Mumbai: Reliance Petroleum Ltd (RPL) has completed 90 per cent work at its upcoming Jamnagar complex and expects start trial runs in July. The company expects to commission the 580,000 barrels per day oil refinery in September.

RPL had earlier said it expects to start the plant late in the second quarter or early in the third quarter, well ahead of its official December target.

The 580,000 barrels per day refinery complex is coming up in a special economic zone at Jamnagar.

The company has mobilised sufficient site infrastructure to sustain construction on a fast-track in the coming months, RPL said in a release published on its website.

Reliance Industries, the parent company of Reliance Petroleum Ltd, operates a 660,000-bpd refinery close to the new project.

Chevron Corporation of the US holds a five per cent stake in RPL.

The two refineries together will form the world's largest refining complex, processing 1.24 million barrels crude daily.

The new refinery will process medium grade crude with an API (American Petroleum Institute) gravity of 24 degrees.

Reliance has also tied up 150,000 bpd of long-term crude supplies with Venezuelan state oil firm PDVSA beginning June.

Reliance, meanwhile, has offered term diesel to select trading houses for June 2008-May 2009 supplies, including first cargoes from the new plant.

The export-oriented refiner will offer gas oil with 0.05 per cent sulphur content and even cleaner grades.

Reliance reported refining margins for the March quarter of $15.5 (Rs618.5 at current rates) a barrel, more than double the benchmark Asian Dubai crack margin, which averaged about $7 a barrel.

This is because the company's running 660,000 bpd refinery in Gujarat can process cheaper, high-sulphur crude oil, bolstering its margins.