Since its inception in 1983, state-owned Ghana National Petroleum Corp. (GNPC) has been tasked with promoting, exploring, and developing Ghana’s hydrocarbon resources. To date, GNPC has acquired 18,641 miles (30,000 km) of
2-D and 1,931 sq miles (5,000 sq km) of 3-D seismic data and has drilled 18 onshore wells, 55 shallow-water wells,
and six deepwater wells.

Exploration in Ghana began in 1896, but the first commercial discovery was not until 1970 when Signal-Amoco Consortium discovered Saltpond field 8 miles (13 km) offshore. Since then, there have been several discoveries in the region, including the prolific Jubilee field and, most recently, the Owo field.

Owo discovery, Jubilee field
In July 2010, Tullow Oil plc announced the Owo-1 exploration well in the Deepwater Tano license had intersected a gross vertical reservoir interval of 505 ft (154 m) containing 174 ft (53 m) of net oil pay in two zones of high-quality stacked reservoir sandstones, establishing Owo as a major new oil field. Owo-1 was drilled to a depth of 12,766 ft (3,891 m) in 4,685 ft (1,428 m) water depth.

Map of Ghana offshore

Currently there are 12 licenses offshore Ghana with a number of foreign companies operating in the basins. (Map courtesy of Ghana National Petroleum Corp.)

In September, a sidetrack drilled 0.4 miles (0.6 km) east of the discovery well to a final depth of 13,117 ft (3,998
m) in 4,685 ft water depth, encountered an additional 52 ft (16 m) of net oil pay. Pressure data confirmed at
least 226 ft (69 m) of total net oil pay in a gross column of 656 ft (200 m).

Tullow discovered the Jubilee field with the Mahogany-1 well in 2007 which lies approximately 37 miles (60 km) offshore Ghana in 4,101 ft (1,250 m) water depth. Jubilee holds oil reserves of 600 MMbbl with an upside potential of 1.8 Bbbl.

Jubilee field appraisal drilling began at the end of 2008 with the Odum, Mahogany-2, Mahogany-3, and Hyedua-2 wells drilled to date. Results of the first appraisal in February 2008 proved Jubilee’s reservoirs were highly productive. During the second flow test in July, Mahogany-2 flowed 4,448 b/d of oil and approximately 5.1 MMcf/d of associated natural gas.

Hyedua-2 was drilled in 4,088 ft (1,246 m) water depth in December 2008, defining a gross reservoir interval of 394 ft (120 m). Once onstream, Mahogany-2 and Hyedua-2 are expected to produce more than 20,000 b/d of oil.

Mahogany-3 was drilled in January 2009 and discovered Mahogany Deep, an additional extensive sand. Tullow
expects first oil from Jubilee in 4Q 2010, 3.5 years from discovery to delivery of major deepwater production. “This has been a major collaborative effort between the field partners and contractors both in Ghana and internationally,”
Stuart Wheaton, Ghana development manager for Tullow, said. “It sets a new industry benchmark.”

Additional activity
While Tullow moves ahead with its appraisals, Hess Corp. is planning to drill the Kola prospect on its 100%-owned Deepwater Tano Cape Three Points block directly south of Jubilee field. In late 2008, Hess drilled the Ankobra-1 well which was completed without encountering commercially significant hydrocarbons.

Eni also is in the game. The company drilled the Asase Ya Duru-1 exploration well on the South Cape Three Points
block in April 2010, but has not provided progress updates.

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