Offshore West Africa offers exceptional opportunities

P. Gawenda
J-M. Conne
A. Hayman
M. Marchat
IHS Energy

Although West Africa's vast potential is often restrained by domestic insta-bility, recent E&P achievements remain an engine for growth. Interest in the area remains high due to the changing geo-politics, stunning results of exploration offshore Nigeria and Angola, and sizable discoveries made elsewhere in the region.

West Africa offers almost unparalleled opportunities for both the major and independent players. While international oil companies (IOCs) develop deepwater areas demanding considerable initial expenditures, smaller companies impress with success in riskier regions where they find abundant acreage and favorable terms.

Mauritania

A Woodside-led group appraised the 2001 deepwater Chinguetti discovery. In early 2003, Chinguetti 4-5 tested up to 15,800 b/d and 6.6 MMcf/d and in late 2003, the group made additional discoveries with Chinguetti 4-6 (Tiof) and Chinguetti 4-7 (Tiof West). The Tiof wells, 25 km north of Chinguetti, encountered oil/gas in the Miocene-age reservoirs and could hold 300 MMbbl. Total reserves discovered since the onset of the Mauritanian venture may exceed 500 MMboe. A combined development plan has been put forward, including development drilling, subsea facilities installation, and an FPSO in 2004-2005. First oil should flow in 2006 at a rate of 60,000-80,000 b/d.

Last December, Dana Petroleum made a gas discovery in wildcat Pelican 1 in block 7. The well, in 1,700-m water depth, encountered gas-bearing reservoirs and good oil shows in the Paleocene, confirming the existence of a new hydrocarbon play.

Equatorial West Africa

Vast areas of prospective acreage are available along the continental margin from Senegal to Benin. Sierra Leone, Liberia, and Benin want to instigate new bid rounds; other countries are encouraging bidders.

Results of the most recent exploration drilling in the area were mixed. Kerr-McGee drilled non-commercial wells off Benin (Fifa 1, Hihon 1), Devon Energy a dry well off Ghana (Tarpon 1-1), Hunt Oil an unsuccessful (UK-1) off Togo, Canadian Natural Resources a successful well (Acajou 1) off Côte d'Ivoire. Several new wells are planned.

Nigeria

In 2003, exploration/appraisal drilling in deepwater to ultra-deepwater areas concentrated on appraisal. ChevronTexaco made the most significant new discovery with Nsiko 1 in OPL 249. The discovery, 25 km southwest of the giant Bonga Southwest/ Aparo field, would help to validate prospectivity in adjoining blocks OPL 248 (Zebra/ ConocoPhillips), OPL 250 (ChevronTexaco and partners), OPL 214 (ExxonMobil and partners), all scheduled for drilling in 2004. Other deepwater blocks that could see first drilling this year include OPLs 242, 256 (Devon Energy), OPL 245 (Shell) and OPL 324 (Petrobras).

Two exploratory wells were drilled in OPL 246 (Total/South Atlantic Petroleum). Ultra-deepwater well Egina 1ST was completed before year end, while Preowei 1B in the north of the block is presumed to be testing the extension of the Bolia/Chota structure into OPL 246 and was active at year-end. Another ongoing exploration program is Agip's high-pressure high-temperature (HP/HT) well Agbara Deep 1 in OML 116, testing deeper horizons of the offshore Agbara field. More HP/HT prospects elsewhere on the shelf will be drilled in 2004.

Excellent results were recorded in appraisal drilling. ChevronTexaco's Aparo 3 proved the extension of the Bonga South-west/Aparo structure into OPL 249 and confirms a unitized development of this giant accumulation – possibly 1 Bbbl recoverable. In OML 91 on the shelf, appraisal well Sonam 4ST proved the gas/condensate field commercial. It will either be tied back to Escravos or exploited via a new floating terminal. In OPL 216, ChevronTexaco and partners completed appraisal well Agbami 5, announcing field development for 2004.

ExxonMobil drilled well Bosi 3 in OPL 209 and tested an oil rim around the Bosi gas find. The well is considered successful enough to allow development of Bosi independently of nearby Erha, where the company intends one or more appraisals in 2004.

