ANGOLA - DALIA
The second development in Block 17, Dalia, began producing oil in 2006. This project was notable both for its size (71 wells, 75 kilometers of umbilicals) and its density: six wells could be connected to each manifold. Dalia was also unique for its productivity and for the required reliability and availability rate of its infrastructure: the equipment needed to provide 20 years of continuous production at considerable depths, amid seabed temperatures of 4°C and 140 bars of external pressure.
This new field posed an additional challenge that had not existed at Girassol. The treatment process was similar, but the oil was more complex and more viscous, and it was to be produced from a larger number of wells. Nonetheless, thanks to Total’s capacity for innovation and concerted action, first oil at Dalia came just six years after the start of basic engineering studies for the site. The process included five major milestones:
- December 2000: Basic engineering studies for the project get underway.
- April 2003: The construction contract for the Dalia FPSO was awarded.
- February 2005: Drilling began.
- December 2005: Work began on the offshore facilities.
- June 2006: The Dalia FPSO was delivered.
Construction of this gigantic facility required eight million hours of work by 3,500 operators working simultaneously. Dalia was the first project in which produced water was reinjected into the reservoirs. At Pazflor, the reinjection rate ultimately climbed to 80%.
Covering a larger area and presenting more production challenges than Girassol, Dalia proved to be another international benchmark in deepwater projects and a demonstration of Total’s renewed capacity to industrialize past achievements and make them standard practice today.
Yves-Louis Darricarrère, President, Exploration & Production
Dalia at a Glance
- Location: 135 kilometers off the Angolan coast.
- Area: 230 square kilometers.
- Water depth: 1,200 to 1,500 meters.
- Estimated recoverable reserves: nearly one billion barrels.
- 71 wells, including 37 producers, 31 water injectors and 3 gas injectors.
- Nine manifolds.
- Four production loops.
- Eight flexible risers (Integrated Production Bundles).
- 75 kilometers of umbilicals.
- Equipment produced in Angola: the first production and injection control umbilicals, loading buoy, coiled pipes on the spool base.
It took three million work hours to complete the 4,200 subsea connections needed to position and install Dalia’s production infrastructure. Thanks to proper training, strict compliance with procedures and seamlessly coordinated teamwork, safety remained a priority at all times. Safety is central to Total's risk management strategy, especially when deploying facilities of such a colossal size.
Manifold: A module placed on the seabed and used to connect a variety of equipment needed for well operations (valves, connectors, remote-control devices, etc.) to a flow line.
A More Complex Oil
With a multiphase oil that was not only highly viscous (with an API density of 21° to 23°, compared to 32° for Girassol) but also acidic and cold and in an extreme environment (temperatures of 4°C and 140 bars of pressure), ensuring a proper flow posed an unprecedented problem. In response, Total E&P Angola deployed the biggest flexible risers ever constructed, using new technology known as Integrated Production Bundles (IPBs) and an exceptionally high-performance insulation system for the flow lines.
The Dalia FPSO
Construction of the Dalia FPSO began in January 2004 on the South Korean island of Geoje and was completed in March 2006. It involved the installation of 30,000 tons of superstructure comprising 12 modules for separating and treating the fluids, generating power, exporting the oil to the offloading buoy, storing and compressing the oil and exporting the gas to the Angola LNG plant in Soyo. Construction of the gigantic facility required eight million hours of work by 3,500 operators working simultaneously.
An FPSO is truly a floating city, with living quarters, treatment and production plants and more. Thanks to the power of information technology, a capable team of workers can monitor this array of functions 24/7.
The Dalia FPSO: Key Figures
- Length: 300 meters.
- Width: 60 meters.
- Production capacity: 240,000 barrels/day.
- Water injection capacity: the equivalent of 405,000 barrels/day.
- Gas compression capacity: 8 million cubic meters/day.
- Living quarters: up to 190 people.
- Weight of superstructure facilities: 30,000 tons.
Total’s ongoing advances in 3D seismic acquisition proved instrumental to its exploration activities at Dalia, yielding high-resolution images as early as 1999. The seismic signatures of the different Dalia reservoirs were so distinct that the various components of their lithology (sand and clay in particular) could be directly and accurately assessed. When paired with interference testing, they could be used to model each reservoir and identify the optimal location for the production and injection wells so as to have as few as possible. Given the cost of drilling, Total E&P Angola set out to maximize the volume of recoverable reserves and minimize the number of wells to be drilled while creating the simplest possible trajectories. By combining horizontal subsea tree technology with a lightweight well architecture designed to reduce drilling times and enhance operational productivity, engineers were able to reduce the project’s total cost. The number of manifolds used for well connections was also reduced, with just 9 manifolds for 37 wells at Dalia, compared to 13 manifolds for 23 wells at Girassol.
Lithology: The nature of the rock that comprises the reservoir.
The first 2D seismic acquisitions were used to view geological sections of the subsoil. Those images gave way to 3D acquisitions, which provided a volumetric image of a field at a given moment, similar to images from the seismic interpretation unit at the CSTJF engineering and research center in Pau.
Then came 4D acquisition, which was used at fields such as Girassol and Dalia to monitor a reservoir’s evolution over time and track changes in the proportion of oil, gas and water within the reservoir’s various compartments as it is depleted.