Offshore oil field development
The Barryroe oil field is located in the Standard Exploration Licence 1/11 (SEL 1/11) of the North Celtic Sea Basin, Ireland, in water depths of 100m. It is operated by Providence Resources (80%), while Lansdowne (20%) is the co-owner.
Providence Resources is currently pursuing partners to farm-out the field to initiate the development. The project is expected to significantly benefit from the rise in oil prices and lower operating and capital costs.
The field is part of the SEL 1/11 license area covering an area of 614km². The SEL 1/11 license area initially covered more than 500km². In 2014, the Irish Department of Communications, Energy and Natural Resources offered a 160km² license extension, providing further appraisal opportunities for the oil field.
The license area was further increased by 118km² into licensing option 12/4 in November 2015.
The developers have also been granted a two-year extension to the term of the current phase of the SEL 1/11 licence to July 2017 and extension of the second phase to July 2019.
Oil reserves at the Barryroe reservoir are found in the Cretaceous Middle and Lower Wealden sandstones respectively located 1,400m and 2,300m (approximately 4,600ft and 7,550ft) below sea level.
The 1C, 2C and 3C reserves of the field are estimated to be 89 million barrels of oil (mmbo), 311mmbo and 624mmbo respectively.
Additional resources have been identified in the Lower Wealden and Purbeckian reservoir. Proven, probable and possible in place oil resources in these sandstones are estimated at 456mmbo, 778mmbo and 1,165mmbo respectively.
A total of five wells have been drilled to appraise the Barryroe field. Esso Corporation drilled two wells in 1973 and 1974, which tested oil. The first well, 48/24-1, flowed oil from the Middle Wealden sands at the rate of 1,300 barrels of oil a day (bopd), while the second well, 48/28-1, flowed at 1,527bopd.
A third well, 48/24-3, drilled by Marathon in 1990 tested oil from Lower Wealden sands flowing at the rate of 1,619bopd.
Providence Resources drilled the 48/24-10 well using the GSF Arctic III semi-submersible rig following the acquisition of extensive 3D seismic data in 2011. The well flowed at the rate of 3,500bopd with 43° API oil with a wax content between 17% and 20%.
A phased development of the field is planned to gradually increase the production rates. The field development is expected to begin with a smaller early production phase, followed by future phases of field appraisal and development. An initial peak production rate of 30,000bopd is planned to be achieved in the early production phase.
A number of factors such as cost, operating conditions, field life and oil properties were taken into consideration to design the development options for the field. The final development concept proposed includes three platforms equipped with processing facilities, accommodation quarters and other utilities. The platforms will be anchored to the seabed using steel supports and jack-up rigs.
Produced oil and gas is planned to be transported onshore either through a subsea pipeline, or floating storage units and shuttle tankers. The production life of the field is estimated to be 25 years.
Mott MacDonald was contracted to design the field development options. Procyon Oil & Gas, a part of Mott MacDonald, designed the development options.
The competent persons report was prepared by Netherland Sewell & Associates. Rothschild has been appointed as adviser for the farm-out process of the field.
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