Companies and agencies interested in what likely will be one of the largest energy projects in the world showed their hands Friday night when the state of Alaska unsealed bids to build a massive natural gas pipeline from the frozen North Slope to the lower 48.

Bids were received from China Petroleum & Chemical Corp., also known as Sinopec, TransCanada Corp., AEnergia LLC, the Alaska Natural Gasline Development Authority and the Alaska Gasline Port Authority.

Earlier Friday, Houston-based ConocoPhillips submitted a pipeline proposal to the state separate from the formal bidding process.

If built, the pipeline likely would dwarf any energy project in recent years. A 48-inch-diameter pipe would run 1,700 miles from Prudhoe Bay to Edmonton, Alberta, a major pipeline hub that then would carry the gas to U.S. markets. Cost estimates vary from $20 billion to $40 billion.