Total and partners drilled three appraisal wells on the Usan 1 discovery in OPL 222 extending the URR to more than 300 MMbbl. During 2004, Total will drill a series of as-yet-untested exploration prospects in the neighborhood of Usan. Successful wells will be tied back as satellites. The Ukot accumulation in the same block should add >100 MMbbl recoverable reserves.

SNEPCO (Shell)'s appraisal wells Bonga 21 and 21ST (Bonga Northwest) discovered previously untested oil-bearing horizons, adding a further 140 MMbbl to Bonga Main reserves.

Equatorial Guinea

Marathon announced wildcat Bococo 1 in the Niger delta block D, 5 km east of the 1998 Ambar 1 oil discovery, as a new gas find. The company wants to develop the discovery as a satellite to the Alba field, with production possibly feeding the proposed Bioko LNG Project. Marathon will continue drilling in its Alba block and block D, with ExxonMobil active in block B, but the majority of the wells are expected in the Rio Muni area. New wells are likely in Amerada Hess' blocks F and G, block H (Atlas/Roc Oil), block K (Nexen), block L (ChevronTexaco), block N (Petronas) and block P (Devon Energy).

Angola

The year was marked by new drilling successes in ultra-deepwater blocks 31 and 32 in the Congo fan. In block 31, BP drilled wells Saturno 1 and Marte 1. Saturno 1, in 1,805 m water depth 14 km northeast of the 2002 Plutão oil find, tested oil at a maximum rate of 5,000 b/d and is considered a significant discovery. Marte 1 tested up to 5,200 b/d of light oil found in Tertiary channel sands. BP is considering development options for the discoveries.

In block 32, Total drilled wildcat Gindungo 1 and announced that the well tested 7,400 b/d and 5,700 b/d of light oil from two separate zones. The discovery, in 1,445 m water depth close to the limit of block 32 and CNR-operated block 16, is rated as promising.

In deepwater blocks 15 and 17, operators ExxonMobil and Total had six new finds. ExxonMobil made four oil discoveries in block 15 prior to the expiry of the PSA, bringing the total number of oil finds in the license since 1998 to fifteen. The new discoveries are Bavuca 1, Clochas 1, Kakocha 1, and Tchi-humba 1. Clochas 1 encountered an oil-bearing reservoir and flowed 1,764 b/d. Kakocha 1 tested 4,500 b/d, and Tchihumba 1 tested 7,469 b/d from an undisclosed interval. All three wells are sited in the southwestern portion of block 15. No test results are available for the Bavuca well, which lies north of the Kizomba B complex.

In April 2003, Total announced Acacia 1 and Hortensia 1 in block 17 as new oil finds. These new oil finds bring the successes in block 17 to 15 since the award in 1993. New finds may prompt the company to establish a new production complex centered over the Perpetua discovery in the eastern part of block.

Results of two recent wells in BP's deep-water block 18 are not yet available.

Further drilling efforts are expected in ultra-deepwater blocks 31, 32, 33, and 34 and deepwater blocks 14 and 16, all within the Congo fan. Drilling is also expected in blocks 10 and 24 in the Benguela basin to the south.

Other areas

Exploration success off Mauritania seems to have invigorated activities in the entire under-explored area from West Sahara to Guinea.

In the Nigeria/São Tome é Príncipe joint development zone, acreage awards are exp-ected in the first half of 2004. Exploration should verify industry's high expectations, though drilling might not begin for a couple of years.

In Gabon, Energy Africa, ENI, and Perenco discovered oil with their respective wells Akoum Marin B-1, Simba Marine 1, and Orindi 1, but the finds are considered marginal. In Congo, ENI encountered oil in its Mwafi Sud Est Marine 1 well.

Vast offshore acreage is open in Namibia further to the south. Vanco Energy may drill a well in Namibia's Namibe basin in 2004. In South Africa's offshore Orange basin, Forest Oil completed wells A-AA 2, A-X1 in block 2A with gas. The Ibhubezi project may take off in 2004.