Total has started drilling off French Guiana in a wildcat operation being closely watched by environmental groups.

The Ensco DS-9 spudded the Nasua-1 exploration well on the Guyane Maritime permit just before Christmas and operations are ongoing, Upstream has learned

The well site is 170 kilometres north-northeast of the capital Cayenne in about about 200 metre of water.

The location is located on the central part of the 24,000-square-kilometre permit and is testing a different play to that probed by Total’s former partners Shell and Tullow Oil between 2011 and 2013.

Shell and Tullow withdrew after four wildcats failed to confirm the potential of the initially promising Zaedyus find.

Upstream reported earlier this year that the 3D seismic data was acquired over the central zone of the permit in 2012.

Nasua-1 will be drilled on the edge of the abyssal plain, targeting reservoirs at depths below sea level between 4800 and 6000 metres.

The primary targets are Campanian and Santonian sands with a secondary Maastrichtian target.

The cost of the probe is assumed to be around €100 million ($114 million).

Total also holds a major exploration position over the maritime border with Brazil, in the Foz de Amazonas basin.

Brazilian federal environmental regulator Ibama has so far rejected Total’s application for drilling permits, however, after finding fault with the environmental impact survey, particularly on the issue of spill modelling.

Conservation groups have focused on the possible impact that operations may have on a little-studied reef near the mouth of the Amazon river, but Total says such fears are technically groundless.

Total recently invited conservation groups to a special visit to the Ensco drillship to see safety precautions off French Guiana but also warned that there will be a 500-metre exclusion zone around the drillship and five support vessels during drilling.