New finds spark West African oil rush

Oil companies step up exploration and production across the continent, but most notably in Nigeria.

Deepwater areas off the coasts of Ghana, Ivory Coast, Liberia and Sierra Leone could become a major new oil province with production-growth to rival Angola’s, according to geologists close to exploration there.

The world’s largest oil companies are seeking exploration licences and service companies are already moving in. In September, the US company Anadarko drilled the first deepwater well in Sierra Leone’s offshore, making a discovery which showed a hydrocarbons column nearly 14 metres high. In June 2007, another US firm, Kosmos, had discovered the Jubilee oilfield with a deepwater well in an unpromising area off Ghana.

Linking the two finds, more than 1,000 kilometres apart, is the fact that they were made in the same type of geological structure. According to Kosmos – which works closely with Anadarko – previous explorers had been searching for structural traps because they show up best on seismic surveys. But Kosmos decided to search-out more subtle traps – stratigraphic traps, in which oil is held in place by changes in the porosity and permeability of overlying rocks, and combination traps with stratigraphic and structural features.

The company’s strategy paid-off when it found Jubilee with its first well, so Anadarko decided to search its areas for the same type of structure – a stratigraphic trap in a large turbidite fan system, in upper cretaceous rocks. The result was the Venus find off Sierra Leone. Anadarko and Tullow have the largest licence holdings in the four countries, but many small companies also have licences and they are likely to need farm-in partners before drilling. The farm-ins have already started – Eni has bought into a licence off Ghana held by Vitol, where a find was made in September, and will take over as operator.


Sonatrach selected a short-list of contractors for the lead contract to construct a 300,000 barrels/day refinery at Tiaret. CB&I Lummus, a Saipem-Chiyoda partnership, Sinopec and Technip are vying for the front-end engineering and design contract.


An extended well-test was started in November at the Coco-1 oil discovery, made in 2008 in the onshore Cabinda South licence. The operator, Argentina’s Pluspetrol, is also planning a new exploration well, Castanha-1, targeting a difficult pre-salt structure.


The first well to be drilled in the promising Rovuma basin for over 20 years was drilling in November. Anadarko was drilling the well, Mercupa-1, in the onshore part of the basin. The company was also mobilising the Belford Dolphin drillship to the offshore part of the basin for a four-well campaign, marking the first deepwater drilling off Mozambique.


Afren said its Phase 1a development plan for Ebok has received Department of Petroleum Resources approval and work is “on-track to deliver 15,000 barrels/day in first-half 2010”. The firm’s recent Ebok-5 appraisal well found a gross oil column of 81.1 metres, which confirms the recoverable reserves estimate of 25mn barrels proven and possible for the Ebok West structure and 78mn barrels for the whole field. Afren says there is potential for an additional 74mn barrels. Exploration will be stepped-up in the OPL310 block, in the Benin basin off the western part of the country, following an agreement under which Afren will take over as operator. Afren says prospects in the block are raised by the Aje field in the neighbouring block. The OPL310 licence was awarded to a small Nigerian firm, Optimum Petroleum, in 1992.


The world’s largest oil companies were bidding for a share in the Lake Albert Rift Basin oilfields in November. Tullow, which made the discoveries, is selling up to 50% of its interests to fund the development of the fields. The firm said it is seeking “a likeminded partner who will also bring downstream expertise to the development” – because the government wants a refinery to be constructed as part of the development. Tullow says it will resume drilling early in 2010 with a multi-well exploration and appraisal programme.

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