Sierra Leone partners start deepwater search

Aug. 26, 2009
Drilling is under way on the Venus-B prospect off Sierra Leone, according to Tullow Oil.

Offshore staff

LONDON -- Drilling is under way on the Venus-B prospect off Sierra Leone, according to Tullow Oil. Operator Anadarko contracted the semisub Belford Dolphin to drill the well, which is expected to take 45 days to complete.

This is the first deepwater well in the region, Tullow says, and it hopes to prove a new petroleum system in the deepwater Liberian basin, in the process expanding the western limit of the Jubilee play offshore Ghana.

Tullow is participating in this program following its acquisition this January of a 25% interest in three Liberian offshore blocks, all operated by Anadarko. The partners then commissioned a 6,164-sq km (2,380-sq mi) 3D seismic survey across the acreage. Earlier this month, the Sierra Leone government approved a further transaction, giving Tullow 10% of offshore blocks SL-107 and SL-06/07, again operated by Anadarko.

Once the Venus well is complete, the rig will transfer southeast to Cote d’Ivoire to drill South Grand Lahou, in block CI-105 which is also an analogue of the Jubilee field.

Elsewhere off Cote d’Ivoire, Tullow has committed to acquiring further 3D seismic and to drill one well in CI-103. Here the company has concluded a farm-out to Anadarko, reducing its interest in the block from 85% to 45%.

Offshore Ghana, Tullow’s Mahogany-3 well this January proved a southeastern extension of Jubilee field and discovered another underlying sand named Mahogany Deep. The next appraisal well, Mahogany-4, should get under way next month followed by Mahogany Deep-2 during the first half of 2010.

The Twenoboa-1 discovery, drilled this March, extended the Turonian Jubilee play further west into the Deepwater Tano block. An appraisal well is planned in January. Later in 2010, Tullow expects to spud an exploratory well on the Teak prospect in the West Cape Three Points license.

The company has identified other strong prospects in its deepwater Ghana acreage, some of which may be drilled later in 2010. Numerous large Turonian leads are emerging following analysis of seismic east of Jubilee.