Through a joint venture, Irving Oil has acquired the former ExxonMobil marine terminal in South Portland. The terminal gives Irving, based in Saint John, N.B., added capacity to serve customers across the Northeast with products including gasoline, heating oil and diesel fuel.

Under the terms of the venture, Iriving will have use of a majority of the 725,000 gallon storage terminal.

“We feel we’re getting a first-class asset in a market that’s very important to us,” said Gary Bischof, Irving’s general manager.

Financial terms of the deal weren’t disclosed.

The acquisition reflects a 50-50 arrangement with Buckeye Partners L.P. of Houston. Buckeye Partners is a publicly-traded partnership that owns more than 100 terminals and 6,000 miles of petroleum pipeline.

Buckeye also became the sole owner of a 140,000 barrel terminal in Bangor, along with a 124-mile pipeline connecting the two storage facilities.

“We will be using the pipeline and the new Buckeye terminal to serve our customers in Bangor,” Bischof said.

Irving had sought to buy the two terminals outright in 2009. That plan was blocked by the Federal Trade Commission, which said it could reduce competition and lead to higher gasoline prices in southern Maine and Bangor. Settlement talks led to the agreement and final purchase that was announced Tuesday.

The joint venture builds on a similar arrangement Irving has had for the past eight years in Portland Harbor with Citgo. Along with Irving/Citgo and Irving/Buckeye, Portland now is served by terminals operated by Sprague Energy, Global Petroleum and Gulf Oil.

Irving is a family-owned refining and marketing company with a major presence in Maine and New England. It operates an oil refinery in Saint John, N.B., that produces 75 percent of Canada’s gasoline exports.

A lot of that petroleum is used in New England, where three out of five vehicles in Boston run on Irving gasoline, the company estimates. While the Northeast gasoline market is flat and hasn’t grown since 2005, Bischof said delivery trucks that fill at the Irving-Citgo terminal have been experiencing longer wait times, a condition that will be eased by the new terminal.

“We felt we needed more capacity,” he said.