on the other side of the Atlantic Rift.
Wells identified oil-bearing turbidite fans of Cretaceous age but subsequent drilling has failed to follow up on this success and the whole area remains high risk with a shortage of sufficiently large trapping possibilities.
Globalshift predicts older Mesozoic troughs below the shelf but these have not been drilled and cannot be inferred due to the poor quality of seismic data at depth.
The first wells drilled offshore French Guiana were in 1975 and 1978 on the Demerara Rise. Both were dry holes. After a long break Tullow acquired the Guyane Maritime licence covering an extensive offshore area along the continental slope. This was part of its acquisition of Hardman Resources in 2007.
In 2009, Tullow farmed out a substantial interest to Shell and Total, and a further interest to Shell and operatorship in 2010. A 2,500 sq km 3D seismic programme began in September 2009 targeting the Eastern Slope section of the licence where leads matching the Jubilee field in Ghana were identified. The first well, Zaedyus-1, was commenced in March 2011.
This well proved that similarities with West Africa were present. It encountered 72m of net oil pay in high quality reservoir intervals - a turbidite sand called the Cingulata sand system. However a further four wells (3 appraisal and 1 exploration) in 2012 and 2013 were unsuccessful. No drilling has been conducted since November 2013.
Owing to these later failures and the lower oil price, Globalshift forecasts no new oil or gas production from the country in the short and medium term.
For recent events see News
FRENCH GUIANA: OFFSHORE STRUCTURES
Globalshift.co.uk (source: Northern Petroleum)
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