An issue with the turret bearing of theFPSOKwame Nkrumah, which came to light in February, necessitated new operating and offtake procedures.
The vessel was shut down for an extended period in April with production resuming in early May. Since then, 18 offtakes to the storage tanker have been completed using a dynamically-positioned shuttle tanker.
Tullow expects these new procedures to remain in place throughout the rest of the year, with oil production averaging 85,000 b/d during the second half.
For the longer term, the partners favor converting the FPSO to a permanently spread-moored facility with offtake through a new deepwater offloading buoy.
Assuming approval from Ghana’s government, this would involve installing a stern anchoring system in place of the three heading control tugs currently at the field.
Installation should be completed by the end of 2016 but will require short periods of reduced production. A second-phase program would follow to rotate the FPSO to its optimal spread moor heading during the first half of 2017.
The anticipated cost of these measures is $100-150 million, and would involve shutting down the FPSO for up to 12 weeks next year.
On completion, the partners plan further measures to improve the efficiency of offtake procedures in order to restore output to previous levels. These may include use of a larger dynamically positioned shuttle tanker.
Additional opex related to the revised procedures could be around $115 million this year and $80 million next year.
During the first half of 2017 a deepwater offloading buoy will likely be installed, dispensing with the need for the DP shuttle and storage tankers and the associated operating costs.
Tullow has issued enquiries to the market to estimate the cost and schedule for fabrication and installation of this buoy.
Elsewhere offshore Ghana the company’sTEN project is more than 96% complete and set to deliver first oil within the next three to six weeks.
Hookup and commissioning of the FPSO - connecting the pre-drilled wells to the vessel via the extensive subsea infrastructure - is nearing completion.
During July, the integrated start-up sequence will likely begin with water injection to the Enyenra reservoir, followed by oil production. This sequence will then be repeated for the Ntomme reservoir.
Oil output should ramp-up toward the FPSO’s capacity of 80,000 b/d around the end of 2016 as performance testing of the facilities is completed and wells are brought up to optimum rates.
Production from TEN this year should average around 23,000 b/d.
However, drilling is not expected to recommence until after the resolution of the Côte d’Ivoire/Ghana border dispute through the ITLOS tribunal – the latter is expected to announce its decision in late 2017.
Associated gas produced at TEN will be re-injected into the Ntomme reservoir gas cap until gas export begins. This was due to occur 12 months after field start-up, with the Tweneboa gas reservoir coming onstream 12 months later.
However, options to accelerate gas export are under evaluation as fabrication of the gas export facilities is likely to be completed late this year, around six months ahead of schedule.
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