In a statement today, minority stakeholder Roc Oil said the Chinguetti-18 had this morning been drilled and cased to a depth of 1833m. The Atwood Hunter rig was currently preparing to drill ahead in a 12¼-inch hole.

Spudded on December 29, the well is expected to reach a total depth of 2912m and be completed by the end of next month.

Chinguetti-18 is located within the southern part of the oil and gas field in 819m of water, about 80km southwest of the Mauritanian capital Nouakchott.

It is the first well in a $100 million program designed to boost faltering production at the Chinguetti oil project.

The $US700 million ($A930 million) Chinguetti field originally started pumping more than 70,000 barrels of oil per day (bopd) when it first came onstream in late February last year. Output then declined steadily before stabilising around 31,000bopd in the September quarter.

Roc said it would not issue any further drilling updates until operations at the well are completed.

The Chinguetti joint venture comprises Woodside (47.38448%), Hardman (19.008%), Société Mauritanienne des Hydrocarbures (12%), BG (10.2344%), Premier group companies (8.12328%) and Roc Oil (3.24984%).