Located approximately 50km off the coast of Gabon, the Tortue oil field is part of the Ruche Exclusive Exploitation Area (EEA) production licence within the Dussafu Marin permit.
The Dussafu Marin permit is owned by a joint venture (JV) of BW Energy (operator with 73.5% interest), Tullow Oil (10%), Gabon Oil Company (9%), and Panoro Energy (7.5%).
The oil field was developed in two phases. The Phase one development included two horizontal production wells and commenced production in 2018. The Tortue Phase two development was approved in 2018 and involved an estimated investment of $250m. The drilling activities of the second phase commenced in the fourth quarter (Q4) of 2019 and continued until July 2021.
The field produces sweet crude oil with API gravity between 28° and 30°. It recorded an average production of approximately 9,000 barrels of oil a day during the third quarter (Q3) of 2021, achieving a gross production of 0.8 million barrels of oil over the quarter.
Tortue Phase one development details
The drilling of the DTM-2H horizontal production well commenced using the Borr Norve jack-up rig in January 2018. The DTM-3 appraisal well was successfully drilled in May 2018. The objective of the appraisal well was to appraise the western flank of the Tortue field and expand the hydrocarbon resources within the Gamba and Dentale formations.
The appraisal well confirmed the presence of oil and intersected approximately 30m of the hydrocarbon-bearing reservoir within the Gamba and Dentale subcrop sandstones. It also confirmed additional reservoirs in the Dentale D2B and Dentale D6 reservoirs.
Production from the Tortue Phase one commenced in September 2018. The first cargo of 550,000 barrels of oil was successfully offloaded from the BW Adolo floating production storage and offloading (FPSO) facility at the Tortue field, in December 2018.
Tortue Phase two development details
The Tortue Phase two development involved the drilling of four additional production wells in the Tortue field, increasing the total production wells within the field to six. Three of the wells were drilled targeting the Gamba reservoir, while the fourth one targeted the Dentale 6 reservoir.
The first two production wells, DTM-4H and DTM-5H, were drilled by the Borr Norve jack-up rig as horizontal production wells at a water depth of 116m.
Developed across two clusters, the four wells are tied back to the BW Adolo FPSO. The first oil from the Tortue Phase two development was achieved in February 2020. The DTM-4H entered production three days after the DTM-5H commenced production.
The remaining two production wells, DTM-6H and DTM-7H, were successfully hooked-up and commissioned in October 2021.
BW Adolo FPSO details
The BW Adolo is the production hub for the fields in the Dussafu Marin permit. It is a converted very large crude carrier (VLCC), which is spread moored in the Tortue field. The vessel is contracted for operations at the field until 2038. It is installed with a nitrogen generation unit, while a new gas lift compressor is also planned to be installed to optimise production.
The FPSO has an oil processing capacity of approximately 40,000 barrels per day (bpd) and a gas handling capacity of 18 million metric standard cubic feet per day (MMscfd). The vessel has a storage capacity of 1.35 million barrels and a water injection capacity of 60,000bpd.
Ruche EEA details
The Ruche EEA is spread across 850km² with water depths ranging between 70m in the northeast corner and 650m in the southwest corner. It hosts six oil discoveries, namely Tortue, Hibiscus, Moubenga, Ruche, Ruche North East, and Walt Whitman.
The water depth at the Tortue, Hibiscus, Ruche, and Ruche NE fields is approximately 116m. The fields are located within the central region of the Ruche EEA.