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The Ebok oilfield is located in OML 67, offshore Nigeria. The field was discovered in 1968 by an ExxonMobil/NNPC joint venture. Oriental Energy Resources (Oriental Energy) assumed ownership of the field in May 2007.
Afren signed a farm-in agreement with Oriental Energy to take part in the development of the Ebok field in March 2008. Under the terms of the agreement, Afren will fund appraisal and development costs and recover these from 100% of field revenues. After the cost recovery, Afren and Oriental will share the revenue equally.
Production began at the field in February 2011 at a rate of 3,300bopd. By January 2012, all production wells in the initial phases of development were brought onstream, increasing its production to 40,000bopd.
Drilling and appraisal
Following the discovery of oil at the Ebok field by Ebok-1, the joint venture drilled two appraisal wells, Ebok-2 and Ebok-3, in 1970. Further appraisal or development was not undertaken until 2008.
The Ebok-4 appraisal well was drilled with the Trident IV drilling rig. It was spudded on 24 November 2008 and completed in February 2009. The well encountered a gross oil column of 284ft in high-quality reservoir sands. Well test analysis and reservoir simulation confirmed that rates of 3,500bpd per well in a production scenario can be achieved. This is consistent with offset production data from analogous fields in the area.
Spudded in September 2009, Ebok-5 was drilled using the Transocean Adriatic IX jack-up rig. The well was drilled to a total depth of 3,743ft on the West Fault block. Appraisal drilling concluded on 17 November 2009. The well encountered a 54ft gross oil column in the D series reservoirs.
The Ebok-6 well was drilled in the D2 Southern Lobe using the Transocean Adriatic IX jack-up rig. The well was spudded on 20 November 2009 and drilled to a depth of 4,296ft. The drilling was completed on 27 November 2009. The well encountered a gross 107ft oil column in the D series reservoirs.
In June 2010, Afren completed drilling a deep exploration well at the field. The well was drilled to a depth of 11,375ft by the GSF High Island VII jack-up rig. It encountered two sandstone intervals of 370ft in the Biafra and Isongo formations. The well was abandoned for future development.
Ebok’s gross 2P reserves were independently estimated at 106.2 million barrels by oil consultancy NSAI, as of December 2010. Drilling of the Ebok-6 well increased the field’s resource potential to 182 million barrels. Total gross resource potential as certified by NSAI is estimated at 508 million barrels.
Prospective resources from the undeveloped North fault block are estimated at 35 million barrels.
Ebok field development
The Ebok field is under development and the partners have adopted a phased approach.
Phase 1 began in December 2009 after the three appraisal wells were successfully completed. The plan includes drilling a water injection well and six horizontal production wells; one targeting the D1 and five targeting the D2. In March 2010, Afren secure $450m for the field’s development. By December 2010, three of the five production wells of phase I were completed and flow tested at a rate of 12,500bopd. The phase I well-head platform was also installed at the field.
The phase II development focuses on the West Fault block area of the field. The development plan incorporates the installation of a second dedicated wellhead platform at the West Fault block location. Four horizontal producers and two water injectors are part of this phase.
Afren will carry out further development work in 2012 to bring Ebok’s production to full capacity. The firm will drill in the North fault block.
The major infrastructure at the Ebok oilfield includes two 12-slot well-head platforms: the Veer Prem mobile offshore production unit (MOPU) and the Virini Prem floating storage offloading vessel (FSO).
The Veer Prem MOPU was converted from a jack-up drilling rig at the Gulf Copper shipyard. The MOPU has a production capacity of 50,000bpd, a water injection capacity of 25,000bwpd and gas lift/injection capacity of 9mmcfd/6mmcfd. An accommodation unit with a capacity of 30 staff and a helideck are also part of the facility.
The Virini Prem FSO was refurbished at the Yulian shipyard in China, and has a storage capacity of 1.2 million barrels. It weighs 174,917t and will store and offload crude oil processed by the Veer Prem MOPU onto tankers.
The joint venture will seek to leverage synergies created by the Ebok production infrastructure to effectively produce future developments in the area, including the nearby Okwok field and any future discoveries on the surrounding OML 115.
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