Beyond the obvious Heavy Sweet barrels, a group of medium-gravity, super-sweet West African crudes can provide bunker blenders with a different route to solving the 0.50% VLSFO pool.
In our resid fuel and bunker blending universe, our attention tends to gravitate towards extremes.
For West Africa, our hard and fast rule towards 0.5%-relevant crudes is Dalia, Pazflor, Kribi and Meleck.
Yet the operational margin in IMO 2020 VLSFO (0.50% S) formulation belongs to a segment blenders often ignore:
The marginal sweet barrel.
A crude oil does not need to test below 26.0° API to solve a bunker blender’s linear program.
If a barrel is super-sweet, its atmospheric residue unlocks a pricing and blending arbitrage that Heavy Sweet barrels cannot replicate.
Gunvor demonstrates this with how they deploy Tortue (Dussafu Blend) from Gabon:
At approximately 29° API, they give up roughly 15% to 20% of straight-run residue yield compared to an ultra-heavy grade.
Tortue yields approximately 45%–50% atmospheric bottoms vs. ~65%+ for a 20° API barrel.
However, because Tortue’s whole-crude sulphur is just 0.14%, its atmospheric residue concentrates to 0.22%–0.28% S.
That 0.25% S residue cut functions as a sponge for high-sulphur fuel oil (HSFO).
In a commercial VLSFO pool running against a statutory 0.50% sulphur ceiling, with a standard 0.49% operating target, every metric ton of Tortue residue can absorb 10% to 15% of discounted, high-viscosity 380 cSt HSFO at 3.0%–3.5% S.
Rather than paying for expensive low-sulphur marine gasoil (ULSD/MGO) to cut pool viscosity and density, blenders use the lower viscosity of Tortue residue to bring heavier components on-spec.
The volume lost overhead into middle distillates is recouped on the bottom end by converting cheap high-sulphur residual components into finished, premium-priced bunker fuel.
Tortue is not an isolated anomaly.
It is part of a distinct geological family of Gabonese and Nigerian medium-gravity, low-sulphur crudes that function as versatile blending levers.
~31.0°–32.5° API | 0.12%–0.15% S
Produced offshore via the Etame Marine terminal, Etame is the slightly lighter sister to Tortue.
While its atmospheric residue yield drops towards ~42%, its sulphur content matches Tortue’s.
It provides blenders with a clean viscosity-breaking diluent that drops pool density without risking asphaltene fallout.
~29.0°–31.0° API | 0.20%–0.25% S
Lifted offshore via the FSO Fernan Vaz, Oguendjo sits squarely in the sweet margin.
With residue sulphur stabilising around 0.35% S, it offers clean, standalone compliance for bunker desks without requiring sweet hydrotreated dilution.
~26.4°–28.0° API | 0.25%–0.28% S
Produced offshore shallow-water Niger Delta (OML 123) and loaded via the Antan Terminal (FPSO Knock Adoon / APL hub), Antan straddles the immediate heavy/medium divide.
With an atmospheric residue yield near ~55% and residue sulphur stabilising around 0.40% S, it offers blenders a sweet, low-TAN straight-run residual foundation that slides directly into the 0.50% VLSFO pool without needing high-cost hydrotreated cutters.
~28.5°–29.5° API | 0.24%–0.26% S
Lifted offshore deepwater Nigeria via the Shell-operated Bonga FPSO (OML 118), Bonga sits alongside Tortue in the medium-sweet sweet spot.
While its lighter profile yields ~40%–45% atmospheric residue, its residue sulphur concentrates to just ~0.38%–0.42% S.
It gives blenders a low-metals, low-viscosity component capable of absorbing heavier, high-sulphur residual cuts without tripping density limits or triggering the severe acid discounts typical of deeper-water West African Heavy Sweet crudes.
While Gunvor, Trafigura and Glencore dominate physical trading headlines vis-à-vis Gabon, the physical tollbooth of Gabon’s hydrocarbon logistics is held by a private operator: Perenco Gabon SA.
Perenco controls the FSO Fernan Vaz, which exclusively processes and exports the sweet Oguendjo stream.
Unlike independent E&Ps that rely on traders for reserve-based lending, Perenco is 100% privately owned by the Perrodo family.
Perenco commercialises its equity barrels through an in-house marketing team based in London and Paris.
