After a lengthy delay, Marathon Oil plans to significantly ramp up work next summer that will expand its oil refinery in southwest Detroit, creating more than a thousand construction jobs.

The Houston-based oil company is on track to complete the $2.2-billion refinery expansion by the end of 2012, said Gary Heminger, Marathon's executive vice president of downstream operations.

Currently, 650 contractors are working on the project but that is to rise to 1,800 to 2,000 by next summer when most of the construction is to occur.

The company has also started the process of hiring 135 new employees for the refinery, half of whom will be contract workers. Engineering work on the project is expected to be finished by year's end.

The expansion of Michigan's only oil refinery was supposed to be completed in this year's fourth quarter. But in October 2008, Marathon delayed the project because of the downturn in the economy. The refinery supplies 20% of Michigan's gasoline.

Marathon employs 400 workers at the refinery.

When construction is complete, the Detroit refinery will be able to process 120,000 barrels of oil a day, up from 106,000 barrels. But in a major change, most of the oil will be heavier crude from Canada's oil sands rather than light crude from the Gulf of Mexico, Oklahoma and other areas.

Clarence Cazalot Jr., Marathon's CEO and president, toured the construction site Wednesday. On Thursday, he spoke to the Detroit Economic Club, saying the oil industry is taking steps to prevent disasters like the BP oil spill.

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