Tullow said the Carapa well in the Kanuku offshore block contains oil with less than 1% sulphur content and is indicated to be 27 degrees API, a reading which measures oil density versus water and pointed to medium sour crude.

“The thinness of the oil column, combined with no information on the quality of the reservoir, suggests to us this is not commercial,” Canaccord analysts said in a note.

The London-listed firm said it had struck the oil at about 4 meters of net pay, which analysts believe is unlikely to be commercially viable.

Guyana, a global exploration hotbed, has become an increasingly important region for Tullow after a series of missteps at its flagship fields in Ghana and projects in Kenya and Uganda have also run into delays.