Aseng Field, Equatorial Guinea

Aseng Field (previously known as Benita) is an oil and gas field offshore Equatorial Guinea, West Africa. The field lies at a water depth of about 3,100ft (945m).

It was discovered as a gas-condensate resource in Block I in 2007. Two appraisal wells were subsequently drilled to confirm the down dip reservoir limits and resources. The field is expected to start-up in late 2011.

The total cost of the field development is estimated to be $1.3bn. Noble Energy is the operator of the Aseng field and holds 40% interest in the project. Other partners include Atlas Petroleum International (29%), Glencore Exploration (25%) and PA Resources (6%).

Aseng field development

The Aseng field development plan was approved by the Ministry of Mines, Industry and Energy of the Republic of Equatorial Guinea and Noble Energy partners in July 2009. The design, engineering and awarding of contracts were all completed in 2010. A semisubmersible rig of Atwood Hunter was leased in the same year to start work on the location.

The Aseng development consists of five subsea wells connected to a floating production, storage, and offloading vessel (FPSO).

Oil from the field will be stored on the vessel unit while gas and water will be reinjected to maintain the pressure. The field has three water injectors and two gas injectors.

Drilling of all the development wells has been completed by 2011 and the subsea installations are being carried out. The wells are designed horizontally to enhance recovery and oil productivity.

The field will have infrastructure to support other future developments. A second field called Alen field is under development in Block O.

Aseng FPSO

Noble Energy has chartered the Aseng FPSO vessel for production from the field. It is being reconstructed at the Keppel Shipyard in Singapore.

The upgrades to the vessel include fabrication and integration of internal turrets, installation and integration of the topsides, refurbishment of the accommodation areas and extension of the life of the vessel. The work is on schedule to be delivered in October 2011.

The vessel will be moored at 3,100ft (945m) in water. The FPSO will handle about 120,000 barrels of liquids a day. It will have a capacity to store 1.7 million barrels of oil and condensate (MMbbl) and process 80,000 barrels of oil a day (bopd).

Production at the Equatorial Guinea-owned gas field

The field will produce about 50,000bopd. Noble Energy estimates to recover about 120 million barrels of hydrocarbon liquids over the life of the project. The FPSO can re-inject 170 million cubic feet a day (mcf/d) of natural gas to maintain pressure and maximise oil recovery.

Natural gas resources of about 550bcf/d will be recovered for monetisation after completion of the oil recovery pressure maintenance phase.

Contracts awarded

The Aseng FPSO will be operated by Aseng Production Company, a joint venture between Compania Nacional de Petroleo de Guinea Ecuatorial and SBM Offshore.

In November 2009, Dresser-Rand was contracted to supply turbomachinery such as power generation and supply gas compression packages for the FPSO. The net oil resources at the field are estimated to be 40mmbbl.

Acteon company InterMoor was awarded the designing, engineering, procurement and installation contract in April 2010 for five preset moorings in the field. In July 2010 Castrol Offshore was contracted to supply Transaqua HT2 hydraulic fluid medium for controlling subsea production.

Champion Technologies will supply specialised chemicals for flow assurance from the field under a contract received in May 2011.

Subsea system

Technip is laying the flexible pipeline system for the Aseng field. The scope of work includes engineering, supplying, installing and pre-commissioning of about 30km flexible subsea pipeline.

The contract includes installation of subsea production system, six flexible risers, jumpers and flexible flowlines.

Future development of the West African offshore gas field

The $1.6bn Alen field (previously Belinda) development in Block O was approved by the Ministry of Mines, Industry, and Energy in January 2010.

Condensate from the field is planned to be piped about 24km to Aseng FPSO platform for processing, while the natural gas will be re-injected. It is expected to start-up in 2013.