TANO FIELDS MARKED FOR DEVELOPMENT OFF GHANA

May 2, 1994
An expected shortfall in electrical power generation has prompted Ghana National Petroleum Corp. (GNPC) to develop its offshore Tano oil and gas fields to fuel a coastal power station. Ghana has about 1.2 million kw of power generating capacity throughout the country largely based on hydroelectric plants operated by state utility Volta River Authority (VRA). However, water reservoir depletion is reducing capacity while many of the power stations are due for long term maintenance in the next 5

An expected shortfall in electrical power generation has prompted Ghana National Petroleum Corp. (GNPC) to develop its offshore Tano oil and gas fields to fuel a coastal power station.

Ghana has about 1.2 million kw of power generating capacity throughout the country largely based on hydroelectric plants operated by state utility Volta River Authority (VRA).

However, water reservoir depletion is reducing capacity while many of the power stations are due for long term maintenance in the next 5 years.

"This means 140,000 kw is required initially to replace these expected losses," said Ian Knights, associate director and Tano project manager at Stone & Webster Engineering Ltd., Milton Keynes, U.K.

"There is also an expected rise in electricity demand due to development of the Ashanti gold field and expansion of Ghana's railway network."

Ghana imports power to meet peak demand despite its normal role as a net electricity exporter to neighboring countries.

DEVELOPMENT PLAN

GNPC named Stone & Webster consulting engineer to plan development of two Tano fields and a power plant and to help in fund raising and contract awards.

The project is expected to call for a monohull production vessel with an oil storage barge moored alongside, a gas export pipeline to shore, and a power plant on the coast feeding into the VRA grid.

Knights said GNPC expects the project to require $200 million capital investment and plans to bring it on stream in first quarter 1996.

GNPC hopes to secure financial backing from banks in September, after which development "...will be with a rush."

North and South Tano fields lie in the far west of Ghana's offshore territory near the boundary with Ivory Coast (see map, OGJ, July 17, 1989, p. 44).

Phillips Petroleum Co. made the first discoveries in the Tano basin in 1978 but relinquished its exploration license in 1982.

A study by Atlantic Richfield Co. concluded North Tano field reserves were 53.6 million bbl of oil and 102 bcf of gas.

A study by Petrleo Brasileiro SA estimated South Tano field reserves at 82 million bbl of oil and 100 bcf of gas.

CAPACITIES

GNPC estimates combined production from the fields will be 12,000 b/d of oil and 30 MMcfd of gas with field life estimated at 15 years.

Ghana has only one field on production at the moment. It is Saltpond offshore oil field, which averaged 1,800 b/d in 1992. Knights said the Tano production vessel is likely to be a converted tanker. Oil and gas will be separated on board. Oil will then be shipped by shuttle tanker to Ghana's 26,600 b/d Tema refinery.

Gas will be sent through a 40-80 km, 16 in. pipeline directly to a terminal at the power plant. Length of the pipeline will depend on which of two proposed sites is chosen.

Power plant capacity is expected to be 100,000-140,000 kw. It has not been decided whether to select a single or combined cycle design.

Stone & Webster said the unit cost of power generated under this plan would be half the cost of power generated from a grassroots, oil fired power plant due to the high cost of imported fuel oil.