The headline is incorrect. It doesn’t refine oil at all.
And it's not a refinery. It's a floating "gas plant".
Natural gas naturally occurs in oilfields (just as crude oil -- or "distillates" -- occur naturally in gas fields).
Heretofore, that natural gas which was captured by production platforms in oilfields has been flared off -- there being no economically feasible way of storing and transporting the gas to shore.
The "Prelude" solves the economic feasibility issue -- collecting and processing the gas, then trans-shipping the product to a tanker.