If there is a Man to respect concerning the Geology and geophysical issues on Africa, Tako Koning, is the man. A former employee of Chevron Nigeria and presently with Tullow Oil, Angola, he shared his broad view on the topic above.
At the Luanda Chapter of the Society of Petrophysicists & Well Log Analysts (SPWLA), in April 15, 2009,he presented the Paper on the above topic.

Excerpts:

Angola is the second largest oil producer in Africa after Nigeria which is producing about 2.0 million barrels of oil per day. The oil and gas industry in Angola continues to experience significant growth. A decade ago Angola was producing 750,000 barrels of oil per day and since that time production increased significantly to 1.9 million barrels of oil per day during 2008.

During 2008, the average production from West Africa oil-producing countries was:

Nigeria 2,000,000 BOPD (barrels of oil per day)

Angola 1,900,000

Equatorial Guinea 320,000

Congo Brazaville 240,000

Gabon 235,000

Chad 145,000

Cameroon 85,000

Ivory Coast 30,000

Congo DRC 25,000

Mauritania 10,000

Ghana 6,000

Total 4,996,000 BOPO

Due to the exploration successes experienced by industry in Angola during the past 13 years (since 1996 when Elf discovered the Girassol oil field on Block 17), Angola has become one of the premier countries worldwide for deepwater petroleum exploration. Indeed, to quote one of the world’s most authoritative oil industry magazines, the Oil & Gas Journal, May 23, 2005 issue: “Hardly anywhere in the world measures up to the recent exploration significance of AngoIa’

PRE-SALT & PINDA OlIL FIELDS: Until the commencement of oil production from the deepwater Tertiary-age fields (Kuito in 1999 and Girassol in 2001), almost all of Angola’s production was obtained from Cretaceous (Albian) carbonates of the Pinda formation, although in the Cabinda area in (Chevron Block 0), significant production is also obtained from pre-salt lacustrine clastics and carbonates. Reserves of some 3 billion barrels have been discovered in the Pinda and pre-salt. The Pinda carbonates are dolomitized oncoid-ooid grainstones, packstones and wackestones which were deposited in north-south trending shoals. Salt-rafting and down-to-the-basin gravity sliding of Pinda “rafts” has resulted in numerous oil fields which consist of separate blocks of Pinda carbonate, each with distinct hydrocarbon contacts. Indeed, the global type-area for salt raft tectonics is the continental margin of Angola.

As part of this presentation, the Lombo East oil field, located in the shallow water part of the LowerCongoBasin in Block 2, is reviewed as a typical Angolan rafted carbonate oil field. The reservoir consists of a high energy shoal facies containing vuggy dolomites with porosities in the range of 15 — 20%. The field covers 1600 acres and had an original oil column of 130 meters. The oil API is 40 degrees. Production from the field peaked at 21,000 BOPD and cumulative production is approximately 140 million barrels oil.

TERTIARY OIL FIELDS: In 1996 Elf discovered the Girassol oil field in Oligocene turbidite clastics. The water depth of the field is 1400 meters and the reservoir is relatively shallow at 2400 meters, thus the sedimentary section overlying the reservoir is only 1000 meters thick. Since 2001, Girassol was on production at a steady 200,000 BOPO until 2007 when production declines finally commenced. Production of up to 30,000 BOPD has been achieved from single wells.

Elf (subsequently Total) followed up the discovery of Girassol with 15 other oil fields on Block 17

(informally called “the Golden Block”) and estimated reserves for the block are in the range of some 4.0 billion barrels oil.

Since the discovery of Girassol, over 70 oil fields with reserves of some 14 billion barrels have been discovered in the Tertiary sediments of the LowerCongoBasin. These fields occur in the follow blocks: Sonangot P&P Block 4, BP Block 18, Total Block 17, Esso Block 15, Chevron Block 14, BP Block 31 and Total Block 32. The reservoirs occur in the Miocene and Oligocene turbidites associated with the ancestral Congo River drainage system. This play continues to expand as indicated by the recent announcement that BP discovered its 17th oil field in Block 31 or which 5 have been sub-salt discoveries. Block 32 has also announced its 15th oil discovery.

The activity in the deepwater of Angola has had a major impact with the result that almost 213’s of

Angola’s current oil production is from Tertiary turbidites. In 2007 the oil consultancy firm of Wood Mackenzie predicted that Angola production could reach 2.7 million barrels oil per day, assuming no production constraints imposed by OPEC.

WORLD CLASS & WORLD RECORD SETTING PROJECTS: The world-class geology which has endowed Angola’s LowerCongoBasin has also resulted in world-class production facilities, as illustrated by the following:

• Girassol, with a storage capacity of 2 million barrels oil, was the largest EPSO ever built worldwide and held that record until 2004 when Esso’s Kizomba A project went on production.

• The Chevron Block 0 Sanha condensate project is the world’s first LPG FPSO. It also contains the world’s largest offshore gas compression facility.

• The Benguela-Belize Compliant-Piled Tower (CPT) on Chevron Block 14 installed in 400 meters water (1300 feet) is the 5th largest free-standing structure in the world and is the tallest man made structure in Africa.

• BP’s Greater Plutonio FPSO includes a composite riser tower which is the longest of its kind in the world.

PRE-SALT POTENTIAL: The conjugate margins of Angola were juxtaposed with Brazil in pre-drift time. Angola’s sedimentary basins in the Cretaceous, including the Lower Congo and KwanzaBasins are the pre-drift eastern equivalent to the pre-drift Cretaceous basins in Brazil such as the SantosBasin. The recent giant oil discoveries in Brazil in the pre-salt reservoirs, such as Tupi and Jubarte, has major geological and economic implications for the pre-salt of Angola which in the deepwater has been minimally evaluated by drilling. Accordingly, the favorable geological conditions present in Angola will likely ensure that Angola will continue to experience many more discoveries and remain as one of Africa’s major oil producers for decades to come.

You may contact Koning at tako.koning©tullowoil.com