Shell said in a statement that it was too early to put a figure on the reserves discovered along with venture energy partners Total, Tullow and Northpet but said that the first results were "encouraging".

"As part of the Tullow-operated joint venture, Shell today confirms an oil discovery in the Guyane Maritime permit approximately 150-kilometres offshore

French Guiana."

"The GM-ES-1 well... to date has drilled to a depth of 5,711 metres."

Shell's executive vice president Exploration and Commercial, Dave Lawrence, said the company was "pleased with the preliminary results of this first ever deepwater well offshore French Guiana.

"We are early in the evaluation, but the initial results are encouraging for this new play. The joint venture will continue to drill ahead, evaluate the well results, and determine next steps," he added in the statement.