Agbami Oilfield, Nigeria
The $3.5bn Agbami oilfield project is Nigeria's largest deepwater development. The field lies in OPL blocks 216 and 217, approximately 220 miles south-east of Lagos and 70 miles offshore Nigeria, in the central Niger Delta.
In late 1996, Texaco and Nigerian independent oil company Famfa were granted exploration rights to the 617,000 acre block 216. Agbami was proven in this block by Texaco in 1998 and two years later Statoil's Ekoli-1 well confirmed that the discovery extended into block 217.
Development of the field was unitised between the two blocks. Chevron Corporation (Chevron) has a 68.15% interest and operates the field through its Nigerian affiliate, Star Deep Water Petroleum. The remaining working interests are held by Statoil (18.85%) and Petrobras (13%).
The field is owned by the terms of a deepwater production-sharing contract (PSC) between Chevron and Famfa.
The discovery well Agbami-1, completed in January 1999, encountered 420 net feet of pay in multiple oil zones from 8,200ft to a total depth of 12,400ft.
The well penetrated stacked reservoir sands saturated with oil, ranging in overall column thickness from 400ft to over 1,000ft.
The quality of the oil from these zones is 35-45° API gravity, with a very low sulphur content.
The well was spudded on 15 July 1999 in 4,700ft of water, making it the deepwater well in Nigeria. It reached its total depth in late November 1999 and was temporarily suspended to allow for flow testing and possible production at a later date.
In January 2000, Texaco drilled the Agbami-2 appraisal well with the drillship Glomar Explorer. This confirmed the size of the Agbami structure.
The Agbami-2 appraisal well was drilled in 4,800ft of water to a total depth of 15,683ft. The well encountered 534ft of pay in five separate oil-bearing zones, one of which flowed at a maximum rate of 10,000bpd with a well-head pressure of 2,200lb per square inch (psi). Surface equipment limitations prevented the achievement of a higher flow rate.
Oil from the reservoir is light, sweet crude (45° API gravity) with very low levels of contaminants such as vanadium, nickel and iron.
Total reserves in the Agbami oilfield are estimated at around one billion oil-equivalent barrels.
Agbami field development
Agbami was developed with a subsea production system tied back to an FPSO.
The field came onstream in July 2008 and reached its peak production rate of 250,000bpd in August 2009.
A ten-well development programme will increase crude oil production capacity to compensate for the field's decline. Drilling of the wells began in May 2010 and will continue until 2014.
Pacific Drilling's rig Pacific Bora began operations at the Agbami oilfield in August 2011 under a three-year contract.
The FPSO was built by South Korea's Daewoo Shipbuilding & Marine Engineering. In 2005, it awarded the contract for engineering design and procurement services for the topsides to KBR and the class contract to ABS.
With an overall storage capacity of 2.15 million barrels of crude oil, the Agbami FPSO, which arrived amid secrecy at the field at the end of 2007, is one of the largest facilities of this type ever built.
The Agbami development is expected to be of value to less-complex refiners, especially those with no vacuum residuum conversion. It has 13 topside modules containing the main process and utility systems. Weighing about 30,000t, the vessel topsides generate 75MW of power and have living quarters for 100 personnel. It cost $1.2bn to construct.
The FPSO is moored in about 4,800ft of water, and at least 40 subsea wells will likely be necessary to fully exploit the field.
The vessel is designed to handle 250,000bpd, 450 million cubic feet of gas production and 450,000 barrels of injected water a day.
Designed to store about 2.2 million barrels of oil, the FPSO will be on location for more than 20 years.
Agbami is expected to be of value to less-complex refiners, especially those with no vacuum residuum conversion, limited hydrotreating / sulphur recovery and limited cracking capacity.