Using the Atwood Hunter drilling rig, Woodside started drilling the Chinguetti-18 well on Friday, December 29, and expects the well to reach a total depth of 2912m and be completed by late February.

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.

Further infill drilling is expected to wait until after a 4D seismic dataset is interpreted.

Woodside decided to create the 4D dataset by analysing existing and new 3D data to understand fluid flows better and to optimise the location of future wells, in an attempt to offset the unpredicted production decline at the field.

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. Output then declined steadily before stabilising around 31,000bopd in the September quarter.

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%).