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 EQUATORIAL
GUINEA
West Africa
Equatorial Guinea has a coastline of only around 200
km on the mainland but its ownership of Bioko Island gives it a much
larger offshore area of which the bulk is in deep waters.
Oil production, which all comes from offshore, began in
1991 and is rising fast. The country’s economy, once negligible, has
grown at 40% annually since 1996. There is very little open acreage
available and the government has created a new state firm called
Petrogesa to handle the operational issues and licensing.
 Equatorial Guinea overlies parts of two sedimentary
basins with petroleum systems – the distal part of the Niger delta north
of the Cameroon Axis and the Rio Muni and Douala basins in the south.
Approximately one quarter of its offshore area lies in shallow waters in
the north, here called the Bioko area. The other 75% is mostly
deepwaters of the Rio Muni basin.
The sedimentary section beneath both Bioko and Rio Muni
extends to the offshore territorial limit of Equatorial Guinea where the
distal Niger Delta and the deepwater Rio Muni and Douala basins merge.
Thick sequences of Tertiary to Quaternary sands and shales were
deposited as a wedge of clastic sediments in the distal Niger Delta.
Shelf edge sedimentation led to deposition of reservoir and source rocks
by a variety of gravity-driven processes.
Blocks were first offered by the Spanish administration
in 1965 with awards going to groups operated by Mobil and Spanish Gulf
Oil but exploration efforts failed to locate commercial hydrocarbons.
After independence in 1968, petroleum activity was
reduced and further significant exploration did not occur until after
1979 when a local joint venture called GEPSA including the Spanish oil
company, Hispanoil, began exploring the Bioko area and discovered
gas/condensate.
Bioko area: The Bioko area has established oil and
gas production from the Alba and Zafiro fields plus a number of other
discoveries. GEPSA discovered the Alba gas/condensate field north of
Bioko Island in 1983. Alba has reserves of around 100 Bcm gas and 400 mm
Bbls of liquids but it was not immediately developed.
In 1990 the Alba acreage was awarded to US independent
Walter International who commenced production of condensate in 1991 from
two new wells. United Meridian Corporation (now Ocean Energy) licensed
Bioko Blocks A and B in 1992, and blocks C and D (now operated by
Marathon) in 1995 and drilled the Dorado-1 well in Block A. Mobil then
farmed-into Block B and drilled the Delta-1 well in 1994 and the Zafiro
discovery well in 1995.
Mobil made a series of other small discoveries including
Azurita (1997), Berilo (1998) and Turmelina (1998). Six exploration
wells were drilled in Block D and resulted in small discoveries at
Tsavorita, Estaurolita, Apatito and Ambar (all in 1997).
By 1995 Alba was producing at a rate of around 1.8 mm
cubic metres per day to yield nearly 7,000 Bbls per day of condensate
with all the gas being flared. In 1995 Nomeco (now CMS Oil and Gas)
acquired Walter and they expanded onshore processing capacity to cope
with increased production from additional wells.
Other exploration in the Alba block led to a series of
small gas/condensate discoveries including North Alba (1992), South Luba
(1996), Riaba-1 and East Luba (1997) and Estrella (2001). All CMS
assets were acquired by Marathon in January 2002 at which time the field
was producing 5.5 mm cubic metres per day to generate 14,000 Bbls of
condensate and 2,000 Bbls of LPG per day.
Around 0.4 Bcm per year of the gas has been used to
generate electricity on Bioko Island since 1999 and around 1 Bcm per
year has been used in a methanol plant on Bioko Island since 2001. The
rest is used on the field or re-injected.
Marathon is continuing with investment and expansion of
Alba and exploration on the Alba Block and Block D, discovering the
Bococo (2003) and Deep Luba (2004) gas/condensate fields in 2003/2004
which will eventually also be developed for LNG and liquids.
All the remaining gas is re-injected into the Alba
reservoir for later production when an LNG plant is built. BG has signed
a long-term agreement to purchase LNG when it begins producing in late
2007. The plant will be located on the northwest side of Bioko Island at
Punta Europa, near the capital, Malabo. The plant is expected to be
expanded rapidly after completion.
Mobil discovered the Zafiro oil field 60 km west of Alba
in 1995 in Block B and brought it onstream in 1997, expanding it each
year after that. In late 1999 a 60,000 Bbls per day fixed platform
facility (Jade) was added and in 2000, the Zafiro Producer FPSO was
converted to an FPU with crude oil being stored in a separate FSO. Gas
is separated from the oil on board the FPU and the oil is sent to the
FSO where it is stored until it can be exported to tankers via a Single
Point Mooring (SPM) system. Gas is also separated from the crude on the
Jade platform and the oil exported via pipeline to the FPU. Other
discoveries that have been made on Block B include the Opalo East,
Topacio, Amatista, Rubi and Serpentina fields.
Rio Muni deep water area: The southern part of
Equatorial Guinea’s offshore sector overlies the Rio Muni Basin, which
forms part of the West African margin basin system, formed during
continental separation and creation of the South Atlantic Ocean through
the Cretaceous and Tertiary. This basin system contains a thick wedge of
Cretaceous to Tertiary sediments built over an early Cretaceous rift.
Rio Muni is contiguous with the Douala basin of Cameroon
to the north and the North Gabon Basin to the south. During the 1980s,
Total and Elf explored onshore and offshore the Rio Muni basin, drilling
4 wells but without success.
The Ministry of Mines and Energy announced the country’s
first deepwater licensing round in 1999 with acreage available mostly in
the Rio Muni rift basin south of the Cameroon Axis. The round was not
well received but Triton had already licensed two large blocks (F & G)
in the south of the basin in 1997 covering much of the shallow water
area but also including an extensive deepwater area up to 1500m.
In September 1999 the company drilled the Mbini-1 well
(now called the Ceiba field) in Block G in 715m of water and tested at
12,400 Bbls per day. There followed a surge of interest in Equatorial
Guinea. Triton fast-tracked its development of the Ceiba field and first
production was achieved in November 2000. Initial production during 2001
was from 5 wells into the Sendje Berge FPSO. In January 2002, this
vessel was replaced by the Sendje Ceiba, which has a liquids processing
capacity of 160,000 Bbls per day and facilities to inject water into the
Ceiba reservoir to maintain field pressure and optimise oil recovery.
Triton also made two further discoveries, Oveng and Okume
(2001), 20 km NE of Ceiba, before being bought by Amerada Hess in 2001.
Amerada Hess appraised both fields confirming significant accumulations
and went on to discover four more fields in 2002, Ebano, Akom, Elon and
Abang.
In 2003 Block G yielded three further discoveries, Elon
Extension, Abang and G-13. The Elon, Oveng and Okume fields were
developed through a shared processing facility on an FPSO moored in
shallow water. Subsequent development phases will incorporate the Ebano,
Akom and Abang fields.
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