"We need to take advantage of the significant shift in ethane availability triggered by the U.S. shale gas boom," says Mark Garrett, Borealis' chief executive.
The new agreement would go into effect in 2016, when Sunoco Logistics anticipates its second Mariner East pipeline would begin service.
Sunoco Logistics, which is based in Philadelphia, has been looking to sign up new customers to commit to a second pipeline that would parallel its first Mariner East pipeline. The first Mariner East project, which involves converting an existing 80-year-old fuel pipeline, is scheduled to begin transporting gas liquids to Marcus Hook this year.
The new project, championed by the Corbett administration and gas-industry leaders, has created apprehension and opposition from some residents, especially in densely developed Chester County.
Sunoco Logistics is asking the Pennsylvania Public Utility Commission to declare its project a public utility, which would expedite its acquisition of rights-of-way and zoning approvals.
Borealis is the second European petrochemical producer to sign up to load its ships at Marcus Hook.
INEOS Europe in 2012 signed a 15-year agreement to ship Marcellus Shale ethane to Norway, providing the Mariner East project with its anchor customer.
Borealis on Thursday said it has signed a 10-year deal to buy ethane from Antero Resources Corp., which is producing natural gas from the Marcellus Shale in Pennsylvania and West Virginia and the Utica Shale in Ohio.
Antero announced in July that it is an anchor shipper on the second Mariner East project for 51,500 barrels a day of liquids - 11,500 barrels of ethane, 28,000 barrels of propane, and 12,000 barrels of butane.
Antero said the Marcus Hook facility gives it the ability to market the fuels to local markets in the Northeast as well as export markets.
Sunoco Logisitics, which is selling its Mariner East project as a cheaper shipping alternative than pipelines to the Gulf Coast, has not finalized plans for its second Mariner East project and has been circumspect about details.
During a conference call with investment analysts on Thursday, Sunoco Logistics president Michael J. Hennigan said the company was confident the project would move forward, but asked for patience on revealing specific details.
"We want everybody to feel good at the outcome; we think it's a great project and it's in the public interest," said Hennigan. "So we look forward to it being a successful project at some point. But like I said, we're not in a position to talk about the details of it at this time."