Pazflor achieves first oil
West African success demonstrates the key benefits subsea separation can deliver in large-scale deepwater oil and gas development projects.
The Pazflor projectThe Pazflor project offshore Angola began producing oil and gas using gas/liquid subsea separation equipment supplied by FMC Technologies, Inc., under contract to Total Exploration & Production Angola, in September 2011. The Pazflor project marks the first-ever use of subsea separation technology offshore West Africa, and it’s also a world-first use of subsea separation technology in a development of such scale.
Located in the prolific Block 17, some 93 miles (150 km) offshore of Angola, Pazflor will produce oil and gas from 25 subsea wells, supported by 22 water injection and two gas injection wells, drilled in four separate reservoirs in water depths of 2,000 to 4,000 feet (600 to 1,200 m). The field covers an area of 238 square miles (600 km2). A system of flowlines and risers transport the produced fluids to a floating production, storage and offloading vessel (FPSO) with processing capacity of 220,000 bopd.
Three of the four Pazflor reservoirs contain very heavy, viscous oil at relatively low reservoir pressures. Subsea separation is the key enabling technology making efficient production of this oil possible. The heavy oil will comprise about two-thirds of the liquids produced at Pazflor.
In addition to the three Subsea Separation Units (SSU), FMC Technologies’ scope of supply to Pazflor includes the 49 tree and wellhead systems, three 4-slot production manifolds, production control and umbilical distribution systems, gas export and flowline connection systems, ROV tooling, and local support for installation and startup.
Why subsea separation?
FMC Technologies’ SSUs offered solutions to several challenges involved in producing Pazflor’s heavy oil. Low reservoir pressure of 2,900 psi (200 bar) meant artificial lift would be needed. Gas lift and multiphase pumping were assessed but found less efficient than liquid/gas separation with liquid boosting. Subsea separation allows use of a gas-tolerant hybrid pump to lift the oil and water to the surface, while the gas flows under its own pressure. Separation results in more stable flow in the risers.
Separation also simplifies Pazflor’s hydrate prevention strategy. Since the separators operate at a pressure of 333 psi (23 bar), fluids downstream of each SSU remain outside the hydrate formation window. Upstream of the SSUs, simple depressurization prevents hydrate formation in the event of an extended shutdown, without any chemical injection from the surface.
The subsea separation system was instrumental in the development of such an enormous field and available from the first day of production. Ultimately, The Pazflor project would not have been feasible without the introduction of Subsea Separation technology.
Next generation subsea technology
The Pazflor SSUs represent the next generation of subsea separation technology. Combining a vertical separator and hybrid pumping system, each massive SSU stands over 80 feet high (24 m), weighs some 1,190 tons (1,100 mt), and can handle 110,000 bpd of liquids. They have a design life of 20 years. The separator walls are four inches thick to resist internal and external pressures. Their modular configuration offers flexibility during installation, optimized maintenance and component retrieval, and possible pump modification during later field life.
Thanks to Total’s willingness to invest in new technology, FMC Technologies has established, in supplying the SSUs for Pazflor, several new world firsts: for two-phase separation and liquid boosting at the mudline; for application in a mega-scale project; for hybrid pump technology; and for vertical separator technology. Given these achievements, we believe that Total has not exaggerated in calling the use of subsea separation at Pazflor a “bold innovation” and “audacious solution.”