It bought the 300,000-barrel cargo for March loading at a premium of $27-$28 a barrel to dated Brent from Japanese explorer Inpex Corp, the sources said.
The deal could not be independently verified as the companies do not comment on deals.
Japanese traders Mitsui and PetroSummit have paid record premiums to secure Australian heavy sweet crude supplies in recent months.
The trading companies blend the crude with other fuel to produce Very Low Sulphur Fuel Oil (VLSFO), a new ship fuel containing 0.5% sulphur which meets emission rules set by the International Maritime Organization which took effect this month.
(Reporting by Florence Tan)