Africa’s west coast as a whole is getting serious competition from its east coast cousin, where a surge of exploration success has resulted in giant gas discoveries offshore Mozambique, Tanzania, and Kenya.

However, it is still mainly proven deepwater oil plays with large associated gas resources that the west coast can offer, along with an established logistical and supply network. With the outstanding success of early fast-track developments in countries such as Ghana led by independents Tullow Oil Plc, Anadarko Petroleum Corp., and Ophir Energy Plc, an increasing number of new entrants has been encouraged to join the party, tempted by the open access and relatively attractive leasing terms.

This has fueled growing activity in previously underexplored acreage offshore Ghana, Gabon, Sierra Leone, Liberia, Equatorial Guinea, and the Congo and also is being increasingly driven by the analogies emerging between the twin basins of West Africa and Brazil. The potential for West Africa’s presalt and post-salt potential to reflect the major success being enjoyed by Petrobras and its partners in the Campos, Santos, and Sergipe-Alagoas basins is generating great expectations, not only in the emerging countries but also in Angola and Nigeria.

‘Golden Triangle’

rig image

The Eirik Raude semisubmersible rig drilled the Fortuna West-1 discovery well offshore Equatorial Guinea, prompting operator Ophir Energy to raise its area reserves estimate and push for a fast-track LNG development. (Photo courtesy of Ocean Rig)

West Africa’s role as one of the three points of the Atlantic Ocean’s “Golden Triangle” is, of course, no new occurrence. According to the latest research from analysts GlobalData, offshore oil and gas production from the region has grown from 843.7 MMboe in 2001 to 1,564.2 MMboe in 2011.

Nigeria retains its role as the biggest producer with output of 699.4 MMboe in 2011, accounting for 44.7% of the total offshore output in West Africa.

GlobalData forecasted that offshore production is expected to grow at an average rate of 3.8% between 2011 and 2020, from 1,564.2 MMboe in 2011 to 2,201.6 MMboe in 2020. It will hit 2,011.4 MMboe by 2015 due to a number of major projects coming onstream in Nigeria and Angola.

According to the analyst’s “Deep Offshore Oil and Gas Exploration and Production in West Africa to 2020” report, Angola remains the biggest source of new discoveries, accounting for 17 (36.2%) of the 47 discoveries made in the region between 2009 and June 2012, with operators such as Total and BP having outstanding success. After Angola, however, it is one of the newer kids on the block – Ghana – that comes in second, with 11 discoveries recorded over the same period.

This is where one of the more adventurous companies in the region has built its reputation. Tullow’s giant Jubilee project in Ghana’s deep waters has been a company-maker for the independent, with the development viewed by many as a prime example of how to tackle a major scheme in the emerging Gulf of Guinea.

Tullow partnered with fellow pioneers in the area like Kosmos Energy and Anadarko to develop the field, which is now flowing at around 90,000 b/d of oil after Phase 1 began flowing in late 2010. This is partly due to a successful acid stimulation program on certain problematic wells, which helped raise output from 63,000 b/d earlier in 2012.

The Jubilee Phase 1A development also is progressing well, Tullow reported, with five of eight wells drilled, all of which have encountered good quality reservoir. Capacity production for the FPSO in the West Cape Three Points Block is expected to be reached in the first half of 2013 as further Phase 1A production and injection wells come online.

TEN plan submitted

Tullow and partners also submitted their plan of development to Ghana’s Ministry of Energy in November for the second major offshore project in Ghana’s deep waters: the Tweneboa, Enyenra, and Ntomme (TEN) complex. The company said the development is being designed with sufficient flexibility to allow both TEN resources and nearby discoveries to be tied into the planned FPSO.

Following the recent Wawa discovery in the Anadarkooperated Deepwater Tano Block last July, an appraisal program is now being evaluated. Results also were expected from the Okure exploration well to the south as E&P went to press. The rig will then move to drill the Sapele exploration well to the southwest of Jubilee, completing the current exploration campaign on the block.

Although Tullow has other producing assets in the region offshore Equatorial Guinea on the Ceiba field and from the M’Boundi field offshore Congo (Brazzaville), it continues to look to extend its interests. The company recently acquired a 40% stake and operatorship of a deepwater block in the Transform Margin offshore the republic of Guinea, where it plans to drill a well by April 2014.

Tullow also is continuing with its exploration program offshore Sierra Leone, Liberia, and the C?te d’Ivoire. In the first two countries, the company has proven an oil and gas condensate system but has so far only found what it described as “satellite-class” discoveries. In C?te d’Ivoire, however, the company described the CI-103 Block where it made the Paon-1 discovery as having “TEN-type” exploration potential. Paon-1 hit 31 m (102 ft) of net oil pay.

Surrounding potential

Anadarko is keen to stress the continued exploration potential around the TEN and Jubilee hub areas. Flagging the Wawa discovery in its latest operations report, with the find hitting 13 m (43 net ft) of light oil pay and 20 m (65 net ft) of gas condensate pay in Turonian-age reservoirs, the company said pressure data indicated it is a separate distinct accumulation from the adjacent TEN complex.

The company also highlighted a successful drillstem test on the Akasa-1 well, demonstrating strong flow rates of good quality oil. The results are being incorporated into an evaluation of development options and further appraisal plans for the Mahogany, Teak, Akasa, and Banda (MTAB) complex adjacent to the Jubilee field in the West Cape Three Points Block. A first phase of development for MTAB may well see it tied back to the existing Jubilee field facility, although multiple scenarios including a standalone facility are also on the drawing board.

Another independent, Ophir Energy, is focusing mainly on Equatorial Guinea and Gabon, where it said it has defined significant new oil plays and prospects.

In Equatorial Guinea, the company is targeting a fast-track LNG development. After successfully completing a three-well drilling program in Block-R during 2012, resulting in the discovery of an additional 1 Tcf of recoverable resources in the Fortuna West-1 exploration well and increasing contingent recoverable resource estimates to 3 Tcf, the company wants to proceed with a single LNG train supplied by the Block R gas.

Fortuna West-1 was drilled by the Eirik Raude semisubmersible rig in a water depth of 1,758 m (5,768 ft) and was the sixth gas discovery in the block, which Ophir operates with an 80% stake.