Texas-based Energy Transfer LP put its 350-mile Mariner East 2 natural gas liquids pipeline into service Dec. 29.

The pipeline transports domestically produced ethane, propane and butane east from processing plants in Ohio across West Virginia and Pennsylvania to the company's Marcus Hook Industrial Complex in Delaware County, Pa. In the complex, natural gas liquids are stored for distribution to local, domestic and waterborne markets.

Gas producers, particularly Antero Resources Corp. and Range Resources Corp., were counting on a portion of the 345,000-barrel-per-day Mariner East 2 pipeline to open by the end of the year. Antero spent at least $50 million more than planned in 2018 in anticipation of Mariner East 2 opening on time, CEO Paul Rady told analysts on the company's Nov. 1 earnings conference call.

The Mariner East pipelines are the subject of a criminal probe in Chester County, Pa., with potential charges including environmental crimes, criminal mischief and corrupt organizations. Construction of Mariner East 2 has been plagued with problems over the past two years, resulting in $12.6 million in fines assessed by the state's Department of Environmental Protection and numerous work stoppages ordered by either the environmental department or the Public Utility Commission